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? mobile amd-k6 processor power supply design publication # 22495 rev: c amendment/ 0 issue date: may 1999 application note ?
trademarks amd, the amd logo, k6, 3dnow!, and combinations thereof, and super7 are trademarks, and risc86 and amd-k6 are registered trademarks of advanced micro devices, inc. microsoft, windows, and windows nt are registered trademarks of microsoft corporation. mmx is a trademark of intel corporation. winstone is a registered trademark of ziff-davis, inc. other product names used in this publication are for identification purposes only and may be trademarks of their respective companies. ? 1999 advanced micro devices, inc. all rights reserved. the contents of this document are provided in connection with advanced micro devices, inc. (amd) products. amd makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication and reserves the right to make changes to specifications and product descriptions at any time without notice. no license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this publication. except as set forth in amds standard terms and conditions of sale, amd assumes no liability whatsoever, and disclaims any express or implied warranty, relating to its products including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or infringement of any intellectual property right. amds products are not designed, intended, authorized or warranted for use as components in systems intended for surgical implant into the body, or in other applications intended to support or sustain life, or in any other application in which the failure of amds product could create a situation where personal injury, death, or severe property or environmental damage may occur. amd reserves the right to discontinue or make changes to its products at any time without notice.
contents iii 22495c/0may 1999 mobile amd-k6 ? processor power supply design contents revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 mobile amd-k6 ? processor family power requirements. . . . . . . . . 3 voltage planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 power supply specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 selecting a power supply design . . . . . . . . . . . . . . . . . . . 6 switching regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 decoupling and layout recommendations . . . . . . . . . . . . . . . . . . . . 11 power distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 current transient response . . . . . . . . . . . . . . . . . . . . . . 12 output voltage response measurement techniques . . . . . . 18 output voltage response measurement utility. . . . . . 19 decoupling capacitance and component placement. . . . . . . 20 bulk decoupling for the i/o supply. . . . . . . . . . . . . . . . 24 high-frequency decoupling . . . . . . . . . . . . . . . . . . . . . . 25 power sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 power supply solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 digital-to-analog converter (dac) . . . . . . . . . . . . . . . . 31 elantech el7571 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 linear technology lt1435 . . . . . . . . . . . . . . . . . . . . . . . 35 maxim max798 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 voltage regulator vendor information . . . . . . . . . . . . . . . . . . . . . . . 40
iv contents mobile amd-k6 ? processor power supply design 22495c/0may 1999
list of figures v 22495c/0may 1999 mobile amd-k6 ? processor power supply design list of figures figure 1. 321-pin cpga v cc and ground pins location . . . . . . . . . 4 figure 2. 360-pin cbga v cc and ground pins location . . . . . . . . . 5 figure 3. linear and switching voltage regulators. . . . . . . . . . . . . 7 figure 4. basic asynchronous design. . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 5. basic synchronous design . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 6. power distribution model . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 7. load current step versus output voltage response. . . 14 figure 8. bulk decoupling versus output voltage response for a 1.8v processor core @ 6.25 amps . . . . . . . . . . . . . . 16 figure 9. bulk decoupling versus output voltage response for a 2.0v processor core @ 6.0 amps . . . . . . . . . . . . . . . 17 figure 10. bulk decoupling versus output voltage response for a 2.2v processor core @ 8.5 amps . . . . . . . . . . . . . . . 18 figure 11. via layout for low inductance . . . . . . . . . . . . . . . . . . . . 21 figure 12. cpga suggested component placement. . . . . . . . . . . . . 22 figure 13. cbga suggested component placement. . . . . . . . . . . . . 23 figure 14. 0.1 m f (c1) and 0.01 m f (c2) x7r capacitor impedance vs. frequency . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 15. decoupling inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 16. power sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 figure 17. elantech el7571 switching power supply design. . . . . 33 figure 18. linear lt1435 2.0v switching power supply design . . 36 figure 19. maxim max798 switching power supply design . . . . . 38
vi list of figures mobile amd-k6 ? processor power supply design 22495c/0may 1999
list of tables vii 22495c/0may 1999 mobile amd-k6 ? processor power supply design list of tables table 1. voltage error budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 table 2. representative esr values. . . . . . . . . . . . . . . . . . . . . . . . 20 table 3. inductance contributions of components . . . . . . . . . . . . 21 table 4. decoupling capacitor values . . . . . . . . . . . . . . . . . . . . . . 24 table 5. capacitor recommendations . . . . . . . . . . . . . . . . . . . . . . 24 table 6. voltage output vid codes . . . . . . . . . . . . . . . . . . . . . . . . 31 table 7. mobile voltage output vid codes . . . . . . . . . . . . . . . . . . 32 table 8. elantec el 7571 bill of materials. . . . . . . . . . . . . . . . . . . 34 table 9. linear lt1435 bill of materials . . . . . . . . . . . . . . . . . . . . 37 table 10. maxim max798 bill of materials . . . . . . . . . . . . . . . . . . . 39
viii list of tables mobile amd-k6 ? processor power supply design 22495c/0may 1999
revision history ix 22495c/0may 1999 mobile amd-k6 ? processor power supply design revision history date rev description jan 1999 a initial published release. apr 1999 b revised output voltage response measurement utility on page 19 to reflect the latest recommended utility. may 1999 c changed title and added first sentence on page 1 to reflect that the information in this document applies to the mobile amd-k6 ? processor family. may 1999 c revised the introduction section. may 1999 c added example 3 on page 14, figure 9 on page 17, and figure 10 on page 18. may 1999 c added bulk decoupling for the i/o supply on page 24. may 1999 c added new vendor to voltage regulator vendor information on page 40.
x revision history mobile amd-k6 ? processor power supply design 22495c/0may 1999
22495c/0may 1999 mobile amd-k6 ? processor power supply design introduction 1 application note mobile amd-k6 ? processor power supply design unless otherwise noted, the information in this application note pertains to all mobile processors in the amd-k6 ? family, which includes the mobile amd-k6 processor, the mobile amd-k6-2 processor, and the mobile amd-k6-iii-p processor. introduction this application note is intended to guide the board designer through the process of developing a reliable power supply for the mobile amd-k6 processor family. amd encourages designers to support adjustable voltage by using regulators with vid inputs. this programmable voltage feature facilitates the transition to the next generation of processors. additionally, as mobile processors are pushed for higher performance and faster clock speeds, the current requirements will continue to rise. higher currents will require more decoupling capacitors, and can be planned for by including pads on the board today even if they are not populated. designs that support higher currents will extend the life of a mobile system. this application note also provides basic guidelines on circuit decoupling for reduction of noise generated by fast current transients.
