AD7829-1 Analog Devices, AD7829-1 Datasheet - Page 11

• Manufacturer Part Number: AD7829-1
• Description: 3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC
• Manufacturer: Analog Devices

Specifications of AD7829-1

• Resolution (bits): 8bit
• # Chan: 8
• Sample Rate: 2MSPS
• Interface: Par
• Analog Input Type: SE-Uni
• Ain Range: 2 V p-p,2.5V p-p,Uni 2.0V,Uni 2.5V
• Adc Architecture: Flash
• Pkg Type: SOIC,SOP

A suggestion is to tie CONVST
pull-up or pull-down resistor. A rising edge on the CONVST
pin causes the AD7829-1 to fully power up. For applications
where power consumption is of concern, the automatic power-
down at the end of a conversion should be used to improve
power performance (see the
If the AD7829-1 is operated outside normal V
example, a brown-out), it may take two conversions to reset the
part once the correct V
4.5V TO 5.5V
ADC TRANSFER FUNCTION
The output coding of the AD7829-1 is straight binary. The
designed code transitions occur at successive integer LSB values
(that is, 1 LSB, 2 LSBs, and so on). The LSB size is equal to
V
(V
is shown in
REF
DD
SUPPLY
/256 (V
3.75V INPUT
= 3 V). The ideal transfer characteristic for the AD7829-1
1.25V TO
10µF
DD
Figure 8.
(V
(V
11111111
00000000
10000000
111...110
111...000
000...010
000...001
000...111
DD
DD
= 5 V), or the LSB size is equal to (0.8 V
Figure 7. Typical Connection Diagram
= 3V) V
= 5V) V
Figure 8. Transfer Characteristic
MID
MID
V
V
AGND
V
DGND
DD
0.1µF
1LSB
IN1
IN2
IN8
1LSB = V
– 1.25V
– 1V
ANALOG INPUT VOLTAGE
has been established.
(V
V
DD
DD
Power vs. Throughput section).
AD7829-1
= 5V)
REF
V
to V
MID
AD780
/256
1LSB = 0.8V
2.5V
V
V
V
REF
MID
MID
DD
DB0 TO DB7
(V
+ 1.25V – 1LSB
+ 1V – 1LSB
or DGND through a
DD
CONVST
V
= 3V)
MID
REF
EOC
RD
CS
A0
A1
A2
/256
DD
PARALLEL
INTERFACE
limits (for
REF
µC/µP
)/256
Rev. 0 | Page 11 of 20
ANALOG INPUT
The AD7829-1 has eight input channels. Each input channel has
an input span of 2.5 V or 2.0 V, depending on the supply voltage
(V
“V
when V
V
glitch rejection; for example, a glitch from 5.5 V to 2.7 V up to
60 ns wide does not trip the V
The V
range of AGND to V
the default input range is AGND to 2.0 V (V
that is, centered about 1.0 V; or AGND to 2.5 V (V
that is, centered about 1.25 V. When using the default input range,
the V
decoupled to AGND with a 0.1 μF capacitor.
If, however, an external V
is from V
V
The range of values of V
value of V
be applied to V
V
ranges of V
Figure 9 illustrates the input signal range available with various
values of V
Table 5.
V
5.5
5.0
4.5
3.3
3.0
2.7
DD
DD
MID
DD
DD
DD
falls below 3.8 V. This circuit also possesses a degree of
− 1.25 V when V
). This input span is automatically set up by an on-chip
− 1.25 V to V
detector” circuit. A 5 V operation of the ADCs is detected
MID
MID
V
Internal
1.25
1.25
1.25
1.00
1.00
1.00
DD
MID
pin can be left unconnected; or, in some cases, it can be
MID
pin is used to center this input span anywhere in the
DD
exceeds 4.1 V, and a 3 V operation is detected when
MID
MID
. For V
− 1.0 V to V
.
and the input span for various values of V
MID
V
Maximum
4.25
3.75
3.25
2.3
2.0
1.7
MID
is from 1.0 V to V
DD
MID
DD
DD
= 3 V ± 10%, the range of values that can
+ 1.25 V (V
Ext
. If no input voltage is applied to V
= 5 V ± 10%. Table 5 shows the relevant
MID
MID
MID
that can be applied depends on the
+ 1.0 V (V
is applied, the analog input range
DD
V
3.0 to 5.5
2.5 to 5.0
2.0 to 4.5
1.3 to 3.3
1.0 to 3.0
0.7 to 2.7
IN
detector.
DD
Span
= 5 V ± 10%).
DD
DD
− 1.0 V and is 1.25 V to
= 3 V ± 10%), or from
V
Minimum
1.25
1.25
1.25
1.00
1.00
1.00
DD
MID
= 3 V ± 10%),
Ext
DD
AD7829-1
= 5 V ± 10%),
V
0 to 2.5
0 to 2.5
0 to 2.5
0 to 2.0
0 to 2.0
0 to 2.0
DD
MID
IN
.
Span
,