LT3509IDE-PBF

LT3509 LINER | Alldatasheet

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FEATURES

APPLICATIONS

DESCRIPTION

Dual 36V , 700mA Step-Down Regulator The L T®3509 is a dual, current mode, step-down switching regulator , with internal power switches each capable of providing 700mA output current. This regulator provides a compact and robust solution for multi-rail systems in harsh environments. It incorporates several protection features including overvoltage lockout and cycle by cycle current limit. Thermal shutdown provides additional protection. The loop compensation components and the boost diodes are integrated on-chip. Switching frequency is set by a single external resistor . External synchronization is also possible. The high maximum switching frequency allows the use of small inductors and ceramic capacitors for low ripple. Constant frequency operation above the AM band avoids interference with radio reception, making the L T3509 well suited for automotive applications. Each regulator has an independent shutdown and soft-start control pin. When both converters are powered down, the common circuitry enters a low current shutdown state. 3.3V and 5V Dual Output Step-Down Converter n Two 700mA Switching Regulators with Internal Power Switches n Wide 3.6V to 36V Operating Range n Over-Voltage Lockout Protects Circuit Through 60V Supply T ransients n Short Circuit Robust n Low Dropout Voltage − 95% Maximum Duty Cycle n Adjustable 300kHz to 2.2MHz Switching Frequency Synchronizable Over the Full Range n Uses Small Inductors and Ceramic Capacitors n Integrated Boost Diodes n Internal Compensation n Thermally Enhanced 14 Lead (4 mm × 3 mm) DFN and 16 Lead MSOP Packages n Automotive Electronics n Industrial Controls n Wall T ransformer Regulation n Networking Devices n CPU, DSP , or FPGA Power

3509 TA01a

10μH fSW = 700kHz 0.1μF0.1μF 6.5V TO 36V (T ransient to 60V) 2.2μF 6.8μH3.3V 700mA 700mA 10μF 10.2k 31.6k 53.6k MBRM140MBRM140 1nF 22μF 10.2k60.4k 1nF LOAD CURRENT (A) 0.0 EFFICIENCY (%) 0.7

3509 TA01b

0.1 0.2 0.6 0.50.40.3 VOUT = 3.3V VOUT = 5V VIN = 12V fSW = –700kHz Effi ciency L, L T , L TC and L TM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

RUN/SS, FB, R (Note 1) PIN CONFIGURATION ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T3509EDE#PBF L T3509EDE#TRPBF 3509 14-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L T3509IDE#PBF L T3509IDE#TRPBF 3509 14-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L T3509EMSE#PBF L T3509EMSE#TRPBF 3509 16-Lead Plastic MSOP with Exposed Pad –40°C to 125°C L T3509IMSE#PBF L T3509IMSE#TRPBF 3509 16-Lead Plastic MSOP with Exposed Pad –40°C to 125°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container . 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/ Operating Junction Temperature Range (Notes 3, 5) Lead Temperature (Soldering, 10 sec.) FB1 RUN/SS1 BD SYNC R T RUN/SS2 FB2 DA1 BOOST1 SW1 V IN SW2 BOOST2 DA2 TOP VIEW DE14 PACKAGE 14-LEAD (4mm s 3mm) PLASTIC DFN θJA = 43°C/W , θJC = 4.3°C/W EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB DA1 BOOST1 SW1 V IN VIN SW2 BOOST2 DA2 FB1 RUN/SS1 AGND BD SYNC R T RUN/SS2 FB2 TOP VIEW MSE PACKAGE 16-LEAD PLASTIC MSOP θJA = 43°C/W , θJC = 4.3°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB

ELECTRICAL CHARACTERISTICS

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. Absolute Maximum Voltage at the V IN pin is 60V for non-repetitive 1 second transients and 36V for continuous operation. Note 3. The L T3509E is guaranteed to meet performance specifi cations from 0°C to 125°C junction temperature. Specifi cations over the –40°C to 125°C operating junction temperature range are assured by design, characterization The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C, VIN = 12V , VBD = 5V . (Note 3) PARAMETER CONDITIONS MIN TYP MAX UNITS VIN Undervoltage Lockout 3.3 3.6 V VIN Overvoltage Lockout 37 38.5 40 V Input Quiescent Current Not Switching V FB > 0.8V 1.9 2.2 mA Input Shutdown Current V(RUN/SS[1,2]) < 0.3V 9 15 μA Feedback Pin Voltage l 0.784 0.8 0.816 V Reference Voltage Line Regulation 3.6V < V IN < 36V 0.01 %/V RUN/SS Shutdown Threshold 0.4 0.6 0.8 V RUN/SS Voltage for Full IOUT 2V RUN/SS Pin Pull-up Current 0.7 1 1.3 μA Feedback Pin Bias Current l 90 500 nA Switch Current Limit l 1.05 1.4 1.9 A DA Comparator Current Threshold 0.7 0.95 1.2 A Boost Pin Current I SW = 0.9A 22 36 mA Switch Leakage Current 0.01 1.0 μA Switch Saturation Voltage I SW = 0.9A (Note 4) 0.32 V Minumum Boost Voltage above Switch I SW = 0.9A 1.5 2.2 V Boost Diode Forward Voltage I BD= 20mA 0.7 0.9 V Boost Diode Leakage V R = 30V 0.1 5 μA Switching Frequency R T = 40.2kΩ RT = 180kΩ RT = 14.1kΩ l 0.92 237 2.0 1.0 264 2.2 1.08 290 2.5 MHz kHz MHz Switch Minimum Off Time l 80 150 ns and correlation with statistical process controls. The L T3509I is guaranteed over the full –40°C to 125°C temperature range. Note 4. Switch Saturation Voltage is guaranteed by design. Note 5. This IC includes over-temperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed the maximum operating temperature when overtemperature protection is active. Continuous operation above the specifi ed maximum operating junction temperature may impair device reliability.

TYPICAL PERFORMANCE CHARACTERISTICS ILOAD(A) EFFICIENCY (%) 0.8

3509 G01

0.2 0.4 0.6 VIN = 12V TA = 25ºC VIN = 24V ILOAD(A) EFFICIENCY (%) 0.8

3509 G02

0.2 0.4 0.6 VIN = 12V TA = 25ºC ILOAD(A) EFFICIENCY (%) 0.8

3509 G03

0.2 0.4 0.6 VIN = 12V TA = 25ºC ISW(A) VCE(SAT) (V) 1.00.8

3509 G04

0.05 0.1 0.15 0.2 0.25 0.3 0.2 0.4 0.6 0.35 TA = 25ºC ISW(A) IBOOST (mA) 0.8 1

3509 G05

0.2 0.4 0.6 TA = 25ºC BOOST DIODE CURRENT (mA) Vf (V) 100 150

3509 G06

0.2 0.4 0.6 0.8 1.2 TA = 25ºC RT(kΩ) FREQUENCY (MHz) 120 140100 160 180

3509 G07

0.5 1.0 1.5 2.0 2.2 60 8020 40 TA = 25ºC Effi ciency vs Load Current VOUT = 5V , fSW = 2.0MHz Effi ciency vs Load Current VOUT = 3.3V , fSW = 2.0MHz Effi ciency vs Load Current VOUT = 1.8V , fSW = 0.7MHz Switch VCE(SAT) vs ISW IBOOST vs ISW Boost Diode Characteristics Frequency vs RT

TEMPERATURE(ºC) −50 FSW (MHz) 100 12575

3509 G08

0.98 0.985 0.99 0.995 1.005 1.01 1.015 1.02 1.025 0.975 25 50−25 0 RT = 40.2k −50 100 125 7525 50−25 0 FBREF (V)

3509 G09

0.795 0.8 0.805 0.81 0.79 TEMPERATURE(ºC) FSW vs Temperature FB Pin Voltage vs. Temperature TYPICAL PERFORMANCE CHARACTERISTICS ILOAD (A) MAXIMUM VIN (V) 0.60.4 0.8

3509 G10

0.2 TA = 25ºC TA = 85ºC ILOAD (A) MAXIMUM VIN (V)

3509 G11

40 TA = 25ºC

TA = 85ºC 0.60.4 0.80.2 MINIMUM ON TIME (ns)

