Datasheet

AD7715
Rev. D | Page 16 of 40
OUTPUT NOISE
AD7715-5
Table 15 shows the AD7715-5 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 2.5 V. These numbers are
typical and are generated at a differential analog input voltage
of 0 V with the part used in unbuffered mode (BUF bit of the
setup register = 0). Table 16 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
2.5 V and for the BUF bit of the setup register = 0. These num-
bers are typical, are generated at an analog input voltage of 0 V
and are rounded to the nearest LSB.
Meanwhile, Table 1 7 and Table 18 show rms noise and peak-
to-peak resolution respectively with the AD7715-5 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 15. Output RMS Noise vs. Gain and Output Update Rate for AD7715-5 (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 3.8 1.9 0.6 0.52
60 Hz 25 Hz 15.72 Hz 6.55 Hz 4.8 2.4 0.6 0.62
250 Hz 100 Hz 65.5 Hz 26.2 Hz 103 45 3.0 1.6
500 Hz 200 Hz 131 Hz 52.4 Hz 530 250 18 5.5
Table 16. Peak-to-Peak Resolution vs. Gain and Output Update Rate for AD7715-5 (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 16 14
60 Hz 25 Hz 15.72 Hz 6.55 Hz 16 16 16 13
250 Hz 100 Hz 65.5 Hz 26.2 Hz 13 13 13 12
500 Hz 200 Hz 131 Hz 52.4 Hz 10 10 10 10
Table 17. Output RMS Noise vs. Gain and Output Update Rate for AD7715-5 (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 4.3 2.2 0.9 0.9
60 Hz 25 Hz 15.72 Hz 6.55 Hz 5.1 3.1 1.0 1.0
250 Hz 100 Hz 65.5 Hz 26.2 Hz 103 50 3.9 2.1
500 Hz 200 Hz 131 Hz 52.4 Hz 550 280 18 6
Table 18. Peak-to-Peak Resolution vs. Gain and Output Update Rate for AD7715-5 (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 15 13
60 Hz 25 Hz 15.72 Hz 6.55 Hz 16 16 15 13
250 Hz 100 Hz 65.5 Hz 26.2 Hz 13 13 13 12
500 Hz 200 Hz 131 Hz 52.4 Hz 10 10 10 10