LTC6803-2 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC6803-2' PDF : 40 Pages View PDF
APPLICATIONS INFORMATION
65
4
8
1/2 LT6004
7
1 Y0
2 Y2
VCC
X2
16
15
3Y
X1 14
4
5
Y3 74HC4052 X
Y1
X0
13
12
6 INH
X3 11
7
8
VEE
GND
A 10
B9
CPO2
GPO1
VREG
VTEMP2
1/2 LT6004 8 3
VTEMP1
1
2
4
1µF
V–
PROBE8
PROBE7
PROBE6
PROBE5
PROBE4
PROBE3
PROBE2
PROBE1
680324 F16
Figure 16. Expanding Sensor Count with Multiplexing
LTC6803-4
VREG
VREF
VTEMP2
VTEMP1
NC
V–
200k
200k
680324 F17
Figure 17. Using Diode Sensors as Hot Spot Detectors
LTC6803-2/LTC6803-4
ADDING CALIBRATION AND FULL-STACK
MEASUREMENTS
The general purpose VTEMP ADC inputs may be used to digi-
tize any signals from 0V to 4V with accuracy corresponding
closely with that of the cell 1 ADC input. One useful signal
to provide is a high accuracy voltage reference, such as
3.300V from an LTC6655-3.3. From periodic readings of
this signal, the host software can provide correction of
the LTC6803 readings to improve the accuracy over that
of the internal LTC6803 reference and/or validate ADC
operation. Figure 18 shows a means of selectively pow-
ering an LTC6655-3.3 from the battery stack, under the
control of the GPIO1 output of the LTC6803-2. Since the
operational power of the reference IC would add significant
thermal loading to the LTC6803 if powered from VREG, an
external high voltage NPN pass transistor is used to form
a local 4.4V (Vbe below VREG) from the battery stack. The
GPIO1 signal controls a PMOS FET switch to activate the
reference when calibration is to be performed. Since GPIO
signals default to logic high in shutdown, the reference
will automatically turn off during idle periods.
Another useful signal is a measure of the total stack poten-
tial. This provides a redundant operational measurement
of the cells in the event of a malfunction in the normal
acquisition process, or as a faster means of monitoring
the entire stack potential. Figure 19 shows how a resis-
tive divider is used to derive a scaled representation of a
full cell group potential. A MOSFET is used to disconnect
TOP CELL POTENTIAL
1M
LTC6803-2 35
GPIO1
31
VREG
28
VTEMP1
V– 26
CZT5551
Si2351DS
1µF
10µF
100nF
1
LTC6655-3.3
SHDN GND
8
2 VIN
3 GND
4 GND
VOUT_F 7
VOUT_S 6
GND 5
680324 F18
Figure 18. Providing Measurement of Calibration Reference
680324f
33
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