3509 G12

−50 100 125 7525 50−25 0 TEMPERATURE(ºC) Max VIN for Constant Frequency VOUT = 3.3V , fSW = 2MHz Max VIN for Constant Frequency VOUT = 5V , fSW = 2MHz Min ON Time vs. Temperature ILOAD = 0.3A TEMPERATURE (ºC) –40 ILIM (A) 120

3509 G13

0.5 1.5 0 40 80 DA SWITCH DUTY CYCLE (%) 01 0 ILIM (A) 100

3509 G14

0.2 0.4 0.6 0.8 1.2 1.4 1.6 20 30 40 50 60 70 80 90 1.8 TA = 25ºC ILIM vs Temperature ILIM vs Duty Cycle

DA1, DA2 (Pins 1, 7 / Pins 1, 8): The DA pins are the anode connections for the catch diodes. These are con- nected internally to the exposed ground pad by current sensing resistors. BOOST1, BOOST2 (Pins 2, 6 / Pins 2, 7): The BOOST pins are used to dynamically boost the power transistor base above V IN to minimize the voltage drop and power loss in the switch. These should be tied to the associated switch pins through the boost capacitors. SW1, SW2 (Pins 3, 5 / Pins 3, 6): The SW pins are the internal power switch outputs. These should be connected to the associated inductors, catch diode cathodes, and the boost capacitors. V IN (Pin 4 / Pins 4, 5): The VIN pins supply power to the internal power switches and control circuitry. In the MSE package the V IN pins must be tied together . The input capacitor should be placed as close as possible to the supply pins. FB1, FB2 (Pins 14, 8 / Pins 16, 9): The FB pins are used to set the regulated output voltage relative to the internal reference. These pins should be connected to a resistor divider from the regulated output such that the FB pin is at 0.8V when the output is at the desired voltage. RUN/SS1, RUN/SS2 (Pins 13, 9 / Pins 15, 10): The RUN/SS pins enable the associated regulator channel. If both pins are pulled to ground, the device will shut-down to a low power state. In the range 0.7V to 2.0V, the regulators are enabled but the peak switch current and the DA pin maxi- mum current are limited to provide a soft-start function. Above 2V , the full output current is available. The inputs incorporate a 1μA pull-up so that they will fl oat high or charge an external capacitor to provide a current limited soft-start. The pins are pulled down by approximately 250μA in the case of overvoltage or overtemperature conditions in order to discharge the soft-start capacitors. The pins can also be driven by a logic control signal of up to 5.0V . In this case, it is necessary place a 10k to 50k resistor in series along with a capacitor from the RUN/SS pin to ground to ensure that there will be a soft-start for both initial turn on and in the case of fault conditions. Do not tie these pins to V IN. RT (Pin 10 / Pin 11): The RT pin is used to set the internal oscillator frequency. A 40.2k resistor from RT to ground results in a nominal frequncy of 1MHz. SYNC (Pin 11 / Pin12): The SYNC pin allows the switching frequency to be synchronized to a external clock. Choose R T resistor to set a free-run frequency at least 12% less than the external clock frequency for correct operation. BD (Pin 12 / Pin 13): The BD pin is common anode con- nection of the internal Schottky boost diodes. This provides the power for charging the BOOST capacitors. It should be locally bypassed for best performance. GND (Exposed Pad): This is the reference and supply ground for the regulator . The exposed pad must be soldered to the PCB and electrically connected to supply ground. Use a large ground plane and thermal vias to optimize thermal performance. The current in the catch diodes also fl ows through the GND pad to the DA pins. AGND (Pin 14, MSE Package Only): This is the connected to the ground connection of the chip and may be used as a separate return for the low current control side components. It should not be used as the only ground connection or as a connection return for load side components. (DFN/MSE)

