LT1936 LINER | Alldatasheet
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FEATURES
APPLICATIONS
DESCRIPTION
1.4A, 500kHz Step-Down Switching Regulator The L T®1936 is a current mode PWM step-down DC/DC converter with an internal 1.9A power switch, packaged in a tiny, thermally enhanced 8-lead MSOP. The wide in- put range of 3.6V to 36V makes the L T1936 suitable for regulating power from a wide variety of sources, including automotive batteries, 24V industrial supplies and unregu- lated wall adapters. Its high operating frequency allows the use of small, low cost inductors and ceramic capacitors, resulting in low, predictable output ripple. Cycle-by-cycle current limit, frequency foldback and thermal shutdown provide protection against shorted outputs, and soft-start eliminates input current surge during start-up. T ransient response can be optimized by using external compensation components, or board space can be minimized by using internal compensation. The low current (<2μA) shutdown mode enables easy power management in battery-powered systems. ■ Wide Input Range: 3.6V to 36V ■ Short-Circuit Protected Over Full Input Range ■ 1.9A Guaranteed Minimum Switch Current ■ 5V at 1.4A from 10V to 36V Input ■ 3.3V at 1.4A from 7V to 36V Input ■ 5V at 1.2A from 6.3V to 36V Input ■ 3.3V at 1.2A from 4.5V to 36V Input ■ Output Adjustable Down to 1.20V ■ 500kHz Fixed Frequency Operation ■ Soft-Start ■ Uses Small Ceramic Capacitors ■ Internal or External Compensation ■ Low Shutdown Current: <2μA ■ Thermally Enhanced 8-Lead MSOP Package ■ Automotive Battery Regulation ■ Industrial Control Supplies ■ Unregulated Wall Adapters 3.3V Step-Down Converter Effi ciency VIN 4.5V TO 36V ON OFF 0.22μF 10μH 17.4k 22μF
1936 TA01a
4.7μF VOUT 3.3V 1.2A VIN BOOST VC GND COMP FB L T1936 SHDN SW 10k LOAD CURRENT (A) EFFICIENCY (%) 0.5 1
1936 TA01b
1.5
90 VOUT = 5V
VIN = 12V VOUT = 3.3V L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
ELECTRICAL CHARACTERISTICS
FB, V Operating Temperature Range (Note 2) Maximum Junction Temperature (Note 1) BOOST V IN SW GND COMP V C FB SHDN TOP VIEW MS8E PACKAGE 8-LEAD PLASTIC MSOP θJA = 40°C/W , θJC = 10°C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB The ● denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 12V , VBOOST = 17V , unless otherwise noted. (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS Undervoltage Lockout 3.45 3.6 V Quiescent Current V FB = 1.5V 1.8 2.5 mA Quiescent Current in Shutdown V SHDN = 0V 0.1 2 μA FB Voltage ● 1.175 1.200 1.215 V FB Pin Bias Current (Note 4) V FB = 1.20V , E and I Grades H Grade 200 300 nA nA FB Voltage Line Regulation V IN = 5V to 36V 0.01 %/V Error Amp gm V C = 0.5V , IVC = ±5μA 250 μS Error Amp Voltage Gain V C = 0.8V , 1.2V 150 ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE L T1936EMS8E#PBF L T1936EMS8E#TRPBF L TBMT 8-Lead Plastic MSOP –40°C to 85°C L T1936IMS8E#PBF L T1936IMS8E#TRPBF L TBRV 8-Lead Plastic MSOP –40°C to 125°C L T1936HMS8E#PBF L T1936HMS8E#TRPBF L TBWB 8-Lead Plastic MSOP –40°C to 150°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE L T1936EMS8E L T1936EMS8E#TR L TBMT 8-Lead Plastic MSOP –40°C to 85°C L T1936IMS8E L T1936IMS8E#TR L TBRV 8-Lead Plastic MSOP –40°C to 125°C L T1936HMS8E L T1936HMS8E#TR L TBWB 8-Lead Plastic MSOP –40°C to 150°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. 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/
