ltc6803g-4 Linear Technology Corporation, ltc6803g-4 Datasheet - Page 32

• Manufacturer Part Number: ltc6803g-4
• Description: Ltc6803-2/ltc6803-4 - Multicell Battery Stack Monitor
• Manufacturer: Linear Technology Corporation

LTC6803-2/LTC6803-4
APPLICATIONS INFORMATION
For sensors that require higher drive currents, a buffer
op amp may be used as shown in Figure 15. 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 dissipa-
tion minimized. Since V
op amp (LT6000 shown) is selected for its ultralow power
consumption (12µA).
32
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
NOTE: NOT SHOWN ARE PN DIODES TO ALL OTHER PINS FROM PIN 27
1
2
3
4
5
6
7
8
9
V
C12
S12
C11
S11
C10
S10
C9
S9
C8
S8
C7
S7
C6
S6
C5
S5
C4
S4
C3
S3
C2
S2
C1
S1
C0
+
Figure 13. Internal Protection Diodes
27
V
–
Z
Z
Z
CLAMP
CLAMP
CLAMP
REG
remains always on, the buffer
Z
Z
Z
CLAMP
CLAMP
CLAMP
REF
LTC6803-4
V
V
GPIO2
GPIO1
WDTB
is shut
TEMP2
TEMP1
V
CSBI
SCKI
V
SDO
TOS
REG
SDI
REF
680324 F13
A3
A2
A1
A0
REG
40
39
38
37
32
31
30
29
44
43
42
41
36
35
34
33
Expanding Probe Count
As shown Figure 16, 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 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 sensor connection to the
LTC6803.
Figure 15. Buffering V
LTC6803-4
Figure 14. Driving Thermistors Directly from V
LTC6803-4
V
V
V
V
TEMP2
TEMP1
TEMP2
TEMP1
V
V
V
V
REG
REF
REG
NC
REF
V
NC
V
–
–
1µF
–
REF
+
LT6000
TEMP1
for Higher Current Sensors
1µF
TEMP
and V
100k
input(s). The hottest
10k
100k
NTC
TEMP2
10k
NTC
680324 F14
680324 F15
100k
ADC inputs
10k
100k
NTC
REF
10k
NTC
680324f
TEMP