AD7468BRT-R [ADI]

1.6 V, Micropower 12-/10-/8-Bit ADCs; 1.6 V,微功耗12位/ 10位/ 8位ADC
AD7468BRT-R
型号: AD7468BRT-R
厂家: ADI    ADI
描述:

1.6 V, Micropower 12-/10-/8-Bit ADCs
1.6 V,微功耗12位/ 10位/ 8位ADC

文件: 总28页 (文件大小:583K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
1.6 V, Micropower 12-/10-/8-Bit ADCs  
AD7466/AD7467/AD7468  
FEATURES  
FUNCTIONAL BLOCK DIAGRAM  
V
DD  
Specified for VDD of 1.6 V to 3.6 V  
Low power:  
0.62 mW typical at 100 kSPS with 3 V supplies  
0.48 mW typical at 50 kSPS with 3.6 V supplies  
0.12 mW typical at 100 kSPS with 1.6 V supplies  
Fast throughput rate: 200 kSPS  
Wide input bandwidth:  
71 dB SNR at 30 kHz input frequency  
Flexible power/serial clock speed management  
No pipeline delays  
12-/10-/8-BIT  
SUCCESSIVE  
APPROXIMATION  
ADC  
T/H  
V
IN  
SCLK  
SDATA  
CS  
CONTROL  
LOGIC  
High speed serial interface:  
AD7466/AD7467/AD7468  
SPI/QSPI™/MICROWIRE™/DSP compatible  
Automatic power-down  
GND  
Power-down mode: 8 nA typical  
6-lead SOT-23 package  
Figure 1.  
8-lead MSOP package  
APPLICATIONS  
Battery-powered systems  
Medical instruments  
Remote data acquisition  
Isolated data acquisition  
GENERAL DESCRIPTION  
PRODUCT HIGHLIGHTS  
The AD7466/AD7467/AD74681 are 12-/10-/8-bit, high speed,  
low power, successive approximation analog-to-digital  
converters (ADCs), respectively. The parts operate from a single  
1.6 V to 3.6 V power supply and feature throughput rates up to  
200 kSPS with low power dissipation. The parts contain a low  
noise, wide bandwidth track-and-hold amplifier, which can  
handle input frequencies in excess of 3 MHz.  
1. Specified for supply voltages of 1.6 V to 3.6 V.  
2. 12-, 10-, and 8-bit ADCs in SOT-23 and MSOP packages.  
3. High throughput rate with low power consumption.  
Power consumption in normal mode of operation at  
100 kSPS and 3 V is 0.9 mW maximum.  
4. Flexible power/serial clock speed management.  
The conversion rate is determined by the serial clock,  
allowing the conversion time to be reduced through  
increases in the serial clock speed. Automatic power-down  
after conversion allows the average power consumption to  
be reduced when in power-down. Current consumption is  
0.1 μA maximum and 8 nA typically when in power-down.  
The conversion process and data acquisition are controlled  
CS  
using  
and the serial clock, allowing the devices to interface  
with microprocessors or DSPs. The input signal is sampled on  
CS  
the falling edge of , and the conversion is also initiated at this  
point. There are no pipeline delays associated with the part.  
The reference for the part is taken internally from VDD. This  
allows the widest dynamic input range to the ADC. Thus, the  
analog input range for the part is 0 V to VDD. The conversion  
rate is determined by the SCLK.  
5. Reference derived from the power supply.  
6. No pipeline delay.  
7. The part features a standard successive approximation  
CS  
ADC with accurate control of conversions via a  
input.  
1 Protected by U.S. Patent No. 6,681,332.  
Rev. C  
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. Specifications subject to change without notice. No  
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.  
Trademarks and registeredtrademarks arethe 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: 781.461.3113 ©2003–2007 Analog Devices, Inc. All rights reserved.  
 
 
AD7466/AD7467/AD7468  
TABLE OF CONTENTS  
Features .............................................................................................. 1  
Power Requirement Curves ...................................................... 13  
Terminology.................................................................................... 16  
Theory of Operation ...................................................................... 17  
Circuit Information.................................................................... 17  
Converter Operation.................................................................. 17  
ADC Transfer Function............................................................. 17  
Typical Connection Diagram ................................................... 17  
Analog Input ............................................................................... 18  
Digital Inputs .............................................................................. 18  
Normal Mode.............................................................................. 19  
Power Consumption .................................................................. 20  
Serial Interface ................................................................................ 22  
Microprocessor Interfacing....................................................... 23  
Application Hints ........................................................................... 25  
Grounding and Layout .............................................................. 25  
Evaluating the Performance of the AD7466 and AD7467.... 25  
Outline Dimensions....................................................................... 26  
Ordering Guide .......................................................................... 27  
Applications....................................................................................... 1  
Functional Block Diagram .............................................................. 1  
General Description......................................................................... 1  
Product Highlights ........................................................................... 1  
Revision History ............................................................................... 2  
Specifications..................................................................................... 3  
AD7466.......................................................................................... 3  
AD7467.......................................................................................... 5  
AD7468.......................................................................................... 7  
Timing Specifications .................................................................. 9  
Timing Examples........................................................................ 10  
Absolute Maximum Ratings.......................................................... 11  
ESD Caution................................................................................ 11  
Pin Configurations and Function Descriptions ......................... 12  
Typical Performance Characteristics ........................................... 13  
Dynamic Performance Curves ................................................. 13  
DC Accuracy Curves ................................................................. 13  
REVISION HISTORY  
5/07—Rev. B to Rev. C  
Deleted Figure 3.............................................................................. 10  
Updated Outline Dimensions....................................................... 26  
Changes to Ordering Guide .......................................................... 27  
4/05—Rev. A to Rev. B  
Moved Terminology Section......................................................... 16  
Changes to Ordering Guide .......................................................... 27  
11/04—Rev. 0 to Rev. A  
Updated Format..................................................................Universal  
Changes to General Description .................................................... 1  
Added Patent Number ..................................................................... 1  
Updated Outline Dimensions....................................................... 26  
Changes to Ordering Guide .......................................................... 27  
5/03—Revision 0: Initial Version  
Rev. C | Page 2 of 28  
 
