LTC3300-2_15 Datasheet, PDF (20/42 Pages) Linear Technology – Addressable High Efficiency Bidirectional Multicell Battery Balancer

LTC3300-2
OPERATION
Gate Drivers/Gate Drive Comparators
All secondary-side gate drivers (G1S through G6S) are
powered from the V_REG output, pulling up to 4.8V when
on and pulling down to V^– when off. All primary-side
gate drivers (G1P through G6P) are powered from their
respective cell voltage and the next cell voltage higher in
the stack (see Table 1). An individual cell balancer will only
be enabled if its corresponding cell voltage is greater than
2V and the cell voltage of the next higher cell in the stack
is also greater than 2V. For the G6P gate driver output,
the next higher cell in the stack is C1 of the next higher
LTC3300-2 in the stack (if present) and is only used if the
boosted gate drive is disabled (by connecting BOOST =
V^–). If the boosted gate drive is enabled (by connecting
BOOST = V_REG), only the C6 cell voltage is looked at to
enable balancing of Cell 6. In the case of the topmost
LTC3300-2 in the stack, the boosted gate drive must be
enabled. The boosted gate drive requires an external diode
from C6 to BOOST⁺ and a boost capacitor from BOOST⁺ to
BOOST^–. For information on selecting these components,
refer to the Applications Information section. Also note
that the dynamic supply current referred to in Note 4 of
the Electrical Characteristics table adds to the terminal
currents of the pins indicated in the Voltage When Off and
Voltage When On columns of Table 1.
The gate drive comparators have a DC hysteresis of 70mV.
For improved noise immunity, the inputs are internally
low pass filtered and the outputs are filtered so as to
not transition unless the internal comparator state is
unchanged for 3µs to 6µs (typical). If insufficient gate drive
is detected while active balancing is in progress (perhaps,
for example, if the stack is under heavy load), the affected
balancer(s) and only the affected balancer(s) will shut off.
The balance command remains stored in memory, and
active balancing will resume where it left off if sufficient
gate drive is subsequently restored. This can happen if,
for example, the stack is being charged.
Cell Overvoltage Comparators
In addition to sufficient gate drive being required to en-
able balancing, there are additional comparators which
disable all active balancing if any of the six individual cell
voltages is greater than 5V. These comparators have a
DC hysteresis of 500mV. For improved noise immunity,
the inputs are internally low pass filtered and the outputs
are filtered so as to not transition unless the internal
comparator state is unchanged for 3µs to 6µs (typical).
If any cell voltage goes overvoltage while active balanc-
ing is in progress, all active balancers will shut off. The
balance command remains stored in memory, and active
balancing will resume where if left off if the cell voltage
subsequently comes back in range. These comparators
will protect the LTC3300-2 if a connection to a battery is
lost while balancing and the cell voltage is still increasing
as a result of that balancing.
Voltage Regulator
A linear voltage regulator powered from C6 creates a
4.8V rail at the V_REG pin which is used for powering
certain internal circuitry of the LTC3300-2 including all 6
secondary gate drivers. The V_REG output can also be used
for powering external loads, provided that the total DC
loading of the regulator does not exceed 40mA at which
point current limit is imposed to limit on-chip power dis-
Table 1
DRIVER OUTPUT VOLTAGE WHEN OFF
VOLTAGE WHEN ON
G1P
V-
C2
G2P
C1
C3
G3P
C2
C4
G4P
C3
C5
G5P
C4
C6
G6P
C5
If BOOST = V_REG: BOOST+ (Generated)
If BOOST = V^–: BOOST⁺ = C7*
*C7 is equal to C1 of the next higher LTC3300-2 in the stack if this connection is used.
GATE DRIVE REQUIRED TO ENABLE BALANCING
(C2 – C1) ≥ 2V and (C1 – V^–) ≥2V
(C3 – C2) ≥ 2V and (C2 – C1) ≥2V
(C4 – C3) ≥ 2V and (C3 – C2) ≥2V
(C5 – C4) ≥ 2V and (C4 – C3) ≥2V
(C6 – C5) ≥ 2V and (C5 – C4) ≥2V
(C6 – C5) ≥ 2V
(C7* – C6) ≥ 2V and (C6 – C5) ≥ 2V
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