22.214.171.124 Detailed Design Procedure
The recommended L1 = 22 µH, CBYP = 0.01 µF and low leakage CREF = 10 nF are selected. In order to ensure the fastest recovery of the harvester output voltage to the MPPT level following power extraction, the minimum recommended CIN = 4.7 µF is selected. Because no large system load transients are expected and to ensure fast charge time during cold start, the minimum recommended CSTOR = 4.7 µF. To stop charging when the IC junction temperature is above 65°C, the OT_PROG pin is tied to ground.
- With VBAT_UV < VBAT_OV ≤ 5.5 V, to size the VBAT_OV resistors, first choose RSUMOV = ROV1 + ROV2 = 10 MΩ then solve Equation 3 for
- ROV2 = RSUMOV - ROV1 = 10 MΩ - 5.95 MΩ = 4.05 MΩ → 4.02 MΩ resulting in VBAT_OV = 3.15 V
- To size the VBAT_UV resistors, first choose RSUMUV = RUV1 + RUV2 = 10 MΩ then solve Equation 2 for
- RUV2 = RSUMUV - RUV1 = 10 MΩ - 5.60 MΩ = 4.4 MΩ → 4.42 MΩ closest 1% resistor resulting in
VBAT_UV = 2.2 V.
- With VBAT_OV ≥ VBAT_OK_HYST > VBAT_OK ≥ VBAT_UV, to size the VBAT_OK and VBAT_OK_HYST resistors,
first choose RSUMOK = ROK1 + ROK2 + ROK3 = 10 MΩ then solve Equation 4 and Equation 5 for
- ROK3 = RSUMOK - ROK1 - ROK2 = 10 MΩ - 4.42 MΩ - 4.22 MΩ = 1.36 MΩ → 1.43 MΩ to give
VBAT_OK = 2.44 V and VBAT_OK_HYST = 2.85 V.
- Keeping in mind that VREF_SAMP stores the MPP voltage for the harvester, first choose RSUMOC = ROC1 + ROC2 = 20 MΩ then solve Equation 1 for
- SLURAQ1 provides help on sizing and selecting the resistors.