9.3.1.1.3 Pre-Charge to Fast Charge Transitions and Charge Current Ramping
Whenever a change in the charge current setting is triggered, whether it occurs due to I
2
C programming by the
host, Pre-Charge/Fast Charge transition or JEITA TS control, the device will temporarily disable charging (for ~ 1
ms) before updating the charge current value.
9.3.1.1.4 Termination
The device will automatically terminate charging once the charge current reaches I
TERM
, which is programmable
through I
2
C.
After termination the charger will operate in high impedance mode, disabling the BATFET to disconnect the
battery. Power is provided to the system (PMID) by IN supply as long and V
IN
> V
UVLO
and V
BAT
+V
SLP
< V
IN
<
V
OVP
.
Termination is only enabled when the charger CV loop is active in fast charge operation. No termination will
occur if the charge current reaches I
TERM
while VINDPM or DPPM is active as well as the thermal regulation
loop. Termination is also disabled when operating in the TS WARM region. The charger only goes to termination
when the current drops to I
TERM
due to the battery reaching the target voltage and not due to the charge current
limitation imposed by the previously mentioned control loops.
9.3.1.2 JEITA and Battery Temperature Dependent Charging
The charger can be configured through I
2
C setting to provide JEITA support, automatically reducing the charging
current and voltage depending on the battery temperature as monitored by an NTC thermistor connected to the
BQ25157 TS pin. See
9.3.1.3 Input Voltage Based Dynamic Power Management (VINDPM) and Dynamic Power Path
Management (DPPM)
The VINDPM loop prevents the input voltage from collapsing to a point where charging would be interrupted by
reducing the current drawn by charger in order to keep V
IN
from dropping below V
IN_DPM
. Once the IN voltage
drops to V
IN_DPM
, the VINDPM loops will reduce the input current through the blocking FETs, to prevent the
further drop of the supply voltage. The VINDPM function is disabled by default and may be enabled through I
2
C
command. The V
IN_DPM
threshold is programmable through the I
2
C register from 4.2 V to 4.9 V in 100-mV steps.
On the other hand, the DPPM loop prevents the system output (PMID) from dropping below V
BAT
+ 200mV when
the sum of the charge current and system load exceeds the BQ21061 input current limit setting. If PMID drops
below the DPPM voltage threshold, the charging current is reduced. If PMID continues to drop after BATFET
charging current is reduced to zero, the part will enter supplement mode when PMID falls below the supplement
mode threshold (V
BAT
- V
BSUP1
). NOte that DPPM function is disabled when PMID regulation is set to battery
tracking.
When the device enters these modes, the charge current may be lower than the set value and the corresponding
status bits and flags are set. If the 2X timer is set, the safety timer is extended while the loops are active.
Additionally, termination is disabled.
9.3.1.4 Battery Supplement Mode
While in DPPM mode, if the charging current falls to zero and the system load current increases beyond the
programmed input current limit, the voltage at PMID reduces further. When the PMID voltage drops below the
battery voltage by V
BSUP1
, the battery supplements the system load. The battery stops supplementing the
system load when the voltage on the PMID pin rises above the battery voltage by V
BSUP2
. During supplement
mode, the battery supplement current is not regulated, however, the Battery Over-Current Protection mechanism
is active. Battery charge termination is disabled while in supplement mode.
9.3.2 Protection Mechanisms
9.3.2.1 Input Over-Voltage Protection
The input over-voltage protection protects the device and downstream components connected to PMID, and BAT
against damage from over-voltage on the input supply. When V
IN
> V
OVP
an OVP fault is determined to exist.
During the OVP fault, the device turns the input FET off, sends a single 128-µs pulse on INT, and the
SLUSEC5 – DECEMBER 2020
Copyright © 2020 Texas Instruments Incorporated
19
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Summary of Contents for BQ25157
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