Data Sheet
AD5940
INTERNAL TEMPERATURE SENSOR CHANNEL
ADC CALIBRATION
The AD5940 contains an internal temperature sensor channel.
Because of the multiple input types on the AD5940 (for
example, current, voltage, and temperature), there are multiple
offset and gain calibration options. A built in, self calibration
system is provided to aid the user when calibrating different
ADC input channels, which is included in the AD5940 software
development kit.
The temperature sensor outputs a voltage that is proportional to
the die temperature, linear, and relative to temperature.
For improved accuracy, the temperature sensor can be
configured in chop mode via TEMPSENS, Bits[3:1]. If chopping
is selected, ensure that an even number of ADC conversions
take place on the temperature sensor channel. These results
must be averaged.
Dedicated calibration registers for the temperature sensor
channel are also available, which the ADC uses automatically.
SINC2 FILTER (50 HZ/60 HZ MAINS FILTER)
To enable the 50 Hz or 60 Hz notch filter for filtering mains
noise, clear ADCFILTERCON, Bit 4 = 0 and set AFECON,
Bit 16 = 1. The input is the sinc2 filter output. The input rate is
dependent on the sinc3 and sinc2 settings. If selected, the sinc2
filter output can be read via the SINC2DAT register. Table 40
describes the digital filter settings that support simultaneous
50 Hz or 60 Hz mains rejection.
Table 40. Digital Filter Settings to Support Simultaneous 50 Hz/60 Hz Mains Rejection
ADCFILTERCON, Bits[13:8]
Value
Power Mode
(PMBW, Bit 0)
Sinc3 Oversampling
Setting
Sinc2 Oversampling
Setting
Final ADC Output Update
Rate (SPS)
010111
011011
011011
0 (low power mode)
0 (low power mode)
1 (high power mode)
2
2
2
667
1333
1333
600
300
600
ADCFILTER ADCFILTER
ADCFILTER
CON[11:8]
ADCFILTERCON
[4]
CON[13:12]
CON[6]
DATAFIFO_SINC3
DATAFIFO_SINC2
DATAFIFO_VAR/
MEAN
STATISTICS
ADC
GAIN AND
OFFSET
SINC2 FILTER
CONFIGURABLE
OSR
SINC3 FILTER
OSR5/4/2
STATSCON
DATA
50Hz/60Hz
NOTCH
ADC
[6:4]
FIFO
AFECON[15]
DFT
2 TO 16,384
POINT
DATAFIFO_DFT
1.6MHz
0.8MHz
DFTCON[21:20]
AVG 2/4/8/16
DFTCON[7:4]
HANNING
ADCFILTERCON
[15:14]
ADCFILTER
CON[0]
ADCFILTER
CON[7]
DFTCON[0]
DFT_CORDIC
Figure 31. Postprocessing Filter Options
Rev. 0 | Page 53 of 130
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