LTC6802-1_1 LINER [Linear Technology], LTC6802-1_1 Datasheet - Page 31

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

APPLICATIONS INFORMATION
in this case. Probe loads up to about 1mA maximum are
supported in this configuration. Since V
during the LTC6802-1 idle and shutdown modes, the
thermistor drive is also shut off and thus power dissipa-
tion minimized. Since V
op amp (LT6000 shown) is selected for its ultralow power
consumption (10μA).
Expanding Probe Count
The LTC6802-1 provides general purpose I/O pins, GPIO1
and GPIO2, that may be used to control multiplexing of
several temperature probes. Using just one of the GPIO
pins, the sensor count can double to four as shown in
Figure 16. Using both GPIO pins, up to eight sensor inputs
can be supported.
Using Diodes to Monitor Temperatures in Multiple
Locations
Another method of multiple sensor support is possible
without the use of any GPIO pins. If the sensors are PN
diodes and several used in parallel, then the hottest diode
will produce the lowest forward voltage and effectively
establish the input signal to the V
LTC6802-1
Figure 16. Expanding Sensor Count with Multiplexing
V
V
GPIO1
TEMP2
TEMP1
V
V
REG
REF
NC
V
−
100k
1μF
100k
100k
REG
remains always on, the buffer
TEMP
100k
NTC
OR SIMILAR DEVICE
SN74LVC1G3157
input(s). The hottest
100k
NTC
REF
100k
NTC
is shutdown
100k
NTC
68021 F16
diode will therefore dominate the readout from the V
inputs that the diodes are connected to. In this scenario,
the specific location or distribution of heat is not known,
but such information may not be important in practice.
Figure 17 shows the basic concept.
In any of the sensor configurations shown, a full-scale
cold readout would be an indication of a failed-open sen-
sor connection to the LTC6802-1.
ADDING CALIBRATION AND
FULL-STACK MEASUREMENTS
By adding multiplexing hardware, additional signals can
be digitized by the CELL1 ADC channel. One useful signal
to provide is a high-accuracy voltage reference, such as
from an LT1461A-4. By periodic readings of this signal,
host software can provide correction of the LTC6802-1
readings to improve the accuracy over that of the internal
LTC6802-1 reference, and/or validate ADC operation. An-
other useful signal is a measure of the total stack potential.
This provides a redundant operational measurement of the
cells in the event of a malfunction in the normal acquisi-
tion process, or as a faster means of monitoring the entire
Figure 17. Using Diode Sensors as Hot-Spot Detectors
LTC6802-1
V
V
TEMP2
TEMP1
V
V
REG
REF
NC
V
−
200k
200k
LTC6802-1
68021 F17
31
TEMP
68021fa