LTC6801 datasheet(8/28 Pages) AD

8 / 28 page

LTC6801

Rev. F

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PIN FUNCTIONS

V+ (Pin 1): Supply Voltage. Tied to the most positive

potential in the battery stack. For example, the same

potential as C12 when measuring a stack of 12 cells, or

the same potential as C7 when measuring a stack of 7

cells.

C12, C11, … C1 (Pin 2 to Pin 13): Cell Voltage Inputs.

Up to 12 cells can be monitored. The lowest potential

is tied to V–. The next lowest potential is tied to C1 and

so forth. Due to internal overvoltage protection, each

C input must be tied to a potential equal to or greater

than the next lower numbered C input. See the figures

in the Applications Information section for more details

on connecting batteries to the LTC6801. See Electrical

Characteristics table for voltage range and input bias

current requirements.

V– (Pin 14): Tied to the most negative cell potential (bot-

tom of monitored cell stack).

VTEMP1, VTEMP2 (Pin 15, Pin 16): Temperature Sensor

Inputs. The ADC will measure the voltages on VTEMP1

and VTEMP2 relative to V–. The ADC measurements are

referenced to the VREF pin voltage. Therefore a simple

thermistor and resistor combination connected to the

VREF pin can be used to monitor temperature. These pins

have a fixed undervoltage threshold equal to one half VREF.

A filtering capacitor to V– is recommended. Temperature

sensor input pins may be tied to VREF to disable.

VREF (Pin 17): Reference Output, Nominally 3.058V.

Re-quires a 1µF bypass capacitor to V–. The VREF pin can

drive a 100k resistive load connected to V–. VREF must

be buffered with an LT6003 amplifier, or similar device to

drive heavier loads. VREF becomes high impedance when

the IC is disabled or idle between monitoring events.

VREG (Pin 18): Regulator Output, Nominally 5V. Requires

a 1µF bypass capacitor to V–. The VREG pin is capable of

supplying up to 1mA to an external load and is continually

enabled.

EIN, EIN (Pin 19, Pin 20): Differential Enable Input. A

clock signal greater than 2kHz will enable the LTC6801.

For operation with a single-ended enable signal (up to

10kHz), drive EIN and connect a 1nF capacitor from EIN

to V–.

SOUT, SOUT (Pin 21, Pin 22): Differential Status Output.

Swings V– to VREG. This output will toggle at the same

frequency as EIN/EIN when a valid signal is detected at SIN/

SIN and the battery stack being monitored is within spec-

ified parameters, otherwise SOUT is low and SOUT high.

SIN, SIN (Pin 23, Pin 24): Differential status input from

the IC above. To indicate that the stack is good, SIN must

be the same frequency and phase as EIN. See applications

circuits for interfacing SIN to the SOUT above.

EOUT, EOUT (Pin 25, Pin 26): A Buffered Version of EIN/

EIN. Swings V– to VREG. Must be capacitively coupled to

the EIN/EIN inputs of the next higher voltage LTC6801 in a

stack, or looped to SIN/SIN of the same chip (pins 23, 24).

DC (Pin 27): Duty Cycle Three-Level Input. This pin may

be tied to VREG, VREF or V–. The DC pin selects the duty

cycle of the monitoring function and has an internal

pull-up to VREG. See Table 3.

SLTOK (Pin 28): Self Test Logic Output. SLTOK is held

HIGH (VREG voltage) upon reset or successful comple-

tion of a self test cycle. A LOW output level (V– voltage)

indicates the last self test cycle failed.

SLT (Pin 29): Self Test Open Collector Input/Output.

SLT initiates a self test cycle when it is pulled low exter-

nally. When a high to low transition is detected, the next

scheduled measurement cycle will be a self test cycle. SLT

indicates a self test cycle is in progress when pulled low

internally. A self test is automatically initiated after 1024

measurement cycles. This pin has an internal pull-up to

VREG.

CC0, CC1 (Pin 30, Pin 31): Cell Count Three-Level Inputs.

These pins may be tied to VREG, VREF or V–. CC1 and CC0

select the number of cells attached to the device and each

pin has an internal pull-up to VREG. See Table 5.

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