a
FEATURES
Specified for VDD of 2.7 V to 5.25 V
1.75 MSPS for AD7470 (10-Bit)
1.5 MSPS for AD7472 (12-Bit)
Low Power
AD7470: 3.34 mW Typ at 1.5 MSPS with 3 V Supplies
7.97 mW Typ at 1.75 MSPS with 5 V Supplies
AD7472: 3.54 mW Typ at 1.2 MSPS with 3 V Supplies
8.7 mW Typ at 1.5 MSPS with 5 V Supplies
Wide Input Bandwidth
70 dB Typ SNR at 500 kHz Input Frequency
Flexible Power/Throughput Rate Management
No Pipeline Delays
High Speed Parallel Interface
Sleep Mode: 50 nA Typ
24-Lead SOIC and TSSOP Packages
1.75 MSPS, 4 mW
10-Bit/12-Bit Parallel ADCs
AD7470/AD7472
FUNCTIONAL BLOCK DIAGRAM
AVDD
VIN
T/H
REF IN
VDRIVE
10-/12-BIT
SUCCESSIVE
APPROXIMATION
ADC
OUTPUT
DRIVERS
DVDD
The conversion process and data acquisition are controlled
using standard control inputs, allowing easy interfacing to
microprocessors or DSPs. The input signal is sampled on the
falling edge of CONVST, and conversion is also initiated at
this point. BUSY goes high at the start of conversion and
goes low 531.66 ns after falling edge of CONVST (AD7472
with a clock frequency of 26 MHz) to indicate that the conversion is complete. There are no pipeline delays associated
with the parts. The conversion result is accessed via standard
CS and RD signals over a high speed parallel interface.
The AD7470/AD7472 use advanced design techniques to
achieve very low power dissipation at high throughput rates. With
3 V supplies and 1.5 MSPS throughput rates, the AD7470
typically consumes, on average, just 1.1 mA. With 5 V supplies
and 1.75 MSPS, the average current consumption is typically
1.6 mA. The part also offers flexible power/throughput rate
management. Operating the AD7470 with 3 V supplies and
500 kSPS throughput reduces the current consumption to 713 µA.
At 5 V supplies and 500 kSPS, the part consumes 944 µA.
DB0
CLK IN
CONVST
CONTROL
LOGIC
CS
RD
BUSY
AD7470/AD7472
AGND
GENERAL DESCRIPTION
The AD7470/AD7472 are 10-bit/12-bit high speed, low power,
successive approximation ADCs. The parts operate from a single
2.7 V to 5.25 V power supply and feature throughput rates up to
1.5 MSPS for the 12-bit AD7472 and up to 1.75 MSPS for the
10-bit AD7470. The parts contain a low noise, wide bandwidth
track-and-hold amplifier that can handle input frequencies in
excess of 1 MHz.
DB9 (DB11)
DGND
AD7470 IS A 10-BIT PART WITH DB0 TO DB9 AS OUTPUTS.
AD7472 IS A 12-BIT PART WITH DB0 TO DB11 AS OUTPUTS.
It is also possible to operate the parts in an auto sleep mode,
where the part wakes up to do a conversion and automatically
enters sleep mode at the end of conversion. This method allows
very low power dissipation numbers at lower throughput rates.
In this mode, the AD7472 can be operated with 3 V supplies at
100 kSPS, and consume an average current of just 124 µA. At
5 V supplies and 100 kSPS, the average current consumption is
171 µA.
The analog input range for the part is 0 V to REF IN. The 2.5 V
reference is applied externally to the REF IN pin. The conversion rate is determined by the externally-applied clock.
PRODUCT HIGHLIGHTS
1. High Throughput with Low Power Consumption. The
AD7470 offers 1.75 MSPS throughput and the AD7472
offers 1.5 MSPS throughput rates with 4 mW power
consumption.
2. Flexible Power/Throughput Rate Management. The conversion rate is determined by an externally-applied clock allowing the power to be reduced as the conversion rate is reduced.
The part also features an auto sleep mode to maximize power
efficiency at lower throughput rates.
3. No Pipeline Delay. The part features a standard successive
approximation ADC with accurate control of the sampling
instant via a CONVST input and once off conversion control.
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. Trademarks and
registered trademarks are the property of their respective owners.
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
© 2003 Analog Devices, Inc. All rights reserved.
AD7470/AD7472
V2, REF IN = 2.5 V, fCLKIN = 30 MHz @ 5 V and 24 MHz @ 3 V;
1 (VDD = 2.7 V to 5.25
3
AD7470–SPECIFICATIONS
A Version1
Parameter
DYNAMIC PERFORMANCE
Signal to Noise + Distortion (SINAD)
Signal-to-Noise Ratio (SNR)
Total Harmonic Distortion (THD)
Peak Harmonic or Spurious Noise (SFDR)
Intermodulation Distortion (IMD)
Second-Order Terms
Third-Order Terms
Aperture Delay
Aperture Jitter
Full Power Bandwidth
DC ACCURACY
Resolution
Integral Nonlinearity
Differential Nonlinearity
Offset Error
Gain Error
ANALOG INPUT
Input Voltage Ranges
DC Leakage Current
Input Capacitance
REFERENCE INPUT
REF IN Input Voltage Range
DC Leakage Current
Input Capacitance
LOGIC INPUTS
Input High Voltage, VINH
Input Low Voltage, VINL
Input Current, IIN
Input Capacitance, CIN4
LOGIC OUTPUTS
Output High Voltage, VOH
Output Low Voltage, VOL
Floating-State Leakage Current
Floating-State Output Capacitance
Output Coding
CONVERSION RATE
Conversion Time
Track-and-Hold Acquisition Time
Throughput Rate
POWER REQUIREMENTS
VDD
IDD5
Normal Mode
Quiescent Current
Normal Mode
Quiescent Current
Sleep Mode
Power Dissipation5
Normal Mode
Sleep Mode
TA = TMIN to TMAX , unless otherwise noted.)
Unit
Test Conditions/Comments
5V
60
60
60
60
–83
–75
–85
–75
3V
60
60
60
60
–83
–75
–85
–75
dB min
dB min
dB min
dB min
dB typ
dB max
dB typ
dB max
fS = 1.75 MSPS @ 5 V, fS = 1.5 MSPS @ 3 V
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
–79
–75
–77
–75
5
15
20
–75
–75
–75
–75
5
15
20
dB typ
dB max
dB typ
dB max
ns typ
ps typ
MHz typ
10
±1
± 0.9
± 2.5
±1
10
±1
± 0.9
± 2.5
±1
Bits
LSB max
LSB max
LSB max
LSB max
0 to REF IN
±1
33
0 to REF IN
±1
33
V
µA max
pF typ
2.5
±1
10/20
2.5
±1
10/20
V
µA max
pF typ
2.4
0.4
±1
10
2.4
0.4
±1
10
V min
V max
µA max
pF max
VDRIVE – 0.2
VDRIVE – 0.2
0.4
0.4
± 10
± 10
10
10
Straight (Natural) Binary
V min
V max
µA max
pF max
12
135
1.75
CLK IN Cycles (max)
ns min
MSPS max
12
135
1.5
+2.7/+5.25
V min/max
2.4
900
1.5
800
1
mA max
µA max
mA max
µA max
µA max
12
4.5
5
3
mW max
mW max
µW max
µW max
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
@ 3 dB
fS = 1.75 MSPS @ 5 V; fS = 1.5 MSPS @ 3 V
Guaranteed No Missed Codes to 10 Bits
± 1% for Specified Performance
Track-and-Hold Mode
Typically 10 nA, VIN = 0 V or VDD
ISOURCE = 200 µA
ISINK = 200 µA
VDD = 2.7 V to 5.25 V
Conversion Time + Acquisition Time
CLK IN of 30 MHz @ 5 V and 24 MHz @ 3 V
Digital Inputs = 0 V or DVDD
VDD = 4.75 V to 5.25 V; fS = 1.75 MSPS; Typ 2 mA
VDD = 4.75 V to 5.25 V; fS = 1.75 MSPS
VDD = 2.7 V to 3.3 V; fS = 1.5 MSPS; Typ 1.3 mA
VDD = 2.7 V to 3.3 V; fS = 1.5 MSPS
CLK IN = 0 V or DVDD
Digital Inputs = 0 V or DVDD
VDD = 5 V
VDD = 3 V
VDD = 5 V; CLK IN = 0 V or DVDD
VDD = 3 V; CLK IN = 0 V or DVDD
NOTES
1
Temperature ranges as follows: A Version: –40°C to +85°C.