2 introduction mobile amd-k6 ? processor power supply design 22495c/0may 1999 for power supply design information for desktop amd-k6 processors, see the amd-k6 ? processor power supply design application note , order# 21103. this document contains the following sections: n mobile amd-k6 ? processor family power requirements lists the power requirements for the mobile amd-k6 processor family with an overview of power supply design considerations. this section describes the basic elements of a power supply and the constraints of different design approaches. n decoupling and layout recommendations describes the decoupling and layout recommendations of the power supply design. proper decoupling is required in order to deliver a reliable power source across the power planes and to reduce the noise generated from the fast current transients. n power supply solutions describes several voltage regulator circuits that are developed by voltage regulator vendors. these circuits can be used to generate the proper core and i/o voltages for the mobile amd-k6 processors. amd recommends that board designers consult with the voltage regulator vendors to obtain the most updated information. n for more information about the mobile amd-k6 processor family, refer to the following: ? mobile amd-k6 ? processor data sheet , order# 21049 ? mobile amd-k6 ? -2 processor data sheet , order# 21896 ? mobile amd-k6 ? -iii-p processor data sheet , order# 22655
mobile amd-k6 ? processor family power requirements 3 22495c/0may 1999 mobile amd-k6 ? processor power supply design mobile amd-k6 ? processor family power requirements voltage planes two separate supply voltages are required to support the mobile amd-k6 processors v cc2 and v cc3 . v cc2 provides the core voltage for the processor and v cc3 provides the i/o voltage. the power supply pin assignments for the mobile amd-k6 processors 321-pin cpga package (see figure 1 on page 4) are as follows: the power supply pin assignments for the mobile amd-k6 and the mobile amd-k6-2 processor 360-pin cbga package (see figure 2 on page 5) are as follows: note: the mobile amd-k6-iii-p processor is not available in the cbga package. v cc2 (core): a-07, a-09, a-11, a-13, a-15, a-17, b-02, e-15, g-01, j-01, l-01, n-01, q-01, s-01, u-01, w-01, y-01, aa-01, ac-01, ae-01, ag-01, aj-11, an-09, an-11, an-13, an-15, an-17, an-19 v cc3 (i/o): a-19, a-21, a-23, a-25, a-27, a-29, e-21, e-27, e-37, g-37, j-37, l-33, l-37, n-37, q-37, s-37, t-34, u-33, u-37, w-37, y-37, aa-37, ac-37, ae-37, ag-37, aj-19, aj-29, an-21, an-23, an-25, an-27, an-29 v cc2 (core): f04, f05, f06, f07, g06, g07, h08, h09, h12, h13, j04, j05, j08, j09, j10, j11, j12, j13, k04, k05, k06, k07, k10, k11, l04, l05, l08, l09, l10, l11, l12, l13, m08, m09, m12, m13, n06, n07, p04, p05, p06, p07 v cc3 (i/o): d07, d08, d09, d12, d13, e07, e08, e09, e12, e13, f10, f11, f14, g10, g11, g14, g15, g16, h14, h15, h16, k17, m14, m15, m16, n10, n11, n14, n15, n16, p10, p11, p14, r07, r08, r09, r12, r13, t07, t08, t09, t12, t13
4 mobile amd-k6 ? processor family power mobile amd-k6 ? processor power supply design 22495c/0may 1999 figure 1. 321-pin cpga v cc and ground pins location
mobile amd-k6 ? processor family power requirements 5 22495c/0may 1999 mobile amd-k6 ? processor power supply design figure 2. 360-pin cbga v cc and ground pins location w v u t r p n m l k j h g f e d c b a w v u t r p n m l k j h g f e d c b a 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 other vss pins v cc3 pins v cc2 pins bottom view
6 mobile amd-k6 ? processor family power mobile amd-k6 ? processor power supply design 22495c/0may 1999 power supply specification the maximum current used for power calculations is based on maximum v cc whereas the current used for maximum thermal power calculations is based on nominal v cc . refer to the thermal solution design application note, order# 21085 for more details on thermal calculations for voltage and current specifications of the mobile amd-k6 processor family, refer to their respective data sheets at http://www.amd.com/k6/k6docs/. selecting a power supply design most pc platforms today require dc-to-dc voltage conversion circuits to supply lower voltages to the processor core and i/o. two types of regulators are usedlinear and switching. figure 3 shows the linear and switching regulators. a linear regulator provides excellent dynamic-load response in the low-voltage, high-current environment. it also contributes to simplified design and lower cost. however, the efficiency loss and heat generated by a linear regulator should be addressed by board designs. although most desktop system designs can tolerate the efficiency loss, mobile designs cannot. in a high-current model, the power dissipation from the linear regulator can be as much as that of the processor itself. in order for the voltage regulator thermal solution to meet the case temperature requirement, the linear regulator requires a larger heatsink. linear regulators are not recommended for mobile designs because of the heat and low efficiency. a switching regulator meets the efficiency and size limitations of mobile board designs. switching regulators are found in most notebook computers that require both low-profile design and power-dissipation reduction. the switching regulator uses a series switch in conjunction with the output capacitor (c o ) to control the on/off ratio in order to obtain an average output voltage. because the switch turns off frequently, only a small amount of power is lost during conversion.
