bq2056/T/V
External
Trickle Charge
Enabled
AutoComp™
Phase
V
REG
MIN
Voltage
Voltage Regulation
I
MAX
V
Current
Regulation
2056chg.eps
Figure 2. bq2056 Charge Algorithm
voltage to compensate for the battery’s internal imped-
ance and undesired voltage drops in the circuit.
Voltage Regulation
Voltage regulation feedback is through pin BAT. This pin
is connected directly to the pack in the bq2056 and
bq2056T. This voltage is compared with the voltage
regulation reference, VREG. In the bq2056V, a resistive
divider may be used to generate this input (Figure 4). In
this case, the voltage presented on pin BAT is compared
with the internal reference voltage VREF. The resistor
values RB1 and RB2 (Figure 4) are calculated based on
the following equation:
For bq2056 and bq2056T, the voltage across the battery
pack, VPAK, is
VPAK = VREG + (KCOMP ∗ voltage on pin COMP)
For bq2056V, the compensation voltage is added to the
product of the internal voltage reference, VREF, and the
gain, KDIV, of the external resistive divider between the
battery pack and BAT input, (Figure 4).
R
R
B1
B2
N∗ VCELL
=
− 1
V
PAK = (VREF ∗ KDIV) + (KCOMP ∗ voltage on pin COMP)
VREF
where
N
Sleep Mode
= Number of cells in series
The charge function may be disabled through pin INH.
When INH is driven high, internal current consumption
is reduced, and pins CC and TRKL assumes a high-
impedance output state.
VCELL = Manufacturer-specified charging voltage
Automatic Charge-Rate Compensation
(AutoComp) Feature
To reduce charging time, the bq2056 series uses the pro-
prietary AutoComp technique to compensate safely for
internal impedance of battery and any voltage drops in
the protection circuitry. This maximizes battery’s capac-
ity while reducing charging time. Compensation is
through input pin COMP (Figure 5). A portion of the
current-sense voltage, presented through this pin, is
scaled by a factor of KCOMP and summed with the regu-
lation reference, VREG. This process increases the output
4
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