LT1910ES8

LT1910 LINER

Document overview

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Technical content

n 8V to 48V Power Supply Range n Protected from –15V to 60V Supply Transients n Short-Circuit Protected n Automatic Restart Timer n Open-Collector Fault Flag n Fully Enhances N-Channel MOSFET Switches n Programmable Current Limit, Delay Time and Autorestart Period n Voltage Limited Gate Drive n Defaults to OFF State with Open Input n Available in SO-8 Package n Industrial Control n Avionics Systems n Automotive Switches n Stepper Motor and DC Motor Control n Electronic Circuit Breaker , LTC and LT are registered trademarks of Linear Technology Corporation. The LT 1910 is a high side gate driver that allows the use of low cost N-channel power MOSFETs for high side switching applications. It contains a completely self-con- tained charge pump to fully enhance an N-channel MOSFET switch with no external components. When the internal drain comparator senses that the switch current has exceeded the preset level, the switch is turned off and a fault flag is asserted. The switch remains off for a period of time set by an external timing capacitor and then automatically attempts to restart. If the fault still exists, this cycle repeats until the fault is removed, thus protecting the MOSFET. The fault flag becomes inactive once the switch restarts successfully. The LT1910 has been specifically designed for harsh operating environments such as industrial, avionics and automotive applications where poor supply regulation and/or transients may be present. The device will not sustain damage from supply transients of –15V to 60V. The LT1910 is available in the SO-8 package. FAULT IN TIMER V SENSE GATE LT19105.1k 24V5V FAULT OUTPUT OFF ON GND IRFZ34

1910 TA01

10µF 50V0.1µF 0.01Ω LOAD Fault Protected High Side Switch LOAD CURRENT (A) TOTAL DROP (V) 0.30 0.40 0.50

1910 TA02

0.20 0.10 0.25 0.35 0.45 0.15 0.05 1 2 3 5Switch Drop vs Load Current DESCRIPTIO UFEATURES APPLICATIO SU TYPICAL APPLICATIO U

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IS Supply Current (OFF State) V + = 48V, VIN = 0.8V 1.2 1.9 2.5 mA DIS(ON) Delta Supply Current (ON State) V IN = 2V, Measure Increase in IS 0.8 1.2 mA VINH Input High Voltage l 2V VINL Input Low Voltage l 0.8 V IIN Input Current V IN = 2V l 15 30 50 mA VIN = 5V l 55 110 185 mA CIN Input Capacitance (Note 3) 5p F VT(TH) Timer Threshold Voltage V IN = 2V, Adjust VT l 2.6 2.9 3.2 V VT(CL) Timer Clamp Voltage V IN = 0.8V 3.2 3.5 3.8 V IT Timer Charge Current V IN = VT = 2V 9 14 20 mA VSENSE Drain Sense Threshold Voltage 50 65 80 mV Temperature Coefficient (Note 3) 0.33 %/ °C ISENSE Drain Sense Input Current V + = 48V, VSENSE = 65mV 0.5 1.5 mA VGATE – V+ Gate Voltage Above Supply V + = 8V 4 4.5 6 V V+ = 12V l 7 8.5 10 V V+ = 24V l 10 12 14 V V+ = 48V l 10 12 14 V VF(TH) FAULT Output High Threshold Voltage V IN = 2V, IF = 1mA, Adjust VT 3.1 3.4 3.7 V FAULT Output Low Threshold Voltage 3.0 3.3 3.6 V VFOL FAULT Output Low Voltage I F = 1mA l 0.07 0.4 V tON Turn-On Time V + = 24V, VGATE = 32V, CGATE = 1nF 100 220 400 ms tOFF Turn-Off Time V + = 24V, VGATE = 2V, CGATE = 1nF 25 100 ms tOFF(CL) Current Limit Turn-Off Time V + = 24V, (V+ – VSENSE)fi 0.1V, CGATE = 1nF 20 50 ms (Note 1) + –5V Operating Ambient Temperature Range ABSOLUTE MAXIMUM RATINGSW WW U PACKAGE/ORDER INFORMATIONW UU ORDER PART NUMBER LT1910ES8 S8 PART MARKING 1910ETJMAX = 125°C, qJA = 150°C/W The l denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V+ = 12V to 48V unless otherwise noted. Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1910E is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40 °C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Guaranteed but not tested.

