AD7266 Datasheet, PDF (12/17 Pages) Analog Devices – Differential Input, Dual 2 MSPS, 12-Bit, 3-Channel SAR ADC

AD7266
TRANSFER FUNCTIONS
The designed code transitions occur at successive integer LSB
values (i.e., 1 LSB, 2 LSB, and so on). The LSB size is VREF/4096.
The ideal transfer characteristic for the AD7266 when straight
binary coding is output is shown in Figure 6, and the ideal
transfer characteristic for the AD7266 when twos complement
coding is output is shown in Figure 7.
111...111
111...110
111...000
011...111
1LSB = V_REF/4096
000...010
000...001
000...000
0V ^1LSB
V_REF – 1LSB
ANALOG INPUT
Figure 6. Straight Binary Transfer Characteristic
011...111
011...110
1LSB = 2 × V_REF/4096
000...001
000...000
111...111
100...010
100...001
100...000
–V_REF + 1LSB V_REF – 1LSB +V_REF – 1 LSB
ANALOG INPUT
Figure 7. Twos Complement Transfer Characteristic with VREF ±VREF Input
Range
Preliminary Technical Data
DIGITAL INPUTS
The digital inputs applied to the AD7266 are not limited by the
maximum ratings that limit the analog inputs. Instead, the
digital inputs applied can go to 7 V and are not restricted by the
VDD + 0.3 V limit as on the analog inputs. See the Absolute
Maximum Ratings. Another advantage of SCLK, RANGE,
A0–A2, and CS not being restricted by the VDD + 0.3 V limit is
that power supply sequencing issues are avoided. If one of these
digital inputs is applied before VDD, there is no risk of latch-up,
as there would be on the analog inputs if a signal greater than
0.3 V were applied prior to VDD.
V_DRIVE
The AD7266 also has the VDRIVE feature, which controls the
voltage at which the serial interface operates. VDRIVE allows the
ADC to easily interface to both 3 V and 5 V processors. For
example, if the AD7266 was operated with a VDD of 5 V, the
VDRIVE pin could be powered from a 3 V supply, allowing a large
dynamic range with low voltage digital processors. For example,
the AD7266 could be used with the 2 × VREF input range, with a
VDD of 5 V while still being able to interface to 3 V digital parts.
Rev. PrG | Page 12 of 17