LT1938

DATASHEET SEARCH SITE | WWW.ALLDATASHEET.COM

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 24

Technical content

25V, 2.2A, 2.8MHz Step-Down Switching Regulator The L T®1938 is an adjustable frequency (300kHz to 2.8MHz) monolithic buck switching regulator that accepts input voltages up to 25V . A high efficiency 0.18Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator , control and logic circuitry. Current mode topology is used for fast transient response and good loop stability. The L T1938’s high operating fre- quency allows the use of small, low cost inductors and 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). A power good flag signals when V OUT reaches 90% of the programmed output voltage. The L T1938 is available in a 3mm × 3mm DFN package with Exposed Pad for low thermal resistance. ■ Automotive Battery Regulation ■ Power for Portable Products ■ Distributed Supply Regulation ■ Industrial Supplies ■ Wall T ransformer Regulation ■ Wide Input Voltage Range: 3.6V to 25V ■ 2.2A Maximum Output Current ■ Adjustable Switching Frequency: 300kHz to 2.8MHz ■ Low Shutdown Current: IQ < 1µA ■ Integrated Boost Diode ■ Power Good Flag ■ Saturating Switch Design: 0.18Ω On-Resistance ■ 1.265V Feedback Reference Voltage ■ Output Voltage: 1.265V to 20V ■ Soft-Start Capability ■ Small 10-Pin Thermally Enhanced (3mm × 3mm) 3.3V Step-Down Converter Efficiency (VOUT = 3.3V) FEATURES DESCRIPTION

APPLICATIONS

4.5V TO 25V VOUT 3.3V 2.2A 4.7µF 0.47µF 680pF 22µF200k 16.2k 60.4k 4.7µH 324k GND OFF ON L T1938

1938 TA01

, L T , L TC and L TM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. LOAD CURRENT (A) EFFICIENCY (%) 1.6

1938 G02

VIN = 12V VIN = 7V VIN = 24V L: NEC PLC-0745-4R7 f = 800kHz

ELECTRICAL ChARACTERISTICS

Operating Junction Temperature Range (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage ● 3 3.6 V Quiescent Current from VIN VRUN/SS = 0.2V 0.01 0.5 µA VBIAS = 3V , Not Switching ● 0.4 0.8 mA VBIAS = 0, Not Switching 1.2 2.0 mA Quiescent Current from BIAS VRUN/SS = 0.2V 0.01 0.5 µA VBIAS = 3V , Not Switching ● 0.85 1.5 mA VBIAS = 0, Not Switching 0 0.1 mA Minimum Bias Voltage 2.7 3 V Feedback Voltage 1.25 1.24 1.265 1.265 1.28 1.29 V V FB Pin Bias Current (Note 3)

• 30 100 nA FB Voltage Line Regulation 4V < VIN < 25V 0.002 0.02 %/V The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 10V , VRUN/SS = 10V , VBOOST = 15V , VBIAS = 3.3V unless otherwise noted. (Note 2) AbSOLUTE MAxIMUM RATINgS (Note 1) PIN CONFIgURATION TOP VIEW DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN 3 11 1 RT VC FB BIAS PG BD BOOST SW V IN RUN/SS TJMAX = 125°C, θJA = 45°C/W , θJC = 10°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T1938EDD#PBF L T1938EDD#TRPBF LDFT 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C L T1938IDD#PBF L T1938IDD#TRPBF LDFT 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C Consult L TC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container . Consult L TC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear .com/tapeandreel/

PARAMETER CONDITIONS MIN TYP MAX UNITS Error Amp gm 330 µMho Error Amp Gain 1000 VC Source Current 75 µA VC Sink Current 100 µA VC Pin to Switch Current Gain 3.5 A/V VC Clamp Voltage 2 V Switching Frequency RT = 8.66k RT = 29.4k RT = 187k 2.7 1.25 250 3.0 1.4 300 3.3 1.55 350 MHz MHz kHz Minimum Switch Off-Time

