Datasheet
LTC6802-1
29
68021fa
APPLICATIONS INFORMATION
Battery Interconnection Integrity
The FMEA scenarios that are potentially most damaging are
those that involve a break in the stack of battery cells. When
the battery stack has a discontinuity between groupings
of cells monitored by LTC6802-1 ICs, any load will force
a large reverse potential on the daisy-chain connection.
This situation might occur in a modular battery system
during initial installation or a service procedure. The daisy
chain ports are protected from the reverse potential in this
scenario by external series high-voltage diodes required in
the upper-port data connections as shown in Figure 11.
During the charging phase of operation, this fault would
lead to forward biasing of daisy-chain ESD clamps that
would also lead to part damage. An alternative connection
to carry current during this scenario will avoid this stress
from being applied (Figure 11).
clamping potential. The Zener diodes labeled ZCLAMP are
higher voltage devices with an initial reverse breakdown
of 30V snapping back to 25V. The forward voltage drop
of all Zeners is 0.5V. Refer to this diagram in the event of
unpredictable voltage clamping or current flow. Limiting
the current flow at any pin to ±10mA will prevent damage
to the IC.
Figure 11. Reverse-Voltage Protection for the
Daisy-Chain (One Link Connection Shown)
Internal Protection Diodes
Each pin of the LTC6802-1 has protection diodes to help
prevent damage to the internal device structures caused
by external application of voltages beyond the supply rails
as shown in Figure 12.
The diodes shown are conventional silicon diodes with a
forward breakdown voltage of 0.5V. The unlabeled zener
diode structures have a reverse breakdown characteristic
which initially breaks down at 12V then snaps back to a 7V
RS07J (3x)
PROTECT
AGAINST
BREAK
HERE
OPTIONAL
REDUNDANT
CURRENT
PATH
LTC6802-1
(NEXT HIGHER IN STACK)
V
−
SDO
SDI
SCKI CSBI
LTC6802-1
(NEXT LOWER IN STACK)
V
+
SDOI
SCKO CSBO
68021 F11
68021 F12
LTC6802-1
S1
V
–
SCKO
WDTB
SDOI
CSBO
CSBI
V
MODE
SDO
SDI
SCKI
GPIO2
GPIO1
MMB
TOS
S2
C1
S3
C2
S4
C3
S5
C4
S6
C5
C6
S7
S8
C7
S9
C8
S10
C9
S11
C10
S12
C11
C12
V
+
ZCLAMP
ZCLAMP
ZCLAMP
Figure 12. Internal Protection Diodes