SLUSFH5 May 2024 BQ25856-Q1
ADVANCE INFORMATION
Refer to the PDF data sheet for device specific package drawings
There are two distinct thresholds to limit the charge current (if both are enabled, the lowest limit of these will apply):
To set the maximum charge current using the ICHG pin, a pull-down resistor to PGND is used. It is required to use a 5-mΩ RBAT_SNS sense resistor. The charge current limit is controlled by:
The precharge current limit is defined as IPRECHG_MAX = 20% x ICHG_MAX, and the termination current is ITERM = 10% x ICHG_MAX.
The actual charge current limit is the lower value between ICHG pin setting and I2C register setting (ICHG_REG). For example, if the register setting is 10 A (0xC8), and ICHG pin has a 10-kΩ resistor (KICHG = 50 A-kΩ) to ground for 5 A, the actual charge current limit is 5 A. The device regulates ICHG pin at VREF_ICHG. If ICHG pin voltage exceeds VREF_ICHG, the device enters charge current regulation.
The ICHG pin can also be used to monitor charge current when device is not in charge current regulation. When not in charge current regulation, the voltage on ICHG pin (VICHG) is proportional to the actual charging current. ICHG pin can be used to monitor battery current with the following relationship:
For example, if ICHG pin is set with 10-kΩ resistor, and the ICHG voltage 1.0V, the actual charge current is between 2.4 A to 2.6 A (based on KICHG specified).
If ICHG pin is shorted to PGND, the charge current limit is set by the ICHG_REG register. If hardware charge current limit function is not needed, it is recommended to short this pin to PGND. The ICHG pin function can be disabled by setting the EN_ICHG_PIN bit to 0 (recommended when pin is shorted to PGND). When the pin is disabled, charge current limit and monitoring functions via ICHG pin are not available.
To set the maximum charge current using the ICHG_REG register bits, write to the ICHG_REG register bits. The charge current limit range is from 400 mA to 20,000 mA with 50 mA/step. The default ICHG_REG is set to maximum code, allowing ICHG pin to limit the current in hardware.