5

LTC1153

Auto-Reset Time*

Shutdown Threshold Voltage

MOSFET Gate Drive Current

CC

HARA TERISTICS

A

TYPICALPERFOR

CE

TEMPERATURE (°C)

–50

0.4

0.6

1.O

1.2

1.4

2.4

1.8

0

50

75

LTC1153 • TPC13

0.8

2.0

2.2

1.6

–25

25

100

125

TEMPERATURE (°C)

–25

0.1

1

10

25

LTC1153 • TPC14

–50

125

0

50

75

100

*SECONDS OF DELAY

PER

PI FU CTIO S

Input and Shutdown Pins

The LTC1153 input pin is active high and activates all of the

protection and charge pump circuitry when switched ON.

The shutdown pin is designed to break the circuit if a

secondary fault condition (over temperature, etc.) is de-

tected. The LTC1153 logic and shutdown inputs are high

impedance CMOS gates with ESD protection diodes to

ground and supply and therefore should not be forced

beyond the power supply rails. The shutdown pin should

be connected to ground when not in use.

Timing Capacitor Pin (Auto-Reset Timer)

The small capacitor charging current (4.2

µA) produces

large delays with relatively small valued capacitors, but

care must be taken to ensure that this current is not

shunted to ground through a leaky capacitor or printed

circuit board trace. The timing capacitor voltage is sensed

by a high impedance CMOS comparator input with ESD

clamp diodes to ground and supply and therefore should

not be forced beyond the power supply rails. This pin can

be grounded if the auto-reset function is not used.

MOSFET Gate Drive Pin

The MOSFET gate drive pin is either driven to ground when

the switch is turned OFF or driven above the supply rail

when the switch is turned ON. This pin is a relatively high

impedance when driven above the rail (the equivalent of a

few hundred k

Ω). Care should be taken to minimize any

loading of this pin by parasitic resistance to ground or

supply.

Supply Pin

The supply pin of the LTC1153 serves two vital purposes.

The first is obvious: it powers the input, gate drive, regu-

lation and protection circuitry. The second purpose is less

obvious: it provides a Kelvin connection to the top of the

drain sense resistor for the internal 100mV reference.

The LTC1153 is designed to be

continuously powered so

that the gate of the MOSFET is actively driven at all times.

If it is necessary to remove power from the supply pin and

then re-apply it, the input pin (or enable pin) should be

cycled a few milliseconds

after the power is re-applied to

reset the input latch and protection circuitry. Also, the

input and enable pins should be isolated with 10k resistors

to limit the current flowing through the ESD protection

diodes to the supply pin.

The supply pin of the LTC1153 should never be forced

below ground as this may result in permanent damage to

the device. A 300

Ω resistor should be inserted in series

with the ground pin if negative supply voltage transients

are anticipated.

GATE VOLTAGE ABOVE SUPPLY (V)

1

10

100

1000

0

8

12

16

0.1

4

20

LTC1153 • TPC15