PROTECTION CIRCUITS

DUAL HIGH SIDE SWITCH

The simplest way to protect the device against a

continuous reverse battery voltage (-26V) is to

insert a a small resistor between pin 2 (GND) and

ground. The suggested resistance value is about

150

Ω. In any case the maximum voltage drop on

this resistor should not overcome 0.5V.

If there is no need for the control unit to handle

external analog signals referred to the power

GND, the best approach is to connect the

reference potential of the control unit to the

device ground (see application circuit in fig. 3),

which becomes the common signal GND for the

LOW SIDE SWITCHES

The devices integrate:

CLAMP

PROTECTION:

internally set at 42V, along with the rugged

avalanche

characteristics

of

the

Power

MOSFET stage give this device unrivalled

ruggedness and energy handling capability.

This feature is mainly important when driving

inductive loads.

PROTECTION: these are based on sensing

the chip temperature and are not dependent on

the input voltage. The location of the sensing

element on the chip in the power stage area

ensures fast, accurate detection of the junction

temperature. Overtemperature cutout occurs at

minimum 150

restarted when the chip temperature falls

below 135

overtemperature fault

condition, a

Status

Feedback is provided through the Input pin.

The internal protection circuit disconnects the

input from the gate and connects it instead to

ground via an equivalent resistance of 100

Ω.

The failure can be detected by monitoring the

voltage at the Input pin, which will be close to

ground potential.

Additional features of these devices are ESD

protection according to the Human Body model

and the ability to be driven from a TTL Logic

TRUTH TABLE (for Dual high-side switch only)

I NPUT 1

INPUT 2

SO URCE 1 SOURCE 2

DIAG NO STI C

Normal Operation

L

H

L

H

L

H

H

L

L

H

L

H

L

H

H

L

H

H

H

H

Under-voltage

X

X

L

L

H

T hermal Shut down

Channel 1

HX

L

X

L

Channel 2

XH

X

L

L

O pen Load

Channel 1

H

L

X

L

H

L

X

L

L

L

Channel 2

X

L

H

L

X

L

H

L

L

L

Channel 1

H

L

X

L

H

H

X

L

L

L

Channel 2

X

L

H

L

X

L

H

H

L

L

NOTE: The low-side switches have the fault feedback which can be detected by monitoring the voltage at the input pins.

L = Logic LOW, H = Logic HIGH, X = Don’t care

VN771P

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