CS1107

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CIRCUIT DESCRIPTION

The CS1107 relay driver IC provides up to 350 mA of

drive current in a low–side configuration. The Output driver

pin is controlled through the TTL compatible Control input

pin. A high condition on the Control pin turns the output pin

on.

The Fault pin reports short circuit, open circuit, and

overtemperature conditions on the IC. If a fault is present,

the open collector output Fault pin will be low. Typical

numbers for faults are: exceeding 500 mA of drive current

will report a short circuit. Less than 40 mA (typical) will

report an open circuit. A temperature fault will be reported

when the die temperature exceeds 180

°C (typical). Faults

are only reported when the Control pin is high, due to the low

quiescent current when the Control pin is low and the output

device is turned off.

Overcurrent protection is provided by duty cycle control.

When the Output current exceeds the current limit threshold,

the output enters duty cycle mode to reduce power

dissipation of the IC to a safe level. The higher the threshold

is exceeded the lower the duty cycle becomes.

A 33 V on–chip zener diode on the Output pin protects the

device from flyback pulses when a relay is turned off. The

saturation voltage of this pin will not exceed 1.5 V at 350 mA.

Figure 2. Applications Diagram

10 nF

20 k

Output

Fault

Control

GND

GND

GND

GND

CS1107

microprocessor