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LTC3448 1.5MHz/2.25MHz, 600mA Synchronous Step-Down Regulator with LDO Mode DESCRIPTIO
The LTC(R)3448 is a high efficiency, monolithic, synchronous buck regulator using a constant frequency, current mode architecture. Supply current during operation is only 32A (linear regulator mode) and drops to <1A in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3448 ideally suited for single Li-Ion battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. At moderate output load levels, PWM pulse skipping mode operation provides very low output ripple voltage for noise sensitive applications. The LTC3448 automatically switches into linear regulator operation at very low load currents to maintain <5mVP-P output voltage ripple. Supply current in this mode is typically 32A. The switch to linear regulator mode occurs at a threshold of 3mA. Linear regulator operation can be set to on, off or automatic turn on/off. Switching frequency is selectable at either 1.5MHz or 2.25MHz, allowing the use of small surface mount inductors and capacitors. The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.6V feedback reference voltage. The LTC3448 is available in a low profile 3mm x 3mm DFN package or thermally enhanced 8-lead MSOP.
FEATURES

High Efficiency: Up to 96% Very Low Quiescent Supply Current: 32A During Linear Regulator Operation 600mA Output Current (Buck Converter) Optionally Operates as Linear Regulator Below 3mA--External or Automatic ON/OFF 2.5V to 5.5V Input Voltage Range 1.5MHz or 2.25MHz Constant Frequency Operation or External Synchronization No Schottky Diode Required Low Dropout Operation: 100% Duty Cycle 0.6V Reference Allows Low Output Voltages Shutdown Mode Draws < 1A Supply Current Current Mode Operation for Excellent Line and Load Transient Response Overtemperature Protected Low Profile (3mm x 3mm) 8-Lead DFN and 8-Lead MSOP Packages
APPLICATIO S

Cellular Telephones Personal Information Appliances Wireless and DSL Modems Digital Still Cameras MP3 Players Portable Instruments
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. Others pending.
TYPICAL APPLICATIO
VIN 2.5V TO 5.5V CIN 4.7F VIN
Efficiency and Power Loss vs Load Current
100 90 80 70 EFFICIENCY (%) VIN = 3.6V VOUT = 1.5V TA = 25C 1
1.5V High Efficiency Regulator with Automatic LDO Mode
2.2H SW 474k COUT 4.7F VOUT RUN LTC3448 MODE VFB FREQ SYNC GND VOUT 1.5V 22pF
60 50 40 30
EFFICIENCY POWER LOSS 0.01
316k
20 10 0 0.0001
3448 TA01a
U
U
U
0.1 POWER LOSS (W)
0.001
0.0001 0.001 0.01 0.1 LOAD CURRENT (A) 1
23448 TA01b
3448f
1
LTC3448
ABSOLUTE
AXI U
RATI GS
Input Supply Voltage .................................. - 0.3V to 6V RUN, SYNC Voltages ................... - 0.3V to (VIN + 0.3V) MODE Voltage ............................. - 0.3V to (VIN + 0.3V) FREQ, VFB Voltages...................... - 0.3V to (VIN + 0.3V) SW Voltage .................................. - 0.3V to (VIN + 0.3V) VOUT Voltage ................................ - 0.3V to (VIN + 0.3V) P-Channel Switch Source Current (DC) ............. 800mA N-Channel Switch Sink Current (DC) ................. 800mA
PACKAGE/ORDER I FOR ATIO
TOP VIEW VFB 1 VOUT 2 MODE 3 VIN 4 9 8 7 6 5 RUN SYNC FREQ SW
ORDER PART NUMBER LTC3448EDD
VFB 1 VOUT 2 MODE 3 VIN 4
DD PACKAGE 8-LEAD (3mm x 3mm) PLASTIC DFN
TJMAX = 125C, JA = 43C/ W EXPOSED PAD (PIN 9) IS GND MUST BE SOLDERED TO PCB
DD PART MARKING LBMJ
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. VIN = 3.6V unless otherwise specified.
SYMBOL IVFB VFB PARAMETER Feedback Current Regulated Feedback Voltage (Note 4) Reference Voltage Line Regulation Output Overvoltage Lockout Output Voltage Line Regulation Peak Inductor Current Output Voltage Load Regulation Maximum Output Voltage Input Voltage Range TA = 25C 0C TA 85C -40C TA 85C VIN = 2.5V to 5.5V (Note 4) VOVL = VOVL - VFB VOVL = (VOVL - VOUT) * 100/VOUT VIN = 2.5V to 5.5V (LDO) VFB = 0.5V or VOUT = 90%, Duty Cycle < 35% LDO, 1mA to 10mA (Note 9)
ELECTRICAL CHARACTERISTICS
CONDITIONS
VFB VOVL VOUT IPK VLOADREG VOUT(MAX) VIN
2
U
U
W
WW U
W
(Note 1)
VOUT (LDO) Source Current .................................. 25mA Peak SW Sink and Source Current ........................ 1.3A Operating Temperature Range (Note 2) .. - 40C to 85C Junction Temperature (Notes 3, 7) ...................... 125C Storage Temperature Range ................ - 65C to 125C Lead Temperature (Soldering, 10 sec) MSOP Only ...................................................... 300C
TOP VIEW 8 7 6 5 RUN SYNC FREQ SW
ORDER PART NUMBER LTC3448EMS8E
9
MS8E PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125C, JA = 40C/ W EXPOSED PAD (PIN 9) IS GND MUST BE SOLDERED TO PCB
MS8 PART MARKING LTBMK
MIN 0.5880 0.5865 0.5850 15 2.5 0.7
TYP 0.6 0.6 0.6 0.2 35 5.8 0.1 1 0.5
MAX 30 0.6120 0.6135 0.6150 0.4 55 9.2 0.8 1.3
UNITS nA V V V %/V mV % %/V A %/V V

VIN - 0.7 VIN - 0.3 2.5 5.5
V
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LTC3448
The denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. VIN = 3.6V unless otherwise specified.
