NJM3545

A logic-level change at the input will reset the internal error latch. If the fault still is present at turn-on, the circuit

will once again turn the output off.

Due to a slight delay in the circuit, a high current transient will occur when the output is shorted to V

current transient may reach 8 A during 5

µs. Consequently, switching at high frequencies with a shorted output

may destroy the circuit. If a short circuit condition is detected, stop switching the input and remove fault condition.

Thermal protection

The output of NJM3545 is equipped with a thermal shut-down function, that turns the outputs off at a chip (junction)

tenperature above typically 130

°C.

Normal operation is resumed when the temperature has decreased about 20C.

Error functions

The Error indicating signal occurs on a separate pin. The complete error table is shown in figure 7.

The following conditions generate an error signal:

When the driver is activated and at least one of the following conditions has occurred:

•

thermal overload

•

short circuit to GND

•

short circuit to V

CC

•

open circuit

An output current less than 8 mA might be detected as “open circuit”. Output currents larger than 8 mA and

less than 2 A will definitely not generate an error. The normal operational area is shown in figure 3.

Also when the driver is inactivated an Error indication can occur. That is if the output is shorted to GND. In figure

4 short circuit to GND Error state versus output voltage is shown.

When the Error-detection function is activated, the Error output is capable of sinking 8 mA, supporting direct

connection of an LED. The current has to be externally limited by a series resistor.

Signal diagrams

The signal diagram in figure 8 shows the input signal and the resulting output signals for each error mode. For

details, see error table, figure 7.

V

V

I

V

Error = LOW.

Figure 8. Signal diagram

V

I

OUT

Err

V

IN

V

OUT

Normal

operation

Overload or

short circuit

Short circuit

to GND

Open circuit

Over

temperature

*

>130

° <120°

level