mobile amd-k6 ? processor family power requirements 7 22495c/0may 1999 mobile amd-k6 ? processor power supply design figure 3. linear and switching voltage regulators switching regulator a switching regulator varies the switch duty cycle (on/off ratio) according to the output feedback. a large output capacitor (c o ) is used in the switching design to achieve a constant average output. the switching regulator delivers higher efficiency than a linear regulator, but the tradeoffs are higher ripple voltages (noise) and slower transient current response time. a series inductor is used to supply current to the load during the switch off time, adding complexity to the design. in addition, the inductor and the output capacitor increase the overall cost of the switching regulator design relative to a linear regulator design. the power supply design must account for a minimized current (i cc2 and i cc3 ) drain when the mobile amd-k6 processors enter the stop grant state. the power supply must ensure the minimal current drain does not cause any adverse side effects (drift out of regulation, over-compensation, or shutdown) that could corrupt or damage the functionality of the processor. the mobile amd-k6 processors voltage tolerance requirement on both core and i/o voltage pins can be handled by commonly available linear and switching regulators. this application note describes several high-accuracy designs (starting on page 31) + C r l control v in v out + C feedback efficiency = v out v in + C r l v in v out + C switching regulator linear regulator c o l o
8 mobile amd-k6 ? processor family power mobile amd-k6 ? processor power supply design 22495c/0may 1999 that provide the processor with accurate and stable voltage supplies. in the basic asynchronous circuit design shown in figure 4, q1 turns on to charge c out and builds up the magnetic field in l1. when the feedback from the sense input is too high, the controller turns q1 off. current is supplied to the load by the collapsing magnetic field in l1 and the discharge of c out . when the sense feedback detects a drop in the load voltage, the controller turns on q1 to recharge the circuit. cr2 supplies a return path for l1 when it is supplying current. figure 4. basic asynchronous design the operation of the basic synchronous circuit design shown in figure 5 is essentially the same as the asynchronous design. q1 turns on to charge c out and builds up the magnetic field in l1. when the feedback from the sense input is too high, the controller turns q1 off. current is supplied to the load by the collapsing magnetic field in l1 and the discharge of c out . when the sense feedback detects a drop in the load voltage, the controller turns on q1 to recharge the circuit. q2 supplies a return path for l1 when it is supplying current. when q1 is on, q2 is off and when q1 is off, q2 is on. the main reason the synchronous design is more efficient than the asynchronous design is because the power dissipated in q2 is lower than the power dissipated in cr2. r l c out l 1 cr2 controller q 1 sense
mobile amd-k6 ? processor family power requirements 9 22495c/0may 1999 mobile amd-k6 ? processor power supply design figure 5. basic synchronous design another consideration is power dissipation in the lower mosfet q2 (synchronous) or diode cr2 (asynchronous). as the output voltage decreases, the power dissipation in cr2 (q2) increases. the higher power dissipation may require using a different package type or adding a heat sink to dissipate the additional power. to determine if the transistors or the diode need a heat sink, use the following equation: p = i 2 r duty cycle (q1) p = i 2 r (1C duty cycle) (q2) duty cycle ~ v out /v in compare these calculations with the specifications of the device used. other specifications to consider are the input-voltage range and the number of outputs provided. the input-voltage range must be matched to the batteries and charger. ensure that the charger voltage does not exceed the input-voltage range of the regulator when the battery is removed. generally, the battery stack consists of 5 to 12 nicd cells or 2 to 3 li-ion cells. some parts supply multiple outputs. these devices can save critical space in a mobile design. however, these devices limit some of the voltage and current options, and should be evaluated based on the total requirements of the end product. r l c out q 2 q 1 controller l1 sense vout
10 mobile amd-k6 ? processor family power mobile amd-k6 ? processor power supply design 22495c/0may 1999 mobile systems typically require 12v, 5v, 3.3v, and the specified cpu core voltage for the amd-k6 processor models 7, 8 and 9. each of these voltages can be generated directly from the battery (a technique called distributed power). the more common approach involves producing a 5v main supply and generating the other voltages from this 5v source. this technique is less efficient, yielding a shorter battery life. for example, assume a 90% efficiency to generate 5v from the battery and 90% efficiency to generate 3.3v from 5v. this yields an overall efficiency of 81% between the battery and the 3.3v supply. efficiency is very important because it contributes directly to battery life. to achieve high efficiency at low currents, many converters have a pulse-skipping mode. some companies call this hysteretic mode or burst mode. all of the examples starting on page 33 use synchronous converter designs because they are the most efficient (90%C95%). the additional schottky diode in some designs provides an additional efficiency improvement at low currents. space and weight are also important considerations for mobile designs. some solutions listed use fewer components than others. some use more expensive components. the size of the inductor can be reduced by running the controller at a higher frequency. when choosing a vendor, pick one that meets all the needs of the end product. the product lines of some vendors include battery charger circuits and backlight inverters for the display. in addition, locate the supply as close as possible to the cpu. this placement reduces the distance current transients must travel in the v cc and gnd planes, thereby reducing emi.