• 100 150 nS Switch Current Limit Duty Cycle = 5% 3.1 3.6 4.0 A Switch VCESAT ISW = 2A 360 mV Boost Schottky Reverse Leakage VSW = 10V , VBIAS = 0V 0.02 2 µA Minimum Boost Voltage (Note 4) ● 1.6 2.1 V BOOST Pin Current ISW = 1A 18 30 mA RUN/SS Pin Current VRUN/SS = 2.5V 5 10 µA RUN/SS Input Voltage High 2.5 V RUN/SS Input Voltage Low 0.2 V PG Threshold Offset from Feedback Voltage V FB Rising 100 mV PG Hysteresis 10 mV PG Leakage VPG = 5V 0.1 1 µA PG Sink Current VPG = 0.4V ● 100 300 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 T1938E is guaranteed to meet performance specifications from 0°C to 125°C. Specifications over the –40°C to 125°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The L T1938I specifications are guaranteed over the –40°C to 125°C temperature range. Note 3: Bias current measured in regulation. Bias current flows into 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 specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 10V , VRUN/SS = 10V VBOOST = 15V , VBIAS = 3.3V unless otherwise noted. (Note 2)

Efficiency (VOUT = 5.0V) Efficiency (VOUT = 3.3V) Maximum Load Current Switch Voltage Drop Boost Pin Current Switch Current LimitMaximum Load Current Switch Current Limit Efficiency LOAD CURRENT (A) EFFICIENCY (%) 100 1.6

1938 G01

VIN = 12V VIN = 24V L: NEC PLC-0745-4R7 f = 800kHz LOAD CURRENT (A) EFFICIENCY (%) 1.6 VIN = 12V VIN = 7V VIN = 24V L: NEC PLC-0745-4R7 f = 800kHz SWITCHING FREQUENCY (MHz) EFFICIENCY (%) 1.5

1938 G03

0.5 1 2 2.5 3 VIN = 12V VIN = 24V VOUT = 3.3V L = 10µH LOAD = 1A INPUT VOL TAGE (V) LOAD CURRENT (A)

1938 G04

2.5 10 20 1.5 1.0 4.0 3.5 3.0 2.0 TYPICAL MINIMUM VOUT = 3.3V TA = 25°C L = 4.7µH f = 800kHz INPUT VOL TAGE (V) LOAD CURRENT (A)

1938 G05

2.5 10 20 1.5 1.0 4.0 3.5 3.0 2.0 TYPICAL MINIMUM VOUT = 5V TA = 25°C L = 4.7µH f = 800kHz DUTY CYCLE (%) SWITCH CURRENT LIMIT (A)

1938 G06

2.5 20 60 1.5 1.0 4.0 3.5 3.0 2.0 80 100 TEMPERATURE (°C) –50 SWITCH CURRENT LIMIT (A) 2.0 2.5 3.0 125

1938 G07

1.5 1.0 0 –25 50 25 100 75 0.5 4.5

4.0 DUTY CYCLE = 10 %

DUTY CYCLE = 90 % SWITCH CURRENT (mA) 400 500 700 1500 2500

1938 G08

600VOL TAGE DROP (mV) SWITCH CURRENT (mA) BOOST PIN CURRENT (mA) 2000

1938 G09

1000500 2500 30001500 3500 (TA = 25°C unless otherwise noted)TYPICAL PERFORMANCE ChARACTERISTICS

Feedback Voltage Switching Frequency Frequency Foldback Minimum Switch On-Time Soft-Start RUN/SS Pin Current Boost Diode Error Amp Output Current Minimum Input Voltage TEMPERATURE (°C) –50 FEEDBACK VOL TAGE (V) 1.270 1.280 125

1938 G10

1.260 1.250 0 50 100–25 25 75 1.290 1.265 1.275 1.255 1.285 TEMPERATURE (°C) –50 FREQUENCY (MHz) 1.00 1.10 125

1938 G11

0.90 0.80 0 50 100–25 25 75 1.20 RT = 45.3k 0.95 1.05 0.85 1.15 FB PIN VOL TAGE (mV) SWITCHING FREQUENCY (kHz) 800 1000 1200 600 1000

1938 G12

RT = 45.3k TEMPERATURE (°C) –50 MINIMUM SWITCH ON-TIME (ns) 100 120

1938 G13

–25 0 50 75 100 125 140 RUN/SS PIN VOL TAGE (V) SWITCH CURRENT LIMIT (A) 3.5 1.5

1938 G14

2.0 1.0 0.5 1 2 0.5 4.0 3.0 2.5 1.5 2.5 3 3.5 RUN/SS PIN VOL TAGE (V) RUN/SS PIN CURRENT (µA)

