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Электронный компонент: AD1556AS

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REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
a
AD1555/AD1556
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 2002
FUNCTIONAL BLOCK DIAGRAM
MUX
PGA
REF DIVIDER
DAC
MODE CONTROL
LOGIC
OVERVOLTAGE
DETECTION
CLOCK
GENERATION
LOOP
FILTER
REFIN
REFCAP2
REFCAP1
AGND3
DGND
V
L
V
A
+V
A
AGND2
MODIN
PGAOUT
AGND1
CLKIN SYNC
BW0...BW2 RESET PWRDN GND
V
L
AIN (+)
AIN ()
TIN (+)
TIN ()
AD1555
CB0...CB4
PGA
CONTROL
CONFIGURATION
REGISTER
STATUS
REGISTER
INPUT
MUX
MFLG
MDATA
TDATA
CSEL
MCLK
INPUT SHIFT
REGISTER
DIN
SCLK
CS
R/
W
DOUT
DRDY
RSEL
CLOCK DIVIDER
DATA
OUTPUT
MUX
DATA
REGISTER
AD1556
H/
S
ERROR
PGA0...PGA4
DIGITAL
FILTER
24-Bit - ADC
with Low Noise PGA
FEATURES
AD1555
Fourth Order - Modulator
Large Dynamic Range
116 dB Min, 120 dB Typical @ 1 ms
117 dB Typical @ 0.5 ms
Low Input Noise: 80 nV rms @ 4 ms with
Gain of 34,128
Low Distortion: 111 dB Max, 120 dB Typical
Low Intermodulation: 122 dB
Sampling Rate at 256 kSPS
Very High Jitter Tolerance
No External Antialias Filter Required
Programmable Gain Front End
Input Range: 2.25 V
Robust Inputs
Gain Settings: 1, 2.5, 8.5, 34, 128
Common-Mode Rejection (DC to 1 kHz)
93 dB Min, 101 dB Typical @ Gain of 1
77 mW Typical Low Power Dissipation
Standby Modes
AD1556
FIR Digital Filter/Decimator
Serial or Parallel Selection of Configuration
Output Word Rates: 250 SPS to 16 kSPS
6.2 mW Typ Low Power Dissipation
70 W in Standby Mode
Reference Design and Evaluation Board with
Software Available
APPLICATIONS
Seismic Data Acquisition Systems
Chromatography
Automatic Test Equipment
GENERAL DESCRIPTION
The AD1555 is a complete sigma-delta modulator, combined
with a programmable gain amplifier intended for low frequency,
high dynamic range measurement applications. The AD1555
outputs a ones-density bitstream proportional to the analog
input. When used in conjunction with the AD1556 digital filter/
decimator, a high performance ADC is realized.
The continuous-time analog modulator input architecture avoids
the need for an external antialias filter. The programmable gain
front end simplifies system design, extends the dynamic range,
and reduces the system board area. Low operating power and
standby modes makes the AD1555 ideal for remote battery-pow-
ered data acquisition systems.
The AD1555 is fabricated on Analog Devices' BiCMOS process
that has high performance bipolar devices along with CMOS
transistors. The AD1555 and AD1556 are packaged, respectively,
in 28-lead PLCC and 44-lead MQFP packages and are specified
from 55
C to +85C (AD1556 and AD1555 B Grade) and from
0
C to 85C (AD1555 A Grade).
