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LT1910IS8-PBF

Protected High Side MOSFET Driver

Linear Technology 

LT1910

Pin Functions

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 cur-

rent 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

–

FAULT

+

3.3V

TIMER

2.9V

+

–

1.4V

1.4V

+

75k

IN

–

75k

V+

+– 65mV

SENSE

GATE

OSCILLATOR

AND

CHARGE PUMP

250Ω

1910 BD

Operation (Refer to the Block Diagram)

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. Conversely,

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 14µA 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 gener-

ate 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

1910fb

6

For more information www.linear.com/LT1910

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