LOAD CURRENT (A) EFFICIENCY (%) 100 0.5 1.0
1936 G02
1.5 VOUT = 3.3V TA = 25°C D1 = DFLS140L L1 = 10μH, TOKO D63CB VIN = 5V VIN = 12V VIN = 24V LOAD CURRENT (A) EFFICIENCY (%) 100 0.5 1.0
1936 G01
1.5 VOUT = 5V TA = 25°C D1 = DFLS140L L1 = 15μH, TOKO D63CB VIN = 12V VIN = 24V DUTY CYCLE (%) CURRENT LIMIT (A) 0.5 1.0 1.5 2.0 2.5 3.0 20 40 TYP MIN 60 80
1936 G03
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 T1936E is guaranteed to meet performance specifi cations from 0°C to 70°C. Specifi cations over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation The ● denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 12V , VBOOST = 17V , unless otherwise noted. (Note 2) VC Clamp 1.8 V VC Switch Threshold 0.7 V Internal Compensation R 50 kΩ Internal Compensation C V COMP = 1V 150 pF COMP Pin Leakage V COMP = 1.8V , E and I Grades H Grade μA μA Switching Frequency V FB = 1.1V VFB = 0V 400 500 600 kHz kHz Maximum Duty Cycle ● 87 92 % Switch Current Limit (Note 3) 1.9 2.2 2.6 A Switch V CESAT ISW = 1.2A 410 520 mV Switch Leakage Current 2μ A Minimum BOOST Voltage Above SW I SW = 1.2A 2 2.2 V BOOST Pin Current I SW = 1.2A 28 50 mA BOOST Pin Leakage V SW = 0V 0.1 1 μA SHDN Input Voltage High 2.3 V SHDN Input Voltage Low 0.3 V SHDN Pin Current V SHDN = 2.3V (Note 5) VSHDN = 12V (Note 5) VSHDN = 0V 140 0.01 240 0.1 μA μA μA with statistical process controls. The L T1936I specifi cations are guaranteed over the –40°C to 125°C temperature range. The L T1936H specifi cations are guaranteed over the –40°C to 150°C temperature range. Note 3: Current limit guaranteed by design and/or correlation to static test. Slope compensation reduces current limit at higher duty cycle. Note 4: Current fl ows out of pin. Note 5: Current fl ows into pin. TYPICAL PERFORMANCE CHARACTERISTICS Effi ciency, VOUT = 5V Effi ciency, V OUT = 3.3V Switch Current Limit
INPUT VOL TAGE (V) 1.0 LOAD CURRENT (A) 1.2 1.4 1.6 1.8 10 2051 5 2 5
1936 G04
VOUT = 5V L = 15μH L = 10μH INPUT VOL TAGE (V) 1.0 LOAD CURRENT (A) 1.2 1.4 1.6 1.8 10 2051 5 2 5
1936 G05
VOUT = 3.3V L = 6.8μH L = 10μH SWITCH CURRENT (A) SWITCH VOL TAGE DROP (mV)100 200 300 400 600 0.5 1.0
1936 G06
1.5 500 TA = –45°C TA = 85°C TA = 25°C TEMPERATURE (°C)
1.185 FEEDBACK VOL TAGE (V)
1.195 1.210
1936 G07
1.190 1.205 1.200 –50 –25 0 25 50 75 100 150 125 TEMPERATURE (°C) –50 3.0 UVLO (V) 3.2 3.4 3.6 3.8 –25 0 25 50
1936 G08
TEMPERATURE (°C) –50
400 SWITCHING FREQUENCY (kHz)
–25 0 25 50
1936 G09
FB PIN VOLTAGE (V) 700 TA = 25°C 600 500 400 300 200 100
1936 G10
0.5 1.0 1.5 SWITCHING FREQUENCY (kHz) SHDN PIN VOLTAGE (V) SWITCH CURRENT LIMIT (A) 0.5 1.0 1.5 2.0 2.5
3.0 TA = 25°C
DC = 30% 12 34
1936 G11
SHDN PIN VOLTAGE (V) SHDN PIN CURRENT (μA) 100 150 200
1936 G12
TA = 25°C TYPICAL PERFORMANCE CHARACTERISTICS Maximum Load Current Maximum Load Current Switch Voltage Drop Feedback Voltage Undervoltage Lockout Switching Frequency Frequency Foldback Soft-Start SHDN Pin Current
LOAD CURRENT (mA) 4.0 INPUT VOLTAGE (V) 4.5 5.0 5.5 6.0 6.5 7.0 10 100 1000
1936 G13
VOUT = 5V TA = 25°C L = 15μH LOAD CURRENT (mA) 3.0 INPUT VOLTAGE (V) 3.5 4.0 4.5 5.0 10 100 1000
1936 G14
VOUT = 3.3V TA = 25°C L = 10μH TEMPERATURE (°C) –50 SWITCH CURRENT LIMIT (A) 2.0 2.5 3.0 25 75