0
FREQUENCY Hz
120
200
0
50
AMPLITUDE dBr
100
150
200
250
300
20
100
140
180
60
80
160
40
350
400
450
500
f
IN
= 24.4Hz
SNR = 116.7dB
THD = 120.6dB
Figure 1. FFT Plot, Full-Scale AIN Input, Gain of 1
REV. B
AD1555/AD1556
2
AD1555BP
AD1555AP
Parameter
Notes
Min
Typ
Max
Min
Typ
Max
Unit
PGA Gain Settings
1, 2.5, 8.5, 34, 128
AC ACCURACY
Dynamic Range
1
PGA Gain of 1
116.5
120
116
120
dB
PGA Gain of 2.5
116
119.5
115.5
119.5
dB
PGA Gain of 8.5
114
117.5
114
117.5
dB
PGA Gain of 34
104.5
109.5
104.5
109.5
dB
PGA Gain of 128
98
98
dB
Total Harmonic Distortion
2
PGA Gain of 1
120
111
120
107
dB
PGA Gain of 2.5
116
108
116
107
dB
PGA Gain of 8.5
116
106
116
105
dB
PGA Gain of 34
115
101
115
101
dB
PGA Gain of 128
108
108
dB
Jitter Tolerance
3
300
300
ps
Intermodulation Distortion
4
PGA Gain of 1
122
122
dB
DC ACCURACY
Absolute Gain Error
5
PGA Gain of 1, 2.5
3.5
+3.5
3.5
+3.5
%
PGA Gain of 8.5
4.5
+4.5
4.5
+4.5
%
PGA Gain of 34
10
+10
10
+10
%
Gain Stability Over Temperature
5
15
15
ppm/
C
Offset
5, 6
All PGA Gain
60
60
mV
Offset Drift
5, 6
6
6
V/C
ANALOG INPUT
Full-Scale Nondifferential Input
MODIN
2.25
2.25
V
Input Impedance
MODIN
20
20
k
Full-Scale Differential Input
PGA Gain of 1
2.25
2.25
V
Other PGA Gain Settings
See Table I
See Table I
Differential Input Impedance
AIN, TIN Inputs
140
140
M
Common-Mode Range
2.25
2.25
V
Common-Mode Rejection Ratio
V
CM
=
2.25 V, f
IN
= 200 Hz
PGA Gain of 1
93
101
91
101
dB
PGA Gain of 2.5
95
102
91.5
102
dB
PGA Gain of 8.5, 34
95.5
108
94.5
108
dB
PGA Gain of 128
108
108
dB
Power Supply Rejection Ratio
7
50
50
dB
AIN to TIN Crosstalk Isolation
f
IN
= 200 Hz
130
130
dB
Differential Input Current
130
130
nA
TEMPERATURE RANGE
8
Specified Performance
T
MIN
to T
MAX
55
+85
0
85
C
REFERENCE INPUT
9
Input Voltage Range
2.990
3.0
3.010
2.990
3.0
3.010
V
Input Current
130
130
A
DIGITAL INPUTS OUTPUTS
V
IL
0.3
+0.8
0.3
+0.8
V
V
IH
2.0
V
L
+ 0.3 2.0
V
L
+ 0.3
V
I
IL
10
+10
10
+10
A
I
IH
10
+10
10
+10
A
V
OL
I
SINK
= +2 mA
0.4
0.4
V
V
OH
I
SOURCE
= 2 mA
2.4
2.4
V
AD1555SPECIFICATIONS
(+V
A
= +5 V; V
A
= 5 V; V
L
= 5 V; AGND = DGND = 0 V; MCLK = 256 kHz; T
A
= T
MIN
to
T
MAX
, unless otherwise noted.)
REV. B
3
AD1555/AD1556
AD1556SPECIFICATIONS
AD1556AS
Parameter
Notes
Min
Typ
Max
Unit
FILTER PERFORMANCES
Pass-Band Ripple
0.05
+0.05
dB
Stop-Band Attenuation
All Filters Except F
O
=16 kHz
135
dB
F
O
=16 kHz
86
dB
Filters Characteristics
See Table II
DIGITAL INPUTS OUTPUTS
V
IL
0.3
+0.8
V
V
IH
+2.0
V
L
+ 0.3
V
I
IL
10
+10
A
I
IH
10
+10
A
V
OL
I
SINK
= +2 mA
+0.5
V
V
OH
I
SOURCE
= 2 mA
V
L
0.6
V
POWER SUPPLIES
Specified Performance
V
L
2.85
5.25
V
Quiescent Currents
I(V
L
)
4
5
mA
Power Dissipation
V
L
= 3.3 V, F
O
= 1 kHz
6.2
8.5
mW
In Power-Down Mode
70
W
TEMPERATURE RANGE
*
Specified Performance, T
MIN
to T
MAX
55
+85
C
*
Contact factory for extended temperature range.
Specifications subject to change without notice.