SYMBOL IS PARAMETER Input DC Bias Current Active Mode (Pulse Skip, No LRO) Linear Regulator Operation (LRO) Shutdown fOSC fSYNC VTH(SYNC) RPFET RNFET ILSW VRUNH VRUNL IRUN VFREQH VFREQL IFREQ VMODEH VMODEL IMODE ISYNC ILDO(ON) ILDO(OFF) Oscillator Frequency Synchronization Frequency SYNC Activation Input Threshold RDS(ON) of P-Channel FET RDS(ON) of N-Channel FET SW Leakage RUN Threshold High RUN Threshold Low RUN Leakage Current FREQ Threshold High FREQ Threshold Low FREQ Leakage Current MODE Threshold High MODE Threshold Low MODE Leakage Current SYNC Leakage Current LRO ON Load Current Threshold LRO OFF Load Current Threhold 2.2mH Inductor (Note 8) 8 ISW = 100mA ISW = -150mA VRUN = 0V, VSW = 0V or 5V, VIN = 5V

ELECTRICAL CHARACTERISTICS
CONDITIONS VIN = 3.6V (Note 5) VFB = 0.5V or VOUT = 90%, ILOAD = 0A, 1.5MHz VFB = 0.5V or VOUT = 90%, ILOAD = 0A, 2.25MHz ILOAD ILDO(ON) VRUN = 0V, VIN = 5.5V FREQ = Low, VIN = 3.6V FREQ = High (Note 6)

MIN
TYP 250 275 32 0.1
MAX 375 400 43 1 1.8 2.7 >4 1.3
UNITS A A A A MHz MHz MHz V
1.2 1.8 1.5
1.5 2.25 1 0.4 0.35 0.01
1 0.3
A V V A V V A V V A A mA mA
1.5 0.01 VIN - 1 1 0.01 VIN - 0.15 0.12 0.1 0.01 3 11 1 1 5 17 1 1
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3448E is guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + (PD)(43C/W) Note 4: The LTC3448 is tested in a proprietary test mode that connects VFB to the output of the error amplifier. Note 5: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency. LRO is "linear regulator operation."
Note 6: 4MHz operation is guaranteed by design but is not production tested and is subject to duty cycle limitations. Note 7: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C when overtemperature is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 8: The load current below which the switching regulator turns off and the LDO turns on is, to first order, inversely proportional to the value of the inductor. This effect is covered in more detail in the Operation section. This parameter is not production tested but is guaranteed by design. Note 9: For 2.5V < VIN < 2.7V the output voltage is limited to VIN - 0.7V to ensure regulation in linear regulator mode. This parameter is not production tested but is guaranteed by design.
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LTC3448 TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure1a Except for the Resistive Divider Resistor Values) Efficiency vs Input Voltage
100 95 90 IOUT = 100mA VOUT = 1.8V TA = 25C
EFFICIENCY (%)
EFFICIENCY (%)
80 75 70 65 60 55 50 2
IOUT = 600mA
60 50 40 30 20 10 VIN = 2.7V VIN = 3.6V VIN = 4.2V 0.001 0.01 0.1 LOAD CURRENT (A) 1
23448 G02
EFFICIENCY (%)
85
IOUT = 30mA
3
4 5 INPUT VOLTAGE (V)
Efficiency vs Load Current (Switcher Only)
100 90 80 70 EFFICIENCY (%) 60 50 40 30 20 10 0 0.0001 0.01 0.1 0.001 LOAD CURRENT (A) 1
23448 G04
VIN = 2.7V VOUT = 2.5V TA = 25C REFERENCE VOLTAGE (V)
0.605 0.600 0.595 0.590 0.585 -50 -25
FREQUENCY (MHz)
Oscillator Frequency vs Supply Voltage
1.8 1.7
OUTPUT VOLTAGE (V)
TA = 25C
FREQUENCY (MHz)
1.6 1.5 1.4 1.3 1.2 2 3 4 5 SUPPLY VOLTAGE (V) 6
3448 G07
1.505 1.500 1.495 1.490 1.485 1.480 1.475 0.0001 0.01 0.001 0.1 LOAD CURRENT (A) 1
3448 G08
RDS(ON) ()
4
UW
6
3448 G01
Efficiency vs Load Current
100 90 80 70 VOUT = 1.2V TA = 25C 100 90 80 70 60 50 40 30 20 10
Efficiency vs Load Current
VOUT = 1.5V TA = 25C
0 0.0001
0 0.0001
VIN = 2.7V VIN = 3.6V VIN = 4.2V 0.001 0.01 0.1 LOAD CURRENT (A) 1
23448 G03
Reference Voltage vs Temperature
0.615 0.610 VIN = 3.6V 1.70 1.65 1.60 1.55 1.50 1.45 1.40 1.35 50 25 75 0 TEMPERATURE (C) 100 125
Oscillator Frequency vs Temperature
VIN = 3.6V
1.30 -50
-25
0
50 75 25 TEMPERATURE (C)
100
125
3448 G05
3448 G06
Output Voltage vs Load Current
VIN = 3.6V 1.520 TA = 25C 1.515 1.510 1.525 0.40 0.38 0.36 0.34 0.32 0.30 0.28 0.26 0.24 0.22 0.20
