BQ25890H Datasheet, PDF (20/66 Pages) Texas Instruments – I2C Controlled Single Cell 5-A Fast Charger

BQ25890H
SLUSCC5 – SEPTEMBER 2016
www.ti.com
8.2.3.3.2 Force Input Current Limit Detection
In host mode, the host can force the device to run by setting FORCE_DPDM bit. After the detection is completed,
FORCE_DPDM bit returns to 0 by itself and Input Result is updated.
8.2.3.4 Input Voltage Limit Threshold Setting (VINDPM Threshold)
The device supports wide range of input voltage limit (3.9 V – 14 V) for high voltage charging and provides two
methods to set Input Voltage Limit (VINDPM) threshold to facilitate autonomous detection.
1. Absolute VINDPM (FORCE_VINDPM=1)
By setting FORCE_VINDPM bit to 1, the VINDPM threshold setting algorithm is disabled. Register VINDPM
is writable and allows host to set the absolute threshold of VINDPM function.
2. Relative VINDPM based on VINDPM_OS registers (FORCE_VINDPM=0) (Default)
When FORCE_VINDPM bit is 0 (default), the VINDPM threshold setting algorithm is enabled. The VINDPM
register is read only and the charger controls the register by using VINDPM Threshold setting algorithm. The
algorithm allows a wide range of adapter (V_{VBUS_OP}) to be used with flexible VINDPM threshold.
After Input Voltage Limit Threshold is set, an INT pulse is generated to signal to the host.
8.2.3.5 Converter Power-Up
After the input current limit is set, the converter is enabled and the HSFET and LSFET start switching. If battery
charging is disabled, BATFET turns off. Otherwise, BATFET stays on to charge the battery.
The device provides soft-start when system rail is ramped up. When the system rail is below 2.2 V, the input
current limit is forced to the lower of 200 mA or IINLIM register setting. After the system rises above 2.2 V, the
device limits input current to the lower value of ILIM pin and IILIM register (ICO_EN = 0) or IDPM_LIM register
(ICO_EN = 1).
As a battery charger, the device deploys a highly efficient 1.5 MHz step-down switching regulator. The fixed
frequency oscillator keeps tight control of the switching frequency under all conditions of input voltage, battery
voltage, charge current and temperature, simplifying output filter design.
A type III compensation network allows using ceramic capacitors at the output of the converter. An internal saw-
tooth ramp is compared to the internal error control signal to vary the duty cycle of the converter. The ramp
height is proportional to the PMID voltage to cancel out any loop gain variation due to a change in input voltage.
In order to improve light-load efficiency, the device switches to PFM control at light load when battery is below
minimum system voltage setting or charging is disabled. During the PFM operation, the switching duty cycle is
set by the ratio of SYS and VBUS.
8.2.4 Input Current Optimizer (ICO)
The device provides innovative Input Current Optimizer (ICO) to identify maximum power point without overload
the input source. The algorithm automatically identify maximum input current limit of power source without
entering VINDPM to avoid input source overload.
This feature is enabled by default (ICO_EN=1) and can be disabled by setting ICO_EN bit to 0. After DCP or
MaxCharge type input source is detected based on the procedures previously described (Input Source Type
Detection ). The algorithm runs automatically when ICO_EN bit is set. The algorithm can also be forced to
execute by setting FORCE_ICO bit regardless of input source type detected.
The actual input current limit used by the Dynamic Power Management is reported in IDPM_LIM register while
Input Current Optimizer is enabled (ICO_EN = 1) or set by IINLIM register when the algorithm is disabled
(ICO_EN = 0). In addition, the current limit is clamped by ILIM pin unless EN_ILIM bit is 0 to disable ILIM pin
function.
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