LT1912 LINER | Alldatasheet
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APPLICATIONS
36V, 2A, 500kHz Step-Down Switching Regulator The L T®1912 is an adjustable frequency (200kHz to 500kHz) monolithic step-down switching regulator that accepts input voltages up to 36V . A high effi ciency 0.25Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator , control, and logic cir- cuitry. Current mode topology is used for fast transient response and good loop stability. The L T1912 allows the use of ceramic capacitors resulting in low output ripple while keeping total solution size to a minimum. The low current shutdown mode reduces input supply current to less than 1μA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). The L T1912 is available in 10-Pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance. ■ Automotive Battery Regulation ■ Set Top Box ■ Distributed Supply Regulation ■ Industrial Supplies ■ Wall T ransformer Regulation 3.3V Step-Down Converter SW FB VC RT VIN BD VIN 4.5V TO 36V VOUT 3.3V 4.7μF 0.47μF 470pF 47μF100k 20k 68.1k 6.8μH 316k GND OFF ON L T1912
1912 TA01
Effi ciency LOAD CURRENT (A)
0 EFFICIENCY (%)
0.5 1.0 1.5 2
1912 TA01b
VIN = 12V L = 6.8μF F = 500kHz VOUT = 3.3V VOUT = 5V , L T , L TC and L TM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. ■ Wide Input Range: Operation From 3.6V to 36V ■ 2A Maximum Output Current ■ Adjustable Switching Frequency: 200kHz to 500kHz ■ Low Shutdown Current: IQ < 1μA ■ Integrated Boost Diode ■ Synchronizable Between 250kHz to 500kHz ■ Saturating Switch Design: 0.25Ω On-Resistance ■ 0.790V Feedback Reference Voltage ■ Output Voltage: 0.79V to 20V ■ Soft-Start Capability ■ Small 10-Pin Thermally Enhanced MSOP and (3mm × 3mm) DFN Packages FEATURES DESCRIPTION
ELECTRICAL CHARACTERISTICS
FB, RT , V (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage ● 3 3.6 V Quiescent Current from VIN VRUN/SS = 0.2V VBD = 3V , Not Switching VBD = 0, Not Switching 0.01 450 1.3 0.5 600 1.7 μA μA μA Quiescent Current from BD V RUN/SS = 0.2V VBD = 3V , Not Switching VBD = 0, Not Switching 0.01 0.9 0.5 1.3 μA mA μA Minimum Bias Voltage (BD Pin) 2.7 3 V The ● denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 10V , VRUN/SS = 10V , VBOOST = 15V , VBD = 3.3V unless otherwise noted. (Note 2) Operating Junction Temperature Range (Note 2) Lead Temperature (Soldering, 10 sec) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE L T1912EDD#PBF L T1912EMSE#PBF L T1912EDD#TRPBF L T1912EMSE#TRPBF LDJT LT D J S 10-Lead (3mm × 3mm) Plastic DFN 10-Lead Plastic MSOP –40°C to 125°C –40°C to 125°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. Consult L TC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear .com/tapeandreel/ TOP VIEW DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN 3 11 1 RT VC FB N/C SYNC BD BOOST SW V IN RUN/SS JA = 45°C/W , JC = 10°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB BD BOOST SW V IN RUN/SS R T VC FB N/C SYNC TOP VIEW MSE PACKAGE 10-LEAD PLASTIC MSOP JA = 45°C/W , JC = 10°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
