Datasheet

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UDG-00116
(a) V
BATSET
< 0.25 V
(b) V
BATSET
> 1 V
13
+
9
0.25 V
BATSET
BATP
R2
V
BAT
gm AMPLIFIER
1.196 V
R1
VREF = 5 V
COMP
13
9
+
10
0.25 V
BATSET
BATP
V
BAT
gm AMPLIFIER
1.25 V
COMP
10
bq24702
bq24703
SLUS553E – MAY 2003 – REVISED OCTOBER 2007
The overall accuracy of the battery charge regulation voltage is a function of the bypassed 5-V reference voltage
tolerance as well as the tolerances on R1 and R2. The precision voltage reference has a 0.5% tolerance making
it suitable for the tight battery voltage requirements of Li-ion batteries. Tolerance resistors of 0.1% are
recommended for R1 and R2 as well as any resistors used to set BATSET.
The bq24702/bq24703 provides the capability of using an internal precision voltage reference through the use of
a multiplexing scheme, refer to Figure 4 , on the BATSET pin. When BATSET voltage is less than 0.25 V, an
internal reference is switched in and the BATSET pin is switched out from the g
m
amplifier input. When the
BATSET voltage is greater than 0.25 V, the BATSET pin voltage is switched in to the input of the g
m
amplifier
and the voltage reference is switched out.
NOTE:
The minimum recommended BATSET is 1.0 V, if BATSET is used to set the voltage
loop.
Figure 4. Battery Error Amplifier Input Multiplexing Scheme
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Product Folder Link(s): bq24702 bq24703