The output voltage is programmed by the voltage divider resistors, R_{FB_HS} and R_{FB_LS}. Connect R_{FB_HS} between the FB pin and the positive node of the load, and connect R_{FB_LS} between the FB pin and the VSNS– pin. The recommended R_{FB_LS} value is 10 kΩ, ranging from 1 kΩ to 20 kΩ. Determine R_{FB_HS} by using Equation 1.

Equation 1.

The FB accuracy is determined by two elements. The first element is the accuracy of the internal 600-mV reference, which is applied to the SS/REFIN pin unless an external V_REF is applied. Both TPSM8A28 and TPSM8A29 offer ±0.5% V_INTREF accuracy from a 0°C to 85°C temperature range, and ±1.0% V_INTREF accuracy from a -40°C to 125°C temperature range. The second element is the SS/REFIN-to-FB accuracy, which tells the user how accurately the control loop regulates the FB node to the SS/REFIN pin. The TPSM8A29 offers ±0.6% SS/REFIN-to-FB accuracy from a -40°C to 125°C temperature range. For example, when operating from a 0°C to 85°C temperature range, the total FB accuracy is ±1.1%, which includes the impact from the chip junction temperature and also the variation from part to part.

To improve the overall V_OUT accuracy, using ±1% accuracy or better resistor for FB voltage divider is highly recommended.

Regardless of remote sensing or single-end sensing connection, the FB voltage divider, R_{FB_HS} and R_{FB_LS}, must be always placed as close as possible to the device.