The Motor control ICs of the TDA514x family have been provided with an on-chip current limiter circuit. The current limit value, however, can not be set externally. Therefore the need came-up for an adjustable current limiter circuit. The method of current limiting is based upon the voltage drop across a current sensing resistor in series with the motor supply.
To obtain a negligible effect on the motor torque it is very important that the voltage drop across the current sense resistor is as small as possible. We have to deal with the motor control ICs, i.e. TDA5143, TDA5144 and TDA5145, with on-chip output transistors. In this report a current limiter is given for the ICs with on-chip output drivers and the IC with external output driver.
The input voltage Vin (figure 1), connected to the AMPIN– input of the motor control IC, is used to control the voltage Vmot. The control range of Vin is determined by the resistor divider of 39 KΩ and 10 KΩ, which have been connected to the AMPIN+ input. This part of the circuit is not further discussed.