Datasheet

Data Sheet AD7734
Rev. A | Page 11 of 32
CHOPPING DISABLED
The second mode, in which the AD7734 is configured with
chopping disabled (CHOP = 0), provides faster conversion
time while still maintaining high resolution. Table 7 to Table 9
show the –3 dB frequencies and typical performance versus
the channel conversion time and equivalent output data rate,
respectively. Table 7 shows the typical output rms noise. Table 8
shows the typical effective resolution based on the rms noise.
Table 9 shows the typical output peak-to-peak resolution,
representing values for which there will be no code flicker
within a 6-sigma limit. The peak-to-peak resolutions are not
calculated based on rms noise but on peak-to-peak noise.
These typical numbers are generated from 4096 data samples
acquired in continuous conversion mode with an analog input
voltage set to 0 V and MCLK = 6.144 MHz. The conversion
time is selected via the channel conversion time register.
Table 7. Typical Output RMS Noise in µV vs. Conversion Time and Input Range with Chopping Disabled
FW Conversion Time
Register
Conversion Time
(µs)
Output Data Rate
(Hz)
–3 dB Frequency
(Hz)
RMS Noise
(µV)
127 7Fh 1357 737 670 13.2
92 5Ch 992 1008 920 15.5
44 2Ch 492 2032 1850 22.7
35 23h 398 2511 2290 26.3
16 10h 200 4991 2500 39.0
8 08h 117 8545 7780 57.0
3 03h 65 15398 14000 132
Table 8. Typical Effective Resolution in Bits vs. Conversion Time and Input Range with Chopping Disabled
FW Conversion Time
Register
Conversion Time
(µs)
Output Data Rate
(Hz)
–3 dB Frequency
(Hz)
Input Range/Effective Resolution (Bits)
±10 V 0 V to +10 V ±5 V 0 V to +5 V
127 7Fh 1357 737 670 20.5 19.5 19.5 18.5
92 5Ch 992 1008 920 20.3 19.3 19.3 18.3
44 2Ch 492 2032 1850 19.7 18.7 18.7 17.7
35 23h 398 2511 2290 19.5 18.5 18.5 17.5
16 10h 200 4991 2500 19.0 18.0 18.0 17.0
8 08h 117 8545 7780 18.4 17.4 17.4 16.4
3 03h 65 15398 14000 17.2 16.2 16.2 15.2
Table 9. Typical Peak-to-Peak Resolution in Bits vs. Conversion Time and Input Range with Chopping Disabled
FW Conversion Time
Register
Conversion Time
(µs)
Output Da
ta Rate
(Hz)
–3 dB Frequency
(Hz)
Input Range/Peak-to-Peak Resolution (Bits)
±10 V 0 V to +10 V ±5 V 0 V to +5 V
127
7Fh
1357
737
670
17.6
16.6
16.6
15.6
92 5Ch 992 1008 920 17.4 16.4 16.4 15.4
44 2Ch 492 2032 1850 16.8 15.8 15.8 14.8
35 23h 398 2511 2290 16.6 15.6 15.6 14.6
16 10h 200 4991 2500 16.1 15.1 15.1 14.1
8 08h 117 8545 7780 15.5 14.5 14.5 13.5
3 03h 65 15398 14000 14.3 13.3 13.3 12.3