Datasheet

2. Programmed Full Count (PFC) or initial bat
-
tery capacity:
The initial LMD and gas gauge rate values are pro
-
grammed by using PROG
1
–PROG
4
. The bq2050 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)
Selecting a PFC slightly less than the rated capac
-
ity provides a conservative capacity reference until
the bq2050 “learns” a new capacity reference.
Example: Selecting a PFC Value
Given:
Sense resistor = 0.05
Ω
Number of cells = 2
Capacity = 1000mAh, Li-Ion battery, coke-anode
Current range = 50mA to 1A
Relative display mode
Serial port only
Self-discharge =
NAC
512
per day @ 25°C
Voltage drop over sense resistor = 2.5mV to 50mV
Nominal discharge voltage = 3.6V
Therefore:
1000mAh
*
0.05
Ω
= 50mVh
6
bq2050
PROG
x
Pro-
grammed
Full
Count
(PFC)
PROG
4
= L PROG
4
= Z
Units
1 2 PROG3 = H PROG3 = Z PROG3 = L PROG3 = H PROG3 = Z PROG3 = L
-- -
SCALE =
1/80
SCALE =
1/160
SCALE =
1/320
SCALE =
1/640
SCALE =
1/1280
SCALE =
1/2560
mVh/
count
H H 49152 614 307 154 76.8 38.4 19.2 mVh
H Z 45056 563 282 141 70.4 35.2 17.6 mVh
H L 40960 512 256 128 64.0 32.0 16.0 mVh
Z H 36864 461 230 115 57.6 28.8 14.4 mVh
Z Z 33792 422 211 106 53.0 26.4 13.2 mVh
Z L 30720 384 192 96.0 48.0 24.0 12.0 mVh
L H 27648 346 173 86.4 43.2 21.6 10.8 mVh
L Z 25600 320 160 80.0 40.0 20.0 10.0 mVh
L L 22528 282 141 70.4 35.2 17.6 8.8 mVh
VSR equivalent to 2
counts/sec. (nom.)
90 45 22.5 11.25 5.6 2.8 mV
Table 2. bq2050 Programmed Full Count mVh Selections
Pin
Connection
PROG
5
Compensation/
Self-Discharge
PROG
6
NAC on Reset
DISP
Display State
H Table 4/Disabled PFC LEDs disabled
Z Table 4/
NAC
512
0 LEDs on when charging
L Table 3/
NAC
512
0 LEDs on for 4 sec.
Note: PROG
5
and PROG
6
states are independent.
Table 1. bq2050 Programming