Figure 1. Functional Block Diagram

The L T3509 is a dual, constant frequency, current mode switching regulator with internal power switches. The two independent channels share a common voltage reference and oscillator and operate in phase. The switching frequency is set by a single resistor and can also be synchronized to an external clock. Operation can be best understood by referring to the Block Diagram (Figure 1). Startup and Shutdown When the RUN/SS[1,2] pins are pulled low (<0.3V) the associated regulator channel is shut-down. If both channels are shut down, the common circuitry also enters a low current state. When the RUN/SS pins exceed approximately 0.7V , the common circuitry and the associated regulator are enabled but the output current is limited. From 0.7V up to 2.0V the current limit increases until it reaches the full value. The RUN/SS pins also incorporate a 1μA pull-up to approximately 3V , so the regulator will run if they are left open. A capacitor to ground will cause a current limited soft-start to occur at power-up. In the case of undervoltage, overvoltage or over-temperature conditions the internal circuitry will pull the RUN/SS pins down with a current of approximately 250μA. Thus a new soft-start cycle will occur when the fault condition ends. Voltage and Current Regulation The power switches are controlled by a current-mode regulator architecture. The power switch is turned on at the beginning of each clock cycle and turned off by the Main Current Comparator . The inductor current will ramp up while the switch is on until it reaches the peak current threshold. The current at which it turns off is determined by the Error Amp and the internal compensation network. When the switch turns off, the current in the inductor will cause the SW pin to fall rapidly until the catch diode, D1, conducts. The voltage applied to the inductor will now reverse and the current will linearly fall. The resistor divider , R1 and R2, sets the desired output voltage such that when the voltage at FB reaches 0.8V , the Main Current Comparator threshold will fall and reduce the peak inductor current and hence the average current, until it matches the load current. By making current the controlled variable in the loop, the inductor impedance is effectively removed from the transfer function and the compensation network is simplifi ed. The Main Current Comparator threshold is reduced by the slope compensation signal to eliminate sub-harmonic oscillations at duty cycles >50%. Current Limiting Current mode control provides cycle by cycle current limiting by means of a clamp on the maximum current that can be provided by the switch. A comparator monitors the current fl owing through the catch diode via the DA pin. This comparator delays switching if the diode current is higher than 0.95A (typical). This current level is indicative of a fault condition such as a shorted output with a high input voltage. Switching will only resume once the diode current has fallen below the 0.95A limit. This way the DA comparator regulates the valley current of the inductor to 0.95A during a short circuit. This will ensure the part will survive a short circuit event. Over and Under Voltage Shutdown A basic under voltage lockout prevents switching if V IN is below 3.3V (typical). The overvoltage shutdown stops the part from switching when V IN is greater than 38.5V (typical). This protects the device and its load during momentary overvoltage events. After the input voltage falls below 38.5V , the part initiates a soft start sequence and resumes switching. BOOST Circuit To ensure best effi ciency and minimum dropout voltage the output transistor base drive is boosted above V IN by the external boost capacitors (C4). When the SW pin is low the capacitors are charged via the BOOST diodes and the supply on BD.

20kΩ or less to avoid bias current errors. Where fSW is in MHz and RT is in kΩ. Table 1. Standard E96 Resistors for Common Frequencies Figure 2. Soft-Start

The external synchronization provides a trigger to the internal oscillator . As such, it can only raise the frequency above the free-run value. To allow for device and component tolerances, the free run frequency should be set to at least 12% lower than the lowest supplied external synchronization reference. The oscillator and hence the switching frequency can then pushed up from 12% above the free-run frequency, set by the selected R T. For example, if the minimum external clock is 300kHz, the R T should be chosen for 264KHz. The SYNC input has a threshold of 1.0V nominal so it is compatible with most logic levels. The duty cycle is not critical provided the high or low pulse width is at least 80ns. Design Procedure Before starting detailed design a number of key design parameters should be established as these may affect design decisions and component choices along the way. One of the main things to determine apart from the desired output voltages is the input voltage range. Both the normal operating range and the extreme conditions of surges and/or dips or brown-outs need to be known. Then the operating frequency should be considered and if there are particular requirements to avoid interference. If there are very specifi c frequencies that need to be avoided then external synchronization may be needed. This could also be desirable if multiple switchers are used as low frequency beating between similar devices can be undesirable. For effi cient operation this converter requires a boost supply so that the base of the output transistor can be pumped above the input voltage during the switch on time. Depending on the input and output voltages the boost supply can be provided by the input voltage, one of the regulated outputs or an independent supply such as an LDO. Input Voltage Range Firstly, the L T3509 imposes some hard limits due to the undervoltage lock-out and the overvoltage protection. A given application will also have a reduced, normal operating range over which maximum effi ciency and lowest ripple are obtained. This usually requires that the device is operating at a fi xed frequency without skipping pulses. There may also be zones above and below the normal range where regulation is maintained but effi ciency and ripple may be compromised. At the low end, insuffi cient input voltage will cause loss of regulation and increased ripple–this is the dropout range. At the high end if the duty cycle becomes too low this will cause pulse skipping and excessive ripple. This is the pulse-skip region. Both situations also lead to higher noise at frequencies other than the chosen switching frequency. Occasional excursions into pulse-skip mode, during surges for example, may be tolerable. Pulse skipping will also occur at light loads even within the normal operating range but ripple is usually not degraded because at light load the output capacitor can hold the voltage steady between pulses. To ensure the regulator is operating in continuous mode it is necessary to calculate the duty cycle for the required output voltage over the full input voltage range. This must then be compared with minimum and maximum practical duty cycles.

