Datasheet
REV. A
AD7677
–12–
The Warp Mode allows the fastest conversion rate up to 1 MSPS.
However, in this mode, and this mode only, the full specified accu-
racy is guaranteed only when the time between conversion does
not exceed 1 ms. If the time between two consecutive conversions
is longer than 1 ms, for instance, after power-up, the first conver-
sion result should be ignored. This mode makes the AD7677
ideal for applications where fast sample rates are required.
The Normal Mode is the fastest mode (800 kSPS) without any
limitation about the time between conversions. This mode makes
the AD7677 ideal for asynchronous applications such as data
acquisition systems, where both high accuracy and fast sample
rate are required.
The Impulse Mode, the lowest power dissipation mode, allows
power saving between conversions. The maximum throughput
in this mode is 666 kSPS. When operating at 100 SPS, for
example, it typically consumes only 15 µW. This feature makes
the AD7677 ideal for battery-powered applications.
Transfer Functions
Using the OB/2C digital input, the AD7677 offers two output
codings: straight binary and two’s complement. The ideal trans-
fer characteristic for the AD7677 is shown in Figure 4.
000...000
000...001
000...010
111...101
111...110
111...111
ANALOG INPUT
+FS – 1.5 LSB
+FS – 1 LSB
–FS + 1 LSB–FS
–FS + 0.5 LSB
ADC CODE – Straight Binary
Figure 4. ADC Ideal Transfer Function
TYPICAL CONNECTION DIAGRAM
Figure 5 shows a typical connection diagram for the AD7677.
Different circuitry shown on this diagram is optional and is
discussed below.
Analog Inputs
Figure 6 shows a simplified analog input section of AD7677.
AV DD AGND DGND
DVDD
OVDD OGND
SER/PAR
CNVST
BUSY
SDOUT
SCLK
RD
CS
RESET
PD
REFGND
C
REF
2.5V REF
NOTE 1
REF
100
D
CLOCK
AD7677
C/P/DSP
SERIAL PORT
DIGITAL SUPPLY
(3.3V OR 5V)
ANALOG
SUPPLY
(5V)
DVDD
OB/2C
NOTE 7
BYTESWAP
DVDD
50k
100nF
1M
IN+
ANALOG INPUT+
C
C
2.7nF
U1
NOTE 4
NOTE 5
50
AD8021
–
+
15
NOTE 2
NOTE 3
NOTE 6
ADR421
10F
100nF
+
10F 100nF
+
100nF
+
10F
IN–
ANALOG INPUT–
C
C
2.7nF
U2
NOTE 4
NOTE 5
50
AD8021
–
+
15
50
+
1F
NOTES
1. SEE VOLTAGE REFERENCE INPUT SECTION.
2. WITH THE RECOMMENDED VOLTAGE REFERENCES, C
REF
IS 47F. SEE CHAPTER VOLTAGE REFERENCE INPUT SECTION.
3. OPTIONAL CIRCUITRY FOR HARDWARE GAIN CALIBRATION.
4. THE AD8021 IS RECOMMENDED. SEE DRIVER AMPLIFIER CHOICE SECTION.
5. SEE ANALOG INPUT SECTION.
6. OPTION, SEE POWER SUPPLY SECTION.
7. OPTIONAL LOW JITTER CNVST, SEE CONVERSION CONTROL SECTION.
Figure 5. Typical Connection Diagram