decoupling and layout recommendations 11 22495c/0may 1999 mobile amd-k6 ? processor power supply design decoupling and layout recommendations power distribution in order to maintain a stable voltage supply during fast transients, power planes with high frequency and bulk decoupling capacitors are required. figure 6 shows a power distribution model for the power supply and the processor. the bulk capacitors (c b ) are used to minimize ringing, and the processor decoupling capacitors (c f ) are spread evenly across the circuit to maintain stable power distribution. figure 6. power distribution model + C r l v out + c b c f pcb trace processor power plane + C r l v out c b c f c l esr esl equivalent circuit l trace r trace pcb trace processor power plane
12 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 current transient response in the power distribution model shown in figure 6, c b represents bulk capacitors for the power supply and c f represents high-frequency capacitors for processor decoupling. the bulk capacitors supply current to the processor during sudden excessive current demands that cannot be supplied by the voltage regulator (for example, transistioning from the stop grant state to normal mode). the required c b can be calculated by the following equation (ideal case): where: n d i is the maximum processor current transient n d v is the tolerance times the nominal processor voltage n d t is the voltage regulator response time example 1 assuming the maximum processor current transient is 6a, the voltage tolerance of the processor is 100 mv, and the voltage regulator response time is 10 m s, the minimum capacitance for the bulk decoupling is: c b 3 (6a/0.100v) 10 m s = 600 m f esr (equivalent series resistance) and esl (equivalent series inductance) are introduced in the model shown in figure 6. c b contains esr and esl, which cause voltage drop during current transient activity (see figure 7). the resistive and inductive effect of the capacitors must be taken into account when designing processor decoupling. low esl and esr capacitors should be used to obtain better voltage and current output characteristics. the voltage error budget for esl is shown in table 1 on page 15. taking into account the esr, the following equation is used to calculate c b : c 3 d i d v d t c 3 d i (d v C ( d i esr)) d t
decoupling and layout recommendations 13 22495c/0may 1999 mobile amd-k6 ? processor power supply design example 2 example 1 assumes the maximum processor current transient is 6a, the voltage tolerance of the processor is less than 100mv, and the voltage regulator response time is 10 m s. assuming five tantalum capacitors with 55-m w esr (the parallel resistance is 11m w ) are used as bulk capacitors, the minimum bulk capacitance is: c o 3 ((6a/(0.100 v C [6a 11 m w] )) 10 m s = 1764 m f in example 2, the effect of the esr requires the addition of more capacitance than the ideal shown in example 1. in order to achieve more margin, the total error budget should be distributed between set point tolerance, esl, and esr as shown in figure 7 on page 14 and table 1 on page 15. although the drop from esl is a small factor, it is not negligible. if aluminum electrolytic capacitors are used instead of tantalum capacitors, the esl drop is larger.
14 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 example 3 this example assumes the maximum processor current transient is 8.5a, the voltage tolerance of the processor is less than 100mv, and the voltage regulator response time is 10 m s. assuming seven tantalum capacitors with 55-m w esr (the parallel resistance is 8 m w ) are used as bulk capacitors, the minimum bulk capacitance is: c o 3 ((8.5a/(0.100 v C [8.5a 8 m w] )) 10 m s = 2656 m f in order to achieve more margin, the total error budget should be distributed between set point tolerance, esl, and esr as shown in figure 7 and table 1 on page 15. although the drop from esl is a small factor, it is not negligible. if aluminum electrolytic capacitors are used instead of tantalum capacitors, the esl drop is larger. note: for additional higher current calculations, see the amd-k6 ? power supply design application note, order# 21103. the high-frequency decoupling capacitors (c f ), which are typically smaller in capacitance and esl, maintain the voltage output during average load change until c b can react. see high-frequency decoupling on page 25 for more information. figure 7. load current step versus output voltage response (max) load current output voltage response v cc voltage regulator response (min) (max) (min) i cc esr x d i esl x d i d t d i c d v d t =
decoupling and layout recommendations 15 22495c/0may 1999 mobile amd-k6 ? processor power supply design allocation of the voltage error budget can be determined from figure 7. given a total error budget of 100mv and using good capacitors (five 470 - m f capacitors with a 55-m w esr are assumed), voltage drops can be allocated as shown in table 1. table 1. voltage error budget error budget component calculations* budgeted drop v (set point) 1% 0.020v v (esr) 11 m w x 5.6a (11m w = 55m w /5) 0.062v v (esl) 0.24nh x (6a/100nsec) {0.24nh = (0.6nh + 0.6nh via)/5} 0.014 v total 0.096v note: * calculations assume 5 capacitors
16 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 figure 8 shows the voltage drop as a function of bulk decoupling. the graph was calculated using 55-m w esr 470 - m f capacitors, and gives the designer a visual representation of how much bulk decoupling is required. for example, at 1880 m f, the voltage is 1.72v (6a current transient), leaving little margin for dc-tolerance errors. at 2820 m f, the voltage is 1.75v, allowing 0.05v for set point tolerance. figure 8. bulk decoupling versus output voltage response for a 1.8v processor core @ 6.25 amps output voltage vs. capacitance 1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8 470 940 1410 1880 2350 2820 3290 3760 capacitance in uf voltage volts
decoupling and layout recommendations 17 22495c/0may 1999 mobile amd-k6 ? processor power supply design similarly, figure 9 shows the voltage drop as a function of bulk decoupling. the graph was calculated using 55-m w esr 470 - m f capacitors, and gives the designer a visual representation of how much bulk decoupling is required. for example, at 1880 m f, the voltage is 1.92v (6a current transient), leaving little margin for dc-tolerance errors. at 2820 m f, the voltage is 1.95v, allowing 0.05v for set point tolerance. figure 9. bulk decoupling versus output voltage response for a 2.0v processor core @ 6.0 amps output voltage vs. capacitance 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2 470 940 1410 1880 2350 2820 3290 3760 capacitance in uf voltage volts
18 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 similarly, figure 10 shows the voltage drop as a function of bulk decoupling. the graph was calculated using 55-m w esr 470 - m f capacitors, and gives the designer a visual representation of how much bulk decoupling is required. for example, at 2350 m f, the voltage is 2.11v (8.5a current transient), leaving little margin for dc-tolerance errors. at 3760 m f, the voltage is 2.14v, allowing 0.04v for set point tolerance. figure 10. bulk decoupling versus output voltage response for a 2.2v processor core @ 8.5 amps output voltage response measurement techniques to measure output voltage response, run a program such as dos edit and toggle stpclk# every 40 m s or slower. (amd has developed the maxpwr99.exe utility . see output voltage response measurement utility for more information.) measure the voltage at the back of the board right under the processor. use a scope probe with a ground connection next to the tip. the 3 inch to 6 inch ground leads that come off the side of a scope probe have too much inductance for this type of measurement. the scope bandwidth can be limited to 20mhz, output voltage vs. capacitance 1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 0 470 940 1410 1880 2350 2820 3290 3760 4230 4700 capacitance in uf voltage volts
decoupling and layout recommendations 19 22495c/0may 1999 mobile amd-k6 ? processor power supply design giving a clear indication of the power supplied. while limiting the scope bandwidth for bulk decoupling verification gives a clear indication of the low frequency issues, amd recommends rechecking with at least a 250-mhz bandwidth for verifying the high-frequency decoupling. amd used a tektronix 684b scope with 6245 probes and an hp54720 with 54701 probes. (there was no significant difference between these two instruments.) the data was taken over a 40-second window with the scope set to infinite persistence. amd made measurements running winstone ? under the windows ? 95 operating system, running dos edit pull down, and running maxpwr99.exe while toggling stpclk#. the latter case created the worst measured-case current transient. in addition, this is the case that requires the maximum decoupling capacitance. the table voltage regulator vendor information on page 40 lists some possible power supply solutions. the listed regulators are ones that amd believes can meet the processor requirements (with proper decoupling). amd has not tested any of the mobile power supplies. output voltage response measurement utility amd has developed the maxpwr99.exe utility to assist in designing systems that comply with the amd-k6 processors power and thermal requirements. this utility can verify that the supply voltage remains stable during a transition to a higher power/current consumption level. this utility is dos based. for systems based on the windows 95 or windows 98 operating systems, re-boot in dos mode or boot from a bootable dos floppy disk that contains the utility. for systems based on the windows nt ? and os/2 operating systems, boot from a bootable dos floppy disk that contains the utility. the command line for this utility is as follows: ( note: do not execute the utility in a dos window or with a memory manager loaded. ) c:\>maxpwr99.exe the maxpwr99.exe utility is available under a non-disclosure agreement. contact your local amd sales office for information.