1936 G15
1.5 1.0 –25 0 50 100 150 125 0.5 VSW 10V/DIV IL 500mA/DIV VOUT 20mV/DIV 1μs/DIVVIN = 12V VOUT = 3.3V IOUT = 1A L = 10μH C OUT = 22μF
1936 G16
1μs/DIVVIN = 12V VOUT = 3.3V IOUT = 50mA L = 10μH C OUT = 22μF
1936 G17
TEMPERATURE (°C) –50 –25 0.5 VC VOLTAGE (V) 1.5 05 0 7 5
1936 G18
1.0 2.5 2.0 25 100 150 125 CURRENT LIMIT CLAMP SWITCHING THRESHOLD FB PIN VOLTAGE (V) –60 VC PIN CURRENT (μA) –40 –20
1936 G19
TA = 25°C VC = 0.5V TYPICAL PERFORMANCE CHARACTERISTICS Minimum Input Voltage Minimum Input Voltage Switch Current Limit Switching Waveforms Switching Waveforms, Discontinuous Mode VC Voltages Error Amp Output Current
BOOST (Pin 1): The BOOST pin is used to provide a drive voltage, higher than the input voltage, to the internal bipolar NPN power switch. V IN (Pin 2): The VIN pin supplies current to the L T1936’s internal regulator and to the internal power switch. This pin must be locally bypassed. 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 . GND (Pin 4): Tie the GND pin to a local ground plane below the L T1936 and the circuit components. Return the feedback divider to this pin. SHDN (Pin 5): The SHDN pin is used to put the L T1936 in shutdown mode. Tie to ground to shut down the L T1936. Tie to 2.3V or more for normal operation. If the shutdown feature is not used, tie this pin to the V IN pin. SHDN also provides a soft-start function; see the Applications Infor- mation. Do not drive SHDN more than 5V above V IN. FB (Pin 6): The L T1936 regulates its feedback pin to 1.200V . Connect the feedback resistor divider tap to this pin. Set the output voltage according to V OUT = 1.200V (1 + R1/R2). A good value for R2 is 10k. VC (Pin 7): The VC pin is used to compensate the L T1936 control loop by tying an external RC network from this pin to ground. The COMP pin provides access to an internal RC network that can be used instead of the external components. COMP (Pin 8): To use the internal compensation network, tie the COMP pin to the V C pin. Otherwise, tie COMP to ground or leave it fl oating. Exposed Pad (Pin 9): The Exposed Pad must be soldered to the PCB and electrically connected to ground. Use a large ground plane and thermal vias to optimize thermal performance. R DRIVER Q1S OSC SLOPE COMP FREQUENCY FOLDBACK INT REG AND UVLO VC gm 1.200V 1936 BD Q Q BOOST SW 6FB GND RC 50k CC 150pF VOUT C1D1 VIN VIN ON OFF COMP7 VC SHDN
OPERATION (Refer to Block Diagram) The L T1936 is a constant frequency, current mode step- down regulator . A 500kHz oscillator enables an RS fl ip-fl op, turning on the internal 1.9A power switch Q1. An ampli- fi 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 (not shown) on the V C pin provides current limit. The VC pin is also clamped to the voltage on the SHDN pin; soft-start is implemented by generating a voltage ramp at the SHDN pin using an external resistor and capacitor . An internal regulator provides power to the control circuitry. This regulator includes an undervoltage lockout to prevent switching when V IN is less than ~3.45V . The SHDN pin is used to place the L T1936 in shutdown, disconnecting the output and reducing the input current to less than 2μA. 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 opera- tion. The oscillator reduces the L T1936’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.