TYPICAL PERFOR A CE CHARACTERISTICS UW Supply Current vs Supply Voltage Supply Current vs Temperature Input Voltage vs Temperature Input Current vs Temperature Timer Threshold Voltage vs Temperature Timer Clamp Voltage vs Temperature Timer Charge Current vs Temperature Drain Sense Threshold Voltage vs Temperature MOSFET Gate Voltage Above V+ (VGATE – V+) vs Supply Voltage SUPPLY VOLTAGE (V) SUPPLY CURRENT (mA) 2.4 2.8 3.2 3.6

1910 G01

2.0 1.6 2.2 2.6 3.0 3.4 1.8 1.4 1.2 10 20 30 50 ON STATE OFF STATE TA = 25°C TEMPERATURE (°C) –50 SUPPLY CURRENT (mA) 1.0 2.0 3.0 2.5 –25 0 25 50

1910 G02

4.0 5.0 0.5 1.5 3.5 4.5 100 V+ = 48V ON STATE OFF STATE TEMPERATURE (°C) –50 INPUT VOLTAGE (V) 1.0 1.2 1.4 1.6 2.0 –25 02 5 5 0

1910 G03

1.8 0.8 VINH VINL TEMPERATURE (°C) –50 INPUT CURRENT (µA) 120 –25 0 25 50

1910 G04

VIN = 5V VIN = 2V TEMPERATURE (°C) –50 TIMER THRESHOLD VOLTAGE (V)2.7 2.8 2.9 3.0 3.2 –25 02 5 5 0

1910 G05

3.1 2.6 VIN = 2V TEMPERATURE (°C) –50 TIMER CLAMP VOLTAGE (V) 3.3 3.4 3.5 3.6 3.8 –25 02 5 5 0

1910 G06

3.7 3.2 VIN ≤ 0.8V TEMPERATURE (°C) –50 TIMER CHARGE CURRENT (µA) –25 02 5 5 0

1910 G07

VIN = VT = 2V TEMPERATURE (°C) –50 DRAIN SENSE THRESHOLD VOLTAGE (mV) –25 0 25 50

1910 G08

V+ = 24V SUPPLY VOLTAGE (V) MOSFET GATE VOLTAGE ABOVE V+ (VGATE – V+) (V)16 LTC1266 • F04 10 20 30 50 3551 5 2 5 4 5 TA = 85°C TA = –40°C TA = 25°C

TYPICAL PERFOR A CE CHARACTERISTICS UW MOSFET Gate Drive Current vs VGATE – V+ Fault Threshold Voltage vs Temperature Fault Output Low Voltage vs Temperature Turn-On Time vs Temperature Turn-Off Time vs Temperature Automatic Restart Period vs Temperature TEMPERATURE (°C) –50 FAULT THRESHOLD VOLTAGE (V)3.2 3.3 3.4 3.5 3.7 –25 02 5 5 0

1910 G11

3.6 3.1 VIN = 2V IF = 1mA FAULT HIGH THRESHOLD FAULT LOW THRESHOLD TEMPERATURE (°C) –50 FAULT OUTPUT LOW VOLTAGE (V) 0.04 0.08 0.12 0.10 –25 0 25 50

1910 G012

0.16 0.20 0.02 0.06 0.14 0.18 100 IF = 1mA TEMPERATURE (°C) –50 TURN-ON TIME (µs) 150 200 250 300 400 –25 02 5 5 0

1910 G13

V+ = 24V VGATE = 32V CGATE = 1nF TEMPERATURE (°C) –50 TURN-OFF TIME (µs) –25 0 25 50

1910 G014

V+ = 24V VGATE = 2V CGATE = 1nF NORMAL CURRENT LIMIT TEMPERATURE (°C) –30 100 1000 –10 10 30 50 70

1910 G15

AUTOMATIC RESTART PERIOD (ms) –50 90 V+ = 24V CT = 3.3µF CT = 0.33µF CT = 0.1µF CT = 1µF VGATE – V+ (V) 024 MOSFET GATE DRIVE CURRENT (µA) 100 6 8 10 12 14 16

