SLUSFR7 August 2025 BQ24810
PRODUCTION DATA
The synchronous boost PWM converter uses a fixed frequency voltage control scheme and internal type III compensation network. The LC output filter has a characteristic resonant frequency:

The resonant frequency, fo, is used to determine the compensation to ensure there is sufficient phase margin for the target bandwidth. The LC output filter should be selected to give a resonant frequency of 3.5- to 6.0-kHz nominal for the best performance. Suggested output capacitance versus inductor is shown in Table 7-4. The designer should first determine the inductor value using the tables provided in Section 6.4.6, then use Table 7-4 to determine the appropriate battery only boost output capacitance using that inductor value. These tables are generated based on the battery-only boost configuration, so the output capacitance is measured at the system node, which is the sum of CIN and CSYS as shown on Figure 7-1. The minimum capacitance value is calculated using boost ratio (VSYS / VBATT = VO / VIN) of 1.5 and a resonant frequency of 6.0 kHz. Also, a minimum output capacitance of 60 µF is recommended regardless of resonant frequency to support the transient response. Table 7-4 shows the minimum suggested value. Additional CSYS may be added for improved transient response.
| L1 (µH) | 2.2 | 3.3 | 4.7 | 5.6 | 6.8 | 8.2 |
|---|---|---|---|---|---|---|
| CIN (µF) (Effective after derating) | 20 | 20 | 20 | 20 | 20 | 20 |
| Minimum CSYS(µF) (Effective after derating) | 120 | 80 | 50 | 40 | 40 | 40 |