BQ24171_15 Datasheet, PDF (20/39 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
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Feature Description (continued)
9.3.14 Charge Undercurrent Protection
After the recharge, if the SRP-SRN voltage decreases below 5 mV, then the low-side FET is turned off for the
rest of the switching cycle. During discontinuous conduction mode (DCM), the low-side FET turns on for a short
period of time when the bootstrap capacitor voltage drops below 4 V 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 overvoltage on the
AVCC node and potentially cause damage to the system.
9.3.15 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
No
expired
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
expired
No
Yes
Battery Present,
Begin Charge
Battery Absent
Figure 15. Battery Detection Flow Chart
20
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