SLVSG71 june 2023 TPS62901-Q1
PRODUCTION DATA
The TPS62901-Q1 can be used as a power supply for power LEDs. The FB pin can be easily set to lower values than nominal by using the SS/TR pin. With that, the voltage drop on the sense resistor (R2) is reduced to avoid excessive power loss. Because the SS/TR pin provides 2.5 µA (typical), the feedback pin voltage can be adjusted by an external resistor per Equation 19. This drop, proportional to the LED current, is used to regulate the output voltage (anode voltage) to a proper level to drive the LED. Both analog and PWM dimming are supported with the TPS62901-Q1. Figure 9-64 shows an application circuit, tested with analog dimming.
The resistor at SS/TR defines the FB voltage. The resistor at SS/TR is set to 304 mV by RSS/TR = R4 = 162 kΩ using Equation 19. This cuts the losses on R2 to half from the nominal 0.6 V of feedback voltage while it still provides good accuracy.
The device now supplies a constant current set by resistor R2 from FB/VSET to GND. The minimum input voltage has to be rated according the forward voltage needed by the LED used. More information is available in the Step-Down LED Driver With Dimming With the TPS621-Family and TPS821-Family application report.