ACT8937A
Rev 1, 22-Oct-12
Figure 9. The charger continuously monitors the
temperature of the battery pack by injecting a
102μA (typ) current into the thermistor (via the TH
pin) and sensing the voltage at TH. The voltage at
TH is continuously monitored, and charging is
suspended if the voltage at TH exceeds either of
the internal VTHH and VTHL thresholds of 0.5V and
2.51V, respectively.
Figure 9:
Simple Configuration
The net resistance (from TH to GA) required to
cross the thresholds are given by:
102μA × RNOM × kHOT = 0.5V → RNOM × kHOT
≈ 5kꢀ
102μA × RNOM × kCOLD = 2.51V → RNOM ×
kCOLD ≈ 25kꢀ
where RNOM is the nominal thermistor resistance
at room temperature, and kHOT and kCOLD
represent the ratios of the thermistor's resistance at
the desired hot and cold thresholds, respectively, to
the resistance at 25°C.
Battery Temperature Interrupts
In order to ease detecting the status of the battery
temperature, the charger features the ability to
generate interrupts based upon the status of the
battery temperature. Set the TEMPOUT[ ] bit to 1
and TEMPSTAT[ ] bit to 1 to generate an interrupt
when battery temperature goes out of the valid
temperature range. Set the TEMPIN[ ] bit to 1 and
TEMPSTAT[ ] bit to 1 to generate an interrupt when
battery temperature returns to the valid range.
TEMPDAT[ ] indicates the status of the battery
temperature. A value of 1 indicates the battery
temperature is inside of the valid range, a value of 0
indicates the battery is outside of the valid range.
When an interrupt is generated by the battery
temperature event, reading the TEMPSTAT[ ]
returns a value of 1. TEMPSTAT[ ] is automatically
cleared to 0 upon reading. When no interrupt is
generated by the battery temperature event,
reading the TEMPSTAT[ ] returns a value of 0.
Innovative PowerTM
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ActivePMUTM and ActivePathTM are trademarks of Active-Semi.
I2CTM is a trademark of NXP.
Copyright © 2012 Active-Semi, Inc.
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