LTC6802IG-2 LINER [Linear Technology], LTC6802IG-2 Datasheet - Page 27

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

applicaTions inForMaTion
No resistor should be placed in series with the V
Because the supply current flows from the V
resistance on this pin could generate a significant conver-
sion error for CELL1.
READING EXTERNAL TEMPERATURE PROBES
Using Dedicated Inputs
The LTC6802-2 includes two channels of ADC input, V
and V
(tempco about –4%/°C generally) or diodes (–2.2mV/°C
typical) located within the cell array. Sensors can be
powered directly from V
60µA total).
For sensors that require higher drive currents, a buffer op
amp may be used as shown in Figure 12. Power for the
sensor is actually sourced indirectly from the V
Figure 12. Buffering V
TEMP2
LTC6802-2
Figure 11. Driving Thermistors Directly from V
LTC6802-2
, that are intended to monitor thermistors
V
V
TEMP2
TEMP1
V
V
REG
REF
NC
V
V
V
TEMP2
TEMP1
−
V
V
REG
REF
NC
V
−
REF
REF
as shown in Figure 11 (up to
for Higher Current Sensors
+
–
1µF
LT6000
1µF
100k
100k
NTC
68022 F11
10k
10k
NTC
68022 F12
–
REF
100k
pin, any
REG
100k
NTC
10k
TEMP1
–
10k
NTC
pin.
pin
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
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 14 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 LTC6802-2.
in this case. Probe loads up to about 1mA maximum are
supported in this configuration. Since V
during the LTC6802-2 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 LTC6802-2 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 13. Using both GPIO pins, up to eight sensor inputs
can be supported.
LTC6802-2
Figure 13. 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
LTC6802-2
input(s). The hottest
100k
NTC
REF
100k
NTC
is shutdown
100k

NTC
68022 F13
TEMP
68022fa