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參數資料
| 型號： | AD7864AS-2 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 4-Channel, Simultaneous Sampling, High Speed, 12-Bit ADC |
| 中文描述： | 4-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, PQFP44 |
| 封裝： | PLASTIC, MO-112-AA, MQFP-44 |
| 文件頁數： | 9/19頁 |
| 文件大?。?/td> | 214K |
| 代理商： | AD7864AS-2 |
AD7864
–9–
REV. A
AD7864-1
Figure 2 shows the analog input section of the AD7864-1. Each
input can be configured for
±
5 V or
±
10 V operation on the
AD7864-1. For
±
5 V (AD7864-1) operation, the V
INXA
and
V
INXB
inputs are tied together and the input voltage is applied to
both. For
±
10 V (AD7864-1) operation, the V
INXB
input is tied
to AGND and the input voltage is applied to the V
INXA
input.
The V
INXA
and V
INXB
inputs are symmetrical and fully inter-
changeable. Thus for ease of PCB layout on the
±
10 V range,
the input voltage may be applied to the V
INXB
input while the
V
INXA
input is tied to AGND.
2.5V
REFERENCE
T/H
TO ADC
REFERENCE
CIRCUITRY
6k
V
R2
R3
TO INTERNAL
COMPARATOR
AD7864-1
R1
R4
AGND
V
IN1B
V
IN1A
V
REF
Figure 2. AD7864-1 Analog Input Structure
For the AD7864-1, R1 = 6 k
, R2 = 24 k
,
R3 = 24 k
and
R4 = 12 k
. The resistor input stage is followed by the high
input impedance stage of the track/hold amplifier.
The designed code transitions take place midway between suc-
cessive integer LSB values (i.e., 1/2 LSB, 3/2 LSBs, 5/2 LSBs
etc.) LSB size is given by the formula, 1 LSB = FSR/4096. For
the
±
5 V range, 1 LSB = 10 V/4096 = 2.44 mV. For the
±
10 V
range, 1 LSB = 20 V/4096 = 4.88 mV. Output coding is twos
complement binary with 1 LSB = FSR/4096. The ideal input/
output transfer function for the AD7864-1 is shown in Table I.
Table I. Ideal Input/Output Code Table for the AD7864-1
Analog Input
l
+FSR/2 – 3/2 LSB
2
+FSR/2 – 5/2 LSB
+FSR/2 – 7/2 LSB
AGND + 3/2 LSB
AGND + 1/2 LSB
AGND – 1/2 LSB
AGND – 3/2 LSB
–FSR/2 + 5/2 LSB
–FSR/2 + 3/2 LSB
–FSR/2 + 1/2 LSB
Digital Output Code Transition
011 . . . 110 to 011 . . . 111
011 . . . 101 to 011 . . . 110
011 . . . 100 to 011 . . . 101
000 . . . 001 to 000 . . . 010
000 . . . 000 to 000 . . . 001
111 . . . 111 to 000 . . . 000
111 . . . 110 to 111 . . . 111
100 . . . 010 to 100 . . . 011
100 . . . 001 to 100 . . . 010
100 . . . 000 to 100 . . . 001
NOTES
1
FSR is full-scale range and is 20 V for the
±
10 V range and 10 V for the
±
5 V
range, with V
REF
= +2.5 V.
2
1 LSB = FSR/4096 = 4.883 mV (
±
10 V—AD7864-1) and 2.441 mV (
±
5 V—
AD7864-1) with V
REF
= +2.5 V.
AD7864-2
Figure 3 shows the analog input section of the AD7864-2. Each
input can be configured for 0 V to +5 V operation or 0 V to
+2.5 V operation. For 0 V to +5 V operation, the V
INXB
input is
tied to AGND and the input voltage is applied to the V
INXA
input. For 0 V to 2.5 V operation, the V
INXA
and V
INXB
inputs
are tied together and the input voltage is applied to both. The
V
INXA
and V
INXB
inputs are symmetrical and fully interchange-
able. Thus for ease of PCB layout on the 0 V to +5 V range, the
input voltage may be applied to the V
INXB
input while the V
INXA
input is tied to AGND.
For the AD7864-2, R1 = 6 k
and R2 = 6 k
. Once again, the
designed code transitions occur on successive integer LSB
values. Output coding is straight (natural) binary with 1 LSB =
FSR/4096 = 2.5 V/4096 = 0.61 mV, and 5 V/4096 = 1.22 mV,
for the 0 V to 2.5 V and the 0 V to 5 V options respectively.
Table II shows the ideal input and output transfer function for
the AD7864-2.
2.5V
REFERENCE
T/H
TO ADC
REFERENCE
CIRCUITRY
6k
V
R2
TO INTERNAL
COMPARATOR
AD7864-2
R1
V
IN1B
V
IN1A
V
REF
Figure 3. AD7864-2 Analog Input Structure
Table II. Ideal Input/Output Code Table for the AD7864-2
Analog Input
1
+FSR – 3/2 LSB
2
+FSR – 5/2 LSB
+FSR – 7/2 LSB
Digital Output Code Transition
111 . . . 110 to 111 . . . 111
111 . . . 101 to 111 . . . 110
111 . . . 100 to 111 . . . 101
AGND + 5/2 LSB
AGND + 3/2 LSB
AGND + 1/2 LSB
000 . . . 010 to 000 . . . 011
000 . . . 001 to 000 . . . 010
000 . . . 000 to 000 . . . 001
NOTES
1
FSR is full-scale range and is 0 V to 2.5 V and 0 V to 5 V for AD7864-2 with
V
REF
= +2.5 V.
2
1 LSB = FSR/4096 and is 0.61 mV (0 V to 2.5 V) and 1.22 mV (0 V to 5 V) for
AD7864-2 with V
REF
= +2.5 V.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7864AS-2REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP T/R |
| AD7864AS-2Z | 制造商:Analog Devices 功能描述:ADC 12BIT 4CH 500KSPS 44MQ 制造商:Analog Devices 功能描述:ADC, 12BIT, 4CH, 500KSPS, 44MQFP; Resolution (Bits):12bit; Sampling Rate:520kSPS; Supply Voltage Type:Single; Supply Voltage Min:4.75V; Supply Voltage Max:5.25V; Supply Current:24mA; Digital IC Case Style:MQFP; No. of Pins:44; Input ;RoHS Compliant: Yes |
| AD7864AS-3 | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP 制造商:Analog Devices 功能描述:IC 12-BIT ADC |
| AD7864AS-3REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP T/R |
| AD7864AS-3Z | 制造商:Analog Devices 功能描述:ADC 12BIT 4CH 500KSPS 44MQ 制造商:Analog Devices 功能描述:ADC, 12BIT, 4CH, 500KSPS, 44MQFP; Resolution (Bits):12bit; Sampling Rate:520kSPS; Supply Voltage Type:Single; Supply Voltage Min:4.75V; Supply Voltage Max:5.25V; Supply Current:24mA; Digital IC Case Style:MQFP; No. of Pins:44; Input ;RoHS Compliant: Yes |
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