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LTC6803-2

Multicell Battery Stack Monitor

Linear Technology 

LTC6803-2/LTC6803-4

PIN FUNCTIONS

To ensure pin compatibility with LTC6802-2, the LTC6803‑2

is configured such that the bottom cell input (C0) is con-

nected internally to the negative supply voltage (V–). The

LTC6803-4 offers a unique pinout with an input for the

bottom cell (C0). This simple functional difference offers

the possibility for enhanced cell 1 measurement accuracy,

enhanced SPI noise tolerance and simplified wiring. More

information is provided in the Applications Information

section entitled Advantages of Kelvin Connection for C0.

V+ (Pin 1): Positive Power Supply. Pin 1 can be tied to the

most positive potential in the battery stack or an isolated

power supply. V+ must be greater than the most positive

potential in the battery stack under normal operation. With

an isolated power supply, LTC6803 can be turned off by

simply shutting down V+.

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. The negative terminal of the bottom cell should

be tied to the V– pin for the LTC6803-2, and the C0 pin for

the LTC6803-4. The next lowest potential is tied to C1 and

so forth. See the figures in the Applications Information

section for more details on connecting batteries to the

LTC6803-2 and LTC6803-4. The LTC6803 can monitor a

series connection of up to 12 cells. Each cell in a series

connection must have a common mode voltage that is

greater than or equal to the cells below it. 100mV negative

voltages are permitted.

C0 (Pin 26 on LTC6803-4): Negative Terminal of the Bot-

tom Battery Cell. C0 and V– form a Kelvin connection to

eliminate effect of voltage drop at the V– trace.

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 overcharged, an S output can be used to

discharge the cell. Each S output has 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 LTC6803 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 pull-up PMOS. This allows the

S pins to be used to drive the gates of external MOSFETs

for higher discharge capability.

V– (Pin 26 on LTC6803-2/Pin 27 on LTC6803-4): Connect

V– to the most negative potential in the series of cells.

NC (Pin 27 on LTC6803-2/Pin 28 on LTC6803-4): This pin

is not used and is internally connected to V– through 10Ω.

It can be left unconnected or connected to V– on the PCB.

VTEMP1, VTEMP2 (Pins 28, 29 on LTC6803-2/Pins 29, 30,

on LTC6803-4): Temperature Sensor Inputs. The ADC will

measure the voltage on VTEMPn with respect to V– and store

the result in the TMP register. The ADC measurements

are relative to the VREF pin voltage. Therefore a simple

thermistor and resistor combination connected to the

VREF pin can be used to monitor temperature. The VTEMP

inputs can also be general purpose ADC inputs.

VREF (Pin 30 on LTC6803-2/Pin 31 on LTC6803-4): 3.065V

Voltage Reference Output. This pin should be bypassed

with a 1µF capacitor. The VREF pin can drive a 100k resis-

tive load connected to V–. Larger loads should be buffered

with an LT6003 op amp, or a similar device.

VREG (Pin 31 on LTC6803-2/Pin 32 on LTC6803-4): Linear

Voltage Regulator Output. This pin should be bypassed with

a 1µF capacitor. The VREG is capable of sourcing up to 4mA

to an external load. The VREG pin does not sink current.

TOS (Pin 32 on LTC6803-2/Pin 33 on LTC6803-4): Top

of Stack Input. The TOS pin can be tied to VREG or V– for

the LTC6803. The state of the TOS pin alters the operation

of the SDO pin in the toggle polling mode. See the Serial

Port description.

NC (Pin 33 on LTC6803-2): No Connection.

680324f

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