AD7466/AD7467/AD7468  
SPECIFICATIONS  
AD7466  
VDD = 1.6 V to 3.6 V, fSCLK = 3.4 MHz, fSAMPLE = 100 kSPS, unless otherwise noted. TA = TMIN to TMAX, unless otherwise noted.  
The temperature range for the B version is −40°C to +85°C.  
Table 1.  
Parameter  
B Version  
Unit  
Test Conditions/Comments  
fIN = 30 kHz sine wave  
1.8 V ≤ VDD ≤ 2 V; see the Terminology section  
2.5 V ≤ VDD ≤ 3.6 V  
DYNAMIC PERFORMANCE  
Signal-to-Noise and Distortion (SINAD)  
69  
70  
70  
70  
71  
71  
70.5  
−83  
−85  
dB min  
dB min  
dB typ  
dB min  
dB typ  
dB min  
dB typ  
dB typ  
dB typ  
VDD = 1.6 V  
Signal-to-Noise Ratio (SNR)  
1.8 V ≤ VDD ≤ 2 V; see the Terminology section  
1.8 V ≤ VDD ≤ 2 V  
2.5 V ≤ VDD ≤ 3.6 V  
VDD = 1.6 V  
See the Terminology section  
See the Terminology section  
Total Harmonic Distortion (THD)  
Peak Harmonic or Spurious Noise (SFDR)  
Intermodulation Distortion (IMD)  
fa = 29.1 kHz, fb = 29.9 kHz; see the Terminology  
section  
Second-Order Terms  
Third-Order Terms  
Aperture Delay  
−84  
−86  
10  
dB typ  
dB typ  
ns typ  
Aperture Jitter  
40  
ps typ  
Full Power Bandwidth  
3.2  
1.9  
750  
450  
MHz typ  
MHz typ  
kHz typ  
kHz typ  
@ 3 dB, 2.5 V ≤ VDD ≤ 3.6 V  
@ 3 dB, 1.6 V ≤ VDD ≤ 2.2 V  
@ 0.1 dB, 2.5 V ≤ VDD ≤ 3.6 V  
@ 0.1 dB, 1.6 V ≤ VDD ≤ 2.2 V  
DC ACCURACY  
Maximum specifications apply as typical figures when  
VDD = 1.6 V  
Resolution  
12  
Bits  
Integral Nonlinearity  
Differential Nonlinearity  
1.5  
−0.9/+1.5  
LSB max  
LSB max  
See the Terminology section  
Guaranteed no missed codes to 12 bits; see the  
Terminology section  
Offset Error  
Gain Error  
Total Unadjusted Error (TUE)  
ANALOG INPUT  
1
1
2
LSB max  
LSB max  
LSB max  
See the Terminology section  
See the Terminology section  
See the Terminology section  
Input Voltage Ranges  
DC Leakage Current  
Input Capacitance  
LOGIC INPUTS  
0 to VDD  
1
20  
V
μA max  
pF typ  
Input High Voltage, VINH  
0.7 × VDD  
V min  
1.6 V ≤ VDD < 2.7 V  
2
V min  
2.7 V ≤ VDD ≤ 3.6 V  
Input Low Voltage, VINL  
0.2 × VDD  
0.3 × VDD  
0.8  
1
1
V max  
V max  
V max  
μA max  
μA typ  
pF max  
1.6 V ≤ VDD < 1.8 V  
1.8 V ≤ VDD < 2.7 V  
2.7 V ≤ VDD ≤ 3.6 V  
Typically 20 nA, VIN = 0 V or VDD  
Input Current, IIN, SCLK Pin  
Input Current, IIN, CS Pin  
Input Capacitance, CIN  
10  
Sample tested at 25°C to ensure compliance  
Rev. C | Page 3 of 28  
 
AD7466/AD7467/AD7468  
Parameter  
B Version  
Unit  
Test Conditions/Comments  
LOGIC OUTPUTS  
Output High Voltage, VOH  
Output Low Voltage, VOL  
Floating-State Leakage Current  
Floating-State Output Capacitance  
Output Coding  
VDD − 0.2  
0.2  
1
V min  
ISOURCE = 200 μA, VDD = 1.6 V to 3.6 V  
ISINK = 200 μA  
V max  
μA max  
pF max  
10  
Straight (natural)  
binary  
CONVERSION RATE  
Conversion Time  
Throughput Rate  
POWER REQUIREMENTS  
VDD  
4.70  
200  
μs max  
kSPS max  
16 SCLK cycles with SCLK at 3.4 MHz  
See the Serial Interface section  
1.6/3.6  
V min/max  
IDD  
Digital inputs = 0 V or VDD  
VDD = 3 V, fSAMPLE = 100 kSPS  
VDD = 3 V, fSAMPLE = 50 kSPS  
VDD = 3 V, fSAMPLE = 10 kSPS  
VDD = 2.5 V, fSAMPLE = 100 kSPS  
VDD = 2.5 V, fSAMPLE = 50 kSPS  
VDD = 2.5 V, fSAMPLE = 10 kSPS  
VDD = 1.8 V, fSAMPLE = 100 kSPS  
VDD = 1.8 V, fSAMPLE = 50 kSPS  
VDD = 1.8 V, fSAMPLE = 10 kSPS  
SCLK on or off, typically 8 nA  
See the Power Consumption section  
VDD = 3 V, fSAMPLE = 100 kSPS  
VDD = 2.5 V, fSAMPLE = 100 kSPS  
VDD = 1.8 V, fSAMPLE = 100 kSPS  
VDD = 3 V  
Normal Mode (Operational)  
300  
110  
20  
240  
80  
16  
165  
50  
μA max  
μA typ  
μA typ  
μA max  
μA typ  
μA typ  
μA max  
μA typ  
μA typ  
μA max  
10  
0.1  
Power-Down Mode  
Power Dissipation  
Normal Mode (Operational)  
0.9  
0.6  
0.3  
0.3  
mW max  
mW max  
mW max  
μW max  
Power-Down Mode  
Rev. C | Page 4 of 28  
AD7466/AD7467/AD7468  
AD7467  
VDD = 1.6 V to 3.6 V, fSCLK = 3.4 MHz, fSAMPLE = 100 kSPS, unless otherwise noted. TA = TMIN to TMAX, unless otherwise noted.  
The temperature range for the B version is −40°C to +85°C.  
Table 2.  
Parameter  
B Version  
Unit  
Test Conditions/Comments  
DYNAMIC PERFORMANCE  
Maximum/minimum specifications apply as typical figures  
when VDD = 1.6 V, fIN = 30 kHz sine wave  
Signal-to-Noise and Distortion (SINAD)  
Total Harmonic Distortion (THD)  
Peak Harmonic or Spurious Noise (SFDR) −74  
Intermodulation Distortion (IMD)  
61  
−72  
dB min  
dB max  
dB max  
See the Terminology section  
See the Terminology section  
See the Terminology section  
fa = 29.1 kHz, fb = 29.9 kHz; see the Terminology section  
Second-Order Terms  
Third-Order Terms  
Aperture Delay  
−83  
−83  
10  
dB typ  
dB typ  
ns typ  
Aperture Jitter  
40  
ps typ  
Full Power Bandwidth  
3.2  
1.9  
750  
450  
MHz typ  
MHz typ  
kHz typ  
kHz typ  
@ 3 dB, 2.5 V ≤ VDD ≤ 3.6 V  
@ 3 dB, 1.6 V ≤ VDD ≤ 2.2 V  
@ 0.1 dB, 2.5 V ≤ VDD ≤ 3.6 V  
@ 0.1 dB, 1.6 V ≤ VDD ≤ 2.2 V  
DC ACCURACY  
Maximum specifications apply as typical figures when  
VDD = 1.6 V  
Resolution  
10  
Bits  
Integral Nonlinearity  
Differential Nonlinearity  
0.5  
0.5  
LSB max  
LSB max  
See the Terminology section  
Guaranteed no missed codes to 10 bits; see the  
Terminology section  
Offset Error  
Gain Error  
Total Unadjusted Error (TUE)  
ANALOG INPUT  
0.2  
0.2  
1
LSB max  
LSB max  
LSB max  
See the Terminology section  
See the Terminology section  
See the Terminology section  
Input Voltage Ranges  
DC Leakage Current  
Input Capacitance  
LOGIC INPUTS  
0 to VDD  
1
20  
V
μA max  
pF typ  
Input High Voltage, VINH  
0.7 × VDD  
V min  
1.6 V ≤ VDD < 2.7 V  
2
V min  
2.7 V ≤ VDD ≤ 3.6 V  
Input Low Voltage, VINL  
0.2 × VDD  
0.3 × VDD  
0.8  
1
1
V max  
V max  
V max  
μA max  
μA typ  
pF max  
1.6 V ≤ VDD < 1.8 V  
1.8 V ≤V DD < 2.7 V  
2.7 V ≤ VDD ≤ 3.6 V  
Typically 20 nA, VIN = 0 V or VDD  
Input Current, IIN, SCLK Pin  
Input Current, IIN, CS Pin  
Input Capacitance, CIN  
10  
Sample tested at 25°C to ensure compliance  
LOGIC OUTPUTS  
Output High Voltage, VOH  
Output Low Voltage, VOL  
Floating-State Leakage Current  
Floating-State Output Capacitance  
Output Coding  
VDD − 0.2  
0.2  
1
V min  
ISOURCE = 200 μA, VDD = 1.6 V to 3.6 V  
ISINK = 200 μA  
V max  
μA max  
pF max  
10  
Sample tested at 25°C to ensure compliance  
Straight (natural)  
binary  
CONVERSION RATE  
Conversion Time  
Throughput Rate  
3.52  
275  
μs max  
kSPS max  
12 SCLK cycles with SCLK at 3.4 MHz  
See the Serial Interface section  
Rev. C | Page 5 of 28  
 
