SLVSH61C March 2025 – November 2025 TPS7H4102-SEP , TPS7H4104-SEP
PRODMIX
The resistor divider network RFB_TOPx and RFB_BOTx is used to set the output voltage. For this design, 10kΩ was selected for RFB_TOPx. Additionally, a 20Ω resistor was placed in series with RFB_TOPx to aid in measuring the control loop. Using the combined value of 10.02kΩ and using Equation 1 the bottom resistors are calculated. The real (or selected) resistors were chosen, using the closest value to the calculation (using 0.1% tolerance). To minimize the error due to the reference voltage (VREFx), the center across temperature, rather than the typical value is used for the calculations as presented on Equation 21.
Using the real (or selected) values the expected nominal and error are calculated using Equation 3 and Equation 4. The results are presented on Table 9-8.
| VOUTx (V) | CALCULATED RFB_BOTx (kΩ) | SELECTED RFB_BOTx (kΩ) | VOUTx REAL (V) | VOUTx ERROR (mV) |
|---|---|---|---|---|
| 0.8 | 29.57 | 29.4 | 0.802 | 8.02 |
| 1.2 | 9.94 | 9.88 | 1.204 | 12.07 |
| 1.5 | 6.63 | 6.57 | 1.509 | 15.15 |
| 1.8 | 4.98 | 4.93 | 1.812 | 18.2 |
Lifetime drift data can similarly be added. Group C data can be used to aid in this calculation. For this example, assume the lifetime drift is minimal compared to the other sources of error and is therefore not added.