LTC4367 datasheet(11/30 Pages) AD

11 / 30 page

LTC7000/LTC7000-1

Rev. E

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OPERATION

The LTC7000/LTC7000-1 is designed to receive a ground-

referenced, low voltage digital input signal, INP and

quickly drive and protect a high side N-channel power

MOSFET whose drain can be up to 150V above ground.

The LTC7000/LTC7000-1 is capable of driving a 1nF load

using a 12V bootstrapped supply voltage (VBST–VTS) with

35ns of propagation delay and fast rise/fall times. The

high gate drive voltage reduces external power losses

associated with external MOSFET on-resistance. The

strong drivers not only provide fast turn on and off times

but hold the TGUP and TGDN to TS voltages in the desired

state in the presence of high slew rate transients which

can occur driving inductive loads at high voltages.

Overcurrent Protection

The LTC7000/LTC7000-1 protects a high side N-channel

MOSFET from an overcurrent condition by monitoring the

voltage across an external sense resistor placed in series

with the drain of an external MOSFET and forcing the

external MOSFET to turn off by pulling TGDN to TS when

the voltage across the sense resistor, ΔVSNS, exceeds

the current comparator threshold voltage, ΔVTH, after

a period of time set by the timing capacitor, CT. When

an overcurrent condition is detected with ISET open,

ΔVTH is internally programmed to a low value of 30mV

minimizing the external conduction loss associated with

current sensing by allowing the use of lower value sense

resistors. A resistor placed between ISET and ground

allows ΔVTH to be programmed from 20mV to 75mV.

An adjustable fault and overcurrent timer is enabled by

placing a capacitor, CT from the TIMER pin to ground

and allows the load to continue functioning during

brief overcurrent transient events while protecting the

MOSFET from long periods of high currents. An external

fault flag is available which can warn of an impending

MOSFET turn off. A fast turn-off mode where TGDN

is immediately pulled to TS due to an overcurrent is

available by connecting the TIMER pin to VCC.

Current Monitor (LTC7000 Only)

The LTC7000 provides an output voltage referenced to

ground on the IMON pin that reflects the current flowing

through the external sense resistor connected between

SNS+ and SNS– while TGUP is high. The voltage on IMON

is the voltage difference between the SNS+ and SNS– pins

multiplied by 20x and referenced to ground with a range

of 0V to 1.5V. The IMON output voltage has an output

impedance of 100kΩ and is pulled to ground with a

100kΩ resistor when INP is low.

VCC Power

Power for the MOSFET driver and internal circuitry is

derived from the VCC pin. The VCC pin voltage is gener-

ated from an internal P-channel LDO connected to VIN.

VCC can also be overdriven from a high efficiency exter-

nal source for high frequency switching applications that

require higher power delivered to external MOSFET. VCC

should never be driven higher than VIN or permanent

damage to the LTC7000/LTC7000-1 could occur.

(Refer to Block Diagram)

TIMING DIAGRAM

INPUT (INP)

OUTPUT (TG-TS)

INPUT RISE/FALL TIME < 10ns

tPLH

tPHL

90%

10%

VIH

VIL

7000 TD

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