NJM3548 Просмотр технического описания (PDF) - Japan Radio Corporation

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NJM3548

UNIVERSAL SOURCE DRIVER

Japan Radio Corporation  

NJM3548

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 GND. This

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 NJM3548 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 VCC

• 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 VCC. In figure 4

short circuit to VCC 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.

VIn = Input voltage. Active = LOW.

V = Output voltage.

Out

IOut = Output current from driver.

VErr = Error output voltage. Error = LOW.

VIN

VOUT

I OUT

VErr

Normal

operation

Overload or

short circuit

to GND

>130° <120°

Short circuit Open circuit Over

to VCC

temperature

Figure 8. Signal diagram

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