AD7952
Data Sheet
Rev. A | Page 18 of 32
MODES OF OPERATION
The AD7952 features three modes of operation: warp, normal,
and impulse. Each of these modes is more suitable to specific
applications. The mode is configured with the input pins, WARP
and IMPULSE, or via the configuration register. See
Table 6 for
selection with either pins or configuration register. Note that
when using the configuration register, the WARP and IMPULSE
inputs are don’t cares and should be tied to either high or low.
Warp Mode
Setting WARP = high and IMPULSE = low allows the fastest
conversion rate up to 1 MSPS. 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 AD7952 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 (800 kSPS) without any limitation on
time between conversions. This mode makes the AD7952 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 saving between conversions.
The maximum throughput in this mode is 670 kSPS, and in this
mode, the ADC powers down circuits after conversion, making
the AD7952 ideal for battery-powered applications.
TRANSFER FUNCTIONS
Using the OB/2C digital input or via the configuration register,
the AD7952 offers two output codings: straight binary and twos
characteristic and digital output codes for the different analog
input ranges, VIN. Note that when using the configuration
register, the OB/2C input is a don’t care and should be tied to
either high or low.
000...000
000...001
000...010
111...101
111...110
111...111
A
DC
CO
DE
(
S
tr
ai
g
h
tBi
n
ar
y)
ANALOG INPUT
+FSR – 1.5 LSB
+FSR –1LSB
–FSR + 1 LSB
–FSR
–FSR + 0.5 LSB
06
58
9-
0
26
Figure 26. ADC Ideal Transfer Function
TYPICAL CONNECTION DIAGRAM
Figure 27 shows a typical connection diagram for the AD7952
using the internal reference, serial data, and serial configuration
interfaces. Different circuitry from that shown in
Figure 27 is
optional and is discussed in the following sections.
Table 7. Output Codes and Ideal Input Voltages
VREF = 5 V
Digital Output Code
Description
VIN = 0 V to 5 V
(10 V p-p)
VIN = 0 V to 10 V
(20 V p-p)
VIN = ±5 V
(20 V p-p)
VIN = ±10 V
(40 V p-p)
Straight Binary
Twos Complement
FSR 1 LSB
4.999695 V
9.999389 V
+4.999389 V
+9.998779 V
0x3FFF1
0x1FFF1
FSR 2 LSB
4.999390 V
9.998779 V
+4.998779 V
+9.997558 V
0x3FFE
0x1FFE
Midscale + 1 LSB
2.500610 V
5.000610 V
+1.228 mV
+2.442 mV
0x2001
0x0001
Midscale
2.5 V
5.000000 V
0 V
0x2000
0x0000
Midscale 1 LSB
2.499390 V
4.999389 V
1.228 mV
2.442 mV
0x1FFF
0x3FFF
FSR + 1 LSB
610.4 μV
1.228 mV
4.999389 V
9.998779 V
0x0001
0x2001
FSR
0 V
5 V
10 V
0x00002
0x20002
1 This is also the code for overrange analog input (VIN+ VIN above VREF VREFGND).
2 This is also the code for overrange analog input (VIN+ VIN below VREF VREFGND).