BQ24171 Datasheet, PDF (20/35 Pages) Texas Instruments – JEITA Compliant Stand-Alone Switch-Mode Li-Ion and Li-Polymer Battery Charger with Integrated MOSFETs and Power Path Selector

bq24171
SLUSAF2A – FEBRUARY 2011 – REVISED MAY 2011
www.ti.com
CHARGE UNDER-CURRENT PROTECTION
After the recharge, if the SRP-SRN voltage decreases below 5mV, the low side FET will be turned off for the rest
of the switching cycle. During discontinuous conduction mode (DCM), the low side FET will only turn on for a
short period of time when the bootstrap capacitor voltage drops below 4V to provide refresh charge for the
capacitor. This is important to prevent negative inductor current from causing any boost effect in which the input
voltage increases as power is transferred from the battery to the input capacitors. This can lead to an
over-voltage on the AVCC node and potentially cause damage to the system.
BATTERY DETECTION
For applications with removable battery packs, IC provides a battery absent detection scheme to reliably detect
insertion or removal of battery packs. The battery detection routine runs on power up, or if battery voltage falls
below recharge threshold voltage due to removing a battery or discharging a battery.
POR or RECHARGE
Apply 8mA discharge
current, start 1s timer
V_FB < VBATOWV
No
1s timer
expired
No
Yes
Disable 8mA
discharge current
Yes
Battery Present,
Begin Charge
Enable 125mA charge
current, start 0.5s timer
V_FB > V_RECH
Yes
Disable 125mA
charge current
0.5s timer
No
No
expired
Yes
Battery Present,
Begin Charge
Battery Absent
Figure 18. Battery Detection Flowchart
20
Submit Documentation Feedback
Product Folder Link(s): bq24171
Copyright © 2011, Texas Instruments Incorporated