Datasheet

7.14.1 Overcurrent in Discharge and Short Circuit in Discharge Recovery
OL/SCRelease
Comparator
bq77PL900
Bat
Battery
Off Off
Pack+
Pack
Pack–
S0350-01
Load
bq77PL900
SLUS844B – JUNE 2008 – REVISED JANUARY 2009 ...................................................................................................................................................... www.ti.com
In host-control mode, the host must send a sequence of firmware commands to the bq77PL900 to recover from
overcurrent and short-circuit currents. The command sequence to turn ON the DSG and CHG FETs is as follows:
1. The host must toggle LTCLR from 0 to 1 and back to 0.
2. Then set the DSG and CHG control bits to 1. To reset XALERT high, the STATUS register must be read.
In stand-alone mode, the bq77PL900 has two methods to recover from overcurrent and short-circuit conditions
by setting the SOR bit of OCD_CFG.
SOR = 0: Recover comparator is active after 12.8 s. An internal comparator monitors the PACK+ voltage and
when the PACK+ voltage reaches V
RECSC
, the overcurrent in discharge recovers. When the bq77PL900
detects a charger is attached, the DSG and CHG FETs turn ON and XALERT is reset High.
SOR = 1: After 12.8 s, the bq77PL900 automatically recovers from OC and SC. The DSG and CHG FETs
turn ON and XALERT is reset high. If the OC or SC condition is still present, OC and SC is detected again
and the recovery/detection cycle continues until the fault is removed.
Figure 16. Overcurrent and Short-Circuit Protection Modes
28 Submit Documentation Feedback Copyright © 2008 – 2009, Texas Instruments Incorporated
Product Folder Link(s): bq77PL900