R2 should be 20k or less to avoid bias current errors. Reference designators refer to the Block Diagram. Table 1. Inductor Vendors
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 operation, 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. Choosing L greater than 1.6 OUT + VD) μH prevents subharmonic oscillations at all duty cycles. Catch Diode A 1A Schottky diode is recommended for the catch diode, D1. The diode must have a reverse voltage rating equal to or greater than the maximum input voltage. The ON Semiconductor MBRM140 is a good choice. It is rated for 1A DC at a case temperature of 110°C and 1.5A at a case temperature of 95°C. Diode Incorporated’s DFLS140L is rated for 1.1A average current; the DFLS240L is rated for 2A average current. The average diode current in an L T1936 application is approximately I OUT (1 – DC). Input Capacitor Bypass the input of the L T1936 circuit with a 4.7μF or higher value ceramic capacitor of X7R or X5R type. Y5V types have poor performance over temperature and ap- plied voltage, and should not be used. A 4.7μF ceramic is adequate to bypass the L T1936 and will easily handle the ripple current. However , 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 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 T1936 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 T1936 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 T1936. A ceramic input capacitor combined with trace or cable inductance forms a high quality (under damped) tank circuit. If the L T1936 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the L T1936’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 T1936 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 T1936 to ~3.7V . Output Capacitor The output capacitor has two essential functions. Along with the inductor , it fi lters the square wave generated by the L T1936 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 T1936’s control loop. Ceramic capacitors have very low equivalent series re- sistance (ESR) and provide the best ripple performance. A good value is: C VOUT OUT = 150 where COUT is 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 high value capacitor if the compensation network is also adjusted to maintain the loop bandwidth. A lower value of output capacitor can be used, but transient performance will suffer . With an external compensation network, the loop gain can be lowered to compensate for the lower capacitor value. When using the internal compensa- tion network, the lowest value for stable operation is: C VOUT OUT > 66 APPLICATIONS INFORMATION
higher voltage rating, may be required. achieve low output ripple and small circuit size. tor (CC) and a resistor (RC) in series to ground are used. In addition, there may be lower value capacitor in parallel. used, tie COMP to ground or leave it fl oating. Figure 1. Model for Loop Response Table 2. Capacitor Vendors
1936 F01
Figure 2. T ransient Load Response of the L T1936 with Different Output
1936 F02
output capacitor choices and compensation schemes.
voltage rating of the BOOST pin is not exceeded. ambient temperature is –45°C, increasing to 1.2A at 0°C. section for a 2.5V schematic and performance curves. the absolute maximum rating of the BOOST pin. input voltage to maintain regulation. Figure 3. T wo Circuits for Generating the Boost Voltage
1933 F03
can supply 60μA when the SHDN pin reaches 2.3V . Figure 5. To Soft-Start the L T1936, Add a Resistor and Capacitor to the SHDN Pin. Figure 4. The Minimum Input Voltage Depends on Output Voltage, Load Current and Boost Circuit
1936 F04a
1936 F04b
1936 F05a
1936 F05b