20 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 decoupling capacitance and component placement the high-frequency decoupling capacitors (c5Cc31 in figure 12 on page 22) should be located as close to the processor power and ground pins as possible. to minimize resistance and inductance in the lead length, the use of surface mounted capacitors is recommended. when possible, use traces to connect capacitors directly to the processors power and ground pins. the decoupling capacitors can be placed in the socket 7 cavity on the same side of the processor (component side) or the opposite side (bottom side). suggested component placement for the decoupling capacitors are shown in figure 12 on page 22 for cpga packages and in figure 13 on page 23 for cbga packages. the values of the capacitors are specified in table 4 on page 24. capacitor recommendations are shown in table 5 on page 24. the split voltage planes should be isolated if they are in the same layer of the circuit board. to separate the two power planes, an isolation region with a minimum width of 0.254 mm is recommended. the ground plane should never be split. these recommendations are based on single-sided component assembly and space constraints. the designer should assume these are minimum requirements. if double-sided component assembly is used, it is preferable to use more capacitors of a smaller value, which reduces the total esr and total esl of the capacitors. for example, instead of four 470- m f capacitors, use ten 47- m f capacitors. (check the device specifications shown in table 2 on page 20. occasionally a lower value capacitance has a higher esr.) as the effective esr is lowered, the total required capacitance is reduced. the breakdown voltage and case size both affect the esr value. table 2. representative esr values capacitance device 1 device 2 470 m f55 m w 100 m w 270 m f70 m w 100 m w 100 m f 90 m w 100 m w 68 m f 95 m w 100 m w 47 m f120 m w 250 m w
decoupling and layout recommendations 21 22495c/0may 1999 mobile amd-k6 ? processor power supply design via inductance can be reduced when using double-sided component assembly. components can share vias on the top side and bottom side. this technique reduces the effective via inductance. figure 11 shows another way to reduce via inductance parallel vias. this technique is usually used on bulk decoupling capacitors. the inductance contribution numbers shown in table 3 indicate that a poor layout can negate a good component. figure 11. via layout for low inductance table 3. inductance contributions of components component induction comment capacitor 0.6nh (approximately) esl via 0.7nh (approximately) C 100 mil trace 1.6nh (approximately) 10 mil wide trace capacitor pad dual vias no trace between via and pad
22 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 figure 12. cpga suggested component placement 0.254mm (min.) for isolation region v cc2 (core) plane v cc3 (i/o) plane c1 cc5 cc3 c2 + + + + c5 c6 c7 c8 c9 c10 c17 c18 c19 c20 c21 c22 c23 c24 c25 c26 c27 c28 c29 c30 c31 cc4 + cc6 c14 c15 c16 cc9 cc7 cc10 cc8
decoupling and layout recommendations 23 22495c/0may 1999 mobile amd-k6 ? processor power supply design figure 13. cbga suggested component placement w v u t r p n m l k j h g f e d c b a w v u t r p n m l k j h g f e d c b a 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 bottom view cc6 cc5 cc4 cc3 other vss pins v cc3 pins v cc2 pins c1 c2 note: high-frequency capacitor placement is very layout dependent and is not shown in this figure. cc7 cc10 0.254mm (min.) for isolation region cc9 cc8
24 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 table 4 lists the recommended capacitor values. table 5 lists recommended capacitor types. the recommendations in table 5 are not the only possibilities. based on parts availability and the controller chosen, many solutions exist. the intent of these recommendations is to give insight into the requirements, and not to specify a particular solution. many vendors prefer to use aluminum electrolytics instead of tantalum capacitors. this approach is acceptable as long as good quality, low-esr parts are used. bulk decoupling for the i/o supply the data sheet specifies the v cc3 current at about 0.6 amps. this number only specifies the maximum current consumed by the processor without any load. to calculate the peak demand on the i/o supply, consider what happens when all 64 data bus table 4. decoupling capacitor values item qty location value footprint description note 1 2 c1, c2 47 m f avx size v surface tantalum capacitor, avx part number tpsv476*025r0300 or equivalent v cc3 decoupling 28 cc3 C cc10 470 m f avx size v surface tantalum capacitor, avx part number tpsv477*006r0100 or equivalent v cc2 decoupling 324c5Cc310.1 m f 0805 C c5Cc10 for v cc3 c14Cc31 for v cc2 table 5. capacitor recommendations manufacturer type comment web avx tps exceptional /www.avxcorp.com vishay sprague 594d exceptional /vishay.com/vishay/sprague sanyo sa/sg excellent /www.sanyovideo.com chem-con lvx good /www.chemi-con.com mallory t495 good /www.nacc-mallory.com nemco slr series good /www.nemcocaps.com panasonic eef good /www.panasonic.com/pic panasonic fa good /www.panasonic.com/pic vishay sprague 593d good /vishay.com/vishay/sprague elna rjh/rjj good /www.elna-america.com
