ZHCSO20 may 2021 BQ25723
PRODUCTION DATA
The charger monitors total system power. During forward mode, the input adapter powers the system. During reverse OTG mode and battery only discharge scenario, the battery powers the system and VBUS output. The ratio of PSYS pin output current and total system power, KPSYS, can be programmed in PSYS_RATIO register bit with default 1 μA/W. The input and charge sense resistors (RAC and RSR) are selected in RSNS_RAC bit and RSNS_RSR bit. By default, PSYS_CONFIG=00b and PSYS voltage can be calculated with Equation 1, where IIN>0 when the charger is in forward charging and IIN<0 when charger is in OTG operation; where IBAT>0 when the battery is in charging and IBAT<0 when battery is discharging.
RAC and RSR values are not limited to symmetrical both 5 mΩ or both 10 mΩ. For defined current sense resistors (10 mΩ/5 mΩ), PSYS function is still valid when RAC=5 mΩ(RSNS_RAC=1b) and RSR=10 mΩ(RSNS_RAC=0b), vice versa. As long as RSNS_RAC and RSNS_RSR bit status are consistent with practical resistors used in the system.
Charger can block IBAT contribution to above equation by setting PSYS_CONFIG =01b in forward mode and block IBUS contribution to above equation by setting PSYS_OTG_IDCHG=1b in OTG mode.
To minimize the quiescent current, the PSYS function is disabled by default PSYS_CONFIG = 11b.
| CASE # |
PSYS_CONFIG BITS |
PSYS_OTG_IDCHG BITS |
FORWARD MODE PSYS CONFIGURATION |
OTG MODE PSYS CONFIGURATION |
|---|---|---|---|---|
| 1 | 00b | 0b | PSYS = PBUS+PBAT | PSYS = PBUS + PBAT |
| 2 | 00b | 1b | PSYS = PBUS+PBAT | PSYS =PBAT |
| 3 | 01b | Xb | PSYS = PBUS | PSYS = 0 |
| 4 | 11b | Xb | PSYS = 0 (Disabled) | PSYS = 0 (Disabled) |
| 5 (Reserved) | 10b | Xb | PSYS = 0 (Reserved) | PSYS = 0 (Reserved) |