AD1555BP
AD1555AP
Parameter
Notes
Min
Typ
Max
Min
Typ
Max
Unit
POWER SUPPLIES
Recommended Operating Conditions
+V
A
4.75
5
5.25
4.75
5
5.25
V
V
A
5.25
5
4.75
5.25
5
4.75
V
V
L
4.75
5
5.25
4.75
5
5.25
V
Quiescent Currents
I(+V
A
)
10
8
10
8
10
mA
I(V
A
)
10
8
9.5
8
9.5
mA
I(V
L
)
30
42
30
42
A
Power Dissipation
10
77
96
77
96
mW
PGA in Standby Mode
11
56
70
56
70
mW
In Power-Down Mode
11, 12
Reference Input = 3 V
650
650
W
Reference Input = 0 V
250
250
W
NOTES
1
Tested at the output word rate F
O
= 1 kHz. F
O
is the AD1556 output word rate, the inverse of the sampling rate. See Tables I, Ia, Ib for other output
word rates.
2
Tested with a full-scale input signal at approximately 24 Hz.
3
This parameter is guaranteed by design.
4
Tested at the output word rate F
O
= 1 kHz with input signals of 30 Hz and 50 Hz, each 6 dB down full scale.
5
This specification is for the AD1555 only and does not include the errors from external components as, for instance, the external reference.
6
This offset specification is referred to the modulator output.
7
Characterized with a 100 mV p-p sine wave applied separately to each supply.
8
Contact factory for extended temperature range.
9
Recommended Reference: AD780BR.
10
Specified with analog inputs grounded.
11
See Table III for configuration conditions.
12
Specified with MCLK input grounded.
Specifications subject to change without notice.
(V
L
= 2.85 V to 5.25 V; CLKIN = 1.024 MHz; T
A
= T
MIN
to T
MAX
unless otherwise noted.)
REV. B
AD1555/AD1556
4
Table I. Dynamic and Noise Typical Performances
Input and Gain
MODIN
PGA = 1 (0 dB)
PGA = 2.5 (8 dB)
PGA = 8.5 (19 dB)
PGA = 34 (31 dB)
PGA = 128 (42 dB)
Input Range
1.6 V rms
1.6 V rms
636 mV rms
187 mV rms
47 mV rms
12.4 mV rms
Dynamic Range
F
O
= 16 kHz (1/16 ms)
40 dB
40 dB
40 dB
40 dB
40 dB
40 dB
F
O
= 8 kHz (1/8 ms)
69 dB
69 dB
69 dB
69 dB
69 dB
69 dB
F
O
= 4 kHz (1/4 ms)
98 dB
98 dB
98 dB
98 dB
97 dB
91 dB
F
O
= 2 kHz (1/2 ms)
117 dB
117 dB
116.5 dB
114.5 dB
106.5 dB
95 dB
F
O
= 1 kHz (1 ms)
120 dB
120 dB
119.5 dB
117.5 dB
109.5 dB
98 dB
F
O
= 500 Hz (2 ms)
123 dB
123 dB
122.5 dB
120 dB
112.5 dB
101 dB
F
O
= 250 Hz (4 ms)
126 dB
126 dB
125.5 dB
123 dB
115.5 dB
104 dB
Equivalent Input Noise
F
O
= 16 kHz (1/16 ms)
15.5 mV rms
15.5 mV rms
6.17 mV rms
1.84 mV rms
470
V rms
138
V rms
F
O
= 8 kHz (1/8 ms)
560
V rms
560
V rms
220
V rms
65.5
V rms
16.4
V rms
4.5
V rms
F
O
= 4 kHz (1/4 ms)
20
V rms
20
V rms
8
V rms
2.36
V rms
661 nV rms
351 nV rms
F
O
= 2 kHz (1/2 ms)
2.25
V rms
2.25
V rms
952 nV rms
353 nV rms
225 nV rms
223 nV rms
F
O
= 1 kHz (1 ms)
1.59
V rms
1.59
V rms
674 nV rms
250 nV rms
159 nV rms
159 nV rms
F
O
= 500 Hz (2 ms)
1.13
V rms
1.13
V rms
477 nV rms
187 nV rms
113 nV rms
111 nV rms
F
O
= 250 Hz (4 ms)
797 nV rms
797 nV rms
338 nV rms
133 nV rms
80 nV rms
79 nV rms
Table Ia. Minimum Dynamic Performances (AD1555AP Only)
*
Input and Gain
MODIN
PGA = 1 (0 dB)
PGA = 2.5 (8 dB)
PGA = 8.5 (19 dB)
PGA = 34 (31 dB)
F
O
= 1 kHz (1 ms)
116
116
115.5
114
104.5
F
O
= 500 Hz (2 ms)
119
119
118.5
117
107.5
F
O
= 250 Hz (4 ms)
122
122
121.5
120
110.5
*
Not tested in production. Guaranteed by design.
