ltc6803g-3 Linear Technology Corporation, ltc6803g-3 Datasheet - Page 35

• Manufacturer Part Number: ltc6803g-3
• Description: Ltc6803-1/ltc6803-3 - Multicell Battery Stack Monitor
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
SUPPLY DECOUPLING IF BATTERY-STACK POWERED
As shown in Figure 23, the LTC6803-3 can have filtering
on both V
group potentials is recommended. The Zener suppresses
overvoltages from reaching the IC supply pins. A small
ferrite-bead inductor provides protection for the Zener, par-
ticularly from energetic ESD strikes. Since the LTC6803-1
cannot have a series resistance to V
diodes are needed to prevent ESD-induced reverse-supply
(substrate) currents to flow.
ADVANTAGES OF KELVIN CONNECTION ON C0
The V
drop between the negative end of the bottom battery
cell and V
to the measurement error of the bottom cell voltage for
LTC6803-1. The LTC6803-3 separates C0 from V
ing Kelvin connection on C0 as shown in Figure 24. Any
voltage drop on V
voltage measurement. The Kelvin connection will also
allow RC filtering on V
CELLGROUP
CELLGROUP
CELLGROUP
CELLGROUP
–
trace resistance can cause an observable voltage
+
–
+
–
+
–
and V
pin of LTC6803. This voltage drop will add
BLM31PG330SN1L
BLM31PG330SN1L
CMHZ5265B
CMHZ5265B
Figure 23. Supply Decoupling
–
–
, so differential bypassing to the cell
trace will not affect the bottom cell
LTC6803-1 Configuration
LTC6803-3 Configuration
–
as shown in Figure 23.
100
100
BAT46W
–
100nF
, additional Schottky
V
V
+
–
100
680313 F23
100nF
–
, allow-
V
V
+
–
HARDWARE SHUTDOWN
To completely shut down the LTC6803 a PMOS switch can
be connected to V
power supply. Figure 25 shows an example of a switched
V
1.8V, no current will flow through the stacked MMBTA42s
and the 1M resistors. TP0610Ks will be completely shut
off. If SHDN > 2.5V, M7 will be turned on and all TP0610Ks
will be turned on.
Figure 26 is an example of isolated power supply. This
circuit provides power for two LTC6803s used to monitor
24 series connected battery cells. When 5V is removed, the
LTC6803s will draw 1nA from the battery cells. Note that
use of an external V
SPI operation at low total stack potentials (below 5V).
PCB LAYOUT CONSIDERATIONS
The V
capacitor for best performance. The LTC6803 is capable of
operation with as much as 55V between V
should be taken on the PCB layout to maintain physical
separation of traces at different potentials. The pinout of
+
. The breakdown voltage of DZ4 is about 1.8V. If SHDN <
+
+
+
+
REG
Figure 24. Kelvin Connection on C0 Improving
Bottom Cell Voltage Measurement Accuracy
BATTERY
STACK
I
and V
SUPPLY
R
LTC6803-1/LTC6803-3
REF
C1
V
LTC6803-1
–
+
, or V
pins should be bypassed with a 1µF
+
supply will not protect daisy-chain
+
can be driven from an isolated
+
+
+
+
BATTERY
STACK
I
SUPPLY
R
+
C1
C0
V
LTC6803-3
–
and V
680313 F24
35
–
. Care
680313f