LTC6802-1_1 LINER [Linear Technology], LTC6802-1_1 Datasheet - Page 29

• Manufacturer Part Number: LTC6802-1_1
• Description: Multicell Battery Stack Monitor
• Manufacturer: LINER [Linear Technology]

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).
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
PROTECT
AGAINST
BREAK
HERE
Figure 11. Reverse-Voltage Protection for the
Daisy-Chain (One Link Connection Shown)
REDUNDANT
OPTIONAL
CURRENT
PATH
V
V
−
+
(NEXT HIGHER IN STACK)
(NEXT LOWER IN STACK)
SDO
SDOI SCKO CSBO
LTC6802-1
LTC6802-1
SDI
SCKI CSBI
68021 F11
RS07J (3x)
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.
V
C12
S12
C11
S11
C10
S10
C9
S9
C8
S8
C7
S7
C6
S6
C5
S5
C4
S4
C3
S3
C2
S2
C1
S1
V
+
–
Figure 12. Internal Protection Diodes
ZCLAMP
ZCLAMP
ZCLAMP
LTC6802-1
LTC6802-1
V
GPIO2
GPIO1
WDTB
SCKO
CSBO
SDOI
MODE
MMB
CSBI
SCKI
SDO
TOS
SDI
68021 F12
29
68021fa