Linear Technology LTC6804-1 - Data Acquisition System Diagnostics

LTC6804-1/LTC6804-2
26
680412fc
For more information www.linear.com/LTC6804-1
operaTion
CALIBRATE
MEASURE
C12 TO C11
MEASURE
C11 TO C10
MEASURE
C10 TO C9
MEASURE
C9 TO C8
MEASURE
C8 TO C7
MEASURE
C7 TO C6
ADC2
SERIAL
INTERFACE
t
CYCLE
t
SKEW1
t
SKEW1
ADCVAX + PEC
CALIBRATE
MEASURE
C6 TO C5
MEASURE
C5 TO C4
MEASURE
C4 TO C3
MEASURE
GPIO2
MEASURE
GPIO1
MEASURE
C3 TO C2
MEASURE
C2 TO C1
MEASURE
C1 TO C0
ADC1
t
0
t
1M
t
2M
t
3M
t
4M
t
5M
t
6M
t
7M
t
8M
t
8C
t
REFUP
680412 F06
Figure 6. Timing of ADCVAX Command
Table 8 shows the conversion and synchronization time
for the ADCVAX command in different modes. The total
conversion time for the command is given by t
8C
.
DATA ACQUISITION SYSTEM DIAGNOSTICS
The battery monitoring data acquisition system is com
-
prised of the multiplexers, ADCs, 1st reference, digital
filters, and memory. To ensure long term reliable perfor-
mance there are several diagnostic commands which can
be used to verify the proper operation of these cir
cuits.
Measuring Internal Device Parameters (ADST
AT
Command)
The ADSTAT command is a diagnostic command that
measures the following internal device parameters: sum
of all cells (SOC), internal die temperature (ITMP), analog
power supply (VA) and the digital power supply (VD).
These parameters are described in the section below. All
6 ADC modes are available for these conversions. See the
section on commands for the ADSTAT command format.
Figure 7 illustrates the timing of the ADSTAT command
measuring all 4 internal device parameters.
Table 8. Conversion and Synchronization Times for ADCVAX Command in Different Modes
CONVERSION TIMES (in µs)
SYNCHRONIZATION
TIME (µs)
MODE t
0
t
1M
t
2M
t
3M
t
4M
t
5M
t
6M
t
7M
t
8M
t
8C
t
SKEW1
27kHz 0 57 106 155 216 265 326 375 424 1,564 208
14kHz 0 86 161 237 320 396 479 555 630 1,736 310
7kHz 0 144 278 412 553 687 828 962 1,096 3,133 543
3kHz 0 260 511 761 1,018 1,269 1,526 1,777 2,027 4,064 1009
2kHz 0 493 976 1,459 1,949 2,432 2,923 3,406 3,888 5,925 1939
26Hz 0 29,817 59,623 89,430 119,244 149,051 178,864 208,671 238,478 268,442 119234
Figure 7. Timing for ADSTAT Command Measuring SOC, ITMP, VA, VD
ADC2
SERIAL
INTERFACE
t
CYCLE
t
SKEW
ADSTAT + PEC
CALIBRATE
ITMP
CALIBRATE
VD
CALIBRATE
SOC
MEASURE
VD
MEASURE
ITMP
MEASURE
SOC
ADC1
t
0
t
1M
t
2M
t
4M
t
3M
t
1C
t
2C
t
3C
t
4C
680412 F07
t
REFUP