SLUSEK7 September 2024 BQ25773
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
When charger LDO mode is enabled (EN_LDO=1b) and VBAT voltage falls below VSYS_MIN() during charging, the charger should regulate system output voltage fixed at VSYS_MIN() and battery charging current is regulated by BATFET gate voltage achieving LDO mode operation. Both charger pre-charge and trickle charge status are implemented through this LDO mode operation. Under both pre-charge and trickle charge there are corresponding current limit referring to Battery Charging Profile. Under LDO mode larger VSYS_MIN() minus VBAT delta and larger charge current should generate more thermal dissipation at BATFET which should be properly limited to ensure safe operation. Therefore besides pre-charge and trickle charge current clamp mentioned above, we have additional two levels current clamp to ensure the maximum BATFET dissipation loss below 2W based on the relationship between VBAT and VSYS_MIN() setting referring to Table 7-9. The lower current clamp will dominate the final maximum charge current limit considering IPRECHG() user register upper clamp, battery short trickle charge current clamp (128 mA) and two levels BATFET current clamp below.
NAME | VBAT VS VSYS_MIN() | MAXIMUM CHARGE CURRENT CLAMP |
---|---|---|
IBATFET_CLAMP1 | 1V<VSYS_MIN()-VBAT<4V |
512 mA (Internal Clamp no impact on IPRECHG() register) |
IBATFET_CLAMP2 | 4V<VSYS_MIN()-VBAT |
128 mA (Internal Clamp no impact on IPRECHG() register) |
When charger LDO mode is disabled (EN_LDO=0b), then BATFET will be either fully on or fully off status. When charge is disabled the system voltage is regulated at 5 V (VBAT< 5 V) or VBAT+160 mV (VBAT>5 V); however when charge is enabled then VSYS will be regulated close to VBAT to implement target charging current and VSYS_MIN regulation is not effective.