RDS(ON) vs Input Voltage
TA = 25C
MAIN SWITCH
SYNCHRONOUS SWITCH
2
3
4 5 INPUT VOLTAGE (V)
6
3448 G09
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LTC3448 TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure1a Except for the Resistive Divider Resistor Values) Dynamic Supply Current vs Supply Voltage
340
DYNAMIC SUPPLY CURRENT (A) DYNAMIC SUPPLY CURRENT (A)
RDS(ON) vs Temperature
0.6 0.5 0.4
RDS(ON) ()
0.3 0.2 0.1 MAIN SWITCH SYNCH SWITCH 2.5V 2.5V 3.6V 3.6V 4.2V 4.2V -25 50 25 75 0 TEMPERATURE (C) 100 125
0 -50
Switch Leakage vs Temperature
350 300 VIN = 5.5V RUN = 0V
SWITCH LEAKAGE (nA)
250 200 150 100 50 0 -50 -25
SWITCH LEAKAGE (nA)
MAIN SWITCH
SYNCHRONOUS SWITCH
50 25 75 0 TEMPERATURE (C)
Load Step
VOUT 200mV/DIV AC COUPLED VOUT 100mV/DIV AC COUPLED ILOAD 250mA/DIV IL 500mA/DIV 10s/DIV VIN = 3.6V VOUT = 1.5V ILOAD = 100A TO 200mA COUT = 10F
3448 G16
ILOAD 100mA/DIV IL 500mA/DIV
UW
3448 G10
Dynamic Supply Current vs Temperature
320 300 280 260 1.5MHz 240 220 200 -50 -25 VIN = 3.6V ILOAD = 0A
320 300 280 260 240 220 200 2
ILOAD = 0A TA = 25C
2.25MHz
2.25MHz
1.5MHz
3
4 SUPPLY VOLTAGE (V)
5
6
3448 G11
50 25 75 0 TEMPERATURE (C)
100
125
3448 G12
Switch Leakage vs Input Voltage
10 RUN = 0V TA = 25C MAIN SWITCH RUN 5V/DIV VOUT 1V/DIV
Start-Up from Shutdown
1 SYNCHRONOUS SWITCH 0.1
IL 500mA/DIV 0.01 VIN = 3.6V VOUT = 1.5V ILOAD = 600mA 0 1 2 3 4 INPUT VOLTAGE (V) 5 6
3448 G14
40s/DIV
3448 G15
0.001
100 125
3448 G13
Load Step
10s/DIV VIN = 3.6V VOUT = 1.5V ILOAD = 50mA TO 600mA COUT = 10F
3448 G17
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5
LTC3448 TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values) External Mode Control (Constant 1mA Load)
VOUT 20mV/DIV AC COUPLED SWITCHER LDO SWITCHER
Load Step
VOUT 100mV/DIV AC COUPLED ILOAD 250mA/DIV IL 500mA/DIV VIN = 3.6V 10s/DIV VOUT = 1.5V ILOAD = 100mA TO 600mA
3448 G18
PI FU CTIO S
VFB (Pin 1): Feedback Pin. This pin receives the feedback voltage from an external resistive divider across the output. VOUT (Pin 2): Output Pin. This pin connects to an external resistor divider and the linear regulator output. Connect externally to the inductor and the output capacitor. The internal linear regulator will supply current up to the ILDO(OFF) current. Load currents above that are supplied by the buck regulator. Internal circuitry automatically enables the buck switching regulator at load currents higher than the ILDO(OFF). The minimum required capacitance on this pin is 2F. MODE (Pin 3): Linear Regulator Control. Grounding this pin turns off the linear regulator. Setting this pin to VIN turns on the linear regulator regardless of the load current. Tying this pin midrange (i.e., to VOUT) will place the linear regulator in auto mode, where turn on/off is a function of the load current. In applications where MODE is externally driven high or low, this pin should be held low for 50s after the RUN pin is pulled high. VIN (Pin 4): Main Supply Pin. This pin must be closely decoupled to GND with a 2.2F or greater ceramic capacitor. SW (Pin 5): Switch Node Connection to Inductor. This pin connects to the drains of the internal main and synchronous power MOSFET switches. FREQ (Pin 6): Frequency Select. Switching frequency is set to 1.5MHz when FREQ = 0V and to 2.25MHz when FREQ = VIN. Do not float this pin. SYNC (Pin 7): External Synchronization Pin. The oscillation frequency can be synchronized to an external oscillator applied to this pin. For external frequencies above 2.2MHz, pull FREQ high. RUN (Pin 8): Run Control Input. Forcing this pin above 1.5V enables the part. Forcing this pin below 0.3V shuts down the device. In shutdown, all functions are disabled drawing <1A supply current. Do not leave RUN floating. Exposed Pad (Pin 9): Ground. This pin must be soldered to PCB.
