BQ2050_15 Datasheet, PDF (14/27 Pages) Texas Instruments – Lithium Ion Power Gauge™ IC

Not Recommended For New Designs
bq2050
driver. For example, if SEG3 and SEG6 have pull-up resis-
tors, the contents of PPU are xx100100.
PPD/PPU Bits
7
6
5
4
3
2
1
0
-
- PPU6 PPU₅ PPU4 PPU3 PPU2 PPU1
-
- PPD6 PPD₅ PPD4 PPD3 PPD2 PPD1
Capacity Inaccurate Count Register (CPI)
The read-only CPI register (address=09h) is used to in-
dicate the number of times a battery has been charged
without an LMD update. Because the capacity of a re-
chargeable battery varies with age and operating condi-
tions, the bq2050 adapts to the changing capacity over
time. A complete discharge from full (NAC=LMD) to
empty (EDV1=1) is required to perform an LMD update
assuming there have been no intervening valid charges,
the temperature is greater than or equal to 0°C, and the
self-discharge counter is less than 4096 counts.
The CPI register is incremented every time a valid
charge is detected. When NAC > 0.94 _* LMD, however,
the CPI register increments on the first valid charge;
CPI does not increment again for a valid charge until
NAC < 0.94 _* LMC. This prevents continuous trickle
charging from incrementing CPI if self-discharge decre-
ments NAC. The CPI register increments to 255 with-
out rolling over. When the contents of CPI are incre-
mented to 64, the capacity inaccurate flag, CI, is as-
serted in the FLGS1 register. The CPI register is reset
whenever an update of the LMD register is performed,
and the CI flag is also cleared.
Battery Voltage Register (VSB)
The read-only battery voltage register is used to read the
single-cell battery voltage on the SB pin. The VSB regis-
ter (address = 0Bh) is updated approximately once per sec-
ond with the present value of the battery voltage. VSB =
2.4V _* (VSB/256).
VSB Register Bits
7
6
5
4
3
2
1
0
VSB7 VSB6 VSB5 VSB4 VSB3 VSB2 VSB1 VSB0
Voltage Threshold Register (VTS)
The end-of-discharge threshold voltages (EDV1 and
EDVF) can be set using the VTS register (address =
0Ch). The read/write VTS register sets the EDV1 trip
point. EDVF is set 50mV below EDV1. The default
value in the VTS register is A2h, representing EDV1 =
1.52V and EDVF = 1.47V. EDV1 = 2.4V _* (VTS/256).
VTS Register Bits
7
6
5
4
3
2
1
0
VTS7 VTS6 VTS5 VTS4 VTS3 VTS2 VTS1 VTS0
Compensated Available Charge Registers
(CACH/CACL)
The read-only CACH high-byte register (address = 0Dh)
and the read-only CACL low-byte register (address =
0Eh) represent the available charge compensated for
discharge rate and temperature. CACH and CACL use
piece-wise corrections as outlined in Tables 3A, 3B, 4A,
and 4B, and will vary as conditions change. The NAC
and LMD registers are not affected by the discharge
rate and temperature.
Scaled Available Energy Registers
(SAEH/SAEL)
The read-only SAEH high-byte register (address = 0Fh)
and the read only SAEL low-byte register (address =
10h) are used to scale battery voltage and CAC to a
value which can be translated to watt-hours remaining
under the present conditions. SAEL and SAEH may be
converted to mWh using the formula on page 7.
Reset Register (RST)
The reset register (address = 39h) enables a software-
controlled reset of the device. By writing the RST regis-
ter contents from 00h to 80h, a bq2050 reset is per-
formed. Setting any bit other than the most-significant
bit of the RST register is not allowed and results in im-
proper operation of the bq2050.
Resetting the bq2050 sets the following:
n LMD = PFC
n CPI, VDQ, NACH, and NACL = 0
n CI and BRP = 1
Note: Self-discharge is disabled when PROG5 = H.
Display
The bq2050 can directly display capacity information
using low-power LEDs. If LEDs are used, the program
pins should be resistively tied to VCC or VSS for a pro-
gram high or program low, respectively.
The bq2050 displays the battery charge state in relative
mode. In relative mode, the battery charge is represented
as a percentage of the LMD. Each LED segment repre-
sents 20% of the LMD.
The capacity display is also adjusted for the present bat-
tery temperature. The temperature adjustment reflects
the available capacity at a given temperature but does
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