The TPS61194 is a highly integrated LED driver for medium-sized LCD backlight applications. It includes a DC-DC with an integrated FET, supporting both boost and SEPIC modes, an internal LDO enabling direct connection to battery without need for a pre-regulated supply and four LED current sinks. The VDDIO/EN pin provides the supply voltage for digital IOs (PWM and SYNC inputs) and at the same time enables the device.

The switching frequency on the DC-DC converter is set by a resistor connected to the FSET pin. The maximum voltage of the DC-DC is set by a resistive divider connected to the FB pin. For the best efficiency the output voltage is adapted automatically to the minimum necessary level needed to drive the LED strings. This is done by monitoring LED output voltage drop in real time. For EMI reduction and control two optional features are available:

• Spread spectrum, which reduces EMI noise around the switching frequency and its harmonic frequencies
• DC-DC can be synchronized to an external frequency connected to SYNC pin

The four constant current outputs OUT1, OUT2, OUT3, and OUT4 provide LED current up to 100 mA.Value for the current per OUT pin is set with a resistor connected to ISET pin. Current sinks that are not used must be connected to ground. Grounded current sink is disabled and excluded from adaptive voltage detection loop.

Brightness is controlled with the PWM input. Frequency range for the input PWM is from 100 Hz to 20 kHz. LED output PWM follows the input PWM so the output frequency is equal to the input frequency.

TPS61194 has extensive fault detection features :

• Open-string and shorted LED detections
  • LED fault detection prevents system overheating in case of open or short in some of the LED strings
• V_IN input overvoltage protection
  • Threshold sensing from VIN pin
• V_IN input undervoltage protection
  • Threshold sensing from VIN pin
• Thermal shutdown in case of die overtemperature

Fault condition is indicated through the FAULT output pin.