Texas Instruments BQ25157, Manual

Page: 16 / 110

9.3 Feature Description
9.3.1 Linear Charger and Power Path
The BQ25157 IC integrates a linear charger that allows the battery to be charged with a programmable charge
current of up to 500 mA. In addition to the charge current, other charging parameters can be programmed
through I
2
C such as the battery regulation voltage, pre-charge current, termination current, and input current limit
current.
The power path allows the system to be powered from PMID, even when the battery is dead or charging, by
drawing power from IN pin. It also prioritizes the system load connected to PMID, reducing the charging current,
if necessary, in order to support the load when input power is limited. If the input supply is removed and the
battery voltage level is above V
BATUVLO
, PMID will automatically and seamlessly switch to battery power.
There are several control loops that influence the charge current: constant current loop (CC), constant voltage
loop (CV), input current limit, VDPPM, and VINDPM. During the charging process, all loops are enabled and the
one that is dominant takes control regulating the charge current as needed. The charger input has back to back
blocking FETs to prevent reverse current flow from PMID to IN. They also integrate control circuitry regulating the
input current and prevents excessive currents from being drawn from the IN power supply for more reliable
operation.
The device supports multiple battery regulation voltage regulation settings (V
BATREG
) and charge current
(I
CHARGE
) options to support multiple battery chemistries for single-cell applications.
A more detailed description of the charger functionality is presented in the following sections of this document.
9.3.1.1 Battery Charging Process
The following diagram summarizes the charging process of the BQ25157 charger.
BQ25157
SLUSEC5 – DECEMBER 2020
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