Datasheet

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LT1910

1910fa

TYPICAL APPLICATION

DESCRIPTION

Protected High Side

MOSFET Driver

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-contained 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 ﬂ ag 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 ﬂ ag becomes inactive

once the switch restarts successfully.

The LT1910 has been speciﬁ cally 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 Protected High Side Switch

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

FEATURES

APPLICATIONS

8V to 48V Power Supply Range

Protected from –15V to 60V Supply Transients

Short-Circuit Protected

Automatic Restart Timer

Open-Collector Fault Flag

Fully Enhances N-Channel MOSFET Switches

Programmable Current Limit, Delay Time and

Autorestart Period

Voltage Limited Gate Drive

Defaults to Off State with Open Input

Available in SO-8 Package

Industrial Control

Avionics Systems

Automotive Switches

Stepper Motor and DC Motor Control

Electronic Circuit Breaker

Switch Drop vs Load Current

FAULT

TIMER

SENSE

GATE

LT1910

5.1k

24V5V

FAULT OUTPUT

OFF ON

GND

IRFZ34

1910 TA01

10μF

50V

0.1μF

0.01Ω

LOAD

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

Summary of content (12 pages)

PAGE 1
LT1910 Protected High Side MOSFET Driver FEATURES DESCRIPTION n 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-contained charge pump to fully enhance an N-channel MOSFET switch with no external components.
PAGE 2
LT1910 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Supply Voltage (Pin 8) ............................... –15V to 60V Input Voltage (Pin 4) ..................... (GND – 0.3V) to 15V GATE Voltage (Pin 5)................................................ 75V SENSE Voltage (Pin 6) ........................................ V+ ±5V FAULT Voltage (Pin 3) .............................................. 36V Current (Pins 1, 2, 4, 5, 6, 8) ................................
PAGE 3
LT1910 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. V+ = 12V to 48V unless otherwise noted.
PAGE 4
LT1910 TYPICAL PERFORMANCE CHARACTERISTICS Timer Threshold Voltage vs Temperature Input Current vs Temperature 3.2 TIMER THRESHOLD VOLTAGE (V) 180 INPUT CURRENT (μA) 160 140 VIN = 5V 120 100 80 60 40 VIN = 2V 3.8 VIN = 2V 3.1 TIMER CLAMP VOLTAGE (V) 200 Timer Clamp Voltage vs Temperature 3.0 2.9 2.8 2.7 VIN ≤ 0.8V 3.7 3.6 3.5 3.4 3.3 20 25 50 75 0 TEMPERATURE (°C) 100 2.
PAGE 5
LT1910 TYPICAL PERFORMANCE CHARACTERISTICS Turn-On Time vs Temperature 400 100 300 250 200 AUTOMATIC RESTART PERIOD (ms) TURN-OFF TIME (Ms) TURN-ON TIME (Ms) 1000 V+ = 24V 90 VGATE = 2V CGATE = 1nF 80 V+ = 24V VGATE = 32V 350 CGATE = 1nF 70 60 50 40 30 NORMAL 20 150 CURRENT LIMIT 10 100 –50 Automatic Restart Period vs Temperature Turn-Off Time vs Temperature –25 75 0 25 50 TEMPERATURE (oC) 100 125 0 –50 –25 25 50 75 0 TEMPERATURE (oC) 1910 G13 100 125 1910 G014 V+ = 24V CT = 3.
PAGE 6
LT1910 PIN FUNCTIONS Information). A maximum of 10kΩ can be inserted between 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. BLOCK DIAGRAM V+ 14μA – 3.
PAGE 7
LT1910 OPERATION 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 14μA 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.
PAGE 8
LT1910 APPLICATIONS INFORMATION to the supply at the same point as the positive end of the sense resistor. The drain-sense threshold voltage has a positive temperature coefﬁcient, allowing PTC sense resistors to be used (see Printed Circuit Board Shunts). The selection of RS should be based on the minimum threshold voltage: RS = 50mV/ISET Thus the 0.02Ω drain-sense resistor in Figure 3 will yield a minimum trip current of 2.5A.
PAGE 9
LT1910 APPLICATIONS INFORMATION The turn-on current spike into CLOAD is estimated by: IPEAK = CLOAD • VG – VTH R1• C1 RD 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 . where VTH is the MOSFET gate threshold voltage.
PAGE 10
LT1910 APPLICATIONS INFORMATION 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 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.
PAGE 11
LT1910 APPLICATIONS INFORMATION 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, RS, providing normal operation of the LT1910 protection circuitry.
PAGE 12
LT1910 TYPICAL APPLICATION Protected 1A Automotive Solenoid Driver with Overvoltage Shutdown 8V TO 24V OPERATING 32V TO 60V SHUTDOWN 5V FAULT OUTPUT R1 5.1k 3 INPUT 30V 1N6011B Q1 MTD3055EL GND 1N4148 R2 10k RS 0.03Ω (PTC) LT1910 8 V+ FAULT 6 4 IN SENSE 5 2 TIMER GATE 1 2N3904 R3 5.