decoupling and layout recommendations 25 22495c/0may 1999 mobile amd-k6 ? processor power supply design lines switch from low to high. a typical pc board trace impedance appears as 50 w during the switching time. therefore, the theoretically computed current demand is i = 3.3 v/50 w = 66 ma. if this is multiplied by 64 drivers, the result is 4.22 a. however, the driver acts as a constant current source/sink of about 20 ma for the first 200 psec then it behaves as a 40 ma current source/sink until it is approximately 1 volt from v cc3 when driving high, or 1 volt from ground when driving low. from this point the current linearly decreases to zero. thus instead of a maximum of 4.22 a, the current is limited to 64 40 ma = 2.56 a current demand to charge the bus. using the same techniques as the previous core, the bulk decoupling for the i/o can be computed as follows: this example assumes a maximum processor i/o current transient of 2.6a, the voltage tolerance of the processor is less than 145 mv, and the voltage regulator response time is 1 m s. a linear regulator is assumed in this example to have a 1 m s response time. using three tantalum capacitors with 100-m w esr (the parallel resistance is 33m w ) as bulk capacitors, the minimum bulk capacitance is calculated as: c o 3 ((2.6a/(0.145 v C [2.6a 33m w] )) 1 m s = 44 m f three 22 m f tantalum capacitors with 100-m w esr meet this requirement. however, if the regulator response time is 10 m s then 440 m f would be required. it is difficult to find a 22 m f tantalum capacitors with an esr this low. therefore, it is necessary to use a much larger value of capacitance to get this low of an esr. two 470 m f, 5 5 m w esr parts would meet the requirement. three 100 m f capacitors with an esr of 100 m w would also work. high-frequency decoupling inductance is also a concern for the high-frequency decoupling capacitors. case size can be a significant factor affecting capacitor inductance. for example, a 0603 case has significantly more inductance than a 0612 case. amd recommends the 0612, 1206, 0805, and 0603 case in order of best to worst. inductance can also be reduced by directly connecting the capacitor to the power pin of the processor. in order to minimize its inductance, this trace must be short and as wide as possible. this technique effectively removes two via
26 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 inductances between the capacitor and the processor as shown in figure 15 on page 28. the dotted line shows that connecting the capacitor directly to the processor eliminates two series inductances. however, this trace also has inductanceif it is too long or too narrow it can be worse than the vias. figure 14 on page 28 shows the effect of the inductance at higher frequencies. (the numbers outside the x and y axis indicate the minimum and maximum values plotted). the inductance used is 1.8nh (0.7nh for each of the two vias and 0.4nh for the capacitor itself). the capacitor is a 0.1- m f x7r multilayer ceramic mlc. the inductance of a capacitor is a function of the case type. an 0612 case is assumed here. the following steps show how the number of required capacitors is calculated: 1. decide what to allow as a ripple voltage budget. in this example calculation the ripple-voltage budget (dv) is 30 mv. 2. the measured ac transient current is 0.75a. this transient current has a typical duration (dt) of 2.5 nsec. the amount of capacitance required can now be determined using the following equation: i = c (dv/dt) c = i (dt/dv) = 0.75a (2.5nsec/30mv) = 0.625 m f this equation indicates that if the capacitors didn't have inductance, only six 0.1- m f capacitors would be required. 3. determine the number of capacitors required based on the inductance of the capacitor. use the following formula: v = l (di/dt) = l (0.75a/2.5nsec) = 30mv solving for l, the allowed budget is 100ph. 4. the inductance of the capacitor and via = 1.8nh (0.7nh for each of the two vias and 0.4nh from the capacitor itself). because each capacitor usually has two vias (one on each end), the effective via inductance must be: 2 0.7nh + 0.4nh = 1.8nh
decoupling and layout recommendations 27 22495c/0may 1999 mobile amd-k6 ? processor power supply design 5. solving the following equations for n: 1.8nh/n = 100ph n = 1.8nh/100ph = 18 the number of capacitors required is 18. the following steps repeat the calculation for i/o decoupling: 1. determine the amount of capacitance required using the following equation: i = c (dv/dt) c = i (dt/dv) = 0.5 (2.5nsec/145mv) = 0.0086 m f this equation indicates that if the capacitors didn't have inductance, only one 0.1- m f capacitor would be required. 2. using 0.5a as a typical i cc3 value, repeat the calculations to account for inductance: note: the ripple budget is 145mv because the i/o drivers are not as sensitive to supply variations as the core and the current transient is smaller. l = v (dt/di) = 0.145 (2.5nsec/.5a) = 725ph solving for l, the allowed budget is 725ph. the number of capacitors = 1.8nh/725ph = 2.5. therefore, only three capacitors are required on the i/o. amd recommends six capacitors.
