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ap65452 document number: ds37305 rev. 2 - 2 1 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 4a, 18v, 650khz adaptive co t step-down converter description the ap65452 is an adaptive constant on-time mode synchronous buck converter providing high efficienc y, excellent transient response and high dc output accuracy for low-voltage regulation in digital tv and monitor. the constant-on-time control scheme handles wide input/output voltage ratios and provides low external component count. the internal proprietary circuit enabl es the device to adopt both low equivalent series resistance (esr ) output capacitors, such as sp-cap or poscap and ultra-lo w esr ceramic capacitors. the ap65452 features programmable soft-start, uvlo, otp and ocp to protect the circuit. this ic is available in so-8ep package. features ? fixed frequency emulated constant on-time control ? good stability independent of the output capacitor esr ? fast load transient response ? synchronous rectification: 65m ? internal high-side switch and 36m ? internal low-side switch ? wide input voltage range: 4.5v to 18v ? output voltage range: 0.76v to 6v ? 4a continuous output current ? 650khz switching frequency ? built-in over current limit ? built-in thermal shutdown protection ? programmable soft-start ? pre-biased start-up ? totally lead-free & fully rohs compliant (notes 1 & 2) ? halogen and antimony free. ?green? device (note 3) pin assignments applications ? gaming consoles ? flat screen tv sets and monitors ? set-top boxes ? distributed power systems ? home audio ? consumer electronics ? network systems ? fpga, dsp and asic supplies ? green electronics notes: 1. no purposely added lead. fully eu directiv e 2002/95/ec (rohs) & 2011/6 5/eu (rohs 2) compliant. 2. see http://www.diodes.com/quality/lead_free.html for more in formation about diodes incorporated?s definitions of halogen- a nd antimony-free, "green" and lead-free. 3. halogen- and antimony-free "green? products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total br + cl) and <1000ppm antimony compounds. typical applications circuit figure 1 typical application circuit ap65452 l1 1.5 h r1 8.25k ? r2 22.1k c5 0.1 f c2 44 f c1 20 f c4 8.2n f on off 8 in 4 ss 1 en 3 vreg5 6 sw 7 bst 2 fb c3 1 f 5 gnd input output v out 1.05v v in 12v
ap65452 document number: ds37305 rev. 2 - 2 2 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 pin descriptions pin name pin number function so-8ep en 1 enable input. en is a digital input that turns the regulator on or off. drive en high to turn on the regulator, drive it low to turn off. pull up with 100k ? resistor for automatic startup. fb 2 feedback input. fb senses the output voltage and regulates i t. drive fb with a resistiv e voltage divider connected to it from the output voltage. vreg5 3 internal power supply output pin to connect an additional c apacitor. connect a 1 f (typical) capacit or as close as possible to the vreg5 and gnd. this pi n is not active when en is low. ss 4 soft-start control input pin. ss controls the soft start period. connect a capacitor from ss to gnd to set the soft-start period. gnd 5 ground pin is the main power ground for the switching circuit. sw 6 power switching output. sw is the switching node that supplies power to the output. connect the output lc filter from sw to the output load. note that a capacitor is required from sw to bs to power the high-side switch. bs 7 bootstrap pin. a bootstrap capacitor is connected betw een the bs pin and sw pin. the voltage across the bootstrap capacitor drives the internal high-side nmos switch. a 0.1 f (typical) capacitor is re quired for proper operation. vin 8 supply input pin. a capacitor shoul d be connected between the vin pin and gnd pin to keep the dc input voltage constant. ep connect the exposed thermal pad to gnd on the pcb. functional block diagram figure 2 functional block diagram
ap65452 document number: ds37305 rev. 2 - 2 3 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 absolute maximum ratings (note 4) (@t a = +25c, unless otherwise specified.) symbol parameter rating unit v in supply voltage -0.3 to 20 v v reg5 vreg5 pin voltage -0.3v to +6.0 v v sw switch node voltage -1.0 to v in +0.3 v v bs bootstrap voltage -0.3 to v sw +6.0 v v fb feedback voltage -0.3v to +6.0 v v en enable/uvlo voltage -0.3v to +6.0 v v ss soft-sstart pin -0.3v to +6.0 v v gnd gnd pin voltage -0.3 to 0.3 v t st storage temperature -65 to +150 c t j junction temperature +160 c t l lead temperature +260 c esd susceptibility (note 5) hbm human body model 2 kv mm machine model 200 v notes: 4. stresses greater than the 'absolute maximum ratings' specified above may cause permanent damage to the device. these are stress ratings only; functional operation of the device at these or any other conditions exceeding those indicated in this specification is not implied. device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time. 5. semiconductor devices are esd sensitive and may be damaged by exposure to esd events. suitable esd precautions should be ta ken when handling and transporting these devices. thermal resistance (note 6) symbol parameter rating unit ja junction to ambient so-8ep 70 c/w jc junction to case so-8ep 30 c/w note: 6. test condition: so-8: device mounted on 1"x1" fr-4 substrate pcb, 2oz copper, with minimum recommended pad layout. recommended operating conditions (note 7) (@t a = +25c, unless otherwise specified.) symbol parameter min max unit v in supply voltage 4.5 18.0 v t j operating junction temperature range -40 +125 c t a operating ambient temperature range -40 +85 c note: 7. the device function is not guaranteed outside of the recommended operating conditions.
