Dual-output boost for LED backlight strings
The Texas Instruments TPS61150ADRCT is a dual-output DC-DC boost regulator designed specifically for driving LED backlights in small- to medium-sized LCD panels. Two independent outputs each deliver up to 27V at 34mA, with integrated switches that eliminate the need for external MOSFETs. PWM dimming is supported directly on the control pin, allowing the host processor to set brightness by varying the duty cycle of the dimming signal. The 1.2 MHz switching frequency keeps the inductor and output capacitors small — a 4.7 µH to 10 µH inductor and 1 µF ceramic output cap are typical for a 3-LED series string. Input supply range spans 2.5V to 6V, so the part runs from a single Li-ion cell (3.0V–4.2V) or a regulated 3.3V/5V rail without a separate bias supply.
Output voltage and current — matching the LED string
Each of the two channels is rated for 34mA continuous output current at 27V maximum. That 27V ceiling accommodates up to six white LEDs in series (assuming ~3.2V forward drop per LED) with headroom for the current-sense resistor. If the application needs more than 34mA per channel, this part is not the right fit — the output current is fixed by the internal current-sense threshold. The boost topology means the input current at 2.5V minimum supply can reach about 400 mA at full load (two channels, 34mA each, 27V output, 85% efficiency estimate).