BQ2031PN-A5 Datasheet, PDF (8/19 Pages) Texas Instruments – Lead-Acid Fast-Charge IC

bq2031
n LTF—Low-temperature fault—Lower limit of the
temperature range in which charging is allowed. VLTF
= 0.6 * VCC
A resistor-divider network must be implemented that
presents the defined voltage levels to the TS pin at the
desired temperatures (see Figure 8).
The equations for determining RT1 and RT2 are:
Equation 4
0.6
∗
V_CC
=
1
+
(V_CC − 0.250V )
RT1 ∗ (RT2 + R _LTF )
(RT2 ∗ R _LTF )
Equation 5
0.44 =
1
1 + ^{RT1 ∗ (RT2 + R HTF )}
(RT2 ∗ R _HTF )
where:
n RLTF = thermistor resistance at LTF
n RHTF = thermistor resistance at HTF
TCO is determined by the values of RT1 and RT2. 1%
resistors are recommended.
VCC
bq2031
13
VCC
12
VSS
SNS ⁷
TS ⁸
VSS
RT1
NTC
Thermistor
RT2 ^RT
t
BAT -
RSNS
FG203105.eps
Figure 8. Configuring
Temperature Sensing
Disabling Temperature Sensing
Temperature sensing can be disabled by removing RT
and using a 100kΩ resistor for RT1 and RT2.
Temperature Compensation
The internal voltage reference used by the bq2031 for all
voltage threshold determinations is compensated for
temperature. The temperature coefficient is -3.9mV/°C,
normalized to 25°C. Voltage thresholds in the bq2031
vary by this proportion as ambient conditions change.
Fast-Charge Termination
Fast-charge termination criteria are programmed with
the fast charge algorithm per Table 1. Note that not all
criteria are applied in all algorithms.
Minimum Current
Fast charge terminates when the charging current drops
below a minimum current threshold programmed by the
value of IGSEL (see Table 3). This is used by the Two-
Step Voltage algorithm.
Table 3. I_MIN Termination Thresholds
IGSEL
0
1
Z
IMIN
IMAX/10
IMAX/20
IMAX/30
8