6
UW
MODE PIN 2V/DIV
VOUT = 1.5V TA = 25C
200s/DIV
3448 G19
U
U
U
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LTC3448
FU CTIO AL DIAGRA
SYNC 7
FREQ 6 VIN OSC SLOPE COMP LDO CONTROL LOGIC
VOUT 2
LDO DRIVE
VFB 1
0.6V
VIN RUN 8 0.6V REF 0.6V + OVL SHUTDOWN
OVDET
+
Figure 1
OPERATIO
(Refer to Functional Diagram)
Main Control Loop The LTC3448 uses a constant frequency, current mode, step-down architecture. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are internal. During normal operation, the internal top power MOSFET is turned on each cycle when the oscillator sets the RS latch, and turned off when the current comparator, ICOMP, resets the RS latch. The peak inductor current at which ICOMP resets the RS latch, is controlled by the output of error amplifier EA. When the load current increases, it causes a slight decrease in the feedback voltage FBINT relative to the 0.6V reference, which in turn, causes the EA amplifier's output voltage to increase until the average inductor current matches the new load current. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor current starts to reverse, as indicated by the current reversal comparator IRCMP, or the beginning of the next clock cycle. The
comparator OVDET guards against transient overshoots 5.8% by turning off the main switch and keeping it off until the fault is removed. Pulse Skipping Mode Operation At light loads, the inductor current may reach zero or reverse on each pulse. The bottom MOSFET is turned off by the current reversal comparator, IRCMP, and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the switching regulator. At very light loads, the LTC3448 will automatically skip pulses to maintain output regulation. Low Ripple LDO Mode Operation At load currents below ILDO(ON), and when enabled, the LTC3448 will switch into very low ripple, linear regulating operation (LRO). In this mode, the current is sourced from
3448f
-
IRCMP
+
-
+
W
MODE 3 4 VIN
U
U
U
- + -
EA OSC S R Q Q SWITCHING LOGIC AND BLANKING CIRCUIT ANTISHOOTTHRU ICOMP
+
5
RS LATCH
-
5 SW
9 GND
3448 F01
7
LTC3448
OPERATIO
the VOUT pin and both the main and synchronous switches are turned off. The control loop is stabilized by the load capacitor and requires a minimum value of 2F. The LTC3448 will change back to switching mode and turn off the LDO when the load current exceeds approximately 11mA. When MODE is connected to an intermediate voltage level (i.e., VOUT), this switchover is automatic. If MODE is pulled high to VIN, the LDO remains on and the switcher off regardless of the load current. The LDO is capable of providing a maximum of approximately 15mA before the load regulation will degrade to unacceptable levels. If MODE is pulled to GND, the switcher remains on and the LDO off regardless of the load current.
4.5 4.0 3.5 VOUT = 1.2V
ILDO(ON) (mA)
3.0 2.5 2.0 1.5 1.0 0.5 0 2 3
Figure 2. ILDO(ON) vs VIN, VOUT
5.0 4.5 4.0 3.5 ILDO(ON) (mA) 3.0 2.5 2.0 1.5 1.0 0.5 0 0 2 6 8 4 INDUCTOR VALUE (H) 10 12
3448 F03
Figure 3. ILDO(ON) vs LOUT
8
U
(Refer to Functional Diagram)
Some applications may be able to anticipate the transition from high to low and low to high load currents. In these cases it may be desirable to switch between modes by controlling the MODE pin with a processor signal. In these applications it is important that the MODE pin is pulled high no earlier than 50s after the RUN pin is pulled high. This will ensure proper start-up of internal reference circuitry. The load current ILDO(ON) below which the switcher will automatically turn off and the LDO turn on is independent of the external capacitor, and to first order, independent of supply and output voltage. There is an inverse relationship between ILDO(ON) and the value of the inductor. These dependencies are shown in Figures 2 and 3. Automatic operation with inductor values below 1H is not recommended. At the low load currents at which the switcher to linear regulator transition occurs, the switcher is operating in pulse skipping mode. During each switching cycle in this mode, while the synchronous switch (bottom MOSFET) is on, the inductor current decays until the reverse current comparator is triggered. At this occurrence, the bottom MOSFET is turned off. Ideally, this occurs when the inductor current is precisely zero. In reality, because of onchip delays, this current will be negative at higher output voltages. The internal algorithm which controls the LDO turn-on load current level makes certain assumptions about the amount of charge transferred to the output on each switching cycle. These assumptions are no longer met when the inductor current begins to reverse. This causes the load current at which the transition takes place to move to lower levels at higher output voltages. For this reason use of the LDO auto mode is not recommended for output levels above 2V. For output voltages above 2V, the MODE pin should be driven externally. Short-Circuit Protection When the output is shorted to ground, the main switch cycle will be skipped, and the synchronous switch will remain on for a longer duration. This allows the inductor current more time to decay, thereby preventing runaway.
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VOUT = 1.5V VOUT = 1.8V
TA = 25C L = 2.2H 4 VIN (V)
3448 F02
5
6
VIN = 3.6V VOUT = 1.5V TA = 25C
LTC3448
OPERATIO
1200
MAXIMUM OUTPUT CURRENT (mA)
1000 800 600 400 200 0 VOUT = 1.8V VOUT = 2.5V VOUT = 1.5V
2.5
3.0
Figure 4. Maximum Output Current vs Input Voltage
Dropout Operation As the input supply voltage decreases to a value approaching the output voltage, the duty cycle increases toward the maximum on-time. Further reduction of the supply voltage forces the main switch to remain on for more than one cycle until it reaches 100% duty cycle. The output voltage will then be determined by the input voltage minus the voltage drop across the P-channel MOSFET and the inductor. An important detail to remember is that at low input supply voltages, the RDS(ON) of the P-channel switch increases
APPLICATIO S I FOR ATIO
The basic LTC3448 application circuit is shown on the first page of this data sheet. External component selection is driven by the load requirement and begins with the selection of L followed by CIN and COUT. Inductor Selection For most applications, the value of the inductor will fall in the range of 1H to 4.7H. Its value is chosen based on the desired ripple current. Large value inductors lower ripple current and small value inductors result in higher ripple currents. Higher VIN or VOUT also increases the ripple current as shown in equation 1. A reasonable starting point for setting ripple current is IL = 240mA (40% of 600mA).
U
W
UU
U
(Refer to Functional Diagram)
(see Typical Performance Characteristics). Therefore, the user should calculate the power dissipation when the LTC3448 is used at 100% duty cycle with low input voltage (See Thermal Considerations in the Applications Information section). Low Supply Operation The LTC3448 will operate with input supply voltages as low as 2.5V, but the maximum allowable output current is reduced at this low voltage. Figure 4 shows the reduction in the maximum output current as a function of input voltage for various output voltages. Slope Compensation and Inductor Peak Current Slope compensation provides stability in constant frequency architectures by preventing sub-harmonic oscillations at high duty cycles. It is accomplished internally by adding a compensating ramp to the inductor current signal at duty cycles in excess of 40%. This normally results in a reduction of maximum inductor peak current for duty cycles >40%. However, the LTC3448 uses a patent-pending scheme that counteracts this compensating ramp, which allows the maximum inductor peak current to remain unaffected throughout all duty cycles.
