Dual-Channel Smart High-Side Switch Targets 12-V Vehicle Systems

A high-side switch is responsible for protecting the output during fault cases like cable short circuits. When a short circuit occurs, a low-impedance current path is created that can draw hundreds of amps from the car battery through the high-side switch. When this transient current passes through, it’s recognized as an overcurrent event and the switch is shut off, preventing current flow.

Traditional high-side switches, however, attempt a universal protection scheme with a much higher than necessary current limit. This means protection can’t be guaranteed in all cases, leading directly to requirements for higher cost and complexity safeguards to ensure robustness during soft short-circuit events.

Integrating an adjustable current limit (ILIM) to offer improved protection against short-circuit events assures a quick response, minimizing transient currents and supply droop. Furthermore, it gives automotive manufacturers the ability to maintain high reliability and simplify system design.

To that end, Texas Instruments introduced the TPS2HB50-Q1 dual-channel smart high-side switch designed for usage in 12-V automotive systems. It combines protection and diagnostic features for output port protection, even throughout harmful events like short circuits in automotive systems.

Shown is a simplified schematic of the TI TPS2HB50-Q1 high-side switch.

The device defends against faults through a current limit, which, depending on the device variant, is adjustable from 2 to 18 A. The high current-limit range enables use in loads that need large transient currents, while the low current-limit range provides improved protection for loads that don’t need high peak currents.

Typical applications include in an automotive display module, ADAS module, seat comfort module, transmission control unit, HVAC control module, body control module, and LED lighting.

Designed to operate in the automotive environment, the TPS2HB50-Q1 employs protection mechanisms that allow the device to handle many system-level events, such as load dump, reverse battery, short-to-ground, and more.

The switch also delivers an analog current sense that enables full diagnostics, including current limiting, and allows for immediate feedback to the user on the status of the system. By reporting load current and device temperature to a system MCU, the device can provide predictive maintenance and load diagnostics that improve the system’s lifetime.

There are two protection features that, if triggered, will cause the switch to automatically disable: current limit and thermal shutdown. When triggered TPS2HB50-Q1 will enter the FAULT state. In the FAULT state, the fault indication will be available on the SNS pin. When IOUT reaches the ICL, the channel will switch off immediately. The ICL value will vary with slew rate and a fast current increase that occurs during a powered-on short circuit. The device will register a short-circuit event when the output current exceeds ICL; it’s specified to protect itself during a short-circuit event up to 24 V at 125°C.

The current-limit specification of TPS2HB50-Q1 is based on the part being enabled into a short-circuit condition, with a 5-μH inductor on the input and output and the input resistance being less than 10 mΩ and the output impedance less than 100 mΩ. When the part is enabled into this short-circuit condition, the current will rise up to the specified threshold before it begins to shut off the current.

The device includes a temperature sensor on each power FET as well as within the controller portion of the device. For thermal shutdown, each channel is turned off based on the measurement of the temperature sensor for that channel. Therefore, if the thermal fault is detected on only one channel, the other channel continues operation.

The AEC-Q100-qualified TPS2HB50-Q1 comes in an HTSSOP package, reducing the PCB footprint.

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