PARAMETER CONDITIONS MIN TYP MAX UNITS Feedback Voltage 780 775 790 790 800 805 mV mV FB Pin Bias Current (Note 3) V FB = 0.8V , VC = 0.4V ● 73 0 n A FB Voltage Line Regulation 4V < V IN < 36V 0.002 0.01 %/V Error Amp gm 25 μMho Error Amp Gain 1000 VC Source Current 45 μA VC Sink Current 45 μA VC Pin to Switch Current Gain 3.5 A/V VC Clamp Voltage 2V Switching Frequency R T = 187k 160 200 240 kHz Minimum Switch Off-Time ● 60 150 nS Switch Current Limit Duty Cycle = 5% 3.2 3.7 4.2 A Switch V CESAT ISW = 2A 500 mV Boost Schottky Reverse Leakage V SW = 10V , VBD = 0V 0.02 2 μA Minimum Boost Voltage (Note 4) ● 1.5 2.1 V BOOST Pin Current I SW = 1A 22 35 mA RUN/SS Pin Current V RUN/SS = 2.5V 5 10 μA RUN/SS Input Voltage High 2.5 V RUN/SS Input Voltage Low 0.2 V SYNC Low Threshold 0.5 V SYNC High Threshold 0.7 V SYNC Pin Bias Current V SYNC = 0V 0.1 μA Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The L T1912E is guaranteed to meet performance specifi cations from 0°C to 125°C. Specifi cations over the –40°C to 125°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Bias current fl ows out of the FB pin. Note 4: This is the minimum voltage across the boost capacitor needed to guarantee full saturation of the switch. The ● denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 10V , VRUN/SS = 10V VBOOST = 15V , VBD = 3.3V unless otherwise noted. (Note 2)
SWITCH CURRENT (mA) BOOST PIN CURRENT (mA)
1912 G08
LOAD CURRENT (A) EFFICIENCY (%) 100
1912 G01
VIN = 24V VIN = 34V VIN = 12V L: NEC PLC-0745-5R6 f: 500kHzVOUT = 5V LOAD CURRENT (A) EFFICIENCY (%)
1912 G02
VIN = 12V VIN = 7V L: NEC PLC-0745-5R6 f: 500kHz VIN = 24V VIN = 34V VOUT = 3.3V INPUT VOL TAGE (V) LOAD CURRENT (A)
1912 G03
2.5 10 20 1.5 1.0 4.0 3.5 3.0 2.0 25 3 0 TYPICAL MINIMUM VOUT = 3.3V L = 4.7μH f = 500kHz SWITCH CURRENT (mA) 400 500 700 1500
1912 G07
600VOL TAGE DROP (mV) Effi ciency Effi ciency TYPICAL PERFOR A CE CHARACTERISTICSUW Boost Pin CurrentSwitch Voltage Drop Maximum Load Current TA = 25°C unless otherwise noted. DUTY CYCLE (%) SWITCH CURRENT LIMIT(A)
1912 G05
2.5 20 60 1.5 1.0 4.0 3.5 3.0 2.0 80 100 INPUT VOL TAGE (V) LOAD CURRENT (A)
1912 G04
2.5 10 20 1.5 1.0 3.5 3.0 2.0 25 30 TYPICAL MINIMUM VOUT = 5V L = 4.7μH f = 500kHz TEMPERATURE (°C) SWITCH CURRENT LIMIT (A) 2.0 2.5 3.5 3.0
1912 G06
1.5 1.0 0.5 4.5
4.0 DUTY CYCLE = 10 %
DUTY CYCLE = 90 % –50 25–25 0 50 75 100 150 125 Switch Current Limit Switch Current LimitMaximum Load Current
BOOST DIODE CURRENT (A) BOOST DIODE Vf (V) 0.8 1.0 1.2 2.0
1912 G15
0.6 0.4 0.5 1.0 1.5 0.2 1.4 RUN/SS PIN VOL TAGE (V) SWITCH CURRENT LIMIT (A) 3.5 1.5
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2.0 1.0 0.5 1 2 0.5 4.0 3.0 2.5 1.5 2.5 3 3.5 FB PIN VOL TAGE (mV) SWITCHING FREQUENCY (NORMALIZED) 0.8 1.0 1.2 600
1912 G11
0.6 0.4 200 400 800500100 300 700 900 0.2 TEMPERATURE (˚C) MINIMUM SWITCH ON TIME (ns) 100 120
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–50 25–25 0 50 75 100 15 0125 RUN/SS PIN VOL TAGE (V) RUN/SS PIN CURRENT (μA) 15 25
1912 G14
TEMPERATURE (°C) FEEDBACK VOL TAGE (mV) 800
1912 G09
–50 25–25 0 50 75 100 150 125 TEMPERATURE (°C) FREQUENCY (NORMALIZED) 1.00 1.10
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0.90 0.80 1.20 0.95 1.05 0.85 1.15 –50 25–25 0 50 75 100 150 125 Feedback Voltage Switching Frequency Frequency Foldback Minimum Switch On-Time Soft-Start RUN/SS Pin Current Boost Diode TYPICAL PERFOR A CE CHARACTERISTICSUW TA = 25°C unless otherwise noted. FB PIN ERROR VOL TAGE (V) –200 –50 VC PIN CURRENT (μA) –20 02 0 0
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–40 –100 100 –10 –30 Error Amp Output Current
TEMPERATURE (°C) VC VOL TAGE (V) 1.50 2.00 2.50
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1.00 0.50 CURRENT LIMIT CLAMP SWITCHING THRESHOLD –50 25–25 0 50 75 100 150 125
1912 G21
0.5A/DIV VSW 5V/DIV VOUT 10mV/DIV VIN = 12V; VOUT = 3.3V ILOAD = 110mA 2μs/DIV
1912 G22
VIN = 12V; VOUT = 3.3V ILOAD = 1A 2μs/DIV VC Voltages Switching Waveforms; Discontinuous Operation Switching Waveforms; Continuous Operation TYPICAL PERFOR A CE CHARACTERISTICSUW TA = 25°C unless otherwise noted.