AD7466/AD7467/AD7468  
Parameter  
B Version  
Unit  
Test Conditions/Comments  
POWER REQUIREMENTS  
VDD  
1.6/3.6  
V min/max  
IDD  
Digital inputs = 0 V or VDD  
Normal Mode (Operational)  
210  
170  
140  
0.1  
μA max  
μA max  
μA max  
μA max  
VDD = 3 V, fSAMPLE = 100 kSPS  
VDD = 2.5 V, fSAMPLE = 100 kSPS  
VDD = 1.8 V, fSAMPLE = 100 kSPS  
SCLK on or off, typically 8 nA  
See the Power Consumption section  
VDD = 3 V, fSAMPLE = 100 kSPS  
VDD = 2.5 V, fSAMPLE = 100 kSPS  
VDD = 1.8 V, fSAMPLE = 100 kSPS  
Power-Down Mode  
Power Dissipation  
Normal Mode (Operational)  
0.63  
0.42  
0.25  
mW max  
mW max  
mW max  
Power-Down Mode  
0.3  
μW max  
VDD = 3 V  
Rev. C | Page 6 of 28  
AD7466/AD7467/AD7468  
AD7468  
VDD = 1.6 V to 3.6 V, fSCLK = 3.4 MHz, fSAMPLE = 100 kSPS, unless otherwise noted. TA = TMIN to TMAX, unless otherwise noted.  
The temperature range for the B version is −40°C to +85°C.  
Table 3.  
Parameter  
B Version  
Unit  
Test Conditions/Comments  
DYNAMIC PERFORMANCE  
Maximum/minimum specifications apply as typical figures  
when VDD = 1.6 V, fIN = 30 kHz sine wave  
Signal-to-Noise and Distortion (SINAD) 49  
dB min  
dB max  
dB max  
See the Terminology section  
See the Terminology section  
See the Terminology section  
Total Harmonic Distortion (THD)  
−66  
Peak Harmonic or Spurious Noise  
(SFDR)  
−66  
Intermodulation Distortion (IMD)  
Second-Order Terms  
Third-Order Terms  
fa = 29.1 kHz, fb = 29.9 kHz; see the Terminology section  
−77  
−77  
10  
dB typ  
dB typ  
ns typ  
Aperture Delay  
Aperture Jitter  
40  
ps typ  
Full Power Bandwidth  
3.2  
1.9  
750  
450  
MHz typ  
MHz typ  
kHz typ  
kHz typ  
@ 3 dB, 2.5 V ≤ VDD ≤ 3.6 V  
@ 3 dB, 1.6 V ≤ VDD ≤ 2.2 V  
@ 0.1 dB, 2.5 V ≤ VDD ≤ 3.6 V  
@ 0.1 dB, 1.6 V ≤ VDD ≤ 2.2 V  
DC ACCURACY  
Maximum specifications apply as typical figures when  
VDD = 1.6 V  
Resolution  
8
Bits  
Integral Nonlinearity  
Differential Nonlinearity  
0.2  
0.2  
LSB max  
LSB max  
See the Terminology section  
Guaranteed no missed codes to 8 bits; see the Terminology  
section  
Offset Error  
Gain Error  
Total Unadjusted Error (TUE)  
ANALOG INPUT  
0.1  
0.1  
0.3  
LSB max  
LSB max  
LSB max  
See the Terminology section  
See the Terminology section  
See the Terminology section  
Input Voltage Ranges  
DC Leakage Current  
Input Capacitance  
LOGIC INPUTS  
0 to VDD  
1
20  
V
μA max  
pF typ  
Input High Voltage, VINH  
0.7 × VDD  
V min  
1.6 V ≤ VDD < 2.7 V  
2
V min  
2.7 V ≤ VDD ≤ 3.6 V  
Input Low Voltage, VINL  
0.2 × VDD  
0.3 × VDD  
0.8  
1
1
V max  
V max  
V max  
μA max  
μA typ  
pF max  
1.6 V ≤ VDD < 1.8 V  
1.8 V ≤ VDD < 2.7 V  
2.7 V ≤ VDD ≤ 3.6 V  
Typically 20 nA, VIN = 0 V or VDD  
Input Current, IIN, SCLK Pin  
Input Current, IIN, CS Pin  
Input Capacitance, CIN  
10  
Sample tested at 25°C to ensure compliance  
LOGIC OUTPUTS  
Output High Voltage, VOH  
Output Low Voltage, VOL  
Floating-State Leakage Current  
Floating-State Output Capacitance  
Output Coding  
VDD − 0.2  
0.2  
1
V min  
ISOURCE = 200 μA; VDD = 1.6 V to 3.6 V  
ISINK = 200 μA  
V max  
μA max  
pF max  
10  
Sample tested at 25°C to ensure compliance  
Straight (natural)  
binary  
CONVERSION RATE  
Conversion Time  
Throughput Rate  
2.94  
320  
μs max  
kSPS max  
10 SCLK cycles with SCLK at 3.4 MHz  
See the Serial Interface section  
Rev. C | Page 7 of 28  
 