off-cycle will be forced occasionally to maintain the charge. will be at a sub-multiple of the programmed frequency. for 3.3V and Figure 6 for 5.0V. discrete diodes in parallel. Figure 5. Minimum VIN for 3.3V VOUT

3509 F05

Figure 6. Minimum VIN for 5.0V VOUT

3509 F06

Figure 7. BD Tied to Regulated Output

3509 F07

Figure 8. The circuit in Figure 7 is more effi cient because the boost pin current comes from a lower voltage source. between the BOOST and SW pins is less than 30V . several vendors and types that are suitable. the inductor value and the input and output voltages.

3509 F08

Figure 8. Supplied from VIN

3509 F09

Figure 9. Separate Boost Supply

When the switch is off, the potential across the inductor is the output voltage plus the catch diode forward voltage. This gives the peak-to-peak ripple current in the inductor: ΔID C VV LfL OUT F SW = +(– ) 1 where: DC = Duty Cycle f SW = switching frequency L = inductor value V F = diode forward voltage. The peak inductor and switch current is: II I I SWPK LPK OUT L==+ Δ To maintain output regulation, this peak current must be less than the L T3509’s switch current limit ILIM. This is dependent on duty cycle due to the slope compensation. For I LIM is at least 1.4A at low duty cycles and decreases linearly to 1.0A at DC = 0.8. The theoretical minimum inductance can now be calcu- lated as: L DC f VV IIMIN MIN OUT F LIM OUT = +1–  – Where DCMIN is the minimum duty cycle called for by the application i.e. DC VV VV VMIN OUT MAX F IN MIN SW F () – There is a limit to the actual minimum duty cycle imposed by the minimum on time of the switch. For a robust design it is important that inductor that will not saturate when the switch is at its minimum on time, the input voltage is at maximum and the output is short-circuited. In this case the full input voltage, less the drop in the switch, will appear across the inductor . This doesn’t require an actual short, just starting into a capacitive load will provide the same conditions. The Diode current sensing scheme will ensure that the switch will not turn-on if the inductor current is above the DA current limit threshold, which has a maximum of 1.1A. The peak current under short-circuit conditions can then be calculated from: I Vt L APEAK IN ON MIN=+ .() 11 The inductor should have a saturation current greater than this value. For safe operation with high input voltages this can often mean using a physically larger inductor as higher value inductors often have lower saturation currents for a given core size. As a general rule the saturation current should be at least 1.8A to be short-circuit proof. However , it’s generally better to use an inductor larger than the minimum value. The minimum inductor has large ripple currents which increase core losses and require large output capacitors to keep output voltage ripple low. Select an inductor greater than L MIN that keeps the ripple current below 30% of ILIM. APPLICATIONS INFORMATION

Table 2. Recommended Inductors where fSW is in MHz and LMIN is in μH. RT frequency and not the SYNC frequency. to achieve low output ripple and small PCB footprint.

where ΔIL is the peak-to-peak ripple current in the inductor . may be unacceptable. Use X7R and X5R types.

3509 F10

Figure 10. Small Signal Equivalent Circuit may improve the transient response. the presence of output capacitor series resistance (ESR). and small circuit size, are therefore an option.

