BQ2050_15 Datasheet, PDF (7/27 Pages) Texas Instruments – Lithium Ion Power Gauge™ IC

Not Recommended For New Designs
bq2050
Select:
E(mWh) = (SAEH * 256 + SAEL) *
PFC = 30720 counts or 48mVh
2.4 ∗ SCALE ∗ (R _B1 + R _B2 )
PROG1 = float
PROG2 = low
R _S ∗ R _B2
PROG3 = high
where RB1, RB2 and RS are resistor values in ohms.
PROG4 = float
SCALE is the selected scale from Table 2. SAEH
PROG5 = float
and SAEL are digital values read via DQ.
PROG6 = float
6. Compensated Available Capacity (CAC)
The initial full battery capacity is 48mVh (960mAh)
until the bq2050 “learns” a new capacity with a
qualified discharge from full to EDV1.
CAC counts similar to NAC, but contains the avail-
able capacity compensated for discharge rate and
temperature.
3. Nominal Available Capacity (NAC):
Charge Counting
NAC counts up during charge to a maximum value
of LMD and down during discharge and self-dis- Charge activity is detected based on a positive voltage
charge to 0. NAC is reset to 0 on initialization and on
the first valid charge following discharge to EDV1. To
prevent overstatement of charge during periods of
on the VSR input. If charge activity is detected, the
bq2050 increments NAC at a rate proportional to VSR and,
if enabled, activates an LED display. Charge actions in-
overcharge, NAC stops incrementing when NAC = crement the NAC after compensation for temperature.
LMD.
The bq2050 determines charge activity sustained at a
4. Discharge Count Register (DCR):
continuous rate equivalent to VSRO > VSRQ. A valid
The DCR counts up during discharge independent of
NAC and could continue increasing after NAC has
decremented to 0. Prior to NAC = 0 (empty battery),
both discharge and self-discharge increment the
DCR. After NAC = 0, only discharge increments the
charge equates to sustained charge activity greater
than 256 NAC counts. Once a valid charge is detected,
charge counting continues until VSRO (VSR + VOS) falls
below VSRQ. VSRQ is 210µV, and is described in the
Digital Magnitude Filter section.
DCR. The DCR resets to 0 when NAC = LMD. The
DCR does not roll over but stops counting when it
Discharge Counting
reaches FFFFh.
Discharge activity is detected based on a negative voltage
The DCR value becomes the new LMD value on the
first charge after a valid discharge to VEDV1 if:
on the VSR input. All discharge counts where VSRO < VSRD
cause the NAC register to decrement and the DCR to
increment. VSRD is -200µV, and is described in the
No valid charge initiations (charges greater than ^{Digital Magnitude Filter section.}
256 NAC counts, where VSRO > VSRQ) occurred dur-
ing the period between NAC = LMD and EDV1 de- ^{Self-Discharge Estimation}
tected.
The bq2050 continuously decrements NAC and increments
The self-discharge count is not more than 4096 DCR for self-discharge based on time and temperature. The
counts (8% to 18% of PFC, specific percentage self-discharge count rate is programmed to be a nominal
threshold determined by PFC).
The temperature is ≥ 0°C when the EDV1 level is
reached during discharge.
1
512
*
NAC
per
day
or
disabled.
This is the rate for a bat-
tery whose temperature is between 20°–30°C. The NAC
register cannot be decremented below 0.
The valid discharge flag (VDQ) indicates whether Count Compensations
the present discharge is valid for LMD update.
Discharge Compensation
5. Scaled Available Energy (SAE):
Corrections for the rate of discharge, temperature, and anode
SAE is useful in determining the available energy _{type are made by adjusting an internal compensation factor.}
within the battery, and may provide a more useful _{This factor is based on the measured rate of discharge of the}
capacity reference in battery chemistries with _{battery. Tables 3A and 3B outline the correction factor typi-}
sloped voltage profiles during discharge. SAE may _{cally used for graphite anode Li-Ion batteries, and Tables 4A}
be converted to a mWh value using the following _{and 4B outline the factors typically used for coke anode}
formula:
Li-Ion batteries. The compensation factor is applied to
CAC and is based on discharge rate and temperature.
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