AD7634 Analog Devices, AD7634 Datasheet - Page 18

• Manufacturer Part Number: AD7634
• Manufacturer: Analog Devices

Specifications of AD7634

• Resolution (bits): 18bit
• # Chan: 1
• Sample Rate: 670kSPS
• Interface: Byte,Par,Ser,SPI
• Analog Input Type: Diff-Bip,Diff-Uni
• Ain Range: 10V p-p,20 V p-p,40 V p-p
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

AD7634
Warp Mode
Setting WARP = high and IMPULSE = low allows the fastest
conversion rate of up to 670 kSPS. However, in this mode, the
full-specified accuracy is guaranteed only when the time between
conversions does not exceed 1 ms. If the time between two
consecutive conversions is longer than 1 ms (after power-up),
the first conversion result should be ignored because in warp mode,
the ADC performs a background calibration during the SAR
conversion process. This calibration can drift if the time between
conversions exceeds 1 ms thus causing the first conversion to
appear offset. This mode makes the AD7634 ideal for applications
where both high accuracy and fast sample rate are required.
Normal Mode
Setting WARP = IMPULSE = low or WARP = IMPULSE = high
allows the fastest mode (570 kSPS) without any limitation on
time between conversions. This mode makes the AD7634 ideal
for asynchronous applications such as data acquisition systems,
where both high accuracy and fast sample rate are required.
Impulse Mode
Setting WARP = low and IMPULSE = high uses the lowest power
dissipation mode and allows power savings between conver-
sions. The maximum throughput in this mode is 450 kSPS, and
in this mode, the ADC powers down circuits after conversion,
making the AD7634 ideal for battery-powered applications.
Table 8. Output Codes and Ideal Input Voltages
Description
FSR − 1 LSB
FSR − 2 LSB
Midscale + 1 LSB
Midscale
Midscale − 1 LSB
−FSR + 1 LSB
−FSR
1
2
This is also the code for overrange analog input.
This is also the code for underrange analog input.
V
(10 V p-p)
+4.999962 V
+4.999924 V
+38.15 μV
0 V
−38.15 μV
−4.999962 V
−5 V
IN
= 0 V to +5 V
V
(20 V p-p)
+9.999924 V
+9.999847 V
−76.29 μV
0 V
−76.29 μV
−9.999924 V
−10 V
IN
= 0 V to +10 V
V
REF
= 5 V
Rev. A | Page 18 of 32
V
(20 V p-p)
+9.999924 V
+9.999847 V
−76.29 μV
0 V
−76.29 μV
−9.999924 V
−10 V
IN
= ±5 V
TRANSFER FUNCTIONS
Except in 18-bit parallel interface mode, using the D0/OB/ 2C
digital input or via the configuration register, the AD7634 offers
two output codings: straight binary and twos complement. See
Figure 26
digital output codes for the different analog input ranges, V
Note that when using the configuration register, the D0/OB/
input is a don’t care and should be tied to either high or low.
V
(40 V p-p)
+19.999847 V
+19.999695 V
+152.59 μV
0 V
−152.59 μV
−19.999847 V
−20 V
111...111
111...110
111...101
000...010
000...001
000...000
IN
and
= ±10 V
–FSR + 0.5 LSB
–FSR
Table 8
Figure 26. ADC Ideal Transfer Function
–FSR + 1 LSB
for the ideal transfer characteristic and
Straight Binary
0x3FFFF
0x3FFFE
0x20001
0x20000
0x1FFFF
0x00001
0x00000
ANALOG INPUT
1
2
Digital Output Code
+FSR – 1.5 LSB
Twos Complement
0x1FFFF
0x1FFFE
0x00001
0x00000
0x3FFFF
0x20001
0x20000
+FSR – 1 LSB
1
2
IN
2C
.