ltc6803g-3 Linear Technology Corporation, ltc6803g-3 Datasheet - Page 32

• Manufacturer Part Number: ltc6803g-3
• Description: Ltc6803-1/ltc6803-3 - Multicell Battery Stack Monitor
• Manufacturer: Linear Technology Corporation

LTC6803-1/LTC6803-3
APPLICATIONS INFORMATION
For sensors that require higher drive currents, a buffer
op amp may be used as shown in Figure 17. Power for
the sensor is actually sourced indirectly from the V
pin in this case. Probe loads up to about 1mA maximum
are supported in this configuration. Since V
down during the LTC6803 idle and shutdown modes, the
thermistor drive is also shut off and thus power dissipation
minimized. Since V
amp (LT6000 shown) is selected for its ultralow power
consumption (12µA).
Expanding Probe Count
As shown Figure 18, a dual 4:1 multiplexer is used to ex-
pand the general purpose V
to accept 8 different probe signals. The channel is selected
by setting the general purpose digital outputs GPIO1 and
GPIO2 and the resultant signals are buffered by sections
of the LT6004 micropower dual operational amplifier. The
probe excitation circuitry will vary with probe type and is
not shown here.
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 19 shows the basic concept. In any of the sensor
configurations shown, a full-scale cold readout would be
an indication of a failed open-sensor connection to the
LTC6803.
32
Figure 16. Driving Thermistors Directly from V
LTC6803-1
V
V
TEMP2
TEMP1
V
V
REG
REF
NC
V
–
REG
remains always on, the buffer op
1µF
TEMP1
1µF
TEMP
and V
input(s). The hottest
100k
100k
NTC
TEMP2
680313 F16
REF
ADC inputs
100k
100k
NTC
REF
is shut-
TEMP
REG
V
V
TEMP2
TEMP1
GPO1
CPO2
V
REG
V
Figure 19. Using Diode Sensors as Hot Spot Detectors
–
Figure 18. Expanding Sensor Count with Multiplexing
Figure 17. Buffering V
4
LTC6803-1
–
1/2 LT6004
6
V
V
TEMP2
TEMP1
7
+
V
V
1/2 LT6004
5
REG
REF
1
NC
8
V
LTC6803-1
–
8
4
+
–
V
V
TEMP2
TEMP1
V
V
3
2
REG
REF
NC
V
–
1
2
3
4
5
6
7
8
Y0
Y2
Y
Y3
Y1
INH
V
GND
–
REF
+
EE
LT6000
74HC4052
200k
for Higher Current Sensors
1µF
200k
V
X2
X1
X0
X3
CC
X
A
B
16
15
14
13
12
11
10
9
10k
10k
NTC
680313 F19
680313 F17
680313 F18
10k
10k
NTC
PROBE8
PROBE7
PROBE6
PROBE5
PROBE4
PROBE3
PROBE2
PROBE1
680313f