Maxim Integrated MAX31782, Руководство пользователя

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MaximIntegrated 6-4
MAX31782 User’s Guide
Revision 0; 8/11
The time required for the ADC to make a temperature measurement is greater than the time required for a voltage
measurement . When a temperature conversion is performed, the ADC’s internal current source forces current into the
diode connected to the channel . As the current is being sourced, the ADC integrates the voltage across the diode .
This is known as the integration time (t
INT
) . The integration time lasts approximately 2 .91ms . This integration time is a
constant and does not scale when the ADC clock speed is changed . When the integration time is complete, the ADC
performs a voltage conversion of the integration . The voltage conversion is a normal voltage conversion and takes 34
ADC clock cycles . A temperature conversion requires that this integration and conversion process be performed twice .
The extended acquisition time function does not apply when in temperature sensing mode . The time required for a
complete temperature conversion can be calculated to be:
2 x (t
INT
+ 34 ADC clocks)
Table6-1.ExtendedAcquisitionTimeinTermsofADCClocks
Figure 6-2. Extended Acquisition Time
ADACQ[3:0]
ADCCLOCKDIVIDER
=16
ADCCLOCKDIVIDER
=32
ADCCLOCKDIVIDER
=64
ADCCLOCKDIVIDER
=128
0 16 16 16 16
1 32 32 32 32
2 48 48 48 16
3 64 64 64 32
4 80 80 16 16
5 96 96 32 32
6 112 112 48 16
7 128 128 64 32
8 144 16 16 16
9 160 32 32 32
10 176 48 48 16
11 192 64 64 32
12 208 80 16 16
13 224 96 32 32
14 240 112 48 16
15 256 128 64 32
10 11 1 2 3 4 5 6 7 8 9 18 16 15 14 13 12 28 29 19 20 21 22 23 24 25 26 27 17 34 33 32 31 30 1 19 20
ADACQ
HOLD AND CONVERT SAMPLE 1 HOLD AND CONVERT SAMPLE 2
ADC
STARTUP SAMPLE 1 SAMPLE 2
ADC DATA
VALID
ADCCLK
ADCONV
ADDATA