BD (Pin 1): This pin connects to the anode of the boost Schottky diode. BD also supplies current to the internal regulator . BOOST (Pin 2): This pin is used to provide a drive voltage, higher than the input voltage, to the internal bipolar NPN power switch. SW (Pin 3): The SW pin is the output of the internal power switch. Connect this pin to the inductor , catch diode and boost capacitor . V IN (Pin 4): The VIN pin supplies current to the L T1912’s internal regulator and to the internal power switch. This pin must be locally bypassed. RUN/SS (Pin 5): The RUN/SS pin is used to put the L T1912 in shutdown mode. Tie to ground to shut down the L T1912. Tie to 2.5V or more for normal operation. If the shutdown feature is not used, tie this pin to the V IN pin. RUN/SS also provides a soft-start function; see the Applications Information section. SYNC (Pin 6): This is the external clock synchronization input. Ground this pin when SYNC function is not used. Tie to a clock source for synchronization. Clock edges should have rise and fall times faster than 1μs. See synchronizing section in Applications Information. N/C (Pin 7): This pin should be tied to ground. FB (Pin 8): The L T1912 regulates the FB pin to 0.790V . Connect the feedback resistor divider tap to this pin. V C (Pin 9): The VC pin is the output of the internal error amplifi er . The voltage on this pin controls the peak switch current. Tie an RC network from this pin to ground to compensate the control loop. R T (Pin 10): Oscillator Resistor Input. Connecting a resistor to ground from this pin sets the switching frequency. Exposed Pad (Pin 11): Ground. The Exposed Pad must be soldered to PCB. BLOCK DIAGRA W OSCILLATOR 200kHz–500kHz VC CLAMP SOFT-START SLOPE COMP R VINVIN RUN/SS BOOST SW SWITCH LATCH VC VOUT CF CC RC BD RT GND ERROR AMP FB RT S Q 1912 BD 11 8 INTERNAL 0.79V REF SYNC
The L T1912 is a constant frequency, current mode step- down regulator . An oscillator , with frequency set by RT , enables an RS fl ip-fl op, turning on the internal power switch. An amplifi er and comparator monitor the current fl owing between the V IN and SW pins, turning the switch off when this current reaches a level determined by the voltage at V C. An error amplifi er measures the output voltage through an external resistor divider tied to the FB pin and servos the V C pin. If the error amplifi er’s output increases, more current is delivered to the output; if it decreases, less current is delivered. An active clamp on the V C pin provides current limit. The VC pin is also clamped to the voltage on the RUN/SS pin; soft-start is implemented by generating a voltage ramp at the RUN/SS pin using an external resistor and capacitor . An internal regulator provides power to the control circuitry. The bias regulator normally draws power from the V IN pin, but if the BD pin is connected to an external voltage higher than 3V bias power will be drawn from the external source (typically the regulated output voltage). This improves effi ciency. The RUN/SS pin is used to place the L T1912 in shutdown, disconnecting the output and reducing the input current to less than 1μA. The switch driver operates from either the input or from the BOOST pin. An external capacitor and diode are used to generate a voltage at the BOOST pin that is higher than the input supply. This allows the driver to fully saturate the internal bipolar NPN power switch for effi cient operation. The oscillator reduces the L T1912’s operating frequency when the voltage at the FB pin is low. This frequency foldback helps to control the output current during startup and overload. OPERATION
Reference designators refer to the Block Diagram. Figure 1. Switching Frequency vs. RT Value minimum of ~150ns and turn off for a minimum of ~150ns. the inductor and capacitor values small. chosen according to the following equation.
