TLE4247

Operation Modes

Datasheet

8

Rev. 1.01, 2010-05-04

5

Operation Modes

5.1

Description

The TLE4247 provides two different operation modes: For relay activation, the IC pass element works as an

activated switch with lowest dropout voltage

V

the IC switches to hold mode regulating the relay coil current to constant values (see Figure 3 b).

During commutation, the relay coil current flows from the IC input “IN” to “S” into the relay freewheeling resistor.

A zener structure prevents the IC from overvoltage by limiting the input voltage transient to

V

The relay activation time period

t

current. This time period starts once the IC supply voltage exceeds

V

below the threshold

V

battery voltage.

At low supply voltage, the IC switches to “Low Voltage Mode” with lowest current consumption. As in activation

mode, the IC is working as a switch with lowest dropout voltage.

In order to prevent the IC from excessive power dissipation at high supply voltage, the IC is working as a switch

(High Voltage Mode). A transition to Hold Mode during this mode is not possible.

An overtemperature protection circuit prevents the IC from immediate destruction under fault conditions by

reducing the output current. A thermal balance below 200 °C junction temperature will be established. Please note

that a junction temperature above 150 °C is outside the maximum ratings and reduces the IC lifetime.

Figure 3

Operation as switch or current source