1938 G15

BOOST DIODE CURRENT (A) BOOST DIODE Vf (V) 0.8 1.0 1.2 2.0

1938 G16

0.6 0.4 0.5 1.0 1.5 0.2 1.6 1.4 FB PIN VOL TAGE (V) 1.065 –80 VC PIN CURRENT (µA) –60 –20 1.265 1.465 100

1938 G17

–40 1.165 1.365 LOAD CURRENT (A) 0.001 INPUT VOL TAGE (V) 3.0 3.5

1938 G18

2.5 2.0 0.01 0.1 1 4.5 4.0 VOUT = 3.3V TA = 25°C L = 4.7µH f = 800kHz TYPICAL PERFORMANCE ChARACTERISTICS(TA = 25°C unless otherwise noted)

VC VoltagesMinimum Input Voltage Power Good Threshold Switching Waveforms (Discontinuous Operation) Switching Waveforms (Continuous Operation) LOAD CURRENT (A) 0.001 INPUT VOL TAGE (V) 5.0 5.5

1938 G19

4.5 4.0 0.01 0.1 1 6.5 6.0 VOUT = 5V TA = 25°C L = 4.7µH f = 800kHz TEMPERATURE (°C) –50 THRESHOLD VOL TAGE (V) 1.50 2.00 2.50 25 75 125

1938 G20

1.00 0.50 –25 0 50 100 CURRENT LIMIT CLAMP SWITCHING THRESHOLD TEMPERATURE (°C) –50 THRESHOLD VOL TAGE (V) 1.160 1.180 1.200 25 75 125

1938 G21

1.140 1.120 1.100 –25 0 50 100 PG RISING IL 0.5A/DIV VSW 5V/DIV VOUT 10mV/DIV

1938 G221µs/DIV

VIN = 12V , FRONT PAGE APPLICATION ILOAD = 140mA IL 0.5A/DIV VSW 5V/DIV VOUT 10mV/DIV

1938 G231µs/DIV

VIN = 12V , FRONT PAGE APPLICATION ILOAD = 1A TYPICAL PERFORMANCE ChARACTERISTICS(TA = 25°C unless otherwise noted)

BD (Pin 1): This pin connects to the anode of the boost Schottky diode. 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 T1938’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 T1938 in shutdown mode. Tie to ground to shut down the L T1938. Tie to 2.3V 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. PG (Pin 6): The PG pin is the open collector output of an internal comparator . PG remains low until the FB pin is within 10% of the final regulation voltage. PG output is valid when V IN is above 3.5V and RUN/SS is high. BIAS (Pin 7): The BIAS pin supplies the current to the L T1938’s internal regulator . Tie this pin to the lowest available voltage source above 3V (typically V OUT). This architecture increases efficiency especially when the input voltage is much higher than the output. FB (Pin 8): The L T1938 regulates the FB pin to 1.265V . Connect the feedback resistor divider tap to this pin. V C (Pin 9): The VC pin is the output of the internal error amplifier . The voltage on this pin controls the peak switch current. Tie an RC network from this pin to ground to compensate the control loop. RT (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 the PCB. PIN FUNCTIONS

300kHz–2.8MHz VC CLAMPSOFT-START SLOPE COMP INTERNAL 1.265V REF R VINVIN BIAS RUN/SS BOOST SW SWITCH LATCH VC VOUT CF CC RC BD RT GND ERROR AMP FB RT PG 1.12V S Q 1938 BD 11 8

The L T1938 is a constant frequency, current mode step- down regulator . An oscillator , with frequency set by RT , enables an RS flip-flop, turning on the internal power switch. An amplifier and comparator monitor the current flowing 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 amplifier measures the output voltage through an external resistor divider tied to the FB pin and servos the V C pin. If the error amplifier’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 cir - cuitry. The bias regulator normally draws power from the V IN pin, but if the BIAS 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 efficiency. The RUN/SS pin is used to place the L T1938 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 efficient operation. The oscillator reduces the L T1938’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. The L T1938 contains a power good comparator which trips when the FB pin is at 90% of its regulated value. The PG output is an open-collector transistor that is off when the output is in regulation, allowing an external resistor to pull the PG pin high. Power good is valid when the L T1938 is enabled and V IN is above 3.6V . OPERATION