28 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999 figure 14. 0.1 m f (c1) and 0.01 m f (c2) x7r capacitor impedance vs. frequency figure 15. decoupling inductance 1 10 6 1 10 7 1 10 8 1 10 9 0.1 1 10 100 15.9312 0.191752 zo( ) , , , c2 l r w zo( ) , , , c1 l r w 1e+009 1e+006 w capacitor pad via to gnd cpu via to v cc cpu via to gnd via to v cc cc processor v cc plane gnd plane via via a b c d a b c d
decoupling and layout recommendations 29 22495c/0may 1999 mobile amd-k6 ? processor power supply design power sequencing although the mobile amd-k6 processor requires dual power supply voltages, there are no special power sequencing requirements. the best procedure is to minimize the time between which v cc2 and v cc3 are either both on or both off (see figure 16). however, a good design practice ensures v cc3 is always greater than v cc2 . figure 16. power sequencing v cc2 v cc3 volt minimize time
30 decoupling and layout recommendations mobile amd-k6 ? processor power supply design 22495c/0may 1999
power supply solutions 31 22495c/0may 1999 mobile amd-k6 ? processor power supply design power supply solutions the solutions provided in this section are not all-inclusive. obtain additional circuit diagrams and application assistance from the manufacturers. the manufacturers can customize designs to an oems requirements. the schematics shown in this document have not been tested by amd and are provided as examples only. digital-to-analog converter (dac) voltage identification (vid) codes provide a way to program the digital-to-analog converter (dac) to supply a reference for different output voltages. many manufacturers have dac-controlled devices, however, some do not follow the vid defined codes. the devices listed in the table voltage regulator vendor information on page 40 use the vid codes. table 6 shows the codes and corresponding voltages. table 6. voltage output vid codes d4 d3 d2 d1 d0 output voltage d4 d3 d2 d1 d0 output voltage 100003.50v 000002.05v 100013.40v 000012.00v 100103.30v 000101.95v 100113.20v 000111.90v 101003.10v 001001.85v 101013.00v 001011.80v 101102.90v 001101.75v 101112.80v 001111.70v 110002.70v 010001.65v 110012.60v 010011.60v 110102.50v 010101.55v 110112.40v 010111.50v 111002.30v 011001.45v 111012.20v 011011.40v 111102.10v 011101.35v 11111 off 011111.30v
32 power supply solutions mobile amd-k6 ? processor power supply design 22495c/0may 1999 to meet the special requirements of mobile parts new vid codes separate from the desktop controllers are used. these new mobile vid codes are defined in table 7. . table 7. mobile voltage output vid codes d4 d3 d2 d1 d0 output voltage d4 d3 d2 d1 d0 output voltage 100001.275v 000002.00v 100011.250v 000011.95v 100101.225v 000101.90v 100111.200v 000111.85v 101001.175v 001001.80v 101011.150v 001011.75v 101101.125v 001101.70v 101111.100v 001111.65v 110001.075v 010001.60v 110011.050v 010011.55v 110101.025v 010101.50v 110111.000v 010111.45v 111000.975v 011001.40v 111010.950v 011011.35v 111100.925v 011101.30v 11111 off 01111 off
power supply solutions 33 22495c/0may 1999 mobile amd-k6 ? processor power supply design elantech el7571 the el7571 switching regulator is a flexible, high-efficiency, pwm controller that includes a 5-bit dac adjustable output. this regulator employs synchronous rectification to deliver up to 15a at efficiencies greater than 85% over a supply voltage range of 4.5v to 12.6v. (efficiencies up to 92% can be achieved at 10a.) figure 17 shows an el7571 reference design. the vid code allows the output to be set between 1.3v and 2.05v (in 50mv increments) and 2.1v and 3.5v (in 100mv increments) with a 1% accuracy. table 8 on page 34 shows the bill of materials for the el7571. figure 17. elantech el7571 switching power supply design 0.1uf 5uh 660uf x 6 vout cosc cslope oten ref pwrgd fb cs lsd lx hsd vhi vin 220pf 220pf 0.1uf enable 7.5m w power good 1.4v gndp vid0 vid1 vid2 vid3 voltage i.d. (vid[0:4]) vinp gnd vid4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0.1uf 10 w 4.5v to 12.6v 1.5uh 0.1uf 660uf x3 c3 c4 c5 d2 l2 r1 q2 q1 l2 c1 c7 d1 c6 r2 c2 1.3v to 3.5v ic1
34 power supply solutions mobile amd-k6 ? processor power supply design 22495c/0may 1999 contact information. elantec corporation 675 trade zone blvd. milpitas, ca 95035-1323 tel: (408) 945-1323 fax: (408) 945-9305 www.elantec.com table 8. elantec el 7571 bill of materials reference description part number manufacturer c1, c2 680 m f lxf16vb681m10x20ll united chem-con c3, c4 220pf chip capacitor any c5, c6, c7 0.1 m f chip capacitor any d1 diode bav99 motorola, et-al d2 diode 32ctq030 international rectifier ic1 controller el 7571cm elantec l1 5.1 m h pe-53700 pulse engineering l2 1.5 m h t30-26 7t awg #20 micro metals r1 15m w wsl-2512 dale r2 10 w chip resistor any r3 10 w chip resistor any q1, q2 mosfet si4410 siliconix
power supply solutions 35 22495c/0may 1999 mobile amd-k6 ? processor power supply design linear technology lt1435 the lt1435 is designed to be configured as a synchronous buck converter with a minimum of external components. the input voltage can range from 4.5v to 24v (limited by the external mosfets). the circuit highlights the capabilities of the ltc1435, which uses a current mode, constant frequency architecture to switch a pair of n-channel power mosfets while providing 99% maximum duty cycle. operating efficiencies exceeding 90% are obtained. figure 18 on page 36 shows an lt1435 reference design that can deliver up to 6a. vout = 1.19 (1 + r1/r2). table 9 on page 37 shows the bill of materials for the lt1435. contact information. linear technology corporation 1630 mccarthy blvd. milpitas, ca 95035-7417 tel: (408) 432-1900 fax: (408) 434-0507 www.linear.com
