Infineon BTS436L2 Smart High-Side Power Switch: Features and Application Design

The Infineon BTS436L2 is a smart high-side power switch belonging to the company’s PROFET™ (PROtected FET) family of devices. Designed for robust and efficient power control in automotive and industrial applications, this integrated circuit combines a power MOSFET with comprehensive protection and diagnostic features in a single package. It simplifies design, enhances reliability, and reduces both board space and component count.

Key Features of the BTS436L2

At its core, the BTS436L2 integrates a vertical N-channel power MOSFET with a typical on-state resistance (RDS(on)) of just 16 mΩ. This low resistance is crucial for minimizing conduction losses and improving overall system efficiency, especially in high-current applications.

A standout feature of this device is its comprehensive suite of protection and diagnostic functions. It includes:

- Overload and short-circuit protection: The switch limits the output current to protect itself and the connected load.

- Overtemperature protection: An internal temperature sensor shuts down the device if the junction temperature exceeds a safe threshold, restarting automatically upon cooling.

- Overvoltage protection (including load-dump): This is particularly critical in the harsh electrical environments of automotive systems.

- Reverse battery protection: It can withstand negative voltage at the supply pin, eliminating the need for an external protection diode in many cases.

- Open-load detection: This diagnostic feature can detect whether a load is disconnected during both on and off states.

- Current sense pin: It provides a proportional current output (IS) that is a fraction of the load current, enabling real-time current monitoring without the need for a bulky shunt resistor.

The device is controlled via a 3.3V and 5V logic-compatible input pin, making it easy to interface directly with microcontrollers. It is housed in a TO-263-7 (D2PAK) package, which offers an excellent thermal performance-to-footprint ratio.

Application Design Considerations

The BTS436L2 is engineered for driving resistive or inductive loads in DC systems, such as:

- Automotive body electronics: Heated seats, window lifters, and various motors.

- Industrial automation: Solenoid and valve control.

- Power management units: Distributing power to different subsystems.

When designing with the BTS436L2, several key factors must be considered:

1. Thermal Management: Despite its high efficiency, power dissipation (P_loss = I_load² × RDS(on)) can generate significant heat. Proper PCB layout with a sufficient copper area for the D2PAK tab is essential to act as a heat sink and ensure the junction temperature remains within limits.

2. Inductive Load Handling: When switching inductive loads like motors or solenoids, the energy stored in the inductance must be dissipated during turn-off. The BTS436L2's integrated clamp circuit handles this energy, but the design must ensure the resulting voltage spikes do not exceed the absolute maximum ratings of other components in the system.

3. Current Sensing: The IS pin provides a valuable diagnostic tool. The current sense ratio (k_ILIS) is typically 16,500. An external sense resistor (R_IS) converts this current into a measurable voltage for the microcontroller's ADC. The value of R_IS should be chosen to provide a usable voltage signal without exceeding the pin's maximum current capability.

4. Diagnostics: The status pin (or the behavior of the input pin in some configurations) provides feedback on fault conditions like overtemperature or open-load. The system microcontroller should be programmed to interpret these signals and take appropriate action, such as notifying the user or implementing a restart procedure.

ICGOOODFIND

The Infineon BTS436L2 stands out as an exceptionally robust and feature-rich solution for high-side switching. Its integration of a low-RDS(on) MOSFET, advanced protection mechanisms, and accurate diagnostic capabilities significantly reduces design complexity and boosts system reliability. It is an ideal choice for engineers developing applications that demand high current handling, robust protection, and intelligent control in challenging electrical environments.

Keywords:

1. Smart High-Side Switch

2. Overcurrent Protection

3. Diagnostic Features

4. Thermal Management

5. Automotive Applications