1910 G10

0.1 V+ = 8V V+ = 12V V+ ‡ 24V TA = 25°C

GND (Pin 1): Common ground. TIMER (Pin 2): A timing capacitor CT from the TIMER pin to ground sets the restart time following overcurrent detection. Upon detection of an overcurrent condition, CT is rapidly discharged to less than 1V and then recharged by a 14mA nominal current source back to the 2.9V timer threshold, whereupon the restart is attempted. Whenever TIMER pulls below 2.9V, the GATE pin pulls low to turn off the external switch. This cycle repeats until the overcur- rent condition goes away and the switch restarts success- fully. During normal operation the pin clamps at 3.5V nominal. FAULT (Pin 3): The FAULT pin monitors the TIMER pin voltage and indicates the overcurrent condition. When- ever the TIMER pin is pulled below 3.3V at the onset of a current limit condition, the FAULT pin pulls active LOW. The FAULT pin resets HIGH immediately when the TIMER pin ramps above 3.4V during autorestart. The FAULT pin is an open-collector output, thus requiring an external pull-up resistor and is intended for logic interface. The resistor should be selected with a typical 1mA pull-up at low status and less than 2mA under worst-case condi- tions. IN (Pin 4): The IN pin threshold is TTL/CMOS compatible and has approximately 200mV of hysteresis. When the IN pin is pulled active HIGH above 2V, an internal charge pump is activated to pull up the GATE pin. The IN pin can be pulled as high as 15V regardless of whether the supply is on or off. If the IN pin is left open, an internal 75k pull- down resistor pulls the pin below 0.8V to ensure that the GATE pin is inactive LOW. GATE (Pin 5): The GATE pin drives the power MOSFET gate. When the IN pin is greater than 2V, the GATE pin is pumped approximately 12V above the supply. It has relatively high impedance (the equivalence of a few hun- dred kW ) when pumped above the rail. Care should be taken to minimize any loading by parasitic resistance to ground or supply. The GATE pin pulls LOW when the TIMER pin falls below 2.9V. SENSE (Pin 6): The SENSE pin connects to the input of a supply-referenced comparator with a 65mV nominal off- set. When the SENSE pin is taken more than 65mV below supply, the MOSFET gate is driven LOW and the timing capacitor is discharged. The SENSE pin threshold has a 0.33%/°C temperature coefficient (TC), which closely matches the TC of the drain sense resistor formed from the copper trace of the PCB. For loads requiring high inrush current, an RC timing delay can be added between the drain sense resistor and the SENSE pin to ensure that the current-sense comparator does not false trigger during start-up (see Applications Information). A maximum of 10k W can be inserted be- tween a drain sense resistor and the SENSE pin. If current sensing is not required, the SENSE pin is tied to supply. V + (Pin 8): In addition to providing the operating current for the LT1910, the V + pin also serves as the Kelvin connection for the current sense comparator. The V+ pin must be connected to the positive side of the drain sense resistor for proper current sensing operation.

+ +– +3.3V TIMER IN 14µA 2.9V 1.4V 75k 75k FAULT 1.4V 250Ω 1910 BD GATE SENSE 65mV OSCILLATOR AND CHARGE PUMP OPERATIOU The LT1910 GATE pin has two states, OFF and ON. In the OFF state it is held LOW, while in the ON state it is pumped to 12V above the supply by a self-contained 750kHz charge pump. The OFF state is activated when either the IN pin is below 0.8V or the TIMER pin is below 2.9V. Con- versely, for the ON state to be activated, the IN pin must be above 2V and the TIMER pin must be above 2.9V. The IN pin has approximately 200mV of hysteresis. If it is left open, the IN pin is held LOW by a 75k resistor. Under normal conditions, the TIMER pin is held a diode drop above 2.9V by a 14 mA pull-up current source. Thus the TIMER pin automatically reverts the GATE pin to the ON state if the IN pin is above 2V. The SENSE pin normally connects to the drain of the power MOSFET, which returns through a low value drain sense resistor to supply. In order for the sense comparator to accurately sense the MOSFET drain current, the V + pin must be connected directly to the positive side of the drain sense resistor. When the GATE pin is ON and the MOSFET drain current exceeds the level required to generate a 65mV drop across the drain sense resistor, the sense comparator activates a pull-down NPN which rapidly pulls the TIMER pin below 2.9V. This in turn causes the timer comparator to override the IN pin and set the GATE pin to the OFF state, thus protecting the power MOSFET. When the TIMER pin is pulled below 3.3V, the fault comparator also activates the open-collector NPN to pull the FAULT pin LOW, indicating an overcurrent condition. When the MOSFET gate voltage is discharged to less than 1.4V, the TIMER pin is released. The 14mA current source then slowly charges the timing capacitor back to 2.9V where the charge pump again starts to drive the GATE pin HIGH. If a fault condition still exists, the sense comparator threshold will again be exceeded and the timer cycle will repeat until the fault is removed. The FAULT pin becomes inactive HIGH if the TIMER pin charges up successfully above 3.4V (see Figure 1). (Refer to the Block Diagram)

