Datasheet

The CACD value is the available charge compensated
for the rate of discharge. At high discharge rates, CACD
is reduced. The reduction is maintained until a valid
charge is detected. The CACT value is the available
charge compensated for the rate of discharge and tem
-
perature. The CACT value is used to drive the LED dis
-
play.
Charge Compensation
The bq2050H also monitors temperature during charge.
If the temperature is <0°C, NAC will only increment up
to 0.94 * LMD, inhibiting VDQ from being set. This
keeps a “learn” cycle from occurring when the battery is
charged at very low temperatures. If the temperature
rises above 0°C, NAC will be allowed to count up to NAC
= LMD.
Self-Discharge Compensation
The self-discharge compensation is programmed for a
nominal rate of
1
512
∗ NAC per day. This is the rate that
NAC is reduced for a battery within the 20–30°C tem
-
perature range. This rate varies across 8 ranges from
<10°C to >70°C, as shown in Table 5.
Self-discharge may be disabled by connecting PROG
5
=H.
Digital Magnitude Filter
The bq2050H has a digital filter to eliminate charge and
discharge counting below a set threshold. The minimum
charge (V
SRQ
) and discharge (V
SRD
) threshold for the
bq2050H is 250µV.
Pack Protection Supervision
The bq2050H can monitor the charge FET in a Li-Ion
pack protector circuit as shown in Figure 3. If the bat
-
tery voltage is too high or the temperature is out of the
0—60°C range, the bq2050H disables the charge FET
with the CFC output, which turns off the charge to the
pack.
The PSTAT input is used to monitor the protector state. If
PSTAT is above 2.5V, bit 5 of FLGS1 is set to 1. If PSTAT
is below 0.5V, bit 5 of FLGS1 is cleared to zero. Using this
input, the system can monitor the state of the charge con
-
8
bq2050H
Temperature Range
Typical Rate
PROG
5
= Z or L
< 10°C
NAC
2048
10–20°C
NAC
1024
20–30°C
NAC
512
30–40°C
NAC
256
40–50°C
NAC
128
50–60°C
NAC
64
60–70°C
NAC
32
> 70°C
NAC
16
Table 5. Self-Discharge Compensation
Approximate Discharge
Rate
Available Capacity
Reduction
<
0.5C 0
≥
0.5C
0.05 ∗ LMD
Table 3A. Graphite Anode
Temperature
Available Capacity
Reduction
≥
10°C 0
0°C to 10°C
0.05 ∗ LMD
-20°C to 0°C
0.15 ∗ LMD
≤
-20°C
0.37 ∗ LMD
Table 3B. Graphite Anode
Approximate Discharge
Rate
Available Capacity
Reduction
<
0.5C 0
≥
0.5C
0.10 ∗ LMD
Table 4A. Coke Anode
Temperature
Available Capacity
Reduction
≥
10°C 0
0°C to 10°C
0.10 ∗ LMD
-20°C to 0°C
0.30 ∗ LMD
≤
-20°C
0.60 ∗ LMD
Table 4B. Coke Anode