2
The AD7470 functionally works at 2.35 V. Typical specifications @ 25°C for SNR (100 kHz) = 59 dB; THD (100 kHz) = –84 dB; INL ± 0.8 LSB.
3
The AD7470 will typically maintain A-grade performance up to 125°C, with a reduced CLK of 20 MHz @ 5 V and 16 MHz @ 3 V. Typical sleep mode current @ 125°C is 700 nA.
4
Sample tested @ 25°C to ensure compliance.
5
See Power vs. Throughput Rate section.
Specifications subject to change without notice.
–2–
REV. B
AD7470/AD7472
V , REF IN = 2.5 V, A and B Versions: f
AD7472–SPECIFICATIONS1 (V20 MHz= 2.7@ V3 toV, 5.25
T = T to T , unless otherwise noted.)
2
DD
A
Parameter
A Version
DYNAMIC PERFORMANCE
5V
Signal to Noise + Distortion (SINAD) 69
68
Signal-to-Noise Ratio (SNR)
70
68
Total Harmonic Distortion (THD) –83
–83
–75
Peak Harmonic or Spurious Noise
(SFDR)
–86
–86
–76
Intermodulation Distortion (IMD)
Second-Order Terms
–77
–86
Third-Order Terms
–77
–86
Aperture Delay
5
Aperture Jitter
15
Full Power Bandwidth
20
DC ACCURACY
Resolution
Integral Nonlinearity
1
B Version
MIN
1
CLKIN
MAX
Unit
Test Conditions/Comments
3V
69
68
70
68
–78
–84
–75
5V
69
68
70
68
–83
–83
–75
3V
69
68
70
68
–78
–84
–75
dB typ
dB min
dB typ
dB min
dB typ
dB typ
dB max
fS = 1.5 MSPS @ 5 V, fS = 1.2 MSPS @ 3 V
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 100 kHz Sine Wave
–81
–86
–76
–86
–86
–76
–81
–86
–76
dB typ
dB typ
dB max
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 100 kHz Sine Wave
–77
–86
–77
–86
5
15
20
–77
–86
–77
–86
5
15
20
–77
–86
–77
–86
5
15
20
dB typ
dB typ
dB typ
dB typ
ns typ
ps typ
MHz typ
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
12
±2
12
±1
12
±1
Bits
LSB max
Differential Nonlinearity
± 1.8
± 1.8
± 0.9
± 0.9
LSB max
Offset Error
Gain Error
± 10
±2
± 10
±2
± 10
±2
± 10
±2
LSB max
LSB max
ANALOG INPUT
Input Voltage Ranges
DC Leakage Current
Input Capacitance
0 to REF IN 0 to REF IN
±1
±1
33
33
0 to REF IN 0 to REF IN
±1
±1
33
33
V
µA max
pF typ
REFERENCE INPUT
REF IN Input Voltage Range
DC Leakage Current
Input Capacitance
2.5
±1
10/20
2.5
±1
10/20
2.5
±1
10/20
2.5
±1
10/20
V
µA max
pF typ
LOGIC INPUTS
Input High Voltage, VINH
Input Low Voltage, VINL
Input Current, IIN
Input Capacitance, CIN3
2.4
0.4
±1
10
2.4
0.4
±1
10
2.4
0.4
±1
10
2.4
0.4
±1
10
V min
V max
µA max
pF max
LOGIC OUTPUTS
Output High Voltage, V OH
Output Low Voltage, V OL
Floating-State Leakage Current
Floating-State Output Capacitance
Output Coding
VDRIVE – 0.2 VDRIVE – 0.2
0.4
0.4
± 10
± 10
10
10
Straight (Natural) Binary
VDRIVE – 0.2 VDRIVE – 0.2
0.4
0.4
± 10
± 10
10
10
Straight (Natural) Binary
V min
V max
µA max
pF max
CONVERSION RATE
Conversion Time
14
14
14
14
135
1.5
135
1.2
135
1.5
135
1.2
CLK IN
Cycles (max)
ns min
MSPS max
POWER REQUIREMENTS
VDD
IDD4
Normal Mode
Quiescent Current
Normal Mode
Quiescent Current
Sleep Mode
Power Dissipation4
Normal Mode
Sleep Mode
@ 3 dB
fS = 1.5 MSPS @ 5 V , fS = 1.2 MSPS @ 3 V
12
±2
Track-and-Hold Acquisition Time
Throughput Rate
+2.7/+5.25
+2.7/+5.25
V min/max
2.4
900
1.5
800
1
2.4
900
1.5
800
1
mA max
µA max
mA max
µA max
µA max
12
4.5
5
3
12
4.5
5
3
mW max
mW max
µW max
µW max
Guaranteed No Missed Codes to 11 Bits
(A Version)
Guaranteed No Missed Codes to 12 Bits
(B Version)
± 1% for Specified Performance
Track-and-Hold Mode
Typically 10 nA, VIN = 0 V or VDD
ISOURCE = 200 µA
ISINK = 200 µA
VDD = 2.7 V to 5.25 V
Conversion Time + Acquisition Time
Digital Inputs = 0 V or DV DD
VDD = 4.75 V to 5.25 V; Typ 2 mA; f S = 1.5 MSPS
VDD = 4.75 V to 5.25 V; fS = 1.5 MSPS
VDD = 2.7 V to 3.3 V; Typ 1.3 mA; fS = 1.2 MSPS
VDD = 2.7 V to 3.3 V; fS = 1.2 MSPS
CLK IN = 0 V or DVDD
Digital Inputs = 0 V or DV DD
VDD = 5 V
VDD = 3 V
VDD = 5 V; CLK IN = 0 V or DV DD
VDD = 3 V; CLK IN = 0 V or DV DD
NOTES
1
Temperature ranges as follows: A and B Versions: –40°C to +85°C.
2
The AD7472 functionally works at 2.35 V. Typical specifications @ 25°C for SNR (100 kHz) = 68 dB; THD (100 kHz) = –84 dB; INL ± 0.8 LSB.
3
Sample tested @ 25°C to ensure compliance.
4
See Power vs. Throughput Rate section.
Specifications subject to change without notice.
REV. B
= 26 MHz @ 5 V and
–3–
AD7470/AD7472
2
= 2.7 V to 5.25 V , REF IN = 2.5 V,Y Version: fCLKIN = 20 MHz @ 5 V and
1 (V14DDMHz
@ 3 V; T = T to T , unless otherwise noted.)