1910 F01

Figure 1. Timing Diagram prevent ground transients from damaging control logic. The LT1910 easily interfaces to low cost optoisolators. the OFF State (see Figure 2). as the reference input for the current sense comparator. Figure 2. Isolating the Input

1910 F03

Figure 3. Drain Sense Configuration

generate large current transients at turn-on. across each inductive load normally serves this purpose. VGS + 0.7V) across it, resulting in high dissipation peaks. LOAD • (¶V/¶t) during capacitor in-rush. the current sense comparator. controlled by controlling the ¶V/¶t on the gate.

1910 F04

Figure 4. Latch-Off Configuration (Autorestart Defeated)

1910 F05

Figure 5. Control and Current Limit Delay

• 11 where VTH is the MOSFET gate threshold voltage. V G is obtained by plotting the equation: I V RGATE GATE= 1 on the graph of Gate Drive Current (IGATE) vs Gate Voltage (VGATE) as shown in Figure 6. The value of V GATE at the intersection of the curves for a given supply is V G. For example, if V+ = 24V and R1 = 100k, then VG = 18.3V. For VTH = 2V, C1 = 0.1mF and CLOAD = 1000mF, the estimated IPEAK = 1.6A. The diode and the second resistor in the network ensure fast current limit turn-off. When turning off a capacitive load, the source of the MOSFET can “hang up” if the load resistance does not discharge CLOAD as fast as the gate is being pulled down. If this is the case, a 15V zener may be added from gate to source to prevent VGS(MAX) from being exceeded. and CD delay the overcurrent trip for drain currents up to approximately 10 • ISET, above which the diode conducts and provides immediate turn-off (see Figure 7). To ensure proper operation of the timer, CD must be £ CT. APPLICATIO S I FOR ATIOWU UU

Figure 7. Current Limit Delay Time

1910 F06

Figure 6. Gate Drive Current vs Gate Voltage

0.01 TRIP DELAY TIME (1 = RDCD)

1910 F07

“free” drain sense resistor made out of PC trace material.

Low Voltage/Wide Supply Range Operation When the supply is less than 12V, the LT1910’s charge pump does not produce sufficient gate voltage to fully enhance the standard N-channel MOSFET. For these appli- cations, a logic-level MOSFET can be used to extend the operating supply down to 8V. If the MOSFET has a maxi- mum V GS rating of 15V or greater, then the LT1910 can also operate up to a supply voltage of 60V (absolute maximum rating of the V+ pin). Protecting Against Supply Transients The LT1910 is 100% tested and guaranteed to be safe from damage with 60V applied between the V+ and GND pins. However, when this voltage is exceeded, even for a few microseconds, the result can be catastrophic. For this reason it is imperative that the LT1910 is not exposed to supply transients above 60V. A transient suppressor, such as Diodes Inc.’s SMAJ48A, should be added between the V + and GND pins for such applications. For proper current sense operation, the V+ pin is required to be connected to the positive side of the drain sense resistor (see Drain Sense Configuration). Therefore, the supply should be adequately decoupled at the node where the V + pin and drain sense resistor meet. Several hundred microfarads may be required when operating with a high current switch. When the operating voltage approaches the 60V absolute maximum rating of the LT1910, local supply decoupling APPLICATIO S I FOR ATIOWU UU between the V+ and GND pins is highly recommended. An RC snubber with a transient suppressor are an absolute necessity. Note however that resistance should not be added in series with the V + pin because it will cause an error in the current sense threshold. Low Side Driving Although the LT1910 is primarily targeted at high side (grounded load) switch applications, it can also be used for low side (supply connected load) switch applications. Figures 8a and 8b illustrate the LT1910 driving low side power MOSFETs. Because the LT1910 charge pump tries to pump the gate of the N-channel MOSFET above the supply, a clamp zener is required to prevent the V GS (absolute maximum) of the MOSFET from being exceeded. Figure 8a. Low Side Driver with Load Current Sensing Figure 8b. Low Side Driver for Source Current Sensing FAULT IN TIMER V SENSE GATE LT1910 5.1k FAULT OUTPUT INPUT GND IRF63015V 1N4744