be higher than in normal operation. maximum duty cycle (see equation in previous section). switching frequency should be used. and switching frequency will determine the ripple current. must be lower than the L T1912’s switch current limit (ILIM). suffi cient maximum output current (IOUT(MAX)). Table 1. Inductor Vendors
with a lower DCR resulting in higher effi ciency. There are several graphs in the Typical Performance Characteristics section of this data sheet that show the maximum load current as a function of input voltage and inductor value for several popular output voltages. Low inductance may result in discontinuous mode operation, which is okay but further reduces maximum load current. For details of maximum output current and discontinuous mode opera- tion, see Linear Technology Application Note 44. Finally, for duty cycles greater than 50% (V OUT/VIN > 0.5), there is a minimum inductance required to avoid subharmonic oscillations. See AN19. Input Capacitor Bypass the input of the L T1912 circuit with a ceramic capaci- tor of X7R or X5R type. Y5V types have poor performance over temperature and applied voltage, and should not be used. A 4.7μF to 10μF ceramic capacitor is adequate to bypass the L T1912 and will easily handle the ripple current. Note that larger input capacitance is required when a lower switching frequency is used. If the input power source has high impedance, or there is signifi cant inductance due to long wires or cables, additional bulk capacitance may be necessary. This can be provided with a lower performance electrolytic capacitor . Step-down regulators draw current from the input sup- ply in pulses with very fast rise and fall times. The input capacitor is required to reduce the resulting voltage ripple at the L T1912 and to force this very high frequency switching current into a tight local loop, minimizing EMI. A 4.7μF capacitor is capable of this task, but only if it is placed close to the L T1912 and the catch diode (see the PCB Layout section). A second precaution regarding the ceramic input capacitor concerns the maximum input voltage rating of the L T1912. A ceramic input capacitor combined with trace or cable inductance forms a high quality (under damped) tank circuit. If the L T1912 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the L T1912’s voltage rating. This situation is easily avoided (see the Hot Plugging Safely section). Output Capacitor and Output Ripple The output capacitor has two essential functions. Along with the inductor , it fi lters the square wave generated by the L T1912 to produce the DC output. In this role it determines the output ripple, and low impedance at the switching frequency is important. The second function is to store energy in order to satisfy transient loads and stabilize the L T1912’s control loop. Ceramic capacitors have very low equivalent series resistance (ESR) and provide the best ripple performance. A good starting value is: COUT = 100 VOUT fSW where f SW is in MHz, and C OUT is the recommended output capacitance in μF . Use X5R or X7R types. This choice will provide low output ripple and good transient response. T ransient performance can be improved with a higher value capacitor if the compensation network is also adjusted to maintain the loop bandwidth. A lower value of output capacitor can be used to save space and cost but transient performance will suffer . See the Frequency Compensation section to choose an appropriate compen- sation network. When choosing a capacitor , look carefully through the data sheet to fi nd out what the actual capacitance is under operating conditions (applied voltage and temperature). A physically larger capacitor , or one with a higher voltage rating, may be required. High performance tantalum or electrolytic capacitors can be used for the output capacitor . Low ESR is important, so choose one that is intended for use in switching regulators. The ESR should be specifi ed by the supplier , and should be 0.05Ω or less. Such a capacitor will be larger than a ceramic capacitor and will have a larger capacitance, because the capacitor must be large to achieve low ESR. Table 2 lists several capacitor vendors. APPLICATIONS INFORMATION
3 lists several Schottky diodes and their manufacturers. Table 3. Diode Vendors the Hot Plugging Safely section). output capacitor has high ESR. Table 2. Capacitor Vendors
the compensation network to optimize the performance. shows an equivalent circuit for the L T1912 control loop. frequency is much lower than the switching frequency. 500mA to 1500mA and back to 500mA. pin quiescent current comes from a lower voltage source. of the BOOST and BD pins are not exceeded.
1912 F02
Figure 2. Model for Loop Response Figure 3. T ransient Load Response of the L T1912 Front Page
1912 F03
the absolute maximum rating of the BOOST pin. input voltage to maintain regulation. reducing the maximum input current during start-up. up and shut-down waveforms with the soft-start circuit. and peaks that are above 0.8V (up to 6V). T should be chosen for 200kHz. value to prevent subharmonic oscillation.
