BQ2050H_15 Datasheet, PDF (7/30 Pages) Texas Instruments – Low-Cost Lithium Ion Power Gauge™ IC

Not Recommended For New Designs
bq2050H
Select:
PFC = 30720 counts or 48mVh
PROG1 = float
PROG₂ = low
PROG₃ = high
PROG₄ = float
PROG₅ = float
The initial full battery capacity is 48mVh (960mAh)
until the bq2050H “learns” a new capacity with a
qualified discharge from full to EDV1.
3. Nominal Available Capacity (NAC):
NAC counts up during charge to a maximum value
of LMD and down during discharge and self-dis-
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 overcharge, NAC stops incrementing
when NAC = LMD.
4. Discharge Count Register (DCR):
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 in-
crement the DCR. After NAC = 0, only discharge
increments the DCR. The DCR resets to 0 when
NAC = LMD. The DCR does not roll over but stops
counting when it reaches FFh.
The DCR value becomes the new LMD value on the
first charge after a valid discharge to V_EDV1 if all
the following conditions are met:
I No valid charge initiations (charges greater than
2 NAC updates where V_SRO > V_SRQ) occurred
during the period between NAC = LMD and EDV1.
I The self-discharge is less than 6% of NAC.
I The temperature is ≥ 0°C when the EDV1 level
is reached during discharge.
I VDQ is set
The valid discharge flag (VDQ) indicates whether
the present discharge is valid for LMD update. If
the DCR update value is less than 0.94 ∗ LMD, LMD
will only be modified by 0.94 ∗ LMD. This prevents
invalid DCR values from corrupting LMD.
5. Scaled Available Energy (SAE):
SAE is useful in determining the available energy
within the battery, and may provide a more useful
capacity reference in battery chemistries with
sloped voltage profiles during discharge. SAE may
be converted to an mWh value using the following
formula:
E(mWh) = (SAEH ∗ 256 + SAEL) ∗
1.2 ∗ SCALE ∗ (RB1 + RB2)
RS ∗ RB2
where R_B1, R_B2, and R_S are resistor values in
ohms, as shown in Figure 1. SCALE is the selected
scale from Table 2.
6. Compensated Available Capacity (CACT)
CACT counts similarly to NAC, but contains the available
capacity compensated for discharge rate and temperature.
Charge Counting
Charge activity is detected based on a positive voltage
on the SR input. If charge activity is detected, the
bq2050H increments NAC at a rate proportional to V_SR
and, if enabled, activates an LED display.
The bq2050H counts charge activity when the voltage at
the SR input (V_SRO) exceeds the minimum charge
threshold (V_SRQ). A valid charge is detected when NAC
has been updated twice without discharging or reaching
the digital magnitude filter time-out. Once a valid
charge is detected, charge counting continues until V_SR,
including offset, falls below V_SRQ.
Discharge Counting
Discharge activity is detected based on a negative volt-
age on the SR input. All discharge counts where V_SRO
is less than the minimum discharge threshold (V_SRD)
cause the NAC register to decrement and the DCR to
increment.
Self-Discharge Counting
The bq2050H continuously decrements NAC and incre-
ments DCR for self-discharge based on time and tempera-
ture.
Charge/Discharge Current
The bq2050H current-scale registers, VSRH and VSRL,
can be used to determine the battery charge or dis-
charge current. See the Current Scale Register descrip-
tion for details.
Count Compensations
Compensated Available Capacity
Compensated Available Capacity compensation is based
on the rate of discharge, temperature, and negative
electrode type. Tables 3A and 3B outline the correction
factor typically used for graphite-anode Li-Ion batteries,
and Tables 4A and 4B outline the factors typically used for
coke-anode Li-Ion batteries. The compensation factor is
applied to NAC to derive the CACD and CACT values.
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