AD7466/AD7467/AD7468  
Parameter  
B Version  
Unit  
Test Conditions/Comments  
POWER REQUIREMENTS  
VDD  
1.6/3.6  
V min/max  
IDD  
Digital inputs = 0 V or VDD  
VDD = 3 V, fSAMPLE = 100 kSPS  
VDD = 2.5 V, fSAMPLE = 100 kSPS  
VDD = 1.8 V, fSAMPLE = 100 kSPS  
SCLK on or off, typically 8 nA  
See the Power Consumption section  
VDD = 3 V, fSAMPLE = 100 kSPS  
VDD = 2.5 V, fSAMPLE = 100 kSPS  
VDD = 1.8 V, fSAMPLE = 100 kSPS  
VDD = 3 V  
Normal Mode (Operational)  
190  
155  
120  
0.1  
μA max  
μA max  
μA max  
μA max  
Power-Down Mode  
Power Dissipation  
Normal Mode (Operational)  
0.57  
0.4  
0.2  
mW max  
mW max  
mW max  
μW max  
Power-Down Mode  
0.3  
Rev. C | Page 8 of 28  
AD7466/AD7467/AD7468  
TIMING SPECIFICATIONS  
For all devices, VDD = 1.6 V to 3.6 V; TA = TMIN to TMAX, unless otherwise noted. Sample tested at 25°C to ensure compliance. All input  
signals are specified with tr = tf = 5 ns (10% to 90% of VDD) and timed from a voltage level of 1.4 V.  
Table 4.  
Parameter  
Limit at TMIN, TMAX  
Unit  
Description  
fSCLK  
3.4  
10  
20  
150  
MHz max  
kHz min  
kHz min  
kHz min  
Mark/space ratio for the SCLK input is 40/60 to 60/40.  
1.6 V ≤ VDD ≤ 3 V; minimum fSCLK at which specifications are guaranteed.  
VDD = 3.3 V; minimum fSCLK at which specifications are guaranteed.  
VDD = 3.6 V; minimum fSCLK at which specifications are guaranteed.  
tCONVERT  
16 × tSCLK  
12 × tSCLK  
10 × tSCLK  
AD7466.  
AD7467.  
AD7468.  
Acquisition Time  
Acquisition time/power-up time from power-down. See the Terminology section.  
The acquisition time is the time required for the part to acquire a full-scale step  
input value within 1 LSB or a 30 kHz ac input value within 0.5 LSB.  
780  
640  
10  
ns max  
ns max  
ns min  
VDD = 1.6 V.  
1.8 V ≤ VDD ≤ 3.6 V.  
tQUIET  
Minimum quiet time required between bus relinquish and the start of the next  
conversion.  
t1  
t2  
10  
55  
ns min  
ns min  
Minimum CS pulse width.  
CS to SCLK setup time. If VDD = 1.6 V and fSCLK = 3.4 MHz, t2 has to be 192 ns  
minimum in order to meet the maximum figure for the acquisition time.  
t3  
t4  
55  
ns max  
ns max  
Delay from CS until SDATA is three-state disabled. Measured with the load circuit  
in Figure 2 and defined as the time required for the output to cross the VIH or VIL  
voltage.  
Data access time after SCLK falling edge. Measured with the load circuit in Figure 2  
and defined as the time required for the output to cross the VIH or VIL voltage.  
140  
t5  
t6  
t7  
0.4 tSCLK  
0.4 tSCLK  
10  
ns min  
ns min  
ns min  
SCLK low pulse width.  
SCLK high pulse width.  
SCLK to data valid hold time. Measured with the load circuit in Figure 2 and  
defined as the time required for the output to cross the VIH or VIL voltage.  
t8  
60  
ns max  
SCLK falling edge to SDATA three-state. t8 is derived from the measured time taken  
by the data outputs to change 0.5 V when loaded with the circuit in Figure 2. The  
measured number is then extrapolated back to remove the effects of charging or  
discharging the 50 pF capacitor. This means that the time, t8, quoted in the timing  
characteristics, is the true bus relinquish time of the part, and is independent of  
the bus loading.  
7
ns min  
SCLK falling edge to SDATA three-state.  
200μA  
I
OL  
TO OUTPUT  
PIN  
1.4V  
C
L
50pF  
200μA  
I
OH  
Figure 2. Load Circuit for Digital Output Timing Specifications  
Rev. C | Page 9 of 28  
 
 
 
 
AD7466/AD7467/AD7468  
Timing Example 2  
TIMING EXAMPLES  
The AD7466 can also operate with slower clock frequencies.  
As shown in Figure 3, assuming VDD = 1.8 V, fSCLK = 2 MHz,  
and a throughput of 50 kSPS gives a cycle time of tCONVERT + t8 +  
Figure 3 shows some of the timing parameters from Table 4 in  
the Timing Specifications section.  
Timing Example 1  
tQUIET = 20 μs. With tCONVERT = t2 + 15(1/fSCLK) = 55 ns + 7.5 μs =  
As shown in Figure 3, fSCLK = 3.4 MHz and a throughput of  
100 kSPS gives a cycle time of tCONVERT + t8 + tQUIET = 10 μs.  
Assuming VDD = 1.8 V, tCONVERT = t2 + 15(1/fSCLK) = 55 ns +  
4.41 μs = 4.46 μs, and t8 = 60 ns maximum, then tQUIET = 5.48 μs,  
which satisfies the requirement of 10 ns for tQUIET. The part is  
fully powered up and the signal is fully acquired at Point A.  
This means that the acquisition/power-up time is t2 + 2(1/fSCLK  
= 55 ns + 588 ns = 643 ns, satisfying the maximum requirement  
of 640 ns for the power-up time.  
7.55 μs, and t8 = 60 ns maximum, this leaves tQUIET to be 12.39  
μs, which satisfies the requirement of 10 ns for tQUIET. The part is  
fully powered up and the signal is fully acquired at Point A,  
which means the acquisition/power-up time is t2 + 2(1/fSCLK) =  
55 ns + 1 μs = 1.05 μs, satisfying the maximum requirement of  
640 ns for the power-up time. In this example and with other  
slower clock values, the part is fully powered up and the signal  
already acquired before the third SCLK falling edge; however,  
the track-and-hold does not go into hold mode until that point.  
In this example, the part can be powered up and the signal can  
be fully acquired at approximately Point B in Figure 3.  
)
CS  
tCONVERT  
t2  
B
A
SCLK  
1
3
5
13  
15  
16  
2
4
14  
t8  
tQUIET  
ACQUISITION TIME  
AUTOMATIC  
POWER-DOWN  
TRACK-AND-HOLD  
IN TRACK  
TRACK-AND-HOLD IN HOLD  
1/THROUGHPUT  
POINT A: THE PART IF FULLY POWERED UP WITH V FULLY ACQUIRED.  
IN  
Figure 3. AD7466 Serial Interface Timing Diagram Example  
Rev. C | Page 10 of 28  
 
 
AD7466/AD7467/AD7468  
ABSOLUTE MAXIMUM RATINGS  
TA = 25°C, unless otherwise noted. Transient currents of up to  
100 mA do not cause SCR latch-up.  
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 indicated in the operational  
section of this specification is not implied. Exposure to absolute  
maximum rating conditions for extended periods may affect  
device reliability.  
Table 5.  
Parameter  
Rating  
VDD to GND  
−0.3 V to +7 V  
−0.3 V to VDD + 0.3 V  
−0.3 V to +7 V  
−0.3 V to VDD + 0.3 V  
10 mA  
Analog Input Voltage to GND  
Digital Input Voltage to GND  
Digital Output Voltage to GND  
Input Current to any Pin Except Supplies  
Operating Temperature Range  
Commercial (B Version)  
Storage Temperature Range  
Junction Temperature  
SOT-23 Package  
ESD CAUTION  
−40°C to +85°C  
−65°C to +150°C  
150°C  
θJA Thermal Impedance  
θJC Thermal Impedance  
MSOP Package  
229.6°C/W  
91.99°C/W  
θJA Thermal Impedance  
θJC Thermal Impedance  
Lead Temperature, Soldering  
Vapor Phase (60 sec)  
Infrared (15 sec)  
205.9°C/W  
43.74°C/W  
215°C  
220°C  
3.5 kV  
ESD  
Rev. C | Page 11 of 28  
 
AD7466/AD7467/AD7468  
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS  
1
2
3
4
8
7
6
5
V
DD  
1
2
3
6
5
4
CS  
CS  
V
DD  
AD7466/  
AD7467/  
AD7468  
AD7466/  
AD7467/  
AD7468  
TOP VIEW  
(Not to Scale)  
SDATA  
SCLK  
GND  
SDATA  
SCLK  
NC  
GND  
V
V
IN  
IN  
TOP VIEW  
(Not to Scale)  
NC  
NC = NO CONNECT  
Figure 4. SOT-23 Pin Configuration  
Figure 5. MSOP Pin Configuration  
Table 6. Pin Function Descriptions  
Pin No.  
Mnemonic Description  
SOT-23 MSOP  
6
1
CS  
Chip Select. Active low logic input. This input provides the dual function of initiating conversions on the  
devices and frames the serial data transfer.  
1
2
8
7
VDD  
GND  
Power Supply Input. The VDD range for the devices is from 1.6 V to 3.6 V.  
Analog Ground. Ground reference point for all circuitry on the devices. All analog input signals should  
be referred to this GND voltage.  
3
5
6
2
VIN  
SDATA  
Analog Input. Single-ended analog input channel. The input range is 0 V to VDD.  
Data Out. Logic output. The conversion result from the AD7466/AD7467/AD7468 is provided on this  
output as a serial data stream. The bits are clocked out on the falling edge of the SCLK input. The data  
stream from the AD7466 consists of four leading zeros followed by the 12 bits of conversion data,  
provided MSB first. The data stream from the AD7467 consists of four leading zeros followed by the 10  
bits of conversion data, provided MSB first. The data stream from the AD7468 consists of four leading  
zeros followed by the 8 bits of conversion data, provided MSB first.  
4
3
SCLK  
NC  
Serial Clock. Logic input. SCLK provides the serial clock for accessing data from the parts. This clock  
input is also used as the clock source for the conversion process of the parts.  
No Connect.  
4, 5  
Rev. C | Page 12 of 28  
 