1912 FO4
Figure 4. Three Circuits For Generating The Boost Voltage
protects against a shorted or reversed input. a local, unbroken ground plane below these components. Figure 5. The Minimum Input Voltage Depends on
1912 F05
5.5 TO START
Figure 6. To Soft-Start the L T1912, Add a Resisitor
1912 F06
Figure 7. Diode D4 Prevents a Shorted Input from
1912 F07
The SW and BOOST nodes should be as small as possible. traces will shield them from the SW and BOOST nodes. board and on the bottom side. a 5V output at full load operating from 24V .
1912 F08
Figure 8. A Good PCB Layout Ensures Proper , Low EMI Operation 100 LFPM airfl ow, this resistance can fall by another 25%. temperature approaches 125°C.
Power dissipation within the L T1912 can be estimated by calculating the total power loss from an effi ciency measure- ment and subtracting the catch diode loss and inductor loss. The die temperature is calculated by multiplying the L T1912 power dissipation by the thermal resistance from junction to ambient. APPLICATIONS INFORMATION Other Linear Technology Publications Application Notes 19, 35 and 44 contain more detailed descriptions and design information for buck regulators and other switching regulators. The L T1376 data sheet has a more extensive discussion of output ripple, loop compensation and stability testing. Design Note 100 shows how to generate a bipolar output supply using a buck regulator .
Figure 9. A Well Chosen Input Network Prevents Input Voltage Overshoot and
1912 F09
3.3V Step-Down Converter SW FB VC RT VIN BD VIN 6.8V TO 36V VOUT 4.7μF 0.47μF 47μF100k f = 500kHz D: DIODES INC. DFLS240L L: TAIYO YUDEN NP06DZB6R8M D 16.2k 68.1k L 6.8μH 536k GND 470pF ON OFF L T1912
1912 TA02
4.4V TO 36V VOUT 3.3V 4.7μF 0.47μF 47μF100k f = 500kHz D: DIODES INC. DFLS240L L: TAIYO YUDEN NP06DZB4R7M D 20k 68.1k L 6.8μH 316k GND 470pF ON OFF L T1912
1912 TA03
2.5V Step-Down Converter SW FB VC RT VIN BD VIN 4V TO 36V VOUT 2.5V 4.7μF 1μF 47μF100k f = 500kHz D1: DIODES INC. DFLS240L D2: MBR0540 L: TAIYO YUDEN NP06DZB4R7M 20k 68.1k L 6.8μH 215k GND 330pF ON OFF L T1912
1912 TA04
1.8V Step-Down Converter 12V Step-Down Converter SW FB VC RT VIN BD VIN 15V TO 36V VOUT 12V 10μF 0.47μF 22μF50k f = 500kHz D: DIODES INC. DFLS240L L: NEC/TOKIN PLC-0755-100 D 26.1k 68.1kHz L 10μH 715k GND 330pF ON OFF L T1912
1912 TA06
3.5V TO 27V VOUT 1.8V 4.7μF 0.47μF 47μF100k f = 500kHz D: DIODES INC. DFLS240L L: TAIYO YUDEN NP06DZB3R3M D 18.2k 68.1k L 3.3μH 127k GND 330pF ON OFF L T1912
1912 TA08
10-Lead Plastic DFN (3mm × 3mm) (Reference L TC DWG # 05-08-1699) 3.00 ±0.10 (4 SIDES) NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 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 THE TOP AND BOTTOM OF PACKAGE 0.38 ± 0.10 BOTTOM VIEW—EXPOSED PAD 1.65 ± 0.10 (2 SIDES) 0.75 ±0.05 R = 0.115 TYP 2.38 ±0.10 (2 SIDES) 106 PIN 1 TOP MARK (SEE NOTE 6)
0.200 REF
0.00 – 0.05 (DD) DFN 1103 0.25 ± 0.05 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 1.65 ±0.05 (2 SIDES)2.15 ±0.05 0.50 BSC 0.675 ±0.05 3.50 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05
0.50 BSC