3.5 4.0 4.5 SUPPLY VOLTAGE (V)
5.0
5.5
3448 F04
IL =
( )( )
V VOUT 1 - OUT VIN fL 1
(1)
The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Thus, a 720mA rated inductor should be enough for most applications (600mA + 120mA). For better efficiency, choose a low DC-resistance inductor. If the LTC3448 is to be used in auto LDO mode, inductor values less than 1H should not be used.
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LTC3448
APPLICATIO S I FOR ATIO
Inductor Core Selection
Different core materials and shapes will change the size/ current and price/current relationship of an inductor. Toroid or shielded pot cores in ferrite or permalloy materials are small and don't radiate much energy, but generally cost more than powdered iron core inductors with similar electrical characteristics. The choice of which style inductor to use often depends more on the price vs size requirements and any radiated field/EMI requirements than on what the LTC3448 requires to operate. Table 1 shows some typical surface mount inductors that work well in LTC3448 applications.
Table 1. Representative Surface Mount Inductors
PART NUMBER Sumida CDRH3D16 VALUE (H) 1.5 2.2 3.3 4.7 2.2 3.3 4.7 2.2 3.3 4.7 1.0 2.2 4.7 DCR ( MAX) 0.043 0.075 0.110 0.162 0.116 0.174 0.216 0.104 0.138 0.190 0.060 0.097 0.150 MAX DC SIZE CURRENT (A) W x L x H (mm3) 1.55 1.20 1.10 0.90 0.950 0.770 0.750 1.8 1.3 1.2 1.00 0.79 0.65 3.8 x 3.8 x 1.8
Sumida CMD4D06 Coilcraft ME3220 Murata LQH3C
3.5 x 4.3 x 0.8
2.5 x 3.2 x 2.0
2.5 x 3.2 x 2.0
CIN and COUT Selection In continuous mode, the source current of the top MOSFET is a square wave of duty cycle VOUT/VIN. To prevent large voltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by:
CIN required IRMS IOMAX
[
VOUT VIN - VOUT VIN
(
This formula has a maximum at VIN = 2VOUT, where IRMS = IOUT/2. This simple worst-case condition is commonly used for design. Note that the capacitor manufacturer's ripple current ratings are often based on 2000 hours of life. This makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher
10
U
temperature than required. Always consult the manufacturer if there is any question. The selection of COUT is driven by the required effective series resistance (ESR). Typically, once the ESR requirement for COUT has been met, the RMS current rating generally far exceeds the IRIPPLE(P-P) requirement. In any case, if LDO mode is enabled, the value of COUT must have a minimum value of 2F to ensure loop stability. The output ripple VOUT is determined by:
1 VOUT IL ESR + 8fC OUT
W
UU
where f = operating frequency, COUT = output capacitance and IL = ripple current in the inductor. For a fixed output voltage, the output ripple is highest at maximum input voltage since IL increases with input voltage. Aluminum electrolytic and dry tantalum capacitors are both available in surface mount configurations. In the case of tantalum, it is critical that the capacitors are surge tested for use in switching power supplies. An excellent choice is the AVX TPS series of surface mount tantalum. These are specially constructed and tested for low ESR so they give the lowest ESR for a given volume. Other capacitor types include Sanyo POSCAP, Kemet T510 and T495 series, and Sprague 593D and 595D series. Consult the manufacturer for other specific recommendations. Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications. Because the LTC3448's control loop does not depend on the output capacitor's ESR for stable operation, ceramic capacitors can be used freely to achieve very low output ripple and small circuit size. However, care must be taken when ceramic capacitors are used at the input and the output. When a ceramic capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load step at the output can induce ringing at the input, VIN. At best, this ringing can couple to the output and be mistaken as loop instability. At
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)]
1/ 2
LTC3448
APPLICATIO S I FOR ATIO
worst, a sudden inrush of current through the long wires can potentially cause a voltage spike at VIN, large enough to damage the part. When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best temperature and voltage characteristics of all the ceramics for a given value and size. Output Voltage Programming The output voltage is set by tying VFB to a resistive divider according to the following formula:
VOUT
(2)
POWER LOSS (W)
R2 = 0.6V 1 + R1
The external resistive divider is connected to the output, allowing remote voltage sensing as shown in Figure 5.
0.6V VOUT 5.5V R2 VFB LTC3448 GND
3448 F05
R1
Figure 5. Setting the LTC3448 Output Voltage
Efficiency Considerations The efficiency of a switching regulator is equal to the output power divided by the input power times 100%. It is often useful to analyze individual losses to determine what is limiting the efficiency and which change would produce the most improvement. Efficiency can be expressed as: Efficiency = 100% - (L1 + L2 + L3 + ...) where L1, L2, etc. are the individual losses as a percentage of input power. Although all dissipative elements in the circuit produce losses, two main sources usually account for most of the losses in LTC3448 circuits: VIN quiescent current and I2R losses. When in switching mode, VIN quiescent current
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loss dominates the efficiency loss at low load currents, whereas the I2R loss dominates the efficiency loss at medium to high load currents. At very low load currents with the part operating in LDO mode, efficiency can be dominated by I2R losses in the pass transistor and is a strong function of (VIN - VOUT). In a typical efficiency plot, the efficiency curve at very low load currents can be misleading since the actual power lost is of little consequence as illustrated in Figure 6.