AD7466/AD7467/AD7468  
TYPICAL PERFORMANCE CHARACTERISTICS  
SCLK frequency of 3.4 MHz, and sampling at a rate of 100 kSPS  
for the AD7466 (see the Analog Input section).  
DYNAMIC PERFORMANCE CURVES  
Figure 6, Figure 7, and Figure 8 show typical FFT plots for the  
AD7466, AD7467, and AD7468, respectively, at a 100 kSPS  
sample rate and a 30 kHz input tone.  
DC ACCURACY CURVES  
Figure 13 and Figure 14 show typical INL and DNL perform-  
ance for the AD7466.  
Figure 9 shows the signal-to-noise and distortion ratio  
performance vs. input frequency for various supply voltages  
while sampling at 100 kSPS with an SCLK frequency of 3.4 MHz  
for the AD7466.  
POWER REQUIREMENT CURVES  
Figure 15 shows the supply current vs. supply voltage for the  
AD7466 at −40°C, +25°C, and +85°C, with SCLK frequency of  
3.4 MHz and a sampling rate of 100 kSPS.  
Figure 10 shows the signal-to-noise ratio (SNR) performance  
vs. input frequency for various supply voltages while sampling  
at 100 kSPS with an SCLK frequency of 3.4 MHz for the  
AD7466.  
Figure 16 shows the maximum current vs. supply voltage for the  
AD7466 with different SCLK frequencies.  
Figure 17 shows the shutdown current vs. supply voltage.  
Figure 11 shows the total harmonic distortion (THD) vs. analog  
input signal frequency for various supply voltages while sam-  
pling at 100 kSPS with an SCLK frequency of 3.4 MHz for  
the AD7466.  
Figure 18 shows the power consumption vs. throughput rate for  
the AD7466 with an SCLK of 3.4 MHz and different supply  
voltages. See the Power Consumption section for more details.  
Figure 12 shows the THD vs. analog input frequency for  
different source impedances with a supply voltage of 2.7 V, an  
15  
25  
8192 POINT FFT  
8192 POINT FFT  
V
f
= 1.8V  
V
= 1.8V  
= 100kSPS  
= 30kHz  
DD  
DD  
= 100kSPS  
f
f
5
–15  
–35  
–55  
–75  
–95  
–115  
SAMPLE  
SAMPLE  
–5  
–25  
f
= 30kHz  
IN  
IN  
SINAD = 61.51dB  
THD = –80.61dB  
SFDR = –82.10dB  
SINAD = 70.82dB  
THD = –84.18dB  
SFDR = –85.48dB  
–45  
–65  
–85  
–105  
0
5
10  
15  
20  
25  
30  
35  
40  
45  
50  
0
5
10  
15  
20  
25  
30  
35  
40  
45  
50  
FREQUENCY (kHz)  
FREQUENCY (kHz)  
Figure 7. AD7467 Dynamic Performance at 100 kSPS  
Figure 6. AD7466 Dynamic Performance at 100 kSPS  
Rev. C | Page 13 of 28  
 
 
 
AD7466/AD7467/AD7468  
–65  
–67  
–69  
–71  
–73  
–75  
–77  
–79  
–81  
–83  
–85  
5
–5  
8192 POINT FFT  
TEMP = 25°C  
V
f
= 1.8V  
DD  
= 100kSPS  
SAMPLE  
f
= 30kHz  
IN  
–15  
–25  
–35  
–45  
–55  
–65  
–75  
–85  
–95  
SINAD = 49.83dB  
THD = –79.37dB  
SFDR = –70.46dB  
V
= 1.8V  
DD  
V
= 2.2V  
DD  
V
= 1.6V  
DD  
V
= 3V  
DD  
V
= 3.6V  
V
= 2.7V  
DD  
DD  
0
5
10  
15  
20  
25  
30  
35  
40  
45  
50  
10  
100  
INPUT FREQUENCY (kHz)  
FREQUENCY (kHz)  
Figure 11. AD7466 THD vs. Analog Input Frequency  
at 100 kSPS for Various Supply Voltages  
Figure 8. AD7468 Dynamic Performance at 100 kSPS  
–76  
–77  
–78  
–79  
–80  
–81  
–82  
–83  
–84  
–65  
–66  
–67  
–68  
–69  
–70  
–71  
–72  
–73  
TEMP = 25°C  
= 2.7V  
TEMP = 25°C  
V
DD  
R
= 1kΩ  
IN  
R
= 10Ω  
IN  
V
= 1.8V  
V
= 1.6V  
V
= 2.2V  
DD  
DD  
DD  
R
= 510Ω  
R
= 100Ω  
IN  
IN  
V
= 3.6V  
V
= 3V  
V
= 2.7V  
DD  
DD  
DD  
R
= 0Ω  
IN  
10  
100  
10  
100  
INPUT FREQUENCY (kHz)  
INPUT FREQUENCY (kHz)  
Figure 9. AD7466 SINAD vs. Analog Input Frequency  
at 100 kSPS for Various Supply Voltages  
Figure 12. AD7466 THD vs. Analog Input Frequency  
for Various Source Impedances  
–68.0  
–68.5  
–69.0  
–69.5  
–70.0  
–70.5  
–71.0  
–71.5  
–72.0  
–72.5  
–73.0  
1.0  
0.8  
V
= 1.8V  
TEMP = 25°C  
DD  
TEMP = 25°C  
fIN = 50Hz  
fSAMPLE = 100kSPS  
0.6  
0.4  
0.2  
V
= 1.6V  
DD  
V
= 1.8V  
DD  
0
V
= 2.2V  
DD  
–0.2  
–0.4  
–0.6  
–0.8  
–1.0  
V
= 3.6V  
V
= 3V  
V
= 2.7V  
DD  
DD  
DD  
0
512  
1024 1536 2048 2560 3072 3584  
CODE  
4096  
10  
100  
INPUT FREQUENCY (kHz)  
Figure 13. AD7466 INL Performance  
Figure 10. AD7466 SNR vs. Analog Input Frequency  
at 100 kSPS for Various Supply Voltages  
Rev. C | Page 14 of 28  
 
 
 
