The TPS92633 device provides two current output paths for each channel. Current flows from the supply through the R_(SNSx) resistor into the integrated current regulation circuit and to the LEDs through OUTx pin and RESx pin. The current output on both OUTx pin and RESx pin is independently regulated to achieve total required current output. The summed current of OUTx and RESx is equal to the current through the R_(SNSx) resistor in the channel. The OUTx connects to anode of LEDs load in serial directly, however RESx connects to the LEDs through an external resistor to share part of the power dissipation and reduce the thermal accumulation in TPS92633.

The integrated independent current regulation in TPS92633 dynamically adjusts the output current on both OUTx and RESx output to maintain the stable summed current for LED. The TPS92633 always regulates the current output to the RESx pin as much as possible until the RESx current path is saturated, and the rest of required current is regulated from the OUTx. As a result, the most of the current to LED outputs through the RESx pin when the voltage dropout is relatively high between SUPPLY and LED required total forward voltage. In the opposite case, the most of the current to LED outputs through the OUTx pin when the voltage headroom is relatively low between SUPPLY and LED required forward voltage. Figure 7-3 and Figure 7-4 shows the curve of current and power dissipation distributor depending on supply voltage when R_(RESx) is 68.5 Ω.

Figure 7-3 Output Current Distribution vs Supply Voltage

Figure 7-4 Power Dissipation vs Supply Voltage