AD7472–SPECIFICATIONS
Y Version1
Parameter
DYNAMIC PERFORMANCE
Signal to Noise + Distortion (SINAD)
Signal-to-Noise Ratio (SNR)
Total Harmonic Distortion (THD)
Peak Harmonic or Spurious Noise (SFDR)
Intermodulation Distortion (IMD)
Second-Order Terms
Third-Order Terms
Aperture Delay
Aperture Jitter
Full Power Bandwidth
DC ACCURACY
Resolution
Integral Nonlinearity
Differential Nonlinearity
Offset Error
Gain Error
ANALOG INPUT
Input Voltage Ranges
DC Leakage Current
Input Capacitance
REFERENCE INPUT
REF IN Input Voltage Range
DC Leakage Current
Input Capacitance
LOGIC INPUTS
Input High Voltage, VINH
Input Low Voltage, VINL
Input Current, IIN
Input Capacitance, CIN3
LOGIC OUTPUTS
Output High Voltage, VOH
Output Low Voltage, VOL
Floating-State Leakage Current
Floating-State Output Capacitance
Output Coding
CONVERSION RATE
Conversion Time
Track-and-Hold Acquisition Time
Throughput Rate
POWER REQUIREMENTS
VDD
IDD4
Normal Mode
Quiescent Current
Normal Mode
Quiescent Current
Sleep Mode
Power Dissipation4
Normal Mode
Sleep Mode
A
MIN
MAX
Unit
Test Conditions/Comments
fS = 1.2 MSPS @ 5 V, fS = 875 kSPS @ 3 V
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 100 kHz Sine Wave
5V
69
68
70
68
–83
–83
–75
–86
–86
–76
3V
69
68
70
68
–78
–84
–75
–81
–86
–76
dB typ
dB min
dB typ
dB min
dB typ
dB typ
dB max
dB typ
dB typ
dB max
–77
–86
–77
–86
5
15
20
–77
–86
–77
–86
5
15
20
dB typ
dB typ
dB typ
dB typ
ns typ
ps typ
MHz typ
12
±2
± 1.8
± 10
±2
12
±2
± 1.8
± 10
±2
Bits
LSB max
LSB max
LSB max
LSB max
0 to REF IN
±1
33
0 to REF IN
±1
33
V
µA max
pF typ
2.5
±1
10/20
2.5
±1
10/20
V
µA max
pF typ
2.4
0.4
±1
10
2.4
0.4
±1
10
V min
V max
µA max
pF max
VDRIVE – 0.2
VDRIVE – 0.2
0.4
0.4
± 10
± 10
10
10
Straight (Natural) Binary
V min
V max
µA max
pF max
14
140
1200
CLK IN Cycles (max)
ns min
kSPS max
14
140
875
+2.7/+5.25
V min/max
2.4
900
1.5
800
2
mA max
µA max
mA max
µA max
µA max
12
4.5
10
6
mW max
mW max
µW max
µW max
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
fIN = 500 kHz Sine Wave
fIN = 100 kHz Sine Wave
@ 3 dB
fS = 1.2 MSPS @ 5 V; fS = 875 kSPS @ 3 V
Guaranteed No Missed Codes to 11 Bits
± 1% for Specified Performance
Track-and-Hold Mode
Typically 10 nA, VIN = 0 V or VDD
ISOURCE = 200 µA
ISINK = 200 µA
VDD = 2.7 V to 5.25 V
Conversion Time + Acquisition Time
Digital Inputs = 0 V or DVDD
VDD = 4.75 V to 5.25 V; fS = 1.2 MSPS; Typ 2 mA
VDD = 4.75 V to 5.25 V; fS = 1.2 MSPS
VDD = 2.7 V to 3.3 V; fS = 875 kSPS; Typ 1.3 mA
VDD = 2.7 V to 3.3 V; fS = 875 kSPS
CLK IN = 0 V or DVDD
Digital Inputs = 0 V or DVDD
VDD = 5 V
VDD = 3 V
VDD = 5 V; CLK IN = 0 V or DVDD
VDD = 3 V; CLK IN = 0 V or DVDD
NOTES
1
Temperature ranges as follows: Y Version: –40°C to +125°C.
2
The AD7472 functionally works at 2.35 V. Typical specifications @ 25°C for SNR (100 kHz) = 68 dB; THD (100 kHz) = –84 dB; INL ± 0.8 LSB.
3
Sample tested @ 25°C to ensure compliance.
4
See Power vs. Throughput Rate section.
Specifications subject to change without notice.
–4–
REV. B
AD7470/AD7472
TIMING SPECIFICATIONS1 (V
DD
Parameter
fCLK
2
tCONVERT
tWAKEUP
t1
t2
AD7470
Unit
Description
10
26
531.66
1
10
kHz min
MHz max
ns min
µs max
ns min
10
10
15
30
35
0
0
20
15
8
0
ns max
ns max
ns max
ns max
ns max
ns max
ns min
ns min
ns max
ns max
135
140
100
ns max
ns max
ns min
0
0
20
15
8
0
135
t10
Limit at TMIN, TMAX
AD7472
10
30
436.42
1
10
30
t3
t4 3
t5
t6 3
t7 4
t8
t9
= 2.7 V to 5.25 V, REF IN = 2.5 V; TA = TMIN to TMAX, unless otherwise noted.)
100
tCLK = 1/fCLK IN
Wake-Up Time
CONVST Pulse Width
CONVST to BUSY Delay,
VDD = 5 V, A and B Versions
VDD = 5 V, Y Version
VDD = 3 V, A and B Versions
VDD = 3 V, Y Version
BUSY to CS Setup Time
CS to RD Setup Time
RD Pulse Width
Data Access Time After Falling Edge of RD
Bus Relinquish Time After Rising Edge of RD
CS to RD Hold Time
Acquisition Time
A and B Versions
Y Version
Quiet Time
NOTES
1
Sample tested at 25°C to ensure compliance. All input signals are specified with tr = tf = 5 ns (10% to 90% of V DD) and timed from a voltage level of 1.6 V.
See Figure 1.
2
Mark/Space ratio for the CLK inputs is 40/60 to 60/40. First CLK pulse should be 10 ns min from falling edge of CONVST.
3
Measured with the load circuit of Figure 1 and defined as the time required for the output to cross 0.8 V or 2.0 V.
4
t7 is derived from the measured time taken by the data outputs to change 0.5 V when loaded with the circuit of Figure 1. The measured number is then extrapolated
back to remove the effects of charging or discharging the 50 pF capacitor. This means that the time, t 7, quoted in the timing characteristics, is the true bus relinquish
time of the part and is independent of the bus loading.
Specifications subject to change without notice.
200A
TO OUTPUT
PIN
IOL
1.6V
CL
50pF
200A
IOH
Figure 1. Load Circuit for Digital Output Timing Specifications
REV. B
–5–
AD7470/AD7472
ABSOLUTE MAXIMUM RATINGS 1
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . 150°C
θJA Thermal Impedance . . . . . . . . . . . . . . . 75°C/W (SOIC)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115°C/W (TSSOP)
θJC Thermal Impedance . . . . . . . . . . . . . . . 25°C/W (SOIC)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35°C/W (TSSOP)
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
ESD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 kV
(TA = 25°C unless otherwise noted.)
AVDD to AGND/DGND . . . . . . . . . . . . . . . . . –0.3 V to +7 V
DVDD to AGND/DGND . . . . . . . . . . . . . . . . . –0.3 V to +7 V
VDRIVE to AGND/DGND . . . . . . . . . . . . . . . . –0.3 V to +7 V
AVDD to DVDD . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +0.3 V
VDRIVE to DVDD . . . . . . . . . . . . . . . –0.3 V to DVDD + 0.3 V
AGND to DGND . . . . . . . . . . . . . . . . . . . . –0.3 V to +0.3 V
Analog Input Voltage to AGND . . . . –0.3 V to AVDD + 0.3 V
Digital Input Voltage to DGND . . . . –0.3 V to DVDD + 0.3 V
REF IN to AGND . . . . . . . . . . . . . . . –0.3 V to AVDD + 0.3 V
Input Current to Any Pin Except Supplies2 . . . . . . . . ± 10 mA
Operating Temperature Range
Commercial (A and B Versions) . . . . . . . . . –40°C to +85°C
Industrial (Y Version) . . . . . . . . . . . . . . . –40°C to +125°C
Storage Temperature Range . . . . . . . . . . . –65°C to +150°C
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
2
Transient currents of up to 100 mA will not cause SCR latch-up.