ap65452 document number: ds37305 rev. 2 - 2 4 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 electrical characteristics (@t a = +25c, v in = 12v, unless otherwise specified.) parameter symbol conditions min typ max unit supply voltage (vin pin) input voltage v in ? ? ? ? ? a under voltage lockout uvlo threshold v uvlo v in rising test vreg5 voltage 3.45 3.75 4.05 v uvlo hysteresis v hys v in falling test vreg5 voltage 0.19 0.32 0.45 v enable (en pin) en high-level input voltage v enh ? ? ? ? ? ? voltage reference (fb pin) feedback voltage v fb v out =1.05v 0.753 0.765 0.777 v feedback bias current i fb v fb =0.8v -0.1 0 0.1 a vreg5 output vreg5 output voltage v vreg5 6.0v ap65452 document number: ds37305 rev. 2 - 2 5 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 typical performance characteristics (@t a = +25c, v in = 12v, v out = 1.05v, unless otherwise specified.) 85 ? c -40 ? c 25 ? c 85 ? c 25 ? c -40 ? c v in =18v i o =0a i o =1a v in =12v v in =4.5v
ap65452 document number: ds37305 rev. 2 - 2 6 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 typical performance characteristics (cont.) (@t a = +25c, v in = 12v, v out = 1.05v, unless otherwise specified) v o =3.3v vo=5v vo=3.3v vo=2.5v vo=1.8v vo=1.5v vo=1.05v vo=1.2v v o =1.8v v o =1.05v
ap65452 document number: ds37305 rev. 2 - 2 7 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 typical performance characteristics (cont.) (@t a = +25c, v in = 12v, v out = 1.05v, l = 1.5h, c1 = 20f, c2 = 44f, unless otherwise specified.) steady state test 4a time-1s/div startup through v in no load time-500s/div startup through v in 4a load time-500s/div startup with vreg5 no load time-1ms/div shutdown through v in no load time-50ms/div shutdown through v in 4a load time-200s/div startup through v en no load time-500s/div startup through v en 4a load time-500s/div short circuit test time-100s/div shutdown through v en no load time-20ms/div shutdown through v en 4a load time-20ms/div short circuit recovery time-1ms/div 1.05v load transient response time-100s/div voltage ripple at output (i o =4a) time-400ns/div voltage ripple at input (i o =4a) time-400ns/div vin (12v/div ) vout (1v/div ) iout (500ma/div ) sw (10v/div ) vin (12v/div ) vout (1v/div ) iout (4a/div ) sw (10v/div ) vin (12v/div ) vout (1v/div ) iout (4a/div ) sw (10v/div ) vin (12v/div ) vout (1v/div ) iout (500ma/div ) sw (10v/div ) ven (3v/div ) vout (1v/div ) iout (500ma/div ) sw (10v/div ) ven (3v/div ) vout (1v/div ) iout (4a/div ) sw (10v/div ) ven (3v/div ) vout (1v/div ) iout (4a/div ) sw (10v/div ) ven (3v/div ) vout (1v/div ) iout (500ma/div ) sw (10v/div ) vout (500mv/div ) iout (2a/div ) vout (500mv/div ) iout (2a/div ) vin_ac (500mv/div ) vout_ac (50mv/div ) isw (4a/div ) sw (5v/div ) en (3v/div ) vreg5 (5v/div ) vout (500mv/div ) vout_ac (20mv/div ) sw (5v/div ) vout (50mv/div ) iout (2a/div ) vin_ac (100mv/div ) sw (5v/div )
ap65452 document number: ds37305 rev. 2 - 2 8 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 application information figure 3 typical application of ap65452 pwm operation and adaptive on-time control the ap65452 is a synchronous step-down converter with internal powe r mosfets. adaptive constant on time (cot) control is employ ed to provide fast transient response and easy loop stabilization. at the beginning of each cycle, the high-side mosfet is turned on. this mosfet is turned off after internal one shot timer expires. th is one shot is set by the converter input voltage (v in ), and the output voltage (v out ) to maintain a pseudo-fixed frequency over the input voltage range, hence it is called adaptive on-time control. the output voltage variation is sensed by fb voltage. the one-shot timer is reset and the high-side mosfet is turned on again when fb voltage