Table Ib. Minimum Dynamic Performances (AD1555BP Only)
*
Input and Gain
MODIN
PGA = 1 (0 dB)
PGA = 2.5 (8 dB)
PGA = 8.5 (19 dB)
PGA = 34 (31 dB)
F
O
= 1 kHz (1 ms)
116.5
116.5
116
114
104.5
F
O
= 500 Hz (2 ms)
119.5
119.5
119
117
107.5
F
O
= 250 Hz (4 ms)
122.5
122.5
121
120
110.5
*
Not tested in production. Guaranteed by design.
Table II. Filter Characteristics
Output Word Rate F
O
Pass Band
3 dB Frequency
Stop Band
Group Delay
(Sampling Rate in ms)
(Hz)
(Hz)
(Hz)
(ms)
16000 Hz (1/16 ms)
6000
6480
8000
0.984
8000 Hz (1/8 ms)
3000
3267.5
4000
3
4000 Hz (1/4 ms)
1500
1634
2000
6
2000 Hz (1/2 ms)
750
816.9
1000
12
1000 Hz (1 ms)
375
408.5
500
24
500 Hz (2 ms)
187.5
204.2
250
48
250 Hz (4 ms)
93.75
101.4
125
93
REV. B
5
AD1555/AD1556
TIMING SPECIFICATIONS
Symbol
Min
Typ
Max
Unit
CLKIN Frequency
1
f
CLKIN
0.975
1.024
1.075
MHz
CLKIN Duty Cycle Error
45
55
%
MCLK Output Frequency
1
f
CLKIN
/4
SYNC Setup Time
t
1
10
ns
SYNC Hold Time
t
2
10
ns
CLKIN Rising to MCLK Output Falling on SYNC
t
3
20
ns
CLKIN Falling to MCLK Output Rising
t
4
20
ns
CLKIN Falling to MCLK Output Falling
t
5
20
ns
MCLK Input Falling to MDATA Falling
t
6
30
ns
MCLK Input Rising to MDATA and MFLG Valid
t
7
100
ns
TDATA Setup Time after SYNC
t
8
5
ns
TDATA Hold Time
t
9
5
ns
RESET Setup Time
t
10
15
ns
RESET Hold Time
t
11
15
ns
CLKIN Falling to DRDY Rising
t
12
20
ns
CLKIN Rising to DRDY Falling
2
t
13
20
ns
CLKIN Rising to
ERROR Falling
t
14
50
ns
RSEL to Data Valid
t
15
25
ns
RSEL Setup to SCLK Falling
t
16
10
ns
DRDY to Data Valid
t
17
25
ns
DRDY High Setup to SCLK Falling
t
18
10
ns
R/
W to Data Valid
t
19
25
ns
R/
W High Setup to SCLK Falling
t
20
10
ns
CS to Data Valid
t
21
25
ns
CS Low Setup to SCLK Falling
t
22
10
ns
SCLK Rising to DOUT Valid
t
23
25
ns
SCLK High Pulsewidth
t
24
25
ns
SCLK Low Pulsewidth
t
25
25
ns
SCLK Period
t
26
70
ns
SCLK Falling to DRDY Falling
2
t
27
20
ns
CS High or R/W Low to DOUT Hi-Z
t
28
20
ns
R/
W Low Setup to SCLK Falling
t
29
10
ns
CS Low Setup to SCLK Falling
t
30
10
ns
Data Setup Time to SCLK Falling
t
31
10
ns
Data Hold Time after SCLK Falling
t
32
10
ns
R/
W Hold Time after SCLK Falling
t
33
10
ns
NOTES
1
The gain of the modulator is proportional to f
CLKIN
and MCLK frequency.
2
With DRDYBUF low only. When DRDYBUF is high, this timing also depends on the value of the external pull-down resistor.
Specifications subject to change without notice.
(+V
A
= +5 V 5%; V
A
= 5 V 5%; AD1555 V
L
= 5 V
5%, AD1556 V
L
= 2.85 V to 5.25 V;
CLKIN = 1.024 MHz; AGND = DGND = 0 V; C
L
= 50 pF; T
A
= T
MIN
to T
MAX
, unless otherwise noted)
I
OH
I
OL
TO OUTPUT
PIN
1.4V
C
L
50pF
500 A
1.6mA
Figure 2. Load Circuit for Digital Interface Timing