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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. MSOP (MSE) 0603 0.53 ± 0.152 (.021 ± .006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.17 – 0.27 (.007 – .011) TYP 0.127 ± 0.076 (.005 ± .003) 0.86 (.034) REF 0.50 (.0197) BSC 12 3 45 4.90 ± 0.152 (.193 ± .006) 0.497 ± 0.076 (.0196 ± .003) REF8910 7 6 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) NOTE: 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 0.254 (.010) 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 ± 0.127 (.035 ± .005) RECOMMENDED SOLDER PAD LAYOUT 0.305 ± 0.038 (.0120 ± .0015) TYP 2.083 ± 0.102 (.082 ± .004) 2.794 ± 0.102 (.110 ± .004) 0.50 (.0197) BSC BOTTOM VIEW OF EXPOSED PAD OPTION 1.83 ± 0.102 (.072 ± .004) 2.06 ± 0.102 (.081 ± .004) 10-Lead Plastic MSOP (Reference L TC DWG # 05-08-1663) PACKAGE DESCRIPTION
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com © LINEAR TECHNOLOGY CORPORATION 2007 LT 0108 • PRINTED IN USA PART NUMBER DESCRIPTION COMMENTS L T1933 500mA (I OUT), 500kHz Step-Down Switching Regulator in SOT-23 VIN: 3.6V to 36V , VOUT(MIN) = 1.2V , IQ = 1.6mA, ISD <1μA, ThinSOT Package L T3437 60V , 400mA (I OUT), MicroPower Step-Down DC/DC Converter with Burst Mode VIN: 3.3V to 80V , VOUT(MIN) = 1.25V , IQ = 100μA, ISD <1μA, 10-Pin 3mm × 3mm DFN and 16-Pin TSSOP Packages L T1936 36V , 1.4A (I OUT), 500kHz High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 36V , VOUT(MIN) = 1.2V , IQ = 1.9mA, ISD <1μA, MS8E Package L T3493 36V , 1.2A (I OUT), 750kHz High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 40V , VOUT(MIN) = 0.8V , IQ = 1.9mA, ISD <1μA, 6-Pin 2mm × 3mm DFN Package L T1976/L T1977 60V , 1.2A (IOUT), 200kHz/500kHz, High Effi ciency Step- Down DC/DC Converter with Burst Mode VIN: 3.3V to 60V , VOUT(MIN) = 1.2V , IQ = 100μA, ISD <1μA, 16-Pin TSSOP Package L T1767 25V , 1.2A (I OUT), 1.1MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3V to 25V , VOUT(MIN) = 1.2V , IQ = 1mA, ISD <6μA, MS8E Package L T1940 Dual 25V , 1.4A (I OUT), 1.1MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 25V , VOUT(MIN) = 1.2V , IQ = 3.8mA, ISD <30μA, 16-Pin TSSOP Package L T1766 60V , 1.2A (I OUT), 200kHz, High Effi ciency Step-Down DC/DC Converter VIN: 5.5V to 60V , VOUT(MIN) = 1.2V , IQ = 2.5mA, ISD = 25μA, 16-Pin TSSOP Package L T3434/L T3435 60V , 2.4A (IOUT), 200/500kHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode VIN: 3.3V to 60V , VOUT(MIN) = 1.2V , IQ = 100μA, ISD <1μA, 16-Pin TSSOP Package L T3480 38V , 2A (I OUT), 2.4MHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode VIN: 3.6V to 38V , VOUT(MIN) = 0.79V , IQ = 70μA, ISD <1μA, 10-Pin 3mm × 3mm DFN and 10-Pin MSOP Packages L T3481 36V , 2A (I OUT), 2.8MHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode VIN: 3.6V to 34V , VOUT(MIN) = 1.26V , IQ = 50μA, ISD <1μA, 10-Pin 3mm × 3mm DFN and 10-Pin MSOP Packages L T3684 36V , 2A (I OUT), 2.8MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 34V , VOUT(MIN) = 1.26V , IQ = 1.5mA, ISD <1μA, 10-Pin 3mm × 3mm DFN and 10-Pin MSOP Packages L T3685 38V , 2A(I OUT) 2.4MHz Step-Down DC/DC Converter with 60V T ransient Protection VIN: 3.6V to 38V , VOUT(MIN) = 0.79V , IQ = 450μA, ISD < 1μA, 3mm × 3mm DFN, MSOP-10 Packages TYPICAL APPLICATIO U RELATED PARTS SW FB VC RT VIN BD VIN 3.6V TO 27V VOUT 1.2V 4.7μF 0.47μF 47μF f = 500kHz D: DIODES INC. DFLS240L L: TAIYO YUDEN NP06DZB3R3M D 16.2k 68.1k L 3.3μH GND 330pF ON OFF L T1912
1912 TA09
52.3k 1.2V Step-Down Converter