What is the open-load detection function available with low-voltage IPDs?

Example of a circuit that detects an open load by monitoring the output voltage while the output MOSFET is off
Figure 2 Example of a circuit that detects an open load by monitoring the output voltage while the output MOSFET is off

The purpose of open-load detection is to detect a bad contact of a connector or a broken wire in a wire harness connected to an electronic control unit (ECU).

There are two major types of open-load detection:

  1. The output terminal voltage is monitored while the output transistor is off. An open load is signaled when the output voltage exceeds the programmed value.
  2. The current flowing through the output transistor is monitored while it is on. An open load is signaled when the output current falls below the programmed value.

Most of Toshiba’s IPDs for high-side applications use the above type 1 to detect an open load by monitoring the output terminal voltage while the output transistor is off.

What is the open-load detection function available with low-voltage IPDs?

The value of the resistor for open-load detection in this circuit is calculated as follows:

Example of a circuit that detects an open load by monitoring the output current while the output MOSFET is on
Figure 3 Example of a circuit that detects an open load by monitoring the output current while the output MOSFET is on

When the load resistance exceeds the programmed value, the diagnostic output terminal is driven High to signal an open load (i.e., broken wire).

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