falls below the 0.76v. ap65452 uses an adaptive on-time control schem e and does not have a dedicated in board o scillator. it runs with a pseudo-consta nt frequency of 650khz by using the input voltage and output voltage to set the on- time one-shot timer. the on-time is inversely proportional t o the input voltage and proportional to the output voltage. it c an be calculated using the following equation: f v v t in out on ? ? v out is the output voltage v in is the input voltage f is the switching frequency after an on-time period, the ap65452 goes into the off-time peri od. the off-time period length depends on vfb in most case. it will end when the fb voltage decreases below 0.76v, then the on-time period is tr iggered. if the off-time period is less than the minimum off time, the minimum off time will be applied, which is about 260ns typical. enable above the ?en high-level input voltage,? the internal regulator is turned on and the quiescent current can be measured above th is threshold. the enable (en) input allows the user to control turning on or o ff the regulator. to enable the ap65452, en must be pulled above th e ?en high-level input voltage,? and to disable the ap65452, en must be pulled below ?en low-level input voltage.? in figure 3, en has a positive voltage through a 100k ? pull-up to vin. no supply input is required for en. soft-start the soft-start time of the ap65452 is programmable by selecting different c ss value. when the en pin becomes high, the c ss is charged by a 6 a current source, generating a ramp signal fed into non-inverting input of the error comparator. reference voltage v ref or the internal soft-start voltage ss, whichever is smaller, dominates the behavior of the non-inverting inputs of the error amplifier. accordingly, the o utput voltage will follow the ss signal and ramp up smoothly to its target level. the capacitor value required for a given soft-start ramp time ca n be expressed as: ss fb ss ss i v c t ? ? where c ss is the required capacitor between ss pin and gnd, t ss is the desired soft-start time and v fb is the feedback voltage.
ap65452 document number: ds37305 rev. 2 - 2 9 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 application information (cont.) over current protection (ocp) figure 4 shows the over current protection (ocp) scheme of ap65452. in each switching cycle, the inductor current is sensed by monitoring the low-side mosfet in the off period. when the voltage between gnd pi n and sw pin is smaller than the over current trip level, the ocp will be triggered and the controller keeps the off state. a new switch ing cycle will begin when the measured voltage is larger than lim it voltage. the internal counter is incremented when ocp is triggered. after 16 sequential cycles, the internal ocl (over current logic) thresh old is set to a lower level, reducing the available output current. when a switchin g cycle occurs where the switch current is below the lower o cl threshold, the counter is reset and ocl limit is returned to higher value. because the r ds(on) of mosfet increases with temperature, v limit has xppm/ o c temperature coefficient to compensate this temperature dependency of r ds(on) . figure 4 over current protection scheme under voltage lockout the ap65452 provides an under voltage lockout ci rcuit to prevent it from undefined status during startup. the uvlo circuit shut s down the device when v in drops below 3.45v. the uvlo circuit has 320mv hyst eresis, which means the dev ice starts up again when v reg rises to 3.75v (non- latch). thermal shutdown if the junction temperature of the device r eaches the thermal shutdown limit of 160c, the ap65452 shuts itself off, and both h mos and lmos will be turned off. the output is discharged with the internal transis