IN pin will not cause any problems to the device. a larger capacitor such as 4.7μF is preferred.

3509 F11

Figure 11. T ransient Load Response with Different Combinations

will then increase to the typical peak switch current limit. Table 3. Schottky Diodes L T3509 will tolerate a short-circuit on one or both outputs. and up to 2mA could be drawn from the backup supply. IN. This will also protect against a reversed input polarity. These concepts are illustrated in Figure 12.

3509 F12

Figure 12. Reverse Bias Protection

3509 TA03

15μH0.22μF UPS140 UPS140 0.22μF VIN = 4.5V TO 36V TRANSIENT TO 60V 2.2μF 10μHVOUT = 1.8V 0.7A 22μF 10k 178k 12.4k 31.6k 22nF 22μF 10k 22nF CLOCK 1.6V 0.4V VOUT = 3.3V 0.7A NOTE: RT CHOSEN FOR 264kHz 1.8V and 3.3V Outputs, Synchronized to 300kHz to 600kHz TYPICAL APPLICATIONS

3509 TA04

10μH0.22μF0.22μF 2.2μF 6.8μH 10μF 22nF 10k 40.2k 52.3k 10k 90.9k 10μF0.1μF 10k VIN = 9.4V TO 36V DISPLAY POWER CONTROL 0V = OFF 3.3V = ON VOUT = 5V 0.7A VOUT = 8V 0.7A fSW = 1MHz Automotive Accessory Application 5V Logic Supply and 8V for LCD Display with Display Power Controlled by Logic TYPICAL APPLICATIONS

14-Lead Plastic DFN (4mm × 3mm) (Reference L TC DWG # 05-08-1708 Rev B) 3.00 p0.10 (2 SIDES) 4.00 p0.10 (2 SIDES) NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WGED-3) IN JEDEC PACKAGE OUTLINE MO-229 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 0.40 p 0.10 BOTTOM VIEW—EXPOSED PAD 1.70 p 0.10 0.75 p0.05 R = 0.115 TYP R = 0.05 TYP

3.00 REF

1.70 p 0.05 148 PIN 1 TOP MARK (SEE NOTE 6)

0.200 REF

0.00 – 0.05 (DE14) DFN 0806 REV B PIN 1 NOTCH R = 0.20 OR 0.35 s 45o CHAMFER RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 2.20 p0.05 0.70 p0.05 3.60 p0.05 PACKAGE OUTLINE 0.25 p 0.05 0.25 p 0.05

0.50 BSC

3.30 p0.05 3.30 p0.10

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 16-Lead Plastic MSOP, Exposed Die Pad (Reference L TC DWG # 05-08-1667 Rev A) MSOP (MSE16) 0608 REV A 0.53 p 0.152 (.021 p .006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.17 – 0.27 (.007 – .011) TYP 0.86 (.034) REF 0.50 (.0197) BSC 16151413121110 12345678 1 8 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) 0o – 6o TYP DETAIL “A” DETAIL “A” GAUGE PLANE 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 p 0.127 (.035 p .005) RECOMMENDED SOLDER PAD LAYOUT 0.305 p 0.038 (.0120 p .0015) TYP 0.50 (.0197) BSC BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 p 0.102 (.112 p .004) 2.845 p 0.102 (.112 p .004) 4.039 p 0.102 (.159 p .004) (NOTE 3) 1.651 p 0.102 (.065 p .004) 1.651 p 0.102 (.065 p .004) 0.1016 p 0.0508 (.004 p .002) 3.00 p 0.102 (.118 p .004) (NOTE 4) 0.280 p 0.076 (.011 p .003) REF 4.90 p 0.152 (.193 p .006) DETAIL “B” DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. FOR REFERENCE ONL Y NO MEASUREMENT PURPOS