1 VIN = 3.6V FREQ = 0V LDOCNTRL = VOUT(AUTO) 0.1 0.01 0.001 1.2V 1.5V 1.8V 0.001 0.01 0.1 LOAD CURRENT (A) 1
3448 F06
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0.0001 0.0001
Figure 6. Power Loss vs Load Current
1. The VIN quiescent current is due to two components: the DC bias current as given in the Electrical Characteristics and the internal main switch and synchronous switch gate charge currents. The gate charge current results from switching the gate capacitance of the internal power MOSFET switches. Each time the gate is switched from high to low to high again, a packet of charge, dQ, moves from VIN to ground. The resulting dQ/dt is the current out of VIN that is typically larger than the DC bias current and proportional to frequency. Both the DC bias and gate charge losses are proportional to VIN and thus their effects will be more pronounced at higher supply voltages. 2. I2R losses are calculated from the resistances of the internal switches, RSW, and external inductor RL. In continuous mode, the average output current flowing through inductor L is "chopped" between the main switch and the synchronous switch. Thus, the series resistance looking into the SW pin is a function of both
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LTC3448
APPLICATIO S I FOR ATIO
top and bottom MOSFET RDS(ON) and the duty cycle (DC) as follows: RSW = (RDS(ON)TOP)(DC) + (RDS(ON)BOT)(1 - DC) The RDS(ON) for both the top and bottom MOSFETs can be obtained from the Typical Performance Characteristics curves. Thus, to obtain I2R losses, simply add RSW to RL and multiply the result by the square of the average output current. 3. At load currents below the selected threshold the LTC3448 will switch into low ripple LDO mode if enabled. In this case the losses are due to the DC bias currents as given in the electrical characteristics and I2R losses due to the (VIN - VOUT) voltage drop across the internal pass transistor. Other losses when in switching operation, including CIN and COUT ESR dissipative losses and inductor core losses, generally account for less than 2% total additional loss. Thermal Considerations The LTC3448 requires the package backplane metal (GND pin) to be well soldered to the PC board. This gives the DFN and MSOP packages exceptional thermal properties, making it difficult in normal operation to exceed the maximum junction temperature of the part. In most applications the LTC3448 does not dissipate much heat due to its high efficiency. In applications where the LTC3448 is running at high ambient temperature with low supply voltage and high duty cycles, such as in dropout, the heat dissipated may exceed the maximum junction temperature of the part if it is not well thermally grounded. If the junction temperature reaches approximately 150C, both power switches will be turned off and the SW node will become high impedance. To avoid the LTC3448 from exceeding the maximum junction temperature, the user will need to do some thermal analysis. The goal of the thermal analysis is to determine whether the power dissipated exceeds the maximum junction temperature of the part. The temperature rise is given by: TR = PDJA
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where PD is the power dissipated by the regulator and JA is the thermal resistance from the junction of the die to the ambient temperature. The junction temperature, TJ, is given by: TJ = TA + TR where TA is the ambient temperature. As an example, consider the LTC3448 in dropout at an input voltage of 2.7V, a load current of 600mA and an ambient temperature of 70C. From the typical performance graph of switch resistance, the RDS(ON) of the P-channel switch at 70C is approximately 0.52. Therefore, power dissipated by the part is: PD = ILOAD2 * RDS(ON) = 187.2mW For the 3mm x 3mm DFN package, the JA is 43C/W. Thus, the junction temperature of the regulator is: TJ = 85C + (0.1872)(43) = 93C which is well below the maximum junction temperature of 125C. Note that at higher supply voltages, the junction temperature is lower due to reduced switch resistance RDS(ON). Checking Transient Response The regulator loop response can be checked by looking at the load transient response. Switching regulators take several cycles to respond to a step in load current. When a load step occurs, VOUT immediately shifts by an amount equal to (ILOAD * ESR), where ESR is the effective series resistance of COUT. ILOAD also begins to charge or discharge COUT, which generates a feedback error signal. The regulator loop then acts to return VOUT to its steady-state value. During this recovery time VOUT can be monitored for overshoot or ringing that would indicate a stability problem. For a detailed explanation of switching control loop theory, see Application Note 76. A second, more severe transient is caused by switching in loads with large (>1F) supply bypass capacitors. The discharged bypass capacitors are effectively put in parallel
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LTC3448
APPLICATIO S I FOR ATIO
with COUT, causing a rapid drop in VOUT. No regulator can deliver enough current to prevent this problem if the load switch resistance is low and it is driven quickly. The only solution is to limit the rise time of the switch drive so that the load rise time is limited to approximately (25 * CLOAD). Thus, a 10F capacitor charging to 3.3V would require a 250s rise time, limiting the charging current to about 130mA. PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3448. These items are also illustrated graphically in Figures 7 and 8. Check the following in your layout: 1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct and wide.
L
VIN CIN
4 8
VIN RUN
6 7
VFB FREQ SYNC GND 9
Figure 7. LTC3448 Layout Design
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2. Does the VFB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of COUT and ground. 3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETs. 4. Keep the switching node, SW, away from the sensitive VFB node. 5. Keep the (-) plates of CIN and COUT as close as possible. Design Example As a design example, assume the LTC3448 is used in a single lithium-ion battery-powered cellular phone application. The VIN will be operating from a maximum of 4.2V down to about 2.7V. The load current requirement is a maximum of 0.6A but most of the time it will be in standby mode, requiring only 2mA. Efficiency at both low
VOUT COUT RFB2 CFF SW VOUT MODE LTC3448 1 RFB1
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5 2 3
3448 F08
Figure 8. LTC3448 Layout
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LTC3448
APPLICATIO S I FOR ATIO
and high load currents is important. Output voltage is 1.8V. With this information we can calculate L using Equation (1),
L=
( )( )
V VOUT 1 - OUT VIN f IL 1
Substituting VOUT = 1.8V, VIN = 4.2V, IL = 240mA and f = 1.5MHz in Equation (3) gives: L= 1.8 V 1.8 V 1 - = 2.86 H 1.5MHz(240mA) 4.2V
A 2.2H inductor works well for this application. For best efficiency choose a 720mA or greater inductor with less than 0.2 series resistance.