AD7466/AD7467/AD7468  
1.0  
0.8  
2.5  
2.0  
1.5  
1.0  
0.5  
0
V
= 1.8V  
DD  
TEMP = 25°C  
fIN = 50Hz  
fSAMPLE = 100kSPS  
0.6  
TEMP = +85°C  
0.4  
0.2  
0
–0.2  
–0.4  
–0.6  
–0.8  
TEMP = +25°C  
TEMP = –40°C  
0
512  
1024 1536 2048 2560 3072 3584  
CODE  
4096  
1.5  
2.0  
2.5  
3.0  
3.5  
4.0  
SUPPLY VOLTAGE (V)  
Figure 17. Shutdown Current vs. Supply Voltage  
Figure 14. AD7466 DNL Performance  
1.4  
1.2  
1.0  
0.8  
0.6  
0.4  
0.2  
0
290  
265  
240  
215  
190  
165  
140  
115  
90  
fSAMPLE = 100kSPS  
TEMP = –40°C  
TEMP = 25°C  
V
V
= 3.0V  
DD  
DD  
TEMP = +25°C  
= 2.7V  
V
V
= 2.2V  
= 1.8V  
DD  
DD  
TEMP = +85°C  
65  
0
50  
100  
150  
200  
250  
1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8  
SUPPLY VOLTAGE (V)  
THROUGHPUT (kSPS)  
Figure 15. AD7466 Supply Current vs. Supply Voltage, SCLK 3.4 MHz  
Figure 18. AD7466 Power Consumption vs. Throughput Rate, SCLK 3.4 MHz  
560  
TEMP = 25°C  
500  
fSCLK = 3.4MHz, fSAMPLE = 200kSPS  
440  
fSCLK = 2.4MHz, fSAMPLE = 140kSPS  
380  
320  
260  
200  
fSCLK = 1.2MHz, fSAMPLE = 50kSPS  
140  
80  
1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8  
SUPPLY VOLTAGE (V)  
Figure 16. AD7466 Maximum Current vs. Supply Voltage  
for Different SCLK Frequencies  
Rev. C | Page 15 of 28  
 
 
 
 
AD7466/AD7467/AD7468  
TERMINOLOGY  
Integral Nonlinearity (INL)  
Signal-to-Noise and Distortion Ratio (SINAD)  
The measured ratio of signal-to-noise and distortion at the  
output of the ADC. The signal is the rms value of the sine wave,  
and noise is the rms sum of all nonfundamental signals up to  
half the sampling frequency (fS/2), including harmonics, but  
excluding dc.  
The maximum deviation from a straight line passing through  
the endpoints of the ADC transfer function. For the AD7466/  
AD7467/AD7468, the endpoints of the transfer function are  
zero scale, a point 1 LSB below the first code transition, and full  
scale, a point 1 LSB above the last code transition.  
Differential Nonlinearity (DNL)  
Total Unadjusted Error (TUE)  
The difference between the measured and the ideal 1 LSB  
change between any two adjacent codes in the ADC.  
A comprehensive specification that includes gain error, linearity  
error, and offset error.  
Offset Error  
Total Harmonic Distortion (THD)  
The deviation of the first code transition (00 . . . 000) to  
(00 . . . 001) from the ideal (that is, AGND + 1 LSB).  
The ratio of the rms sum of harmonics to the fundamental. For  
the AD7466/AD7467/AD7468, it is defined as  
Gain Error  
V22 +V32 +V42 +V52 +V62  
The deviation of the last code transition (111 . . . 110) to  
(111…111) from the ideal (that is, VREF − 1 LSB) after the offset  
error has been adjusted out.  
(
)
THD dB = 20 log  
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  
sixth harmonics.  
Track-and-Hold Acquisition Time  
The time required for the part to acquire a full-scale step  
input value within 1 LSB, or a 30 kHz ac input value within  
0.5 LSB. The AD7466/AD7467/AD7468 enter track mode on  
Peak Harmonic or Spurious Noise (SFDR)  
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. Typically, the value of this specifica-  
tion is determined by the largest harmonic in the spectrum, but  
for ADCs where the harmonics are buried in the noise floor, it  
is a noise peak.  
CS  
the  
falling edge. The parts remain in hold mode until the following  
CS  
falling edge, and return to hold mode on the third SCLK  
falling edge. See Figure 3 and the Serial Interface section for  
more details.  
Signal-to-Noise Ratio (SNR)  
Intermodulation Distortion (IMD)  
The measured ratio of signal to noise at the output of the ADC.  
The signal is the rms value of the sine wave input. Noise is the  
rms quantization error within the Nyquist bandwidth (fS/2).  
The rms value of the sine wave is half of its peak-to-peak value  
divided by √2, and the rms value for the quantization noise is  
q/√12. The ratio depends on the number of quantization levels  
in the digitization process; the more levels, the smaller the  
quantization noise.  
With inputs consisting of sine waves at two frequencies, fa  
and fb, any active device with nonlinearities creates distortion  
products at sum and difference frequencies of mfa nfb, where  
m, n = 0, 1, 2, 3, and so on. Intermodulation distortion terms  
are those for which neither m nor n are 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).  
For an ideal N-bit converter, the SNR is defined as  
The AD7466/AD7467/AD7468 are tested using the CCIF  
standard where two input frequencies 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 dB.  
SNR = 6.02 N + 1.76 db  
Thus, for a 12-bit converter, it is 74 dB; for a 10-bit converter, it  
is 62 dB; and for an 8-bit converter, it is 50 dB.  
However, in practice, various error sources in the ADCs cause  
the measured SNR to be less than the theoretical value. These  
errors occur due to integral and differential nonlinearities,  
internal ac noise sources, and so on.  
Rev. C | Page 16 of 28  
 
 
AD7466/AD7467/AD7468  
THEORY OF OPERATION  
CHARGE  
REDISTRIBUTION  
DAC  
CIRCUIT INFORMATION  
The AD7466/AD7467/AD7468 are fast, micropower, 12-bit,  
10-bit, and 8-bit ADCs, respectively. The parts can be operated  
from a 1.6 V to 3.6 V supply. When operated from any supply  
voltage within this range, the AD7466/AD7467/AD7468 are  
capable of throughput rates of 200 kSPS when provided with a  
3.4 MHz clock.  
SAMPLING  
CAPACITOR  
A
V
IN  
CONTROL  
LOGIC  
SW1  
SW2  
CONVERSION  
PHASE  
B
COMPARATOR  
AGND  
V
/2  
DD  
Figure 20. ADC Conversion Phase  
The AD7466/AD7467/AD7468 provide the user with an on-  
chip track-and-hold, an ADC, and a serial interface housed in a  
tiny 6-lead SOT-23 or an 8-lead MSOP package, which offer the  
user considerable space-saving advantages over alternative  
solutions. The serial clock input accesses data from the part, but  
also provides the clock source for the successive approximation  
ADC. The analog input range is 0 V to VDD. An external refer-  
ence is not required for the ADC, and there is no on-chip  
reference. The reference for the AD7466/AD7467/AD7468 is  
derived from the power supply, thus giving the widest possible  
dynamic input range.  
ADC TRANSFER FUNCTION  
The output coding of the AD7466/AD7467/AD7468 is straight  
binary. The designed code transitions occur at successive  
integer LSB values; that is, 1 LSB, 2 LSB, and so on. The LSB size  
for the devices is as follows:  
VDD/4096 for the AD7466  
VDD/1024 for the AD7467  
VDD/256 for the AD7468  
The ideal transfer characteristics for the devices are shown in  
Figure 21.  
The AD7466/AD7467/AD7468 also feature an automatic  
power-down mode to allow power savings between conversions.  
The power-down feature is implemented across the standard  
serial interface, as described in the Normal Mode section.  
111...111  
111...110  
CONVERTER OPERATION  
111...000  
011...111  
The AD7466/AD7467/AD7468 are successive approximation  
analog-to-digital converters based around a charge redistribu-  
tion DAC. Figure 19 and Figure 20 show simplified schematics  
of the ADC. Figure 19 shows the ADCs during the 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.  
1LSB = V /4096 (AD7466)  
DD  
1LSB = V /1024 (AD7467)  
DD  
1LSB = V /256 (AD7468)  
DD  
000...010  
000...001  
000...000  
0V 1LSB  
+V – 1LSB  
DD  
ANALOG INPUT  
Figure 21. AD7466/AD7467/AD7468 Transfer Characteristics  
CHARGE  
REDISTRIBUTION  
DAC  
TYPICAL CONNECTION DIAGRAM  
SAMPLING  
CAPACITOR  
A
Figure 22 shows a typical connection diagram for the devices.  
VREF is taken internally from VDD and, therefore, VDD should  
be well decoupled. This provides an analog input range of  
0 V to VDD.  
V
IN  
CONTROL  
LOGIC  
SW1  
B
ACQUISITION  
PHASE  
SW2  
COMPARATOR  
AGND  
V
/2  
DD  
2.5V  
5V  
SUPPLY  
REF192  
Figure 19. ADC Acquisition Phase  
1μF  
TANT  
0.1μF  
10μF  
0.1μF  
240μA  
When the ADC starts a conversion, as shown in Figure 20,  
SW2 opens and SW1 moves to Position B, causing the com-  
parator to become unbalanced. The control logic and the  
charge redistribution DAC are used to add and subtract fixed  
amounts of charge from the sampling capacitor to bring the  
comparator back into a balanced condition. When the com-  
parator is rebalanced, the conversion is complete. The control  
logic generates the ADC output code. Figure 21 shows the ADC  
transfer function.  
680nF  
V
DD  
0VTOV  
DD  
SCLK  
V
IN  
INPUT  
μC/μP  
AD7466  
SDATA  
CS  
GND  
SERIAL  
INTERFACE  
Figure 22. REF192 as Power Supply to AD7466  
Rev. C | Page 17 of 28  
 