36 power supply solutions mobile amd-k6 ? processor power supply design 22495c/0may 1999 4.5v to 24v optional emi filter 2v 2.1v 2.2v 2.0v @ 6a avx tps low esr 22uf avx tps low esr can be substituted for current input caps sanyo mv-gx aluminium electrolitic sgnd connection are connected to ground of output caps u2 ltc1435 cosc 1 run/ss 2 ith 3 sfb 4 sgnd 5 vosens 6 sense- 7 sense+ 8 extvcc 9 pgnd 10 bg 11 intvcc 12 vin 13 sw 14 tg 16 boost 15 rc 10k q1 si4410dy 4 1 2 5 6 7 8 3 q2 si4410dy 4 1 2 5 6 7 8 3 l1 10uh r1 35.7k 1% cout2 100uf 10v c3 4.7uf 16v c1 100pf c2 0.1uf c5 1000pf cc2 51pf c4 0.1uf c6 100pf cosc 100pf cc 330pf d3 mbrs340 d1 mbrs140 e9 l2 2uh cin 220uf 35v cin1 220uf 35v cin3 220uf 35v cin4 220uf 35v cin5 220uf 35v c10 0.1uf c11 0.1 f c8 0.1uf c7 0.1uf rsense1 0.033 rsense2 0.033 css 0.1uf r6 52.3k 1% j1 j3 r7 46.4k 1% r8 42.2k 1% j2 cout 100uf 10v cout3 100uf 10v cout4 100uf 10v cout5 100uf 10v figure 18. linear lt1435 2.0v switching power supply design
power supply solutions 37 22495c/0may 1999 mobile amd-k6 ? processor power supply design table 9. linear lt1435 bill of materials reference description part number manufacturer cc 330pf 50v 10% npo chip capacitor 08055a331kat1a avx cc2 51pf 50v 10% npo chip capacitor 08055a510kat1a avx cin, cin1, 3, 4, 5 220f 35v 20% alum elec. capacitor mv-gx sanyo cout1C5 100f 10v 20% tantalum capacitor tpsd107m010r0080 avx c1, c6, cosc 100pf 50v 10% npo chip capacitor 08055a101kat1a avx c2, c4, css, c7C8, c10C11 0.1f 50v 10% y5v chip capacitor 08055g104kat1a avx c3 4.7f 16v 20% tantalum capacitor tajb475m016 avx c5 1000pf 50v 10% x7r chip capacitor 08055c102kat1a avx d1 bvr = 40v C 1 a schottky diode mbrs150 motorola d2 bvr = 40v C 3 a schottky diode mbrs340t3 motorola jp1 2mm pin header 2802s-03-g2 comm con jp2 2mm pin header 2802s-10-g2 comm con l1 10h inductor bi hm77-25006 pe53663 bi tech pulse engineering l2 2h inductor emi filter (optional) do3316p-222 coil craft q1, q2 n-channel mosfet si4410dy siliconix r1 35.7k 1/10w 1% chip resistor cr21-3572f-t avx r6 52.3k 1/10w 1% chip resistor cr21-5232f-t avx r7 46.4k 1/10w 1% chip resistor cr21-4642f-t avx r8 42.2 k 1/10 w 1% chip resistor cr21-4222f- t avx rc 10k 1/10w 5% chip resistor cr21-103j-t avx rsense 33 milli w 1/2w 1% resistor lr2010-01-r033-f irc u1 16-lead narrow small outline ic ltc1435cs ltc jumper ccij2mm-138-g comm con
38 power supply solutions mobile amd-k6 ? processor power supply design 22495c/0may 1999 maxim max798 the max798 current-mode converter shown in figure 19 converts the input voltage (from the wall adapter or the battery pack) down to the desired 1.8v. the max798 can achieve efficiencies up to 96% and has an input-voltage rage of 4.5v to 30v. the input voltage is switched by the mosfets n1 and n2. this switched voltage is filtered by the lc filter, consisting of l1, c4, and c5. r1 and r2 divide the 1.8v output voltage to 1.6v for the feedback reference (vout = 1.6v (1 + r1/r2). the values in the bill of material (see table 10 on page 39) provide 1.8v at 5.6a. the 560-pf capacitor improves stability by increasing the loop phase at crossover, which increases the phase margin. maxims max1710/11 has vid inputs. figure 19. maxim max798 switching power supply design bst dh lx csl dl pgnd ref ss vl v+ max798 vin csh skip sync shdn fb gnd c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12 d1 d2 l1 n1 n2 r1 r2 r3 u1 vout
power supply solutions 39 22495c/0may 1999 mobile amd-k6 ? processor power supply design contact information. maxim integrated products 120 san gabriel drive sunnyvale, ca 92841 tel: (408) 737-7600 fax: (408) 737-7194 www.maxim-ic.com table 10. maxim max798 bill of materials reference description part number manufacturer c1Cc3 10 m f 30v os-con capacitor 30sa10 sanyo c4, c5 470 m f 4v low esr capacitor 594d477x0004r2t sprague c6, c7 0.1 m f ceramic capacitor any any c8 4.7 m f 16v low esr tantalum capacitor 595d475x0016a2b sprague c9 0.01 m f ceramic capacitor any any c10 0.33 m f ceramic capacitor any any c11 560pf ceramic capacitor any any c12 1.0 m f ceramic capacitor any any ds1 schottky diode, 100ma, 30v cmpsh-3 central semi ds2 schottky diode, 1a, 30v mbrs130lt3 motorola l1 4.7 m h inductor cdrh127-4r7mc sumida n1, n2 n-channel mosfet 30v si4412dy siliconix r1 4.22k, 0.1% resistor any any r2 16.9k, 0.1% resistor any any r3 13m w 1% current sense resistor * wsl-2512-r013f dale u1 dc-dc converter max798ese maxim note: * 2.0 v at 6a.
40 voltage regulator vendor information mobile amd-k6 ? processor power supply design 22495c/0may 1999 voltage regulator vendor information company name and contact part number type remarks* cherry contact: george shuline (401)886-3821 cs5156 switching regulator a) 5 bit vid 1.3 v min elantech contact: steve sacarisen (408) 945-1323 x 345 el7571 switching regulator a) 5 bit vid 1.3 v min linear technology corporation contact: mike gillespie (408) 428-2060 lt 14 35 / 36 /37 lt1439/1339 ltc1538/39 switching regulator switching regulator switching regulator a) voltage set by resistors b) voltage set by resistors c) voltage set by resistors maxim integrated products contact: nancie george-adeh (408) 737-7600 max798 max1630/31/32 m a x 1710 /11 switching regulator switching regulator switching regulator a) voltage set by resistors b) voltage set by resistors c) 4bit/bit dac 0.925v min micro linear contact: doyle slack (408) 433 -5200 ml4880 switching regulator semtech corporation contact: alan moore (805) 498-2111 sc1401 switching regulator voltage set by resistors stmicroelectronics 20041 agrate brianza -italy via c. olivetti, 2 contact: nicola tricomi tel. +39 039 6036512 l4992 l5955 switching regulator switching regulator a) voltage set by resistors b) 4bit/bit dac 1.35v min., 2.0v max. unitrode contact: john oconnor (603) 429-8504 www.unitrode.com ucc3870-1 switching regulator voltage set by resistors or external dacinput range 4C36 volts note: * these regulators all have a wide input-voltage range

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