a shorted or reversed input. Figure 6. Diode D4 Prevents a Shorted Input from Discharging Figure 7. A Good PCB Layout Ensures Low EMI Operation 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. 6.5cm circuit board in still air at a load current of 1.4A.
1936 F06
1936 F07
rings as high as 50V and the input current peaks at 26A. Figure 8. A Well Chosen Input Network Prevents Input Voltage Overshoot and
1936 F08
One method of damping the tank circuit is to add another capacitor with a series resistor to the circuit. In Figure 8b an aluminum electrolytic capacitor has been added. This capacitor’s high equivalent series resistance damps the circuit and eliminates the voltage overshoot. The extra capacitor improves low frequency ripple fi ltering and can slightly improve the effi ciency of the circuit, though it is likely to be the largest component in the circuit. An alternative solution is shown in Figure 8c. A 0.7Ω resistor is added in series with the input to eliminate the voltage overshoot (it also reduces the peak input current). A 0.1μF capacitor improves high frequency fi ltering. This solution is smaller and less expensive than the electrolytic capacitor . For high input voltages its impact on effi ciency is minor , reducing effi ciency by one percent for a 5V output at full load operating from 24V . 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 . Outputs Greater Than 6V For outputs greater than 6V , add a resistor of 1k to 2.5k across the inductor to damp the discontinuous ringing of the SW node, preventing unintended SW current. The 12V Step-Down Converter circuit in the Typical Applica- tions section shows the location of this resistor . Also note that for outputs above 6V , the input voltage range will be limited by the maximum rating of the BOOST pin. The 12V circuit shows how to overcome this limitation using an additional Zener diode. 3.3V Step-Down Converter TYPICAL APPLICATIONS VIN 4.5V TO 36V ON OFF 10μH 17.4k 47μF
1936 TA03
4.7μF 0.22μF VOUT 3.3V 1.2A VIN BOOST VC GND COMP FB L T1936 SHDN SW 10k
1.8V Step-Down Converter 1.2V Step-Down Converter Effi ciency, 1.8V Output Effi ciency, 1.2V Output VIN 3.6V TO 20V ON OFF 4.7μH 10k D1: DFLS140L D2: 1N4148 L1: TOKO D63CB 47μF
1936 TA05a
4.7μF 0.22μF VOUT 1.8V 1.3A VIN BOOST VC GND COMP FB L T1936 SHDN SW 20k LOAD CURRENT (A) EFFICIENCY (%) POWER LOSS (W) 0.5 1.0 1.5 2.0 0.5 1
1936 TA05b
1.5 POWER LOSS VIN = 5V VIN = 12V VOUT = 1.8V TA = 25°C VIN 3.6V TO 20V ON OFF 3.3μH D1: DFLS140L D2: 1N4148 L1: TOKO D63CB 47μF
1936 TA06a
4.7μF 0.22μF VOUT 1.2V 1.3A VIN BOOST VC GND COMP FB L T1936 SHDN SW 100k LOAD CURRENT (A) EFFICIENCY (%) POWER LOSS (W) 0.5 1.0 1.5 2.0 0.5 1
1936 TA06b
1.5 POWER LOSS VIN = 5V VIN = 12V VOUT = 1.2V TA = 25°C VIN 6.3V TO 36V ON OFF 15μH 31.6k 22μF
1936 TA04
4.7μF 0.22μF VOUT 1.2A VIN BOOST VC GND COMP FB L T1936 SHDN SW 10k
2.5V Step-Down Converter Effi ciency, 2.5V Output Minimum Input Voltage 12V Step-Down Converter LOAD CURRENT (A) EFFICIENCY (%) 100 0.5 1.0
1936 TA07b
1.5 VOUT = 2.5V TA = 25°C VIN = 12V VIN = 5V LOAD CURRENT (mA) INPUT VOL TAGE (V) 4.5 5.0
1936 TA07c
4.0 3.5 3.0 10 100 1000 5.5 V OUT = 2.5V TO START TA = –45°C TO RUN TA = –45°C TO START TA = 25°C TO RUN TA = 25°C VIN 3.6V TO 36V ON OFF 6.2μH 11k D1: DFLS140L D2: MBRO540 L1: TOKO D63CB 47μF
1936 TA07a
4.7μF 1μF VOUT 2.5V 1.2A T A > 0°C VIN BOOST VC GND COMP FB L T1936 SHDN SW 10k VIN 14.5V TO 36V ON OFF 22μH 182k C2 22μF
1936 TA08
2.2μF D1: MBRM140 D2: 1N4148 D3: CMDZ5235B 0.22μF 1.8k VOUT 12V 1.2A 6.8V VIN BOOST VC GND COMP FB L T1936 SHDN SW 20k