ORDERING GUIDE
Model
AD7470ARU
AD7470ARU-REEL
AD7470ARU-REEL7
AD7472AR
AD7472AR-REEL
AD7472AR-REEL7
AD7472ARU
AD7472ARU-REEL
AD7472ARU-REEL7
AD7472BR
AD7472BR-REEL
AD7472BRU
AD7472BRU-REEL
AD7472BRU-REEL7
AD7472YR
AD7472YR-REEL
AD7472YRU
AD7472YRU-REEL
AD7472YRU-REEL7
EVAL-AD7470CB2
EVAL-AD7472CB2
EVAL CONTROL BRD23
Temperature
Range
Resolution
(Bits)
Package
Options1
Package
Description
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
10
10
10
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
RU-24
RU-24
RU-24
R-24
R-24
R-24
RU-24
RU-24
RU-24
R-24
R-24
RU-24
RU-24
RU-24
R-24
R-24
RU-24
RU-24
RU-24
TSSOP
TSSOP
TSSOP
SOIC
SOIC
SOIC
TSSOP
TSSOP
TSSOP
SOIC
SOIC
TSSOP
TSSOP
TSSOP
SOIC
SOIC
TSSOP
TSSOP
TSSOP
Evaluation Board
Evaluation Board
Controller Board
NOTES
1
R = SOIC; RU = TSSOP.
2
This can be used as a standalone evaluation board or in conjunction with the EVAL-CONTROL BOARD for evaluation/demonstration purposes.
3
This board is a complete unit allowing a PC to control and communicate with all Analog Devices evaluation boards ending in the CB designators.
To order a complete evaluation kit, you need to order the specific ADC evaluation board, for example, EVAL-AD7472CB, the EVAL CONTROL
BRD2, and a 12 V ac transformer. See the relevant evaluation board application note for more information.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD7470/AD7472 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper
ESD precautions are recommended to avoid performance degradation or loss of functionality.
–6–
REV. B
AD7470/AD7472
PIN CONFIGURATIONS
DB7 1
24 DB6
DB9 1
24
DB8 2
23 DB5
DB10 2
23
DB7
(MSB) DB9 3
22 DB4
(MSB) DB11 3
22
DB6
AVDD 4
21
VDRIVE
REF IN 5
20
DVDD
21 VDRIVE
AVDD 4
REF IN 5
AD7470
20 DVDD
AD7472
DB8
VIN 6
TOP VIEW 19 DGND
AGND 7 (Not to Scale) 18 DB5
VIN 6
TOP VIEW 19 DGND
AGND 7 (Not to Scale) 18 DB3
CS 8
17 DB2
CS 8
17
DB4
RD 9
16 DB1
RD 9
16
DB3
CONVST 10
15 DB0 (LSB)
CONVST 10
15
DB2
CLKIN 11
14 NC
CLKIN 11
14
DB1
BUSY 12
13 NC
BUSY 12
13
DB0 (LSB)
NC = NO CONNECT
PIN FUNCTION DESCRIPTIONS
Mnemonic
Function
CS
Chip Select. Active low logic input used in conjunction with RD to access the conversion result. The conversion
result is placed on the data bus following the falling edge of both CS and RD. CS and RD are both connected to
the same AND gate on the input so the signals are interchangeable. CS can be hardwired permanently low.
Read Input. Logic input used in conjunction with CS to access the conversion result. The conversion result is
placed on the data bus following the falling edge of both CS and RD. CS and RD are both connected to same
AND gate on the input so the signals are interchangeable. CS and RD can be hardwired permanently low, in
which case the data bus is always active and the result of the new conversion is clocked out slightly before to the
BUSY line going low.
Conversion Start Input. Logic input used to initiate conversion. The input track-and-hold amplifier goes from
track mode to hold mode on the falling edge of CONVST, and the conversion process is initiated at this point.
The conversion input can be as narrow as 10 ns. If the CONVST input is kept low for the duration of conversion
and is still low at the end of conversion, the part will automatically enter sleep mode. If the part enters this sleep
mode, the next rising edge of CONVST wakes up the part. Wake-up time for the part is typically 1 µs.
Master Clock Input. The clock source for the conversion process is applied to this pin. Conversion time for the
AD7472 takes 14 clock cycles, and conversion time for the AD7470 takes 12 clock cycles. The frequency of this
master clock input, therefore, determines the conversion time and achievable throughput rate. While the ADC is
not converting, the clock-in pad is in three-state and thus no clock is going through the part.
BUSY Output. Logic output indicating the status of the conversion process. The BUSY signal goes high after the
falling edge of CONVST and stays high for the duration of conversion. Once conversion is complete and the conversion result is in the output register, the BUSY line returns low. The track-and-hold returns to track mode just
prior to the falling edge of BUSY, and the acquisition time for the part begins when BUSY goes low. If the CONVST
input is still low when BUSY goes low, the part automatically enters its sleep mode on the falling edge of BUSY.
Reference Input. An external reference must be applied to this input. The voltage range for the external reference
is 2.5 V ± 1% for specified performance.
Analog Supply Voltage, 2.7 V to 5.25 V. This is the only supply voltage for all analog circuitry on the AD7470/
AD7472. The AVDD and DVDD voltages should ideally be at the same potential and must not be more than 0.3 V
apart even on a transient basis. This supply should be decoupled to AGND.
Digital Supply Voltage, 2.7 V to 5.25 V. This is the supply voltage for all digital circuitry on the AD7470/
AD7472 aside from the output drivers. The DVDD and AVDD voltages should ideally be at the same potential and
must not be more than 0.3 V apart even on a transient basis. This supply should be decoupled to DGND.
Analog Ground. Ground reference point for all analog circuitry on the AD7470/AD7472. All analog input signals
and any external reference signal should be referred to this AGND voltage. 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.
RD
CONVST
CLK IN
BUSY
REF IN
AVDD
DVDD
AGND
REV. B
–7–
AD7470/AD7472
PIN FUNCTION DESCRIPTIONS (continued)
Mnemonic
Function
DGND
Digital Ground. This is the ground reference point for all digital circuitry on the AD7470 and AD7472. 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 Input. Single-ended analog input channel. The input range is 0 V to REF IN. The analog input presents a
high dc input impedance.
Supply Voltage for the Output Drivers, 2.7 V to 5.25 V. This voltage determines the output high voltage for the
data output pins. It allows AVDD and DVDD to operate at 5 V (and maximize the dynamic performance of the
(ADC), while the digital outputs can interface to 3 V logic.
Data Bit 0 to Data Bit 9 (AD7470) and DB11 (AD7472). Parallel digital outputs that provide the conversion result
for the part. These are three-state outputs that are controlled by CS and RD. The output high voltage level for these
outputs is determined by the VDRIVE input.
VIN
VDRIVE
DB0–DB9/11
–8–
REV. B
AD7470/AD7472
TERMINOLOGY
Integral Nonlinearity
Peak Harmonic or Spurious Noise
Peak harmonic or spurious noise is defined as the ratio of the
rms value of the next largest component in the ADC output
spectrum (up to fS/2 and excluding dc) to the rms value of the
fundamental. Normally, the value of this specification is determined by the largest harmonic in the spectrum, but for ADCs
where the harmonics are buried in the noise floor, it will be a
noise peak.
This is the maximum deviation from a straight line passing
through the endpoints of the ADC transfer function. The endpoints of the transfer function are zero scale, a point 1/2 LSB
below the first code transition, and full scale, a point 1/2 LSB
above the last code transition.
