BQ2014H Datasheet, PDF (6/22 Pages) Texas Instruments – Low-Cost NiCd/NiMH Gas Gauge IC

bq2014H Preliminary
2. Programmed Full Count (PFC) or initial bat- Example: Selecting a PFC Value
tery capacity:
Given:
The initial LMD and gas gauge rate values are pro-
grammed by using PROG1–PROG4. The bq2014H
is configured for a given application by selecting a
PFC value from Table 2. The correct PFC may be
determined by multiplying the rated battery capac-
ity in mAh by the sense resistor value:
Battery capacity (mAh) _* sense resistor (Ω) =
PFC (mVh)
Sense resistor = 0.05Ω
Number of cells = 10
Capacity = 3500mAh, NiMH
Current range = 50mA to 1A
Relative display mode
Self-discharge
=
NAC
47
per
day
@
25°C
Voltage drop over sense resistor = 2.5mV to 50mV
Nominal discharge voltage = 1.2V
Therefore:
Selecting a PFC slightly less than the rated capac-
ity provides a conservative capacity reference until
the bq2014H “learns” a new capacity reference.
3500mAh _* 0.05Ω = 175mVh
Pin
Connection
H
Z
L
Table 1. Self-Discharge and Capacity Compensation
PROG₅
Self-Discharge Rate
Disabled
NAC
64
NAC
47
DISP
Display State
LEDs disabled
LEDs on when charging
LEDs on for 4s
Table 2. bq2014H Programmed Full Count mVh, V_SR Gain Selections
PROGx
12
Pro-
grammed
Full
Count
(PFC)
--
-
HH
49152
HZ
45056
HL
40960
ZH
36864
ZZ
33792
ZL
30720
LH
27648
LZ
25600
LL
22528
V_SR equivalent to 2
counts/s (nom.)
PROG₄ = L
PROG4 = Z or H
PROG₃ = H
SCALE =
1/80
614
563
512
461
422
384
346
320
282
PROG3 = Z PROG3 = L PROG3 = H PROG3 = Z PROG3 = L Units
SCALE = SCALE = SCALE = SCALE = SCALE = mVh/
1/160
1/320
1/640
1/1280
1/2560 count
307
154
76.8
38.4
19.2
mVh
282
141
70.4
35.2
17.6
mVh
256
128
64.0
32.0
16.0
mVh
230
115
57.6
28.8
14.4
mVh
211
106
53.0
26.4
13.2
mVh
192
96.0
48.0
24.0
12.0
mVh
173
86.4
43.2
21.6
10.8
mVh
160
80.0
40.0
20.0
10.0
mVh
141
70.4
35.2
17.6
8.8
mVh
90
45
22.5
11.25
5.6
2.8
mV
6