Reference designators refer to the Block Diagram. the inductor and capacitor values small. IN and BOOST pins, and on operating mode. Figure 1. Switching Frequency vs RT Value

25V are acceptable regardless of the switching frequency. maximum duty cycle (see equation in previous section). switching frequency should be used. and switching frequency will determine the ripple current. Table 1. Inductor Vendors

Of course, such a simple design guide will not always re- sult in the optimum inductor for your application. A larger value inductor provides a slightly higher maximum load current and will reduce the output voltage ripple. If your load is lower than 2A, then you can decrease the value of the inductor and operate with higher ripple current. This allows you to use a physically smaller inductor , or one with a lower DCR resulting in higher efficiency. 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 T1938 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 T1938 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 significant inductance due to long wires or cables, additional bulk capacitance may be necessary. This can be provided with a low 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 T1938 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 T1938 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 T1938. A ceramic input capacitor combined with trace or cable inductance forms a high quality (under damped) tank circuit. If the L T1938 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the L T1938’s voltage rating. This situation is easily avoided (see the Hot Plugging Safety section). For space sensitive applications, a 2.2µF ceramic capaci- tor can be used for local bypassing of the L T1938 input. However , the lower input capacitance will result in in- creased input current ripple and input voltage ripple, and may couple noise into other circuitry. Also, the increased voltage ripple will raise the minimum operating voltage of the L T1938 to ~3.7V . Output Capacitor and Output Ripple The output capacitor has two essential functions. Along with the inductor , it filters the square wave generated by the L T1938 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 T1938’s control loop. Ceramic capacitors have very low equivalent series resistance (ESR) and provide the best ripple performance. A good starting value is: C VfOUT OUT SW = 100 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. APPLICATIONS INFORMATION

operating conditions (applied voltage and temperature). electrolytic capacitors can be used for the output capacitor . several Schottky diodes and their manufacturers. Table 3. Diode Vendors output capacitor has high ESR. Table 2. Capacitor Vendors

the compensation network to optimize the performance. shows an equivalent circuit for the L T1938 control loop. frequency is much lower than the switching frequency. Figure 3. T ransient Load Response of the L T1938 Front Page Figure 2. Model for Loop Response

1938 F02

500mA to 1500mA and back to 500mA. pin quiescent current comes from a lower voltage source. of the BOOST and BIAS pins are not exceeded.

1938 F03

to start will be the same as the minimum input to run. input voltage to maintain regulation. Figure 4. Three Circuits For Generating The Boost Voltage Figure 5. The Minimum Input Voltage Depends on

1938 F04

1938 F05

reducing the maximum input current during start-up. up and shut-down waveforms with the soft-start circuit. protects against a shorted or reversed input. a local, unbroken ground plane below these components. 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. Figure 6. To Soft-Start the L T1938, Add a Resisitor

1938 F06

Figure 7. Diode D4 Prevents a Shorted Input from

1938 F07

Figure 8. A Good PCB Layout Ensures Proper , Low EMI Operation

1938 F08

a 5V output at full load operating from 24V . 100 LFPM airflow, this resistance can fall by another 25%.

temperature approaches 125°C. Figure 9. A Well Chosen Input Network Prevents Input Voltage Overshoot and

1938 F09

3.3V Step-Down Converter SW BIAS FB VC PG RT VIN BD VIN 6.3V TO 25V VOUT 2.2A 4.7µF 0.47µF 22µF200k f = 800kHz D: DIODES INC. DFLS230L L: TAIYO YUDEN NP06DZB6R8M D 20k 60.4k L 6.8µH 590k GND 680pF ON OFF L T1938

1938 TA02

4.4V TO 25V VOUT 3.3V 2.2A 4.7µF 0.47µF 22µF200k f = 800kHz D: DIODES INC. DFLS230L L: TAIYO YUDEN NP06DZB4R7M D 16.2k 60.4k L 4.7µH 324k GND 680pF ON OFF L T1938