Differential Nonlinearity
This is the difference between the measured and the ideal 1 LSB
change between any two adjacent codes in the ADC.
Offset Error
This is the deviation of the first code transition (00 . . . 000) to
(00 . . . 001) from the ideal, i.e., AGND + 0.5 LSB.
Gain Error
The last transition should occur at the analog value 1.5 LSB
below the nominal full scale. The first transition is a 0.5 LSB
above the low end of the scale (zero in the case of AD7470/
AD7472). The gain error is the deviation of the actual difference
between the first and last code transitions from the ideal difference between the first and last code transitions with offset errors
removed.
Track-and-Hold Acquisition Time
The track-and-hold amplifier returns into track mode after the
end of conversion. Track-and-Hold acquisition time is the time
required for the output of the track-and-hold amplifier to reach
its final value, within ± 1 LSB, after the end of conversion.
Signal to (Noise + Distortion) Ratio
This is the measured ratio of signal to (noise + distortion) at the
output of the A/D converter. The signal is the rms amplitude of
the fundamental. Noise is the sum of all nonfundamental signals up to half the sampling frequency (fS/2), excluding dc. The
ratio is dependent on the number of quantization levels in the
digitization process; the more levels, the smaller the quantization
noise. The theoretical signal to (noise + distortion) ratio for an
ideal N-bit converter with a sine wave input is given by
Signal to (Noise + Distortion) = (6.02 N + 1.76) dB
Thus for a 12-bit converter, this is 74 dB and for a 10-bit converter is 62 dB.
Total Harmonic Distortion (THD)
Total harmonic distortion is the ratio of the rms sum of harmonics to the fundamental. For the AD7470/AD7472 it is
defined as
THD (dB) = 20 log
(V22 + V32 + V42 + V52 + V62)
V1
where V1 is the rms amplitude of the fundamental and V2, V3,
V4, V5, and V6 are the rms amplitudes of the second through the
sixth harmonics.
REV. B
–9–
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities will create distortion
products at sum and difference frequencies of mfa ± nfb where
m, n = 0, 1, 2, 3, etc. Intermodulation distortion terms are
those for which neither m nor n is equal to zero. For example,
the second-order terms include (fa + fb) and (fa – fb), while the
third-order terms include (2fa + fb), (2fa – fb), (fa + 2fb) and
(fa – 2fb).
The AD7470/AD7472 are tested using the CCIF standard
where two input frequencies near the top end of the input bandwidth are used. In this case, the second-order terms are usually
distanced in frequency from the original sine waves while the
third-order terms are usually at a frequency close to the input
frequencies. As a result, the second- and third-order terms are
specified separately. The calculation of the intermodulation
distortion is as per the THD specification where it is the ratio
of the rms sum of the individual distortion products to the rms
amplitude of the sum of the fundamentals expressed in dBs.
Aperture Delay
In a sample-and-hold, the time required after the hold command
for the switch to open fully is the aperture delay. The sample is,
in effect, delayed by this interval, and the hold command would
have to be advanced by this amount for precise timing.
Aperture Jitter
Aperture jitter is the range of variation in the aperture delay.
In other words, it is the uncertainty about when the sample is
taken. Jitter is the result of noise which modulates the phase
of the hold command. This specification establishes the ultimate timing error, hence the maximum sampling frequency
for a given resolution. This error will increase as the input
dV/dt increases.
AD7470/AD7472
CIRCUIT DESCRIPTION
CONVERTER OPERATION
TYPICAL CONNECTION DIAGRAM
The AD7470/AD7472 are 10-bit/12-bit successive approximation analog-to-digital converters based around a capacitive
DAC. The AD7470/AD7472 can convert analog input signals in
the range 0 V to VREF. Figure 2 shows a very simplified schematic of the ADC. The control logic, SAR, and the capacitive
DAC are used to add and subtract fixed amounts of charge
from the sampling capacitor to bring the comparator back into a
balanced condition.
COMPARATOR
CAPACITIVE
DAC
VIN
In Figure 5 the VDRIVE pin is tied to DVDD, which results in logic
output voltage values being either 0 V or DVDD. The voltage
applied to VDRIVE controls the voltage value of the output logic
signals. For example, if DVDD is supplied by a 5 V supply and
VDRIVE by a 3 V supply, the logic output voltage levels would be
either 0 V or 3 V. This feature allows the AD7470/AD7472 to
interface to 3 V parts while still enabling the ADC to process
signals at 5 V supply.
SWITCHES
VREF
SAR
CONTROL
INPUTS
Figure 5 shows a typical connection diagram for the AD7470/
AD7472. Conversion is initiated by a falling edge on CONVST.
Once CONVST goes low, the BUSY signal goes high, and at
the end of conversion, the falling edge of BUSY is used to activate an interrupt service routine. The CS and RD lines are then
activated in parallel to read the 10- or 12-data bits. The recommended REF IN voltage is 2.5 V providing an analog input
range of 0 V to 2.5 V, making the AD7470/AD7472 a unipolar
ADC. It is recommended to perform a dummy conversion after
power-up as the first conversion result could be incorrect. This
also ensures that the part is in the correct mode of operation.
The CONVST pin should not be floating when power is applied
as a rising edge on CONVST might not wake up the part.
CONTROL LOGIC
OUTPUT DATA
10-/12-BIT PARALLEL
+
Figure 2. Simplified Block Diagram of AD7470/AD7472
10F
Figure 3 shows the ADC during its acquisition phase. SW2 is
closed and SW1 is in Position A. The comparator is held in a
balanced condition and the sampling capacitor acquires the
signal on VIN.
DVDD
1nF
REF IN
10F
PARALLED
INTERFACE
VIN
0V TO
REF IN
DB0–
DB9 (DB11)
CS
2k⍀
SW1
AD7470/
AD7472
C/P
CAPACITIVE
DAC
A
0.1F
ANALOG
SUPPLY
47F 2.7V–5.25V
VDRIVE AVDD
2.5V*
0.1F
VIN
+
B
CONVST
RD
BUSY
CONTROL LOGIC
SW2
COMPARATOR
AGND
*RECOMMENDED REF IN VOLTAGE
Figure 3. ADC Acquisition Phase
Figure 4 shows the ADC during conversion. When conversion
starts, SW2 will open and SW1 will move to position B, causing
the comparator to become unbalanced. The ADC then runs
through its successive approximation routine and brings the
comparator back into a balanced condition. When the comparator is rebalanced, the conversion result is available in the SAR
register.
Figure 5. Typical Connection Diagram
CAPACITIVE
DAC
VIN
2k⍀
A
SW1
B
CONTROL LOGIC
SW2
AGND
COMPARATOR
Figure 4. ADC Conversion Phase
–10–
REV. B
AD7470/AD7472
ADC TRANSFER FUNCTION
DC ACQUISITION TIME
The output coding of the AD7470/AD7472 is straight binary.
The designed code transitions occur midway between successive integer LSB values (0.5 LSB, 1.5 LSB, etc). The LSB
size is equal to (REF IN)/4096 for the AD7472 and to (REF
IN)/1024 for the AD7470. The ideal transfer characteristic for
the AD7472 is shown in Figure 6.
The ADC starts a new acquisition phase at the end of a conversion and ends it on the falling edge of the CONVST signal. At
the end of conversion there is a settling time associated with the
sampling circuit. This settling time lasts approximately 135 ns.
The analog signal on VIN is also being acquired during this
settling time; therefore, the minimum acquisition time needed is
approximately 135 ns.
