SLVAE30E February 2021 – March 2021 TPS1H000-Q1 , TPS1H100-Q1 , TPS1H200A-Q1 , TPS1HA08-Q1 , TPS25200-Q1 , TPS27S100 , TPS2H000-Q1 , TPS2H160-Q1 , TPS2HB16-Q1 , TPS2HB35-Q1 , TPS2HB50-Q1 , TPS4H000-Q1 , TPS4H160-Q1
Resistive loads are the simplest loads to drive as they follow Ohm’s Law.
It's simple because the designer knows the voltage (typically 13.5V for a car battery) and the resistance of the load (by measuring it with an Ohm meter). With these two parameters they can calculate the maximum current that will be flowing through the circuit. Knowing this information is the first step in selecting the correct device to drive this load since each high side switch has an associated ON resistance that limits the amount of nominal current allowed through the device without hitting thermal shutdown. In typical applications the current through the load needs to be varied to provide the intended output. It is also important to have features such as current sensing that can correlate back to the microcontroller what current is actually going through the load. The most basic way to vary the current through the load is through pulse width modulating (PWM) the enable pin. This introduces more complications with regard to the thermal calculations.
In this section we will look into the application of resistive loads and show what relevant features are useful when driving them. We will also see how TI's Smart High Side Switches' feature set aligns well with the requirements for loads. Finally, in order to pick the correct high side switch we must learn how to calculate the power dissipation of the switch and relate that to the junction temperature and set the current limit appropriately so that the high side switch will be able to properly drive the resistive load.