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. PACKAGE DESCRIPTION 8-Lead Plastic MSOP , Exposed Die Pad (Reference LTC DWG # 05-08-1662 Rev E) MSOP (MS8E) 0908 REV E 0.53 ± 0.152 (.021 ± .006) SEATING PLANE 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 0.18 (.007) 0.254 (.010) 1.10 (.043) MAX 0.22 – 0.38 (.009 – .015) TYP 0.86 (.034) REF 0.65 (.0256) BSC 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE 12 3 4 4.90 ± 0.152 (.193 ± .006) BOTTOM VIEW OF EXPOSED PAD OPTION 7 6 5 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 0.52 (.0205) REF 1.83 ± 0.102 (.072 ± .004) 2.06 ± 0.102 (.081 ± .004) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 2.083 ± 0.102 (.082 ± .004) 2.794 ± 0.102 (.110 ± .004) 0.889 ± 0.127 (.035 ± .005) RECOMMENDED SOLDER PAD LAYOUT 0.42 ± 0.038 (.0165 ± .0015) TYP 0.65 (.0256) BSC 0.1016 ± 0.0508 (.004 ± .002) DETAIL “B” DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. FOR REFERENCE ONL Y NO MEASUREMENT PURPOSE
0.05 REF
0.29 REF
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com © LINEAR TECHNOLOGY CORPORATION 2006 LT 1108 REV D • PRINTED IN USA RELATED PARTS TYPICAL APPLICATION 2.5V Step-Down Converter Minimum Input Voltage PART NUMBER DESCRIPTION COMMENTS L T1676 60V , 440mA (I OUT), 100kHz, High Effi ciency Step-Down DC/DC Converter VIN: 7.4V to 60V , VOUT(MIN) = 1.24V , IQ = 3.2mA, ISD = 2.5μA, L T1765 25V , 2.75A (I OUT), 1.25MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3V to 25V , VOUT(MIN) = 1.20V , IQ = 1mA, ISD = 15μA, SO-8 and 16-Lead TSSOPE Packages L T1766 60V , 1.2A (I OUT), 200kHz, High Effi ciency Step-Down DC/DC Converter VIN: 5.5V to 60V , VOUT(MIN) = 1.20V , IQ = 2.5mA, ISD = 25μA, 16-Lead TSSOP/TSSOPE Packages L T1767 25V , 1.2A (I OUT), 1.25MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3V to 25V , VOUT(MIN) = 1.20V , IQ = 1mA, ISD = 6μA, MS8/MS8E Packages L T1776 40V , 550mA (I OUT), 200kHz, High Effi ciency Step-Down DC/DC Converter VIN: 7.4V to 40V , VOUT(MIN) = 1.24V , IQ = 3.2mA, ISD = 30μA, N8/SO-8 Packages L T1933 600mA, 500kHz, Step-Down Switching Regulator in SOT-23 V IN: 3.6V to 36V , VOUT(MIN) = 1.25V , IQ = 1.6mA, ISD < 1μA, ThinSOT™ Package L T1940 25V , Dual 1.4A (I OUT), 1.1MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3V to 25V , VOUT(MIN) = 1.2V , IQ = 3.8mA, ISD < 1μA, 16-Lead TSSOPE Package L T1956 60V , 1.2A (I OUT), 500kHz, High Effi ciency Step-Down DC/DC Converter VIN: 5.5V to 60V , VOUT(MIN) = 1.20V , IQ = 2.5mA, ISD = 25μA, 16-Lead TSSOP/TSSOPE Packages L T1976 60V , 1.2A (I OUT), 200kHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 60V , VOUT(MIN) = 1.20V , IQ = 100μA, ISD < 1μA, 16-Lead TSSOPE Package L T3010 80V , 50mA, Low Noise Linear Regulator V IN: 1.5V to 80V , VOUT(MIN) = 1.28V , IQ = 30μA, ISD < 1μA, LT C 3407 Dual 600mA (I OUT), 1.5MHz, Synchronous Step-Down DC/DC Converter VIN: 2.5V to 5.5V , VOUT(MIN) = 0.6V , IQ = 40μA, ISD < 1μA, 10-Lead MSE Package L TC3412 2.5A (I OUT), 4MHz, Synchronous Step-Down DC/DC Converter VIN: 2.5V to 5.5V , VOUT(MIN) = 0.8V , IQ = 60μA, ISD < 1μA, 16-Lead TSSOPE Package L TC3414 4A (I OUT), 4MHz, Synchronous Step-Down DC/DC Converter V IN: 2.3V to 5.5V , VOUT(MIN) = 0.8V , IQ = 64μA, ISD < 1μA, 20-Lead TSSOPE Package L T3430/L T3431 60V , 2.75A (I OUT), 200kHz/500kHz, High Effi ciency Step-Down DC/DC Converters VIN: 5.5V to 60V , VOUT(MIN) = 1.20V , IQ = 2.5mA, ISD = 30μA, 16-Lead TSSOPE Package Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. VIN 3.6V TO 20V ON OFF 8.2μH D1: DFLS140L D2: 1N4148 L1: TOKO D63CB 47μF
1936 TA09a
4.7μF 0.22μF VOUT 2.5V 1.3A VIN BOOST VC GND COMP FB L T1936 SHDN SW 10k 11k LOAD CURRENT (mA) INPUT VOL TAGE (V) 4.5 5.0
1936 TA09b
4.0 3.5 3.0 10 100 1000 5.5 V OUT = 2.5V CONNECTING THE BOOST CIRCUIT TO THE INPUT LOWERS THE MINIMUM INPUT VOL TAGE TO RUN AND TO START TO LESS THAN 3.7V AT ALL LOADS