Figure 8 shows the equivalent charging circuit for the sampling
capacitor when the ADC is in its acquisition phase. R3 represents the source impedance of a buffer amplifier or resistive
network, R1 is an internal switch resistance, R2 is for bandwidth
control, and C1 is the sampling capacitor. C2 is back-plate
capacitance and switch parasitic capacitance.
ADC CODE
111...111
111...110
111...000
1LSB = VREF/4096
011...111
During the acquisition phase the sampling capacitor must be
charged to within ± 1 LSB of its final value.
000...010
000...001
000...000
0V 0.5LSB
VREF –1.5LSB
ANALOG INPUT
R3
VIN
Figure 6. Transfer Characteristic for 12 Bits
R1
125⍀
C1
22pF
R2
636⍀
C2
8pF
AC ACQUISITION TIME
In ac applications it is recommended to always buffer analog
input signals. The source impedance of the drive circuitry must
be kept as low as possible to minimize the acquisition time of
the ADC. Large values of impedance at the VIN pin of the ADC
will cause the THD to degrade at high input frequencies.
The AD8021, AD8047, AD8051, AD9631, and AD797 are
some of the op amps that could be used to buffer the analog
input. Figure 7 shows the AD7470/AD7472 performance for
some of those recommended input buffers.
AD7470/AD7472
DYNAMIC
PERFORMANCE
SPECIFICATIONS
INPUT
BUFFERS
AD8047
AD9631
AD8051
AD797
SNR
500kHz
70
69.5
68.6
70
THD
500kHz
78
80
78
84
Figure 8. Equivalent Sampling Circuit
ANALOG INPUT
Figure 9 shows the equivalent circuit of the analog input structure of the AD7470/AD7472. The two diodes, D1 and D2,
provide ESD protection for the analog inputs. The capacitor C3
is typically about 4 pF and can be primarily attributed to pin
capacitance. The resistor R1 is an internal switch resistance.
This resistor is typically about 125 Ω. The capacitor C1 is the
sampling capacitor, while R2 is used for bandwidth control.
VDD
D1
VIN
TYPICAL AMPLIFIER
CURRENT
CONSUMPTION
5.8mA
17mA
4.4mA
8.2mA
Figure 7. Recommended Input Buffers
Reference Input
The following references are best suited for use with the
AD7470/AD7472.
ADR291
AD780
REF192
ADR421
C3
4pF
C1
22pF
R2
636⍀
C2
8pF
Figure 9. Equivalent Analog Input Circuit
CLOCK SOURCES
The max CLK specification for the AD7470 is 30 MHz, and for
the AD7472, it is 26 MHz. These frequencies are not standard
off-the-shelf oscillator frequencies. Many manufacturers produce oscillator modules close to these frequencies; a typical one
being 25.175 MHz from IQD Limited. AEL Crystals Limited
produces a 25 MHz oscillator module in various packages. Crystal oscillator manufacturers will produce 26 MHz and 30 MHz
oscillators to order. Of course any clock source can be used, not
just crystal oscillators.
For optimum performance, a 2.5 V reference is recommended.
The parts can function with a reference up to 3 V and down to
2 V, but the performance deteriorates.
REV. B
D2
R1
125⍀
–11–
AD7470/AD7472
The data is available on the output bus slightly before the falling
edge of BUSY.
PARALLEL INTERFACE
The parallel interfaces of the AD7470 and AD7472 are 10 bits
and 12 bits wide, respectively. The output data buffers are activated when both CS and RD are logic low. At this point, the contents of the data register are placed onto the data bus. Figure 10
shows the timing diagram for the parallel port.
It is important to point out that data bus cannot change state
while the ADC is doing a conversion as this would have a detrimental effect on the conversion in progress. The data out lines
will go three-state again when either the RD or the CS line goes
high. Thus the CS can be tied low permanently, leaving the RD
line to control conversion result access. Refer to VDRIVE section
for output voltage levels.
Figure 11 shows the timing diagram for the parallel port when
CS and RD are tied permanently low. In this setup, once BUSY
line goes from high to low, the conversion process is completed.
tCONVERT
CONVST*
t9
t2
t10
BUSY
t3
CS
t4
t8
t5
RD
t6
t7
DBx
*CONVST SHOULD GO HIGH WHEN THE CLK IS HIGH OR BEFORE THE FIRST CLK CYCLE.
Figure 10. Parallel Port Timing
tCONVERT
CONVST*
t9
t2
BUSY
DATA N
DBx
DATA N + 1
*CONVST SHOULD GO HIGH WHEN THE CLK IS HIGH OR BEFORE THE FIRST CLK CYCLE.
Figure 11. Parallel Port Timing with CS and RD Tied Low
CLK IN
tCONVERT
CONVST
tWAKEUP
t2
BUSY
t3
CS
t4
t8
t5
RD
t6
t7
DBX
Figure 12. Wake-Up Timing Diagram (Burst Clock)
–12–
REV. B
AD7470/AD7472
tCONVERT
CONVST
tWAKEUP
BUSY
CS
RD
DBx
Figure 13. Mode 2 Operation
OPERATING MODES
The AD7470 and AD7472 have two possible modes of operation, depending on the state of the CONVST pulse at the end of
a conversion, Mode 1 and Mode 2. There is a continuous clock
on the CLKIN pin.
Mode 1 (High Speed Sampling)
In this mode of operation, the CONVST pulse is brought high
before the end of conversion i.e., before BUSY goes low (see
Figure 10). If the CONVST pin is brought from high to low
while BUSY is high, the conversion is restarted. When operating in this mode, a new conversion should not be initiated until
the acquisition time has elapsed after BUSY goes low. This
acquisition time allows the track-and-hold circuit to accurately
acquire the input signal. As mentioned earlier, a read should
not be done during a conversion. This mode facilitates the
fastest throughput times for the AD7470/AD7472.
Mode 2 (Sleep Mode)
Figure 13 shows AD7470/AD7472 in Mode 2 operation where
the ADC goes into sleep mode after conversion. The CONVST
line is brought low to initiate a conversion and remains low until
after the end of conversion. If CONVST goes high and low
again while BUSY is high, the conversion is restarted. Once the
BUSY line goes from a high to a low, the CONVST line has its
status checked and, if low, the part enters sleep mode.
The device wakes up again on the rising edge of the CONVST
signal. There is a wake-up time of typically 1 µs after the rising
edge of CONVST before the BUSY line can go high to indicate
start of conversion. BUSY will only go high once CONVST goes
low. The CONVST line can go from a high to a low during this
wake-up time, but the conversion will still not be initiated until
after the 1 µs wake-up time. Superior power performance can be
achieved in this mode of operation by waking up the AD7470
and AD7472 only to carry out a conversion.
Burst Mode
Burst mode on the AD7470/AD7472 is a subsection of Mode 1
and Mode 2; the clock is noncontinuous. Figure 12 shows how
the ADC works in burst mode for Mode 2. The clock needs to
be switched on only during conversion, a minimum of 12 clock
cycles for the AD7470 and 14 clock cycles for the AD7472.
Because the clock is off during nonconverting intervals, system
power is saved. The BUSY signal can be used to gate the CLKIN
pulses. The ADC does not begin the conversion process until
REV. B
the first CLKIN rising edge after BUSY goes high. The clock
needs to start less than two clock cycles away from the
CONVST active edge, otherwise INL deteriorates. For
example, if the clock frequency is 28 MHz, the clock must start
within 71.4 ns of CONVST going low. In Figure 12, the A/D
converter section is put into sleep mode once conversion is
completed. On the rising edge of CONVST, it is woken up
again. The user must be wary of the wake-up time because it
will reduce the sampling rate of the ADC.
VDRIVE
The VDRIVE pin is used as the voltage supply to the output drivers and is a separate supply from AVDD and DVDD. The purpose
of using a separate supply for the output drivers is that the user
can vary the output high voltage, VOH, from the VDD supply to
the AD7470/AD7472. For example, if AVDD and DVDD is using
a 5 V supply, the VDRIVE pin can be powered from a 3 V supply.