1938 TA03

2.5V Step-Down Converter 5V , 2MHz Step-Down Converter SW BIAS FB VC PG RT VIN BD VIN 4V TO 25V VOUT 2.5V 2.2A 4.7µF 1µF 47µF200k f = 600kHz D1: DIODES INC. DFLS230L D2: MBR0540 L: TAIYO YUDEN NP06DZB4R7M 22.1k 84.5k L 4.7µH 196k GND 680pF ON OFF L T1938

3684 TA04

8.6V TO 22V VOUT 2.2µF 0.47µF 10µF200k f = 2MHz D: DIODES INC. DFLS230L L: SUMIDA CDRH4D22/HP-2R2 D 20k 16.9k L 2.2µH 590k GND 680pF ON OFF L T1938

1938 TA05

2.2A 10µF 0.47µF 22µF100k f = 800kHz D: DIODES INC. DFLS230L L: NEC/TOKIN PLC-0755-100 D 30k 60.4k L 10µH 845k GND 680pF ON OFF L T1938

3684 TA06

1.8V Step-Down Converter SW BIAS FB VC PG RT VIN BD VIN 3.5V TO 25V VOUT 1.8V 2.2A 4.7µF 0.47µF 47µF200k f = 500kHz D: DIODES INC. DFLS230L L: TAIYO YUDEN NP06DZB3R3M D 15.4k 105k L 3.3µH 84.5k GND 680pF ON OFF L T1938

1938 TA07

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. 10-Lead Plastic DFN (3mm × 3mm) (Reference L TC DWG # 05-08-1699) PACKAgE DESCRIPTION 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

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com  LINEAR TECHNOLOGY CORPORA TION 2007 LT 1107 REV A • 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) = 12V , IQ = 1.6mA, ISD < 1µA, ThinSOTTM Package L T3437 60V , 400mA (I OUT), MicroPower Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 80V , VOUT(MIN) = 1.25V , IQ = 100µA, ISD < 1µA, DFN Package L T1936 36V , 1.4A (I OUT), 500kHz High Efficiency 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 Efficiency Step-Down DC/DC Converter VIN: 3.6V to 40V , VOUT(MIN) = 0.8V , IQ = 1.9mA, ISD < 1µA, DFN Package L T1976/L T1977 60V , 1.2A (IOUT), 200kHz/500kHz, High Efficiency Step- Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 60V , VOUT(MIN) = 1.20V , IQ = 100µA, ISD < 1µA, TSSOP16E Package L T1767 25V , 1.2A (I OUT), 1.1MHz, High Efficiency Step-Down DC/DC Converter VIN: 3V to 25V , VOUT(MIN) = 1.20V , IQ = 1mA, ISD < 6µA, MS8E Package L T1940 Dual 25V , 1.4A (I OUT), 1.1MHz, High Efficiency Step-Down DC/DC Converter VIN: 3.6V to 25V , VOUT(MIN) = 1.20V , IQ = 3.8mA, ISD < 30µA, TSSOP16E Package L T1766 60V , 1.2A (I OUT), 200kHz, High Efficiency Step-Down DC/DC Converter VIN: 5.5V to 60V , VOUT(MIN) = 1.20V , IQ = 2.5mA, ISD < 25µA, TSSOP16E Package L T3434/L T3435 60V , 2.4A (IOUT), 200/500kHz, High Efficiency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 60V , VOUT(MIN) = 1.20V , IQ = 100µA, ISD < 1µA, TSSOP16E Package L T3481 36V , 2A (I OUT), Micropower 2.8MHz, High Efficiency Step-Down DC/DC Converter VIN: 3.6V to 36V , VOUT(MIN) = 1.265V , IQ = 5µA, ISD < 1µA, 3mm × 3mm DFN and MS10E Packages 1.265V Step-Down Converter SW BIAS FB VC PG RT VIN BD VIN 3.6V TO 25V VOUT 1.265V 2.2A 4.7µF 0.47µF 47µF f = 500kHz D: DIODES INC. DFLS240L L: TAIYO YUDEN NP06DZB3R3M D 13k 105k L 3.3µH GND 680pF ON OFF L T1938

1938 TA08