1910 F08b

10µF 50V CT 1µF RS 0.02Ω HV LOAD51Ω 2N2222 8V TO 24V HV LT1006 51Ω FAULT IN SENSE LT1910 5.1k 12V TO 48V FAULT OUTPUT INPUT GND IRFZ44 15V 1N4744

1910 F08a

100µF 100V C T 1µF RS 0.01Ω (PTC) LOAD GATETIMER 5

APPLICATIO S I FOR ATIOWU UU The LT1910 gate drive is current limited for this purpose so that no resistance is needed between the GATE pin and zener. Current sensing for protecting low side drivers can be done in several ways. In the Figure 8a circuit, the supply voltage for the load is assumed to be within the supply operating range of the LT1910. This allows the load to be returned to supply through current sense resistor R providing normal operation of the LT1910 protection circuitry. If the load cannot be returned to supply through R S, or the load supply voltage is higher than the LT1910 supply, the current sense must be moved to the source of the low side MOSFET. Figure 8b shows an approach to source sensing. An operational amplifier (must common mode to ground) is used to level shift the voltage across R S up to the drain sense pin. This approach allows the use of a small sense resistor which could be made from PC trace material. The LT1910 restart timer functions the same as in the high side switch application. 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .016 – .050 (0.406 – 1.270) .010 – .020 0°– 8° TYP .008 – .010 (0.203 – 0.254) SO8 0303 .053 – .069 (1.346 – 1.752) .014 – .019 (0.355 – 0.483) TYP .004 – .010 (0.101 – 0.254) .050 (1.270) BSC 1 2 3 4 .150 – .157 (3.810 – 3.988) NOTE 3 8 7 6 5 .189 – .197 (4.801 – 5.004) NOTE 3 .228 – .244 (5.791 – 6.197) .245 MIN .160 –.005 RECOMMENDED SOLDER PAD LAYOUT .045 –.005 .050 BSC .030 –.005 TYP INCHES (MILLIMETERS) NOTE: 1. DIMENSIONS IN 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear.com ª LINEAR TECHNOLOGY CORPORATION 2002 LT/TP 0403 2K • PRINTED IN USA RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC®1153 Autoreset Electronic Circuit Breaker Programmable Trip Current, Fault Status Output LTC1155 Dual High Side Micropower MOSFET Driver Operates from 4.5V to 18V, 85 mA ON Current, Short-Circuit Protection LT1161 Quad Protected High Side MOSFET Driver 8V to 48V Supply Range, Individual Short-Circuit Protection LTC1163 Triple 1.8V to 6V High Side MOSFET Driver 0.01 mA Standby Current, Triple Driver in SO-8 Package LTC1255 Dual 24V High Side MOSFET Driver Operates from 9V to 24V, Short-Circuit Protection LTC1477 Protected Monolithic High Side Switch Low R DS(ON) 0.07W Switch, 2A Short-Circuit Protected LTC1623 SMBus Dual High Side Switch Controller 2-Wire SMBus Serial Interface, Built-In Gate Charge Pumps LTC1693 Family High Speed Single/Dual N-Channel/P-Channel 1.5A Peak Output Current, 4.5V £ VCC £ 13.2V, SO-8 Package MOSFET Drivers LTC1710 SMBus Dual Monolithic High Side Switch Two Low R DS(ON) 0.4W /300mA Switches in 8-Lead MSOP Package LTC4412 Low Loss PowerPath TM Controller Implements “Ideal Diode” Function, ThinSOT TM Package PowerPath and ThinSOT are trademarks of Linear Technology Corporation. TYPICAL APPLICATIO U Protected 1A Automotive Solenoid Driver with Overvoltage Shutdown FAULT IN TIMER V SENSE GATE LT1910 5.1k FAULT OUTPUT INPUT POWER GROUND 8V TO 24V OPERATING 32V TO 60V SHUTDOWN GND MTD3055EL 24V SOLENOID

1910 TA03

10µF 100V C T 1µFR3 5.1k 1N4148 2N3904 RS 0.03Ω (PTC) 10k 30V 1N6011B