The ADC has better dynamic performance at 5 V than at 3 V,
so operating the part at 5 V, while still being able to interface to
3 V parts, pushes the AD7470/AD7472 to the top bracket of
high performance 10-bit/12-bit ADCs. Of course, the ADC can
have its VDRIVE and DVDD pins connected together and be powered from a 3 V or 5 V supply.
All outputs are powered from VDRIVE. These are all the data out
pins and the BUSY pin. The CONVST, CS, RD, and CLKIN
signals are related to the DVDD voltage.
POWER-UP
It is recommended that the user perform a dummy conversion
after power-up, because the first conversion result could be
incorrect. This also ensures that the part is in the correct mode
of operation. The recommended power-up sequence is as
follows:
1. GND
2. VDD
3. VDRIVE
4. Digital Inputs
5. REF IN
6. VIN
Power vs. Throughput
The two modes of operation for the AD7470 and AD7472 will
produce different power versus throughput performances,
Mode 1 and Mode 2; see Operating Modes section of the data
sheet for more detailed descriptions of these modes. Mode 2 is
the sleep mode of the part and it achieves the optimum power
performance.
–13–
AD7470/AD7472
Mode 1
Mode 2
Figure 14 shows the AD7472 conversion sequence in Mode 1
using a throughput rate of 500 kSPS and a clock frequency of
26 MHz. At 5 V supply, the current consumption for the part
when converting is typically 2 mA, and the quiescent current is
typically 650 µA. The conversion time of 531.66 ns contributes
2.658 mW to the overall power dissipation in the following way:
Figure 15 shows the AD7472 conversion sequence in Mode 2
using a throughput rate of 500 kSPS and a clock frequency of
26 MHz. At 5 V supply, the current consumption for the part
when converting is typically 2 mA, while the sleep current is 1 µA
max. The power dissipated during this power-down is negligible, and is thus not worth considering in the total power figure. During the wake-up phase, the AD7472 will draw 650 µA
typically. Overall power dissipated is
(531.66 ns/2 µs) × (5 × 2 mA) = 2.658 mW
The contribution to the total power dissipated by the remaining
1.468 µs of the cycle is 2.38 mW.
(531.66 ns / 2 µs) × (5 × 2 mA) + (1 µs / 2 µs) × (5 × 650 µA) = 4.283 mW
(1.468 µs/2 µs) × (5 × 650 µA) = 2.38 mW
Thus the power dissipated during each cycle is
CONVST
2.658 mW + 2.38 mW = 5.038 mW
tWAKEUP
tCONVERT
1s
2s
CONVST
tQUIESCENT
BUSY
tCONVERT
tQUIESCENT
531.66ns
BUSY
1.468s
Figure 15. Mode 2 Power Dissipation
531.66ns
1.468s
2s
Figure 14. Mode 1 Power Dissipation
TPC 1 sand TPC 2 show a typical graphical representation of
Power vs. Throughput for the AD7472 when in (a) Mode 1
@ 5 V and 3 V and Mode 2 @ 5 V and 3 V
–14–
REV. B
Typical Performance Characteristics–AD7470/AD7472
1.0
8
0.8
7
0.6
6
DNL ERROR (LSB)
POWER (mW)
5V
5
4
3V
3
0.4
0.2
0
–0.2
–0.4
2
–0.6
1
–0.8
0
50
–1.0
300
600
800
1000
1100
THROUGHPUT (kHz)
1300
0
1500
512
1024
2048
CODE
2560
3072
3584
4096
TPC 4. Typical DNL for 2.75 V @ 25°C
TPC 1. Power vs. Throughput (Mode 1 @ 5 V and 3 V)
7
72
AD7472 5V
70
6
68
5
AD7472 3V
66
5V
SNR + D (dB)
POWER (mW)
1536
4
3
3V
2
64
AD7470 5V
62
60
AD7470 3V
58
56
1
54
0
52
50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
THROUGHPUT (kHz)
10
TPC 2. Power vs. Throughput (Mode 2 @ 5 V and 3 V)
50
100
200
500
INPUT FREQUENCY (kHz)
1000
2000
TPC 5. Typical SNR + D vs. Input Tone
1.0
90
AD7472 5V
0.8
AD7470 5V
85
80
0.4
AD7472 3V
75
0.2
THD (dB)
INL ERROR (LSB)
0.6
0
–0.2
AD7470 3V
70
65
–0.4
60
–0.6
55
–0.8
–1.0
0
512
1024
1536
2048
CODE
2560
3072
3584
TPC 3. Typical INL for 2.75 V @ 25 °C
4096
50
10
50
100
200
500
INPUT FREQUENCY (kHz)
1000
TPC 6. Typical THD vs. Input Tone
2000
AD7470/AD7472
70.6
0.2
–0.3
70.4
–40ⴗC
3V
–0.8
+25ⴗC
70.2
5V
+85ⴗC
dB
SNR (dB)
–1.3
70.0
–1.8
69.8
–2.3
69.6
–2.8
69.4
69.2
–3.3
–3.8
10
2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25
SUPPLY (V)
100
1000
FREQUENCY (kHz)
10000
100000
TPC 9. Typical Bandwidth
TPC 7. Typical SNR vs. Supply
0
–20
dB
–40
–60
–80
–100
–120
0
100
200
300
400
FREQUENCY (kHz)
500
600
TPC 8. Typical SNR @ 500 kHz Input Tone
–16–
REV. B
AD7470/AD7472
+
10F
0.1F
47F
+
ANALOG
SUPPLY
5V
AVDD
DVDD
1nF
AGND
VIN
DGND
AD780
0.1F
VOUT
1nF
10F
10F
+
+
AD7470/
AD7472
VDRIVE
VREF
0.1F
Figure 16. Decoupling Circuit
GROUNDING AND LAYOUT
POWER SUPPLIES
The analog and digital power supplies are independent and
separately pinned out to minimize coupling between the analog
and digital sections within the device. To complement the excellent noise performance of the AD7470/AD7472, it is imperative
that care be given to the PCB layout. Figure 16 shows a recommended connection diagram for the AD7470/AD7472.
Separate power supplies for AVDD and DVDD are desirable but,
if necessary, DVDD may share its power connection to AVDD.
The digital supply (DVDD) must not exceed the analog supply
(AVDD) by more than 0.3 V in normal operation.
All of the AD7470/AD7472 ground pins should be soldered
directly to a ground plane to minimize series inductance. The
AVDD, DVDD, and VDRIVE pins should be decoupled to both the
analog and digital ground planes. The large value capacitors will
decouple low frequency noise to analog ground; the small value
capacitors will decouple high frequency noise to digital ground.
All digital circuitry power pins should be decoupled to the
digital ground plane. The use of ground planes can physically
separate sensitive analog components from the noisy digital
system. The two ground planes should be joined in only one
place and should not overlap so as to minimize capacitive
coupling between them. If the AD7470/AD7472 is in a
system where multiple devices require AGND to DGND
connections, the connection should still be made at one point
only, a star ground point, which should be established as close
as possible to the AD7470/AD7472.
MICROPROCESSOR INTERFACING
AD7470/AD7472 to ADSP-2185 Interface
Figure 17 shows a typical interface between the AD7470/AD7472
and the ADSP-2185. The ADSP-2185 processor can be used in
one of two memory modes, full memory mode and host mode.
The Mode C pin determines in which mode the processor works.
The interface in Figure 17 is set up to have the processor working in full memory mode, which allows full external addressing
capabilities.
