Datasheet

AD7715
Rev. D | Page 17 of 40
AD7715-3
Table 19 shows the AD7715-3 output rms noise for the selecta-
ble notch and −3 dB frequencies for the part, as selected by FS1
and FS0 of the setup register. The numbers given are for the
bipolar input ranges with a V
REF
of 1.25 V. These numbers are
typical and are generated at an analog input voltage of 0 V with
the part used in unbuffered mode (BUF bit of the setup register
= 0). Table 20 meanwhile shows the output peak-to-peak noise
for the selectable notch and −3 dB frequencies for the part. It is
important to note that these numbers represent the resolution
for which there is no code flicker. They are not calculated based
on rms noise but on peak-to-peak noise. The numbers given are
for the bipolar input ranges with a V
REF
of 1.25 V and for the
BUF bit of the setup register = 0. These numbers are typical,
are generated at an analog input voltage of 0 V and are rounded
to the nearest LSB.
Meanwhile, Table 2 1 and Table 22 show rms noise and peak-
to-peak resolution respectively with the AD7715-3 operating
under the same conditions as above except that now the part is
operating in buffered mode (BUF bit of the setup register = 1).
Table 19. Output RMS Noise vs. Gain and Output Update Rate for AD7715-3 (Unbuffered Mode)
Filter First Notch and Output Data Rate −3 dB Frequency Typical Output RMS Noise (μV)
MCLK IN = MCLK IN = MCLK IN = MCLK IN =
2.4576 MHz 1 MHz 2.4576 MHz 1 MHz Gain = 1 Gain = 2 Gain = 32 Gain = 128
50 Hz 20 Hz 13.1 Hz 5.24 Hz 3.0 1.7 0.7 0.65
60 Hz 25 Hz 15.72 Hz 6.55 Hz 3.4 2.1 0.7 0.7
250 Hz 100 Hz 65.5 Hz 26.2 Hz 45 20 2.2 1.6
500 Hz 200 Hz 131 Hz 52.4 Hz 270 135 9.7 3.3
Table 20. Peak-to-Peak Resolution vs. Gain and Output Update Rate for AD7715-3 (Unbuffered Mode)
Filter First Notch and Output Data Rate −3 dB Frequency Typical Peak-to-Peak Resolution in Bits
MCLK IN = MCLK IN = MCLK IN = MCLK IN =
2.4576 MHz 1 MHz 2.4576 MHz 1 MHz Gain = 1 Gain = 2 Gain = 32 Gain = 128
50 Hz 20 Hz 13.1 Hz 5.24 Hz 16 16 14 12
60 Hz 25 Hz 15.72 Hz 6.55 Hz 16 16 14 12
250 Hz 100 Hz 65.5 Hz 26.2 Hz 13 13 13 11
500 Hz 200 Hz 131 Hz 52.4 Hz 11 11 10 10
Table 21. Output RMS Noise vs. Gain and Output Update Rate for AD7715-3 (Buffered Mode)
Filter First Notch and Output Data Rate −3 dB Frequency Typical Output RMS Noise (μV)
MCLK IN = MCLK IN = MCLK IN = MCLK IN =
2.4576 MHz 1 MHz 2.4576 MHz 1 MHz Gain = 1 Gain = 2 Gain = 32 Gain = 128
50 Hz 20 Hz 13.1 Hz 5.24 Hz 4.5 2.4 0.9 0.9
60 Hz 25 Hz 15.72 Hz 6.55 Hz 5.1 2.9 0.9 1.0
250 Hz 100 Hz 65.5 Hz 26.2 Hz 50 25 2.6 2
500 Hz 200 Hz 131 Hz 52.4 Hz 270 135 9.7 3.3
Table 22. Peak-to-Peak Resolution vs. Gain and Output Update Rate for AD7715-3 (Buffered Mode)
Filter First Notch and Output Data Rate −3 dB Frequency Typical Peak-to-Peak Resolution in Bits
MCLK IN = MCLK IN = MCLK IN = MCLK IN =
2.4576 MHz 1 MHz 2.4576 MHz 1 MHz Gain = 1 Gain = 2 Gain = 32 Gain = 128
50 Hz 20 Hz 13.1 Hz 5.24 Hz 16 16 14 12
60 Hz 25 Hz 15.72 Hz 6.55 Hz 16 16 14 12
250 Hz 100 Hz 65.5 Hz 26.2 Hz 13 13 12 11
500 Hz 200 Hz 131 Hz 52.4 Hz 10 11 10 10