BQ24171_15 Datasheet, PDF (16/39 Pages) Texas Instruments – bq24171 JEITA-Compliant Stand-Alone, Switched-Mode Li-Ion and Li-Polymer Battery Charger With Integrated MOSFETs and Power Path Selector

bq24171
SLUSAF2C – FEBRUARY 2011 – REVISED APRIL 2015
9.3 Feature Description
Regulation Voltage
V_RECH
I _CHRG
Precharge
Current
Regulation
Phase
Fastcharge Current
Regulation Phase
Charge
Current
Fastcharge Voltage
Regulation Phase
www.ti.com
Termination
V_LOWV
10% I_CHRG
Charge
Voltage
Precharge
Timer
Fast Charge Safety Timer
Figure 14. Typical Charging Profile
9.3.1 Battery Voltage Regulation
The bq24171 offers a high-accuracy voltage regulator on for the charging voltage.
The bq24171 uses external resistor divider for voltage feedback and regulate to internal 2.1-V voltage reference
on FB pin. Use the following equation for the regulation voltage for bq24171:
VBAT
= 2.1 V ´
é
êë¹⁺
R2 ù
R1 ^úû
where
• R2 is connected from FB to the battery.
• R1 is connected from FB to GND.
(1)
9.3.2 Battery Current Regulation
The ISET input sets the maximum charging current. Battery current is sensed by current-sensing resistor RSR
connected between SRP and SRN. The full-scale differential voltage between SRP and SRN is 40 mV maximum.
The equation for charge current is:
I_CHARGE =
V_ISET
20 ´ R_SR
(2)
The valid input voltage range of ISET is up to 0.8 V. With 10-mΩ sense resistor, the maximum output current is
4 A. With 20-mΩ sense resistor, the maximum output current is 2 A.
The charger is disabled when ISET pin voltage is below 40 mV and is enabled when the ISET pin voltage is
above 120 mV. For 10-mΩ current-sensing resistor, the minimum fast charge current must be higher than 600
mA.
16
Submit Documentation Feedback
Product Folder Links: bq24171
Copyright © 2011–2015, Texas Instruments Incorporated