When the AD7470/AD7472 has finished converting, the BUSY
line requests an interrupt through the IRQ2 pin. The IRQ2
interrupt has to be set up in the interrupt control register as
edge-sensitive. The DMS (data memory select) pin latches in
the address of the ADC into the address decoder. The read
operation is thus started.
OPTIONAL
CONVST
Noise can be minimized by applying some simple rules to the
PCB layout: analog signals should be kept away from digital
signals; fast switching signals like clocks should be shielded with
digital ground to avoid radiating noise to other sections of the
board and clock signals should never be run near the analog
inputs; avoid running digital lines under the device as these will
couple noise onto the die; the power supply lines to the AD7470/
AD7472 should use as large a trace as possible to provide a low
impedance path and reduce the effects of glitches on the power
supply line; avoid crossover of digital and analog signals and
place traces that are on opposite sides of the board at right angles
to each other.
Noise to the analog power line can be further reduced by use of
multiple decoupling capacitors as shown in Figure 16. Decoupling capacitors should be placed directly at the power inlet to
the PCB and also as close as possible to the power pins of the
AD7470/AD7472. The same decoupling method should be
used on other ICs on the PCB, with the capacitor leads as short
as possible to minimize lead inductance.
REV. B
A0–A15
ADDRESS BUS
AD7470/
AD7472*
ADSP-2185*
DMS
ADDRESS
DECODER
IRQ2
CS
BUSY
RD
RD
100k⍀
MODE C
DB0–DB9
(DB11)
D0–D23
DATA BUS
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 17. Interfacing to the ADSP-2185
AD7470/AD7472 to ADSP-21065 Interface
Figure 18 shows a typical interface between the AD7470/AD7472
and the ADSP-21065L SHARC® processor. This interface is an
example of one of three DMA handshake modes. The MSX
–17–
AD7470/AD7472
control line is actually three memory select lines. Internal
ADDR25–24 are decoded into MS3-0; these lines are then asserted
as chip selects. The DMAR1 (DMA Request 1) is used in this
setup as the interrupt to signal end of conversion. The rest of
the interface is standard handshaking operation.
OPTIONAL
CONVST
ADDR0–ADDR23
MSX
ADSP-21065L*
ADDRESS BUS
AD7470/
AD7472*
ADDRESS
LATCH
ADDRESS
BUS
ADDRESS
DECODER
DMAR1
AD7470/AD7472 to PIC17C4x Interface
Figure 20 shows a typical parallel interface between the AD7470/
AD7472 and the PIC17C42/43/44. The microcontroller sees
the ADC as another memory device with its own specific
memory address on the memory map. The CONVST signal can
be controlled by either the microcontroller or an external
source. The BUSY signal provides an interrupt request to the
microcontroller when a conversion ends. The INT pin on the
PIC17C42/43/44 must be configured to be active on the negative edge. PORTC and PORTD of the microcontroller are
bidirectional and used to address the AD7470/AD7472 and also
to read in the 10-bit (AD7470) or 12-bit (AD7472) data. The
OE pin on the PIC can be used to enable the output buffers on
the AD7470/AD7472 and to perform a read operation.
CS
OPTIONAL
BUSY
RD
RD
DB0–DB9
(DB11)
D0–D31
CONVST
PIC17C4x*
DB0–DB9
(DB11)
AD0–AD15
*ADDITIONAL PINS OMITTED FOR CLARITY
ADDRESS
LATCH
ALE
Figure 19 shows an interface between the AD7470/AD7472
and the TMS320C25. The CONVST signal can be applied
from the TMS320C25 or from an external source. The BUSY
line interrupts the digital signal processor when conversion is
completed. The TMS320C25 does not have a separate RD
output to drive the AD7470/AD7472 RD input directly. This
has to be generated from the processor STRB and R/W outputs
with the addition of some glue logic. The RD signal is OR-gated
with the MSC signal to provide the WAIT state required in the
read cycle for correct interface timing. The following instruction
is used to read the conversion from the AD7470/AD7472:
where D is data memory address and ADC is the AD7470/
AD7472 address. The read operation must not be attempted
during conversion.
OPTIONAL
CONVST
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 20. Interfacing to the PIC17C4x
AD7470/AD7472 to 80C186 Interface
Figure 21 shows the AD7470/AD7472 interfaced to the 80C186
microprocessor. The 80C186 DMA controller provides two
independent high speed DMA channels where data transfer
can occur between memory and I/O spaces. (The AD7470/
AD7472 occupies one of these I/O spaces.) Each data transfer consumes two bus cycles, one cycle to fetch data and the
other to store data.
After the AD7470/AD7472 has finished conversion, the BUSY
line generates a DMA request to Channel 1 (DRQ1). As a result
of the interrupt, the processor performs a DMA READ operation which also resets the interrupt latch. Sufficient priority
must be assigned to the DMA channel to ensure that the DMA
request will be serviced before the completion of the next conversion. This configuration can be used with 6 MHz and 8 MHz
80C186 processors.
ADDRESS BUS
OPTIONAL
AD7470/
AD7472*
TMS320C25*
IS
ADDRESS
DECODER
AD0–AD15
A16–A19
ADDRESS/DATA BUS
CONVST
CS
ALE
ADDRESS
LATCH
STRB
80C186*
RD
R/W
READY
AD7470/
AD7472*
ADDRESS
BUS
BUSY
ADDRESS
DECODER
DRQ1
Q
CS
R
BUSY
S
MSC
RD
RD
DB0–DB9
(DB11)
DMD0–DMD15
CS
RD
BUSY
AD7470/AD7472 to TMS320C25 Interface
IN D,ADC
ADDRESS
DECODER
OE
INT
Figure 18. Interfacing to ADSP-21065L
A0–A15
AD7470/
AD7472*
DATA BUS
DATA BUS
DATA BUS
DB0–DB9
(DB11)
*ADDITIONAL PINS OMITTED FOR CLARITY
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 21. Interfacing to the 80C186
Figure 19. Interfacing to the TMS320C25
–18–
REV. B
AD7470/AD7472
OUTLINE DIMENSIONS
24-Lead Standard Small Outline Package [SOIC]
Wide Body
(R-24)
Dimensions shown in millimeters and (inches)
15.60 (0.6142)
15.20 (0.5984)
24
13
7.60 (0.2992)
7.40 (0.2913)
1
10.65 (0.4193)
10.00 (0.3937)
12
2.65 (0.1043)
2.35 (0.0925)
0.75 (0.0295)
ⴛ 45ⴗ
0.25 (0.0098)
0.30 (0.0118)
0.10 (0.0039)
COPLANARITY
0.10
1.27 (0.0500)
BSC
8ⴗ
0ⴗ
SEATING
0.33 (0.0130)
PLANE
0.20 (0.0079)
0.51 (0.0201)
0.31 (0.0122)
1.27 (0.0500)
0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-013AD
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
24-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-24)
Dimensions shown in millimeters
7.90
7.80
7.70
24
13
4.50
4.40
4.30
6.40 BSC
1
12
PIN 1
0.65
BSC
0.15
0.05
0.30
0.19
0.10 COPLANARITY
1.20
MAX
SEATING
PLANE
0.20
0.09
8ⴗ
0ⴗ
COMPLIANT TO JEDEC STANDARDS MO-153AD
REV. B
–19–
0.75
0.60
0.45
AD7470/AD7472
Revision History
Location
Page
10/03—Data Sheet changed from REV. A to REV. B.
Changes to SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Changes to TIMING SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Changes to ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Changes to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Changes to PIN FUNCTION DESCRIPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Changes to Offset Error description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Changes to Gain Error description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Changes to OPERATING MODES section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Changes to POWER-UP section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Relabeled TPC captions and renumbered subsequent figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
–20–
REV. B
C01127–0–10/03(B)
Added Y version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Universal
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