tor. when the junction cools to the required level (130c nomi nal), the device initiates soft-start as during a normal power -up cycle. setting the output voltage the output voltage can be adjusted from 1.000 to 5v using an external resistor divider. table 1 shows a list of resistor selection for common output voltages. resistor r1 is selected based on a design tr adeoff between efficiency and output voltage accuracy. for high va lues of r1 there is less current consumption in the feedback network. however, the tradeoff is output voltage accuracy due to the bias current i n the error amplifier. r1 can be determined by the following equation: ? ? ? ? ? ? ? ? ? 1 0.765 v r r out 2 1 figure 5 feedback divider network output voltage (v) r1 (k ? ) r2 (k ? ) 1 6.81 22.1 1.05 8.25 22.1 1.2 12.7 22.1 1.5 21.5 22.1 1.8 30.1 22.1 2.5 49.9 22.1 3.3 73.2 22.1 5 124 22.1 table 1 resistor selection for common output
ap65452 document number: ds37305 rev. 2 - 2 10 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 application information (cont.) inductor calculating the inductor value is a critic al factor in designing a buck converter. for most designs, the following equation can be used to calculate the inductor value: sw l in out in out f ? i v ) v (v v l ? ? ? ? ? where l ? i is the inductor ripple current, and sw f is the buck converter switching frequency. choose the inductor ripple current to be 30% of the maximum load current. the maximum inductor peak current is calculated from: 2 ? i i i l load l(max) ? ? peak current determines the required saturation current rating, which influences the size of the inductor. saturating the induc tor decreases the converter efficiency, while increasing the temperatures of the inductor and the intern al mosfets. hence choosing an inductor wi th appropriate saturation current rating is important. a 1h to 3.3h inductor with a dc current rating of at leas t 25% percent higher than the maximum load current is recommended fo r most applications. for highest efficiency, the i nductor?s dc resistance should be less than 100m ? . use a larger inductanc e for improved efficiency under light load conditions. the phase boost can be achieved by addi ng an additional feed forward capacitor (c7) in parallel with r1. output voltage (v) c10 (pf) l1 (h) c5+c9 (f) 1 ? 1.0 - 1.5 22 - 68 1.05 ? 1.0 - 1.5 22 - 68 1.2 ? 1.0 - 1.5 22 - 68 1.5 ? 1.5 22 - 68 1.8 5 - 22 1.5 22 - 68 2.5 5 - 22 2.2 22 - 68 3.3 5 - 22 2.2 22 - 68 5 5 - 22 3.3 22 - 68 table 2 recommended component selection input capacitor the input capacitor reduces the surge current drawn from the i nput supply and the switching noise from the device. the input ca pacitor has to sustain the ripple current produced during the on time on the upp er mosfet. it must have a low esr to minimize the losses. the rms current rating of the input capacitor is a critical paramet er that must be higher than the rms input current. as a rule of thumb, select an input capacitor which has rms rating great er than half of the maximum load current. due to large di/dt through the input capacitors, electrolytic or ceramics should be used. if a tantalum must be used it must be surge protected, otherwise, capacitor failure could occur. for most applicat ions greater than 10f, cerami c capacitor is sufficient. output capacitor the output capacitor keeps the output voltage ripple small, ensures feedback loop stability and reduces the overshoot of the ou tput voltage. the output capacitor is a basic component for the fast response of t he power supply. in fact, during load transient, for the first few microseconds it supplies the current to the load. the converter recognizes the l oad transient and sets the duty cycle to maximum, but the curre nt slope is limited by the inductor value.
