LTC3300-1 Datasheet, PDF (18/44 Pages) Linear Technology – High Effciency Bidirectional Multicell Battery Balancer

LTC3300-1
OPERATION
Balancing High Voltage Battery Stacks
TOP
Balancing series connected batteries which contain >>12
cells in series requires interleaving of the transformer sec-
ondary connections in order to achieve full stack balancing
while limiting the breakdown voltage requirements of the
primary- and secondary-side power FETs. Figure 4 shows
typical interleaved transformer connections for a multicell
battery stack in the generic sense, and Figure 5 for the
specific case of an 18-cell stack. In these examples, the
secondary side of each transformer is connected to the
top of the cell that is 12 positions higher in the stack than
the bottom of the lowest voltage cell in each LTC3300-1
sub-stack. For the top most LTC3300-1 in the stack, it is
not possible to connect the secondary side of the trans-
former across 12 cells. Instead, it is connected to the top
of the stack, or effectively across only 6 cells. Interleaving
in this fashion allows charge to transfer between 6-cell
sub-stacks throughout the entire battery stack.
Max On-Time Volt-Sec Clamps
FROM CELL N-12
SECONDARY
LTC3300-1
PRI POWER STAGES SEC
CELL N
••
•
CELL N-6
TO CELL 24
••
LTC3300-1
•
SEC POWER STAGES PRI
•
+
CELL 18
•
•
••
•
+
CELL 13
•
LTC3300-1
PRI POWER STAGES SEC
The LTC3300-1 contains programmable fault protection
clamps which limit the amount of time that current is
allowed to ramp in either the primary or secondary wind-
ings in the event of a shorted sense resistor. Maximum
on time for all primary connections (active during cell
discharging) and all secondary connections (active during
cell charging) is individually programmable by connecting
resistors from the R_TONP and R_TONS pins to V^– according
to the following equations:
t_{ON(MAX )|PRIMARY}
=
7.2µs
R_TONP
20kΩ
t_{ON(MAX )|SECONDARY}
=
1.2µs
R_TONS
15kΩ
For more information on selecting the appropriate
maximum on-times, refer to the Applications Information
section.
To defeat this function, short the appropriate R_TON pin(s)
to V_REG.
CELL 12
•••
CELL 7
LTC3300-1
SEC POWER STAGES PRI
•
+
••
+
••
+
••
+
••
+
••
+
•
CELL 6
CELL 5
CELL 4
CELL 3
CELL 2
CELL 1
33001 F04
Figure 4. Diagram of Power Transfer Interleaving Through the
Stack, Transformer Connections for High Voltage Stacks
33001f
18
For more information www.linear.com/product/LTC3300-1