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VN220 / VN220(011Y) / VN220(012Y)

1

FUNCTIONAL DESCRIPTIO N

The VN220 provides protection against a short circuit on

the output and senses the output current to detect an

open load. When one of these two faults is detected the

diagnostic output is taken low.

OPEN LOAD DETECTIO N

When the device is first turned on, only the auxiliary

DMOS device is turned on. If the load current remains

below 9mA (typical), the open load signal is active and

the diagnostic output is low. When the load current goes

above 9 mA the open load detection becomes inactive

and the diagnostic goes high. When the load current

exceeds 300 mA, the main DMOS (50 m

Ω) turns on.

When the load current drops below 240 mA, the main

DMOS is turned off but no open load signal is generated

and the auxiliary DMOS is still turned on. If the load

current drops below 9mA, again the open load signal is

generated and the diagnostic output goes low.

SHORT CIRCUIT PROTECTION

Short circuit protection is achieved using the fast

response of the thermal shut-down circuit. The only

current limitation in this condition is the saturation current

of the DMOS devices and the external wiring resistance.

Under this condition the device can survive a short circuit

up to 30V across DMOS devices.

THERMAL PROTECTION

The

device

is

internally

protected

against

over

temperature by the thermal protection circuit. When the

device junction temperature exceeds the protection limit,

the output is latched off. To turn on the output again, the

input signal must be taken low to reset the latch, then

high again to turn on the output. If the junction

temperature has not yet cooled below the lower limit set

by the thermal sensing hysteresis, the device will remain

latched off.

NOTE: When an open load defect appears (or disappears) the

state of the diagnostic output changes only after the filtering time