8.1 Overview

The TPS5420x device is a 1.5-A synchronous buck LED driver up to 28-V input. Current-mode operation provides fast transient response. The optimized internal compensation network minimizes the external component count and simplifies the control loop design.

The TPS5420x device has a fixed 600-kHz switching frequency for a good tradeoff between efficiency and size.

The integrated 150-mΩ high-side MOSFET and 70-mΩ low-side MOSFET allow for a high-efficiency LED driver with continuous output current up to 1.5 A.

The TPS5420x device supports deep dimming in both analog and PWM dimming modes. In analog dimming mode, the internal reference voltage is changed in proportion to the duty cycle of the PWM signal in the 1% to 100% range. In the PWM dimming mode, the LED turns on and off periodically according to the PWM duty cycle. For higher efficiency, the internal reference is halved to 100 mV.

Cycle-by-cycle current limit in the high-side MOSFET protects the converter in overload conditions and is enhanced by a low-side MOSFET freewheeling current limit which prevents current runaway. There is a low-side MOSFET sinking-current limit to prevent excessive reverse current.

For safety and protection, the TPS5420x includes LED-open and -short protection, sense-resistor-open and -short protection, and device thermal protection. The TPS54200 device implements shutdown-and-latch mode protection, whereas the TPS54201 device implements auto-retry mode protection.