LTC6802IG-2 LINER [Linear Technology], LTC6802IG-2 Datasheet - Page 8

• Manufacturer Part Number: LTC6802IG-2
• Description: Multicell Addressable Battery Stack Monitor
• Manufacturer: LINER [Linear Technology]

pin FuncTions
LTC6802-2
V
the battery stack. V
potential as C12.
C12, C11, C10, C9, C8, C7, C6, C5, C4, C3, C2, C1
(Pins 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24): C1
through C12 are the inputs for monitoring battery cell
voltages. Up to 12 cells can be monitored. The lowest
potential is tied to the V
is tied to C1 and so forth. See the figures in the Applica-
tions Information section for more details on connecting
batteries to the LTC6802-2.
S12, S11, S10, S9, S8, S7, S6, S5, S4, S3, S2, S1
(Pins 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25): S1 though
S12 pins are used to balance battery cells. If one cell in a
series becomes over charged, an S output can be used to
discharge the cell. Each S output is an internal N-channel
MOSFET for discharging. See the Block Diagram. The NMOS
has a maximum on-resistance of 20Ω. An external resistor
should be connected in series with the NMOS to dissipate
heat outside of the LTC6802-2 package. When using the
internal MOSFETs to discharge cells, the die temperature
should be monitored. See Power Dissipation and Thermal
Shutdown in the Applications Information section.
The S pins also feature an internal 10k pull-up resistor. This
allows the S pins to be used to drive the gates of external
P-channel MOSFETs for higher discharge capability.
V
the series of cells.
NC (Pin 27): Pin 27 is internally connected to V
10Ω. Pin 27 can be left unconnected or connect Pin 27
to Pin 26 on the PCB.
V
The ADC will measure the voltage on V
to V
measurements are relative to the V
a simple thermistor and resistor combination connected
to the V
V

TEMP1
TEMP
+
–
(Pin 26): Connect V
(Pin 1): Tie Pin 1 to the most positive potential in
–
and store the result in the TMP register. The ADC
inputs can also be general purpose ADC inputs.
, V
REF
TEMP2
pin can be used to monitor temperature. The
(Pins 28, 29): Temperature Sensor Inputs.
+
must be approximately the same
–
to the most negative potential in
–
pin. The next lowest potential
REF
pin voltage. Therefore
TEMPx
with respect
–
through
V
should be bypassed with a 1µF capacitor. The V
drive a 100k resistive load connected to V
should be buffered with an LT6003 op amp, or similar
device.
V
should be bypassed with a 1µF capacitor. The V
capable of sourcing up to 4mA to an external load. The
V
TOS (Pin 32): Top of Stack Input. The TOS pin can be tied
to V
alters the operation of the SDO pin in the toggle polling
mode. See the Serial Port description.
MMB (Pin 33): Monitor Mode Input (Active Low). When
MMB is low (same potential as V
goes into monitor mode. See Modes of Operation in the
Applications Information section.
WDTB (Pin 34): Watchdog Timer Output (Active Low). If
there is no activity on the SCKI pin for 2.5 seconds, the
WDTB output is asserted. The WDTB pin is an open-drain
NMOS output. When asserted it pulls the output down
to V
state. See Watchdog Timer Circuit in the Applications
Information section.
GPIO1, GPIO2 (Pins 35, 36): General Purpose Input/Out-
put. The operation of these pins depends on the state of
the MMB pin.
When MMB is high, the pins behave as traditional GPIOs.
By writing a “0” to a GPIO configuration register bit, the
open drain output is activated and the pin is pulled to V
By writing a logic “1” to the configuration register bit, the
corresponding GPIO pin is high impedance. An external
resistor is needed to pull the pin up to V
By reading the configuration register locations GPIO1
and GPIO2, the state of the pins can be determined. For
example, if a “0” is written to register bit GPIO1, a “0”
is always read back because the output NMOSFET pulls
Pin 35 to V
REF
REG
REG
REG
–
(Pin 30): 3.075V Voltage Reference Output. This pin
(Pin 31): Linear Voltage Regulator Output. This pin
pin does not sink current.
and resets the configuration register to its default
or V
–
–
. If a “1” is written to register bit GPIO1, the
for the LTC6802-2. The state of the TOS pin
–
), the LTC6802-2
REG
–
. Larger loads
.
REF
pin can
REG
68022fa
is
–
.