BQ24901_13 Datasheet, PDF (14/18 Pages) Texas Instruments – OFFLNE APPLICATIONS

bq24901
SLUS527 – DECEMBER 2002
APPLICATION INFORMATION
Charge Termination and Re-Charge
The bq24901 monitors the charging current during voltage regulation. The device declares a DONE condition
and terminates charge when then the current tapers off to charge termination current detect threshold. The
charge termination level is set through TADJ pin as detailed in Table 2 and Figure 7.
Table 2. Charge Termination Adjustment
TADJ INPUT
Connected directly to VREF pin
Connected directly to VSS pin
Connected directly to the mid-point of a resistor
divider between VREF and VSS pins (see Figure 8)
TERMINATION LEVEL
V_SNS
10
V_SNS
20
ǒ Ǔ ǒ Ǔ R2 VSNS
20 (R1 ) R2)
)
V_SNS
20
NOTE: V_SNS is the current regulation threshold.
VREF
R1
TADJ
R2
Figure 7. Charge Termination Adjustment Connection
The bq24901 also features two internal digital filters for detecting termination threshold. The digital filters, with
t_TERMDET1 and t_TERMDET2 response times, are designed to reduce the possibility of early termination due to line
or switching frequency noise.
A new charge cycle is initiated when one of the following conditions are detected:
1. Battery voltage falls below the V_RCH threshold
2. New battery insertion (once battery falls below the V_RCH threshold)
3. Power-on reset (POR)
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