BQ2018TS-E1 Datasheet, PDF (4/25 Pages) Texas Instruments – Power Minder IC

bq2018
BAT+
VCC
HDQ
d
Q1
SST113
s
VCC
C5
0.01µF
C1
0.1µF
R5
100
U1
1
REG
2
3 ^VCC
VSS
4
HDQ
8
WAKE
7
SR1 ₆
SR2
5
RBI
BQ2018
2 D2
BZX84C5V6
C2
0.1µF
C3
R6
1K
R2
100K
R1
0.05
1W
R3
100K
2 D1
BZX84C5V6
0.1µF
D3
R4
C4
BAV99
1M
0.1µF
Figure 2. Typical Application
2018typAp.eps
WAKE
BAT-
PACK-
RBI
RBI Input
The RBI input pin is used with a storage capacitor or ex-
ternal supply to provide back-up potential to the internal
RAM when V_CC drops below 2.4V. The maximum dis-
charge current is 100nA in this mode. The bq2018 out-
puts V_CC on RBI when the supply is above 2.4V, so a di-
ode is required to isolate an external supply.
Charge/Discharge Count Operation
Table 2 shows the main counters and registers of the
bq2018. The bq2018 accumulates charge and discharge
counts into two main count registers, the Discharge
Count Register (DCR) and the Charge Count Register
(CCR). The bq2018 produces charge and discharge
counts by sensing the voltage difference across a low-
value resistor between the negative terminal of the bat-
tery pack and the negative terminal of the battery. The
DCR or CCR counts depending on the signal between
SR1 and SR2.
During discharge, the DCR and the Discharge Time
Counter (DTC) are active. If V_SR1 is less than V_SR2, indi-
cating a discharge, the DCR counts at a rate equivalent to
12.5µV every hour, and the DTC counts at a rate of 1
count/0.8789 seconds (4096 counts per 1 hour). For exam-
ple, a -100mV signal produces 8000 DCR counts and 4096
DTC counts each hour. The amount of charge removed
from the battery can easily be calculated.
Table 2. bq2018 Counters
Name
DCR
CCR
SCR
DTC
Description
Discharge count register
Charge count register
Self-discharge count register
Discharge time counter
CTC
MODE/
WOE
Charge time counter
MODE/
Wake output enable
Range
V_SR1 < V_SR2 (Max. =-200mV) 12.5µVh increments
V_SR1 > V_SR2 (Max. = +200mV) 12.5µVh increments
1 count/hour @ 25°C
1 count/0.8789s default
1 count/225s if STD is set
1 count/0.8789s default
1 count/225s if STC is set
—
RAM Size
16-bit
16-bit
16-bit
16-bit
16-bit
8-bit
4