0.12 REF

0.35 REF

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 0109 • PRINTED IN USA RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1766 60V , 1.2A (I OUT), 200kHz, High Effi ciency Step-Down DC/DC Converter VIN: 5.5V to 60V, VOUT: 1.20V, IQ = 2.5mA, ISD < 25μA, TSSOP16/E Package LT1936 36V , 1.4A (I OUT) , 500kHz High Effi ciency Step-Down DC/DC Converter VIN: 36V to 36V, VOUT: 1.20V, IQ = 1.9mA, ISD < 1μA, MS8E Package LT1939 25V , 2A, 2.5MHz High Effi ciency DC/DC Converter and LDO ControllerVIN: 3.6V to 25V, VOUT: 0.8V, IQ = 2.5μA, ISD < 10μA, 3mm × 3mm DFN-10 L T1976/ L T1977 60V , 1.2A (IOUT), 200/500kHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 60V, VOUT: 1.20V, IQ = 100μA, ISD < 1μA, TSSOP16E Package L T3434/ L T3435 60V , 2.4A (IOUT), 200/500kHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 60V, VOUT: 1.20V, IQ = 100μA, ISD < 1μA, TSSOP16E Package L T3437 60V , 400mA (I OUT),MicroPower Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 60V, VOUT: 1.25V, IQ = 100μA, ISD < 1μA, 3mm × 3mm L T3480 36V with T ransient Protection to 60V , 2A (I OUT), 2.4MHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.6V to 38V, VOUT: 0.78V, IQ = 70μA, ISD < 1μA, 3mm × 3mm L T3481 34V with T ransient Protection to 36V , 2A (I OUT), 2.8MHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.6V to 34V, VOUT: 1.26V, IQ = 50μA, ISD < 1μA, 3mm × 3mm L T3493 36V , 1.4A(I OUT), 750kHz High Effi ciency Step-Down DC/DC Converter VIN: 36V to 36V, VOUT: 0.8V, IQ = 1.9mA, ISD < 1μA, 2mm × 3mm L T3500 36V , 40Vmax, 2A, 2.5MHz High Effi ciency DC/DC Converter and LDO Controller VIN: 3.6V to 36V, VOUT: 0.8V, IQ = 2.5mA, ISD < 10μA, 3mm × 3mm DFN-10 L T3501 25V , Dual 3A (I OUT), 1.5MHz High Effi ciency Step-Down DC/DC Converter VIN: 3.3V to 25V, VOUT: 0.8V, IQ = 3.7mA, ISD = 10μA, TSSOP-20E Package L T3505 36V with T ransient Protection to 40V , 1.4A (I OUT), 3MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 34V, VOUT: 0.78V, IQ = 2mA, ISD < 2μA, 3mm × 3mm L T3506/ L T3506A 25V , Dual 1.6A (IOUT), 575kHz,/1.1MHz High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 25V, VOUT: 0.8V, IQ = 3.8mA, ISD = 30μA, 5mm × 4mm L T3507 36V 2.5MHz, T riple (2.4A + 1.5A + 1.5A (I OUT)) with LDO Controller High Effi ciency Step-Down DC/DC Converter VIN: 4V to 36V, VOUT: 0.8V, IQ = 7mA, ISD = 1μA, 5mm × 7mm QFN-38 L T3508 36V with T ransient Protection to 40V , Dual 1.4A (I OUT), 3MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3.7V to 37V, VOUT: 0.8V, IQ = 4.6mA, ISD = 1μA, 4mm × 4mm L T3510 25V , Dual 2A (I OUT), 1.5MHz High Effi ciency Step-Down DC/DC Converter VIN: 3.3V to 25V, VOUT: 0.8V, IQ = 3.7mA, ISD = 10μA, TSSOP-20E Package L T3684 34V with T ransient Protection to 36V , 2A (I OUT), 2.8MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 34V, VOUT: 1.26V, IQ = 850μA, I SD < 1μA, 3mm × 3mm L T3685 36V with T ransient Protection to 60V , 2A (I OUT), 2.4MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 38V, VOUT: 0.78V, IQ = 70μA, ISD < 1μA, 3mm × 3mm Burst Mode is a trademark of Linear Technology Corporation.

3509 TA02

4.7μH0.1μF0.1μF 2.2μF 6.8μH VOUT = 5V 0.7A VOUT = 3.3V 0.7A 10μF 22nF 10k 16.9k 52.3k 31.6k 10μF 22nF 10k VIN = 6.5V TO 16V TRANSIENT TO 60V fSW = 2MHz 2MHz, 5V and 3.3V Outputs TYPICAL APPLICATIONS