8 COUT 15F CER
CIN 4.7F CER
VOUT RUN LTC3448 3 MODE 6 1 VFB FREQ 7 SYNC GND 9
3448 F09a
2 22pF 632k
EFFICIENCY (%)
VIN 2.7V TO 5.5V
4
VIN
SW
5
2.2H*
316k
CIN: TAIYO YUDEN JMK212BJ475MG COUT: TAIYO YUDEN JMK212BJ475MG *MURATA LQH32CN2R2M11
Figure 9a
VOUT 100mV/DIV AC COUPLED ILOAD 100mA/DIV
IL 500mA/DIV VIN = 3.6V 20s/DIV VOUT = 1.8V ILOAD = 100A TO 200mA
3448 F09c
Figure 9c
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CIN will require an RMS current rating of at least 0.3A ILOAD(MAX)/2 at temperature and COUT will require an ESR of less than 0.25. In most cases, a ceramic capacitor will satisfy this requirement. For the feedback resistors, choose R1 = 316k. R2 can then be calculated from Equation (2) to be: V R2 = OUT - 1 R1 = 632k 0.6 Figure 9 shows the complete circuit along with its efficiency curve. (3)
100 VIN = 3.6V 90 VOUT = 1.8V T = 25C 80 A 70 60 50 40 30 20 10 0 0.0001 0.001 0.01 0.1 LOAD CURRENT (A) 1
3448 F09b
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VOUT 1.8V
Figure 9b
VOUT 100mV/DIV AC COUPLED ILOAD 250mA/DIV
IL 500mA/DIV
3448 F09d
VIN = 3.6V 20s/DIV VOUT = 1.8V ILOAD = 50mA TO 600mA
Figure 9d
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LTC3448
TYPICAL APPLICATIO S
Single Li-Ion 1.5V/600mA Regulator for High Efficiency and Small Footprint
VIN 2.7V TO 5.5V 4 CIN 4.7F CER 8 VIN SW 5 2 22pF 474k 2.2H* COUT 15F VOUT 1.5V
VOUT RUN LTC3448 3 MODE 6 1 VFB FREQ 7 SYNC GND 9
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EFFICIENCY (%)
CIN: TAIYO YUDEN CERAMIC JMK212BJ475MG COUT: TAIYO YUDEN CERAMIC JMK212BJ475MG *MURATA LQH32CN2R2M33
Load Step
VOUT 100mV/DIV AC COUPLED ILOAD 100mA/DIV VOUT 100mV/DIV AC COUPLED ILOAD 250mA/DIV
IL 500mA/DIV VIN = 3.6V 20s/DIV VOUT = 1.5V ILOAD = 100A TO 200mA
3448 TA05
Note: Performance data measured on the LTC3448 with external resistors
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Efficiency vs Output Current
100 90 80 70 60 50 40 30 20 10 0 0.0001 VIN = 2.7V VIN = 3.6V VIN = 4.2V 0.001 0.01 0.1 LOAD CURRENT (A) 1
23448 G03
VOUT = 1.5V TA = 25C
216k
Load Step
IL 500mA/DIV VIN = 3.6V 20s/DIV VOUT = 1.5V ILOAD = 50mA TO 600mA
3448 TA06
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LTC3448
TYPICAL APPLICATIO S
Single Li-Ion 1.2V/600mA Regulator for High Efficiency and Small Footprint
VIN 2.7V TO 5.5V 4 CIN 4.7F CER 8 VIN SW 5 2 2.2H* COUT 10F CER
EFFICIENCY (%)
VOUT RUN LTC3448 3 MODE 6 1 VFB FREQ 7 SYNC GND 9
3448 TA07
CIN: TAIYO YUDEN JMK212BJ475MG COUT: TAIYO YUDEN JMK212BJ475MG *MURATA LQH32CN2R2M33
Load Step
VOUT 100mV/DIV AC COUPLED
VOUT 100mV/DIV AC COUPLED
ILOAD 100mA/DIV
IL 500mA/DIV VIN = 3.6V 20s/DIV VOUT = 1.2V ILOAD = 100A TO 200mA
3448 TA09
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Efficiency vs Output Current
100
VOUT 1.2V
90 80 70 60 50 40 30 20 10
VOUT = 1.2V TA = 25C
22pF
316k
316k
0 0.0001
VIN = 2.7V VIN = 3.6V VIN = 4.2V 0.001 0.01 0.1 LOAD CURRENT (A) 1
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Load Step
ILOAD 250mA/DIV
IL 500mA/DIV 20s/DIV VIN = 3.6V VOUT = 1.2V ILOAD = 50mA TO 600mA
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LTC3448
TYPICAL APPLICATIO S
Single Li-Ion 2.5V/600mA Regulator with 1.8MHz External Synchronization and External MODE
2.2H COUT 10F CER VOUT 2.5V 600mA
VIN 2.5V TO 5.5V
Load Step
VOUT 100mV/DIV AC COUPLED
LDOCNTRL 2V/DIV
ILOAD 250mA/DIV
VIN = 3.6V 40s/DIV VOUT = 2.5V ILOAD = 100A TO 300mA
Single Li-Ion 1.2V/600mA Regulator with 2.5MHz External Synchronization
VIN 2.5V TO 5.5V
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4 CIN 4.7F CER TO PROCESSOR CONTROL 8
VIN
SW
5 2
VOUT RUN LTC3448
1.58M
TO 0V TO 1.3V OR GREATER 1.8MHz EXTERNAL CLOCK
3 MODE 6 1 VFB FREQ 7 SYNC GND 9
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CFF 22pF
500k
Load Step
VOUT 100mV/DIV AC COUPLED LDOCNTRL 2V/DIV
ILOAD 250mA/DIV
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40s/DIV VIN = 3.6V VOUT = 2.5V ILOAD = 100A TO 600mA
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4 CIN 4.7F CER 8
VIN
SW
5 2
2.2H COUT 10F CER
VOUT RUN LTC3448
VOUT 1.2V 600mA
316k 3
CFF 22pF
TO 0V TO 1.3V OR GREATER 2.5MHz EXTERNAL CLOCK
MODE 6 1 VFB FREQ 7 SYNC GND 9
