AD7656-1 Analog Devices, AD7656-1 Datasheet - Page 11

• Manufacturer Part Number: AD7656-1
• Description: 250 kSPS, 6-Channel, Simultaneous Sampling, Bipolar 16-Bit ADC
• Manufacturer: Analog Devices

Specifications of AD7656-1

• Resolution (bits): 16bit
• # Chan: 6
• Sample Rate: 250kSPS
• Interface: Par,Ser,SPI
• Analog Input Type: SE-Bip
• Ain Range: 10V p-p,20 V p-p,Bip 10V,Bip 5.0V
• Adc Architecture: SAR
• Pkg Type: QFP

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Table 7. Pin Function Descriptions
Pin No.
54, 56, 58
33, 36, 39,
42, 45, 48
32, 37, 38, 43,
44, 49, 52, 53,
55, 57, 59
26
9
8, 25
34, 35, 40,
41, 46, 47,
50, 60
21, 22, 23
Mnemonic
REFCAPA, REFCAPB,
REFCAPC
V1 to V6
AGND
DV
V
DGND
AV
CONVST C,
CONVST B, CONVST A
DRIVE
CC
CC
DB14/REFBUF
DB7/HBEN/DCEN
DB10/DOUT C
DB9/DOUT B
DB8/DOUT A
DB4/DCIN B
DB3/DCIN C
Description
Reference Capacitor A, Reference Capacitor B, and Reference Capacitor C. Decoupling capacitors are
connected to these pins to decouple the reference buffer for each ADC pair. Decouple each REFCAP pin
to AGND using a 1 μF capacitor.
Analog Input 1 to Analog Input 6. These pins are single-ended analog inputs. In hardware mode,
the analog input range of these channels is determined by the RANGE pin. In software mode, it is
determined by the RNGC to RNGA bits of the control register (see Table 11).
Analog Ground. This pin is the ground reference point for all analog circuitry on the AD7656-1/
AD7657-1/AD7658-1. Refer all analog input signals and external reference signals to this pin.
Connect all AGND pins to the AGND plane of the system. The AGND and DGND voltages should
ideally be at the same potential and must not be more than 0.3 V apart, even on a transient basis.
Digital Power, 4.75 V to 5.25 V. The DV
and must not be more than 0.3 V apart, even on a transient basis. Decouple this supply to DGND by
placing a 1 μF decoupling capacitor on the DV
Logic Power Supply Input. The voltage supplied at this pin determines the operating voltage of the
interface. This pin is nominally at the same supply as the supply of the host interface.
Digital Ground. This is the ground reference point for all digital circuitry on the AD7656-1/AD7657-1/
AD7658-1. Connect both DGND pins to the DGND plane of a system. The DGND and AGND voltages
should ideally be at the same potential and must not be more than 0.3 V apart, even on a transient
basis.
Analog Supply Voltage, 4.75 V to 5.25 V. This is the supply voltage for the ADC cores. The AV
DV
on a transient basis.
Conversion Start Input A, Conversion Start Input B, and Conversion Start Input C. These logic inputs
are used to initiate conversions on the ADC pairs. CONVST A is used to initiate simultaneous conversions
on V1 and V2. CONVST B is used to initiate simultaneous conversions on V3 and V4. CONVST C is
used to initiate simultaneous conversions on V5 and V6. When one of these pins switches from low
to high, the track-and-hold switch on the selected ADC pair switches from track to hold, and the
conversion is initiated. These inputs can also be used to place the ADC pairs into partial power-
down mode.
DB5/DCIN A
DB2/SEL C
DB1/SEL B
DB6/SCLK
CC
V
DGND
EN/DIS
DB13
DB12
DB11
DRIVE
voltages should ideally be at the same potential and must not be more than 0.3 V apart, even
10
12
13
14
15
16
11
1
2
3
4
5
6
7
8
9
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
PIN 1
Figure 3. Pin Configuration
AD7656-1/AD7657-1/AD7658-1
Rev. C | Page 11 of 32
(Not to Scale)
TOP VIEW
CC
and AV
CC
CC
pin.
voltages should ideally be at the same potential
AD7656-1/AD7657-1/AD7658-1
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
V6
AV
AV
V5
AGND
AGND
V4
AV
AV
V3
AGND
AGND
V2
AV
AV
V1
CC
CC
CC
CC
CC
CC
CC
and