The TPS61169 is a high-efficiency, high-output voltage boost converter in small package size. The device integrates 40V/1.8A switch FET and is designed for output voltage up to 39V with a switch peak current limit of 1.2A minimum. Its large driving capability can drive single or parallel LED strings for small to large size panel backlighting.

The TPS61169 operates in a current mode scheme with quasi-constant frequency. It is internally compensated for maximum flexibility and stability. The switching frequency is 1.2MHz, and the minimum input voltage is 2.7V. During the on-time, the current rises into the inductor. When the current reaches a threshold value set by the internal GM amplifier, the power switch MOSFET is turned off. The polarity of the inductor changes and forward biases the schottky diode which lets the current flow towards the output of the boost converter. The off-time is fixed for a certain V_IN and V_OUT, and therefore maintains the same frequency when varying these parameters.

However, for different output loads, the frequency slightly changes due to the voltage drop across the RDS(ON) of the power switch MOSFET, this has an effect on the voltage across the inductor and thus on t_ON (t_OFF remains fixed). The fixed off-time maintains a quasi-fixed frequency that provides better stability for the system over a wider range of input and output voltages than conventional boost converters. The TPS61169 topology has also the benefits of providing very good load and line regulations, and excellent line and load transient responses.

The feedback loop regulates the FB pin to a low reference voltage (204mV typical), reducing the power dissipation in the current sense resistor.