ap65452 document number: ds37305 rev. 2 - 2 11 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 application information (cont.) output capacitor (cont.) maximum capacitance required can be calc ulated from the following equation: esr of the output capacitor dominates the output voltage ripple. the amount of ripple can be ca lculated from the equation below : esr * ? i vout inductor capacitor ? an output capacitor with ample capacitance and low esr is the best option. for most applications, a 22f to 68f ceramic capaci tor will be sufficient. 2 out 2 out 2 inductor out o v ) v v ( ? ) 2 ? i l(i c ? ? ? ? where ? v is the maximum output voltage overshoot. bootstrap capacitor to ensure the proper operation, a ceramic c apacitor must be connected between the vbst and sw pin. a 0.1f ceramic capacitor is sufficient. vreg5 capacitor to ensure the proper operation, a ceramic capacitor must be conn ected between the vreg5 and gnd pin. a 1f ceramic capacitor is sufficient. pc board layout 1. the ap65452 works at 4a load current, heat dissipation is a ma jor concern in layout the pcb. a 2oz copper in both top and bo ttom layer is recommended. 2. provide sufficient vias in the thermal ex posed pad for heat dissipate to the bottom layer. 3. provide sufficient vias in the output capacit or gnd side to dissipate heat to the bottom layer. 4. make the bottom layer under the device as gnd layer for heat dissipation. the gnd layer should be as large as possible to pr ovide better thermal effect. 5. make the vin capacitors as cl ose to the device as possible. 6. make the vreg5 capacitor as close to the device as possible. 7. the thermal pad of the device should be soldered directly to the pcb exposed copper plane to wo rk as a heatsink. the thermal vias in the exposed copper plane increase the heat transfer to the bottom layer. figure 6 pc board layout
ap65452 document number: ds37305 rev. 2 - 2 12 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 ordering information part number package code part marking identification code tape and reel quantity part number suffix AP65452SP-13 sp so-8ep 2500 -13 marking information (1) so-8ep ( top view ) ap65452 yy ww x logo part no 5 8 4 1 e ww : week : 01~52; 52 yy : year : 08, 09,10~ g : green represents 52 and 53 week e : so-8ep blank so-8 x x : internal code package outline dimensions (all dimensions in mm.) please see ap02002 at http://www.diodes.com /datasheets/ap02002.pdf for latest version. so-8ep (sop-8l-ep) dim min max typ a 1.40 1.50 1.45 a1 0.00 0.13 - b 0.30 0.50 0.40 c 0.15 0.25 0.20 d 4.85 4.95 4.90 e 3.80 3.90 3.85 e0 3.85 3.95 3.90 e1 5.90 6.10 6.00 e - - 1.27 f 2.75 3.35 3.05 h 2.11 2.71 2.41 l 0.62 0.82 0.72 n - - 0.35 q 0.60 0.70 0.65 all dimensions in mm gauge plane seating plane e1 e n e b a 45 e0 h f exposed pad bottom view l q c 7 4 3 9 (all sides) a1 d 14 85
ap65452 document number: ds37305 rev. 2 - 2 13 of 13 www.diodes.com november 2014 ? diodes incorporated a p65452 suggested pad layout please see ap02001 at http://www.diodes.com/dat asheets/ap02001.pdf for the latest version. important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries rese rve the right to make modifications, enhanc ements, improvements, corrections or ot her changes without further notice to this document and any product descri bed herein. diodes incorporated does not assume any liability ari sing out of the application or use of this document or an y product described herein; neither does di odes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or us er of this document or products described herein in such applica tions shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability w hatsoever in respect of any products purchased through unauthoriz ed sales channel. should customers purchase or use diodes inco rporated products for any unintended or una uthorized application, customers shall i ndemnify and hold diodes incorporated and its representativ es harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death a ssociated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. this document is written in english but may be translated into multiple languages for reference. only the english version of t his document is the final and determinative format released by diodes incorporated. life support diodes incorporated products are specifically not authorized for use as critical component s in life support devices or systems without the express written approval of the chief executive offi cer of diodes incorporated. as used herein: a. life support devices or syst ems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when prope rly used in accordance with instructions for use provided in the labeling can be reasonably expected to re sult in significant injury to the user. b. a critical component is any component in a life support devic e or system whose failure to perform can be reasonably expect ed to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifi cations of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-rel ated requirements concerning the ir products and any use of diodes incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or s ystems-related information or support that may be provided by diodes incorporated. further, customers must fully indemnify diodes incorporate d and its representatives against any damages arisi ng out of the use of diodes incorporated pr oducts in such safety-critical, life suppor t devices or systems. copyright ? 2014, diodes incorporated www.diodes.com dimensions value (in mm) c 1.270 x 0.802 x1 3.502 x2 4.612 y 1.505 y1 2.613 y2 6.500 c y1 x1 x y y2 x2

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