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316k
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LTC3448
PACKAGE DESCRIPTIO
3.5 0.05 1.65 0.05 2.15 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5 0.38 0.10 8
PIN 1 TOP MARK (NOTE 6)
(DD8) DFN 1203
0.200 REF
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON TOP AND BOTTOM OF PACKAGE
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DD Package 8-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 0.05 3.00 0.10 (4 SIDES) 1.65 0.10 (2 SIDES) 0.75 0.05 4 0.25 0.05 2.38 0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD 1 0.50 BSC 0.00 - 0.05
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LTC3448
PACKAGE DESCRIPTIO
2.794 0.102 (.110 .004)
5.23 (.206) MIN
0.42 0.038 (.0165 .0015) TYP
RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP
0.254 (.010)
GAUGE PLANE
0.18 (.007)
SEATING PLANE
0.65 (.0256) NOTE: BSC 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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MS8E Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1662)
BOTTOM VIEW OF EXPOSED PAD OPTION 1 2.06 0.102 (.081 .004) 1.83 0.102 (.072 .004)
0.889 0.127 (.035 .005)
2.083 0.102 3.20 - 3.45 (.082 .004) (.126 - .136)
8 3.00 0.102 (.118 .004) (NOTE 3)
0.65 (.0256) BSC
8
7 65
0.52 (.0205) REF
4.90 0.152 (.193 .006)
3.00 0.102 (.118 .004) (NOTE 4)
0.53 0.152 (.021 .006)
DETAIL "A"
1 1.10 (.043) MAX
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4 0.86 (.034) REF
0.22 - 0.38 (.009 - .015) TYP
0.127 0.076 (.005 .003)
MSOP (MS8E) 0603
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LTC3448 RELATED PARTS
PART NUMBER LT1616 LT1776 LTC1877 LTC1879 LTC3403 LTC3405/LTC3405A LTC3406 LTC3406B-2 LTC3407/LTC3407-2 LTC3409 LTC3411 LTC3412 LTC3440 LTC3441 LTC3442 LTC3443 DESCRIPTION 500mA (IOUT), 1.4MHz, High Efficiency Step-Down DC/DC Converter 500mA (IOUT), 200kHz, High Efficiency Step-Down DC/DC Converter 600mA (IOUT), 550kHz, Synchronous Step-Down DC/DC Converter 1.2A (IOUT), 550kHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter with Bypass Transistor 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 2.25MHz, Synchronous Step-Down DC/DC Converter Dual 600mA/800mA (IOUT), 1.5MHz/2.25MHz, Synchronous Step-Down DC/DC Converter 600mA Low VIN Buck Regulator 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 2.5A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter 1.2A (IOUT), 1MHz, Synchronous Buck-Boost DC/DC Converter 1.2A (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter 1.2A (IOUT), 600kHz, Synchronous Buck-Boost DC/DC Converter COMMENTS 90% Efficiency, VIN = 3.6V to 25V, VOUT 1.25V, IQ = 1.9mA, ISD = <1A, ThinSOT Package 90% Efficiency, VIN = 7.4V to 40V, VOUT 1.24V, IQ = 3.2mA, ISD = 30A, N8, S8 Packages 95% Efficiency, VIN = 2.7V to 10V, VOUT 0.8V, IQ = 10A, ISD = <1A, MS8 Package 95% Efficiency, VIN = 2.7V to 10V, VOUT 0.8V, IQ = 15A, ISD = <1A, TSSOP-16 Package 96% Efficiency, VIN = 2.5V to 5.5V, VOUT = Dynamically Adjustable, IQ = 20A, ISD = <1A, DFN Package 96% Efficiency, VIN = 2.5V to 5.5V, VOUT 0.8V, IQ = 20A, ISD = <1A, ThinSOT Package 96% Efficiency, VIN = 2.5V to 5.5V, VOUT 0.6V, IQ = 20A, ISD = <1A, ThinSOT Package 96% Efficiency, VIN = 2.5V to 5.5V, VOUT 0.6V, IQ = 300A, ISD = <1A, ThinSOT Package 96% Efficiency, VIN = 2.5V to 5.5V, VOUT 0.6V, IQ = 40A, ISD = <1A, MS10, DFN Packages 95% Efficiency, VIN = 1.6V to 5.5V, IQ = 65A ISD = <1A, DFN Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT 0.8V, IQ = 60A, ISD = <1A, MS Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT 0.8V, IQ = 60A, ISD = <1A, TSSOP-16E Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT 2.5V, IQ = 25A, ISD = <1A, MS Package 95% Efficiency, VIN = 2.4V to 5.5V, VOUT 2.4V to 5.25V, IQ = 25A, ISD = <1A, DFN Package 95% Efficiency, VIN = 2.4V to 5.5V, VOUT 2.4V to 5.25V, IQ = 35A, ISD = <1A, DFN Package 95% Efficiency, VIN = 2.4V to 5.5V, VOUT 2.4V to 5.25V, IQ = 28A, ISD = <1A, DFN Package
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT/TP 0505 500 * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2005

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