High Side Switches are used and seen most commonly in automotive and industrial applications. High side switches have applications where providing power to off-board loads are essential, providing a point of disconnect between the system, supply, and the load. High-side switches can provide diagnostics during normal operation, such as load current measurement and device temperature monitoring. With load current measurements, the system is able to take measurements of the output current by correlating it with a voltage based output. With device temperature monitoring, the system is able to monitor the internal junction temperature of the switch as it increases during operation using a voltage based output. High side switches also provide diagnostics for faults that can alert when open loads, short-to-GND, loss of battery, or thermal shutdown occur. Each fault brings efficiency to the system by allowing features that help monitor down time and ways to ensure current can continue to be drawn through the switch.

Aside from simple on-off operation, most TI smart high-side switch devices come with diagnostics that help monitor regular operation. Some devices have pins that allow measuring the operating load current on the Current Sense [CS] pin. As the device is best kept operating below a certain temperature threshold, the device junction temperature may also be of interest when monitoring device operation. The following sections discuss how to configure the different operations on devices that are able to and also how to optimize current measurements. Table 2-1 lists the devices that are able to measure load current or both device temperature and load current by using their Current Sense (CS) or Sense (SNS) pins.

For devices that have a configurable output pin for measuring either the operating load current or the device temperature, there are pins that need to be configured to the appropriate logic values to see the respective output. These are the Select High and Low pins (SEL, SHE) or the Select 1 or Select 2 pins (SELx) pins. By pulling either of these pins to the pin’s high or low logic, the diagnostic output is configured to either the device temperature or the operating load current. Table 2-2 shows the different devices and their corresponding SEL/SELx pin.

Devices such as the TPS1HB16 have a single SEL1 pin that can be configured with a high or low signal. It acts as the diagnostics select pin. Depending on its state, one of two outputs will be measurable from the sense output pin SNS. The first is load current, which allows the SNS pin to output a voltage signal that reflects the load current that the switch is outputting. The second is the device’s junction temperature. The junction temperature is the internal temperature of the switch and is important to monitor to ensure the device remains below the thermal thresholds. These different output configurations are shown in Table 2-3.

For devices that have multiple SEL pins such as the TPS1HA08, the device is able to be configured in three ways: device temperature, load current, or supply voltage. As with the single SEL pin devices, device temperature allows for measuring the internal junction temperature and the load current measurement allows for a proportionate voltage signal that reflects the load current. An additional setting allows for monitoring the supply voltage that is supplying power to the output, which is helpful in applications where a battery is involved such as in the automotive industry. For devices with multiple channels, additional SEL pins are used to select which channel to monitor.

Table 2-4 shows the different diagnostics that are used in the SELx pins on the TPS1HA08-Q1 and how to configure them. Table 2-5 shows the configurations that available on the SELx pins on the TPS2HB16 and the settings associated with them.