 
 
 
 
AD7466/AD7467/AD7468  
V
DD  
The conversion result consists of four leading zeros followed by  
the MSB of the 12-bit, 10-bit, or 8-bit result from the AD7466,  
AD7467, or AD7468, respectively. See the Serial Interface  
section. Alternatively, because the supply current required by  
the AD7466/AD7467/AD7468 is so low, a precision reference  
can be used as the supply source to the devices.  
C2  
20pF  
D1  
R1  
V
IN  
C1  
4pF  
D2 CONVERSION PHASE—SWITCH OPEN  
TRACK PHASE—SWITCH CLOSED  
The REF19x series devices are precision micropower, low drop-  
out voltage references. For the AD7466/AD7467/AD7468  
voltage range operation, the REF193, REF192, and REF191 can  
be used to supply the required voltage to the ADC, delivering  
3 V, 2.5 V, and 2.048 V, respectively (see Figure 22). This con-  
figuration is especially useful if the power supply is quite noisy  
or if the system supply voltages are at a value other than 3 V or  
2.5 V (for example, 5 V). The REF19x outputs a steady voltage  
to the AD7466/AD7467/AD7468. If the low dropout REF192 is  
used when the AD7466 is converting at a rate of 100 kSPS, the  
REF192 needs to supply a maximum of 240 μA to the AD7466.  
The load regulation of the REF192 is typically 10 ppm/mA  
(REF192, VS = 5 V), which results in an error of 2.4 ppm (6 μV)  
for the 240 μA drawn from it. This corresponds to a 0.0098 LSB  
error for the AD7466 with VDD = 2.5 V from the REF192. For  
applications where power consumption is important, the  
automatic power-down mode of the ADC and the sleep mode  
of the REF19x reference should be used to improve power  
performance. See the Normal Mode section.  
Figure 23. Equivalent Analog Input Circuit  
For ac applications, removing high frequency components  
from the analog input signal by using a band-pass filter on  
the relevant analog input pin is recommended. In applications  
where harmonic distortion and signal-to-noise ratio are critical,  
the analog input should be driven from a low impedance  
source. Large source impedances significantly affect the ac  
performance of the ADC. This might necessitate the use of an  
input buffer amplifier. The choice of the op amp is a function of  
the particular application.  
Table 8 provides typical performance data for various op amps  
used as the input buffer under constant setup conditions.  
Table 8. AD7466 Performance for Input Buffers  
Op Amp in the  
Input Buffer  
AD7466 SNR Performance (dB)  
30 kHz Input, VDD = 1.8 V  
AD8510  
AD8610  
AD797  
70.75  
71.45  
71.42  
Table 7 provides some typical performance data with various  
references used as a VDD source under the same setup  
conditions. The ADR318, for instance, is a 1.8 V band gap  
voltage reference. Its tiny footprint, low power consumption,  
and additional shutdown capability make the ADR318 ideal for  
battery-powered applications.  
When no amplifier is used to drive the analog input, the source  
impedance should be limited to low values. The maximum  
source impedance depends on the amount of total harmonic  
distortion (THD) that can be tolerated. The THD increases as  
the source impedance increases and performance degrades.  
Figure 12 shows a graph of THD vs. analog input signal  
frequency for different source impedances when using a supply  
voltage of 2.7 V and sampling at a rate of 100 kSPS.  
Table 7. AD7466 Performance for Voltage Reference IC  
Reference Tied to VDD  
ADR318 @ 1.8 V  
ADR370 @ 2.048 V  
ADR421 @ 2.5 V  
ADR423 @ 3 V  
AD7466 SNR Performance (dB)  
70.73  
70.72  
71.13  
71.44  
DIGITAL INPUTS  
The digital inputs applied to the AD7466/AD7467/AD7468  
are not limited by the maximum ratings that limit the analog  
inputs. Instead, the digital inputs applied can go to 7 V and are  
not restricted by the VDD + 0.3 V limit as on the analog input.  
For example, if the AD7466/AD7467/AD7468 are operated with  
a VDD of 3 V, 5 V logic levels could be used on the digital inputs.  
However, the data output on SDATA still has 3 V logic levels  
ANALOG INPUT  
An equivalent circuit of the AD7466/AD7467/AD7468 analog  
input structure is shown in Figure 23. The two diodes, D1 and  
D2, provide ESD protection for the analog inputs. Care must be  
taken to ensure that the analog input signal never exceeds the  
supply rails by more than 300 mV. This causes these diodes to  
become forward-biased and to start conducting current into the  
substrate. Capacitor C1 in Figure 23 is typically about 4 pF and  
can primarily be attributed to pin capacitance. Resistor R1 is a  
lumped component made up of the on resistance of a switch.  
This resistor is typically about 200 Ω. Capacitor C2 is the ADC  
sampling capacitor with a typical capacitance of 20 pF.  
CS  
when VDD = 3 V. Another advantage of SCLK and  
restricted by the VDD + 0.3 V limit is that power supply  
CS  
not being  
sequencing issues are avoided. If  
or SCLK is applied before  
VDD, there is no risk of latch-up as there would be on the analog  
inputs if a signal greater than 0.3 V is applied prior to VDD.  
Rev. C | Page 18 of 28  
 
 
 
 
AD7466/AD7467/AD7468  
The AD7468 automatically enters power-down mode on the  
12th SCLK falling edge.  
NORMAL MODE  
The AD7466/AD7467/AD7468 automatically enter power-  
down at the end of each conversion. This mode of operation is  
designed to provide flexible power management options and to  
optimize the power dissipation/throughput rate ratio for low  
power application requirements. Figure 24 shows the general  
CS  
The AD7466 also enters power-down mode if  
high any time before the 16th SCLK falling edge. The conver-  
CS  
is brought  
sion that was initiated by the  
SDATA goes back into three-state. This also applies for the  
CS  
falling edge terminates and  
CS  
operation of the AD7466/AD7467/AD7468. On the  
falling  
AD7467 and AD7468; if  
is brought high before the conver-  
edge, the part begins to power up and the track-and-hold,  
which was in hold while the part was in power-down, goes into  
track mode. The conversion is also initiated at this point. On  
sion is complete (the 14th SCLK falling edge for the AD7467,  
and the 12th SCLK falling edge for the AD7468), the part enters  
power-down, the conversion terminates, and SDATA goes back  
into three-state.  
CS  
the third SCLK falling edge after the  
and-hold returns to hold mode.  
falling edge, the track-  
CS  
Although  
CS  
can idle high or low between conversions,  
For the AD7466, 16 serial clock cycles are required to complete  
the conversion and access the complete conversion result. The  
AD7466 automatically enters power-down mode on the 16th  
SCLK falling edge.  
bringing  
high once the conversion is complete is recom-  
mended to save power.  
When supplies are first applied to the devices, a dummy conver-  
sion should be performed to ensure that the parts are in power-  
down mode, the track-and-hold is in hold mode, and SDATA is  
in three-state.  
For the AD7467, 14 serial clock cycles are required to complete  
the conversion and access the complete conversion result. The  
AD7467 automatically enters power-down mode on the 14th  
SCLK falling edge.  
Once a data transfer is complete (SDATA has returned to three-  
state), another conversion can be initiated after the quiet time,  
For the AD7468, 12 serial clock cycles are required to complete  
the conversion and access the complete conversion result.  
CS  
tQUIET, has elapsed, by bringing  
low again.  
AD7468 ENTERS POWER-DOWN  
AD7467 ENTERS POWER-DOWN  
THE PART BEGINS  
TO POWER UP  
THE PART IS POWERED UP  
AND V FULLY ACQUIRED  
IN  
AD7466 ENTERS POWER-DOWN  
CS  
1
2
3
12  
14  
16  
SCLK  
SDATA  
VALID DATA  
Figure 24. Normal Mode Operation  
Rev. C | Page 19 of 28  
 
 
 
AD7466/AD7467/AD7468  
This reduced power consumption can be seen in Figure 25,  
which shows the supply current vs. SCLK frequency for various  
supply voltages at a throughput rate of 100 kSPS. For a fixed  
throughput rate, the supply current (average current) drops as  
the SCLK frequency increases because the part is in power-  
down mode most of the time. It can also be seen that, for a  
lower supply voltage, the supply current drops accordingly.  
POWER CONSUMPTION  
The AD7466/AD7467/AD7468 automatically enter power-  
down mode at the end of each conversion or if  
high before the conversion is finished.  
CS  
is brought  
When the AD7466/AD7467/AD7468 are in power-down mode,  
all the analog circuitry is powered down and the current con-  
sumption is typically 8 nA.  
390  
fSAMPLE = 100kSPS  
To achieve the lowest power dissipation, there are some  
considerations the user should keep in mind.  
TEMP = 25°C  
360  
330  
300  
270  
240  
210  
180  
150  
120  
90  
V
V
= 3.6V  
= 3.0V  
DD  
DD  
The conversion time is determined by the serial clock  
frequency; the faster the SCLK frequency, the shorter the  
conversion time. This implies that as the frequency increases,  
the part dissipates power for a shorter period of time when the  
conversion is taking place, and it remains in power-down mode  
for a longer percentage of the cycle time or throughput rate.  
V
V
= 2.7V  
= 1.8V  
DD  
V
= 2.2V  
DD  
DD  
Figure 26 shows two AD7466s running with two different  
SCLK frequencies, SCLK A and SCLK B, with SCLK A having  
the higher SCLK frequency. For the same throughput rate, the  
AD7466 using SCLK A has a shorter conversion time than the  
AD7466 using SCLK B, and it remains in power-down mode  
longer. The current consumption in power-down mode is very  
low; thus, the average power consumption is greatly reduced.  
V
= 1.6V  
2.4  
DD  
60  
2.2  
2.6  
2.8  
3.0  
3.2  
3.4  
3.6  
SCLK FREQUENCY (MHz)  
Figure 25. Supply Current vs. SCLK Frequency  
for a Fixed Throughput Rate and Different Supply Voltages  
1/THROUGHPUT  
CONVERSION TIME B  
CONVERSION TIME A  
CS  
1
1
16  
SCLK A  
SCLK B  
16  
Figure 26. Conversion Time Comparison for Different SCLK Frequencies and a Fixed Throughput Rate  
1/THROUGHPUT B  
1/THROUGHPUT A  
POWER DOWN TIME A  
CONVERSION TIME A  
CS A  
POWER DOWN TIME B  
CONVERSION TIME B  
CS B  
1
16  
SCLK  
Figure 27. Conversion Time vs. Power-Down Time for a Fixed SCLK Frequency and Different Throughput Rates  
Rev. C | Page 20 of 28  
 
 
 
 
 
AD7466/AD7467/AD7468  
Figure 18 shows power consumption vs. throughput rate for a  
3.4 MHz SCLK frequency. In this case, the conversion time is  
the same for all cases because the SCLK frequency is a fixed  
parameter. Low throughput rates lead to lower current con-  
sumptions, with a higher percentage of the time in power-down  
mode. Figure 27 shows two AD7466s running with the same  
SCLK frequency, but at different throughput rates. The A  
throughput rate is higher than the B throughput rate. The  
slower the throughput rate, the longer the period of time the  
part is in power-down mode, and the average power consump-  
tion drops accordingly.  
The average power consumption includes the power dissipated  
when the part is converting and the power dissipated when the  
part is in power-down mode. The average power dissipated  
during conversion is calculated as the percentage of the cycle  
time spent when converting, multiplied by the maximum  
current during conversion. The average power dissipated in  
power-down mode is calculated as the percentage of cycle time  
spent in power-down mode, multiplied by the current figure for  
power-down mode. In order to obtain the value for the average  
power, these terms must be multiplied by the voltage.  
Considering the maximum current for each SCLK frequency  
for VDD = 1.8 V,  
Figure 28 shows the power vs. throughput rate for different  
supply voltages and SCLK frequencies. For this plot, all the  
elements regarding power consumption that were explained  
previously (the influence of the SCLK frequency, the influence  
of the throughput rate, and the influence of the supply voltage)  
are taken into consideration.  
Power Consumption A = ((4.7/20) × 186 μA + (15.3/20) ×  
100 nA) × 1.8 V = (43.71 + 0.076) μA × 1.8 V = 78.8 μW  
= 0.07 mW  
Power Consumption B = ((13/20) × 108 μA + (7/20) ×  
100 nA) × 1.8 V = (70.2 + 0.035) μA × 1.8 V = 126.42 μW  
= 0.126 mW  
1.4  
TEMP = 25°C  
1.2  
It can be concluded that for a fixed throughput rate, the average  
power consumption drops as the SCLK frequency increases.  
V
= 3.0V, SCLK = 2.4MHz  
DD  
1.0  
0.8  
0.6  
0.4  
0.2  
0
Power Consumption Example 2  
This example shows that, for a fixed SCLK frequency, as the  
throughput rate decreases, the average power consumption  
drops. From Figure 27, for SCLK = 3.4 MHz, Throughput A =  
100 kSPS (which gives a cycle time of 10 μs), and Throughput B  
= 50 kSPS (which gives a cycle time of 20 μs), the following  
values can be obtained:  
V
= 3.0V, SCLK = 3.4MHz  
DD  
V
= 1.8V, SCLK = 2.4MHz  
DD  
V
= 1.8V, SCLK = 3.4MHz  
DD  
Conversion Time A = 16 × (1/SCLK) = 4.7 μs  
0
50  
100  
150  
200  
250  
(47% of the cycle time for a throughput of 100 kSPS)  
THROUGHPUT (kSPS)  
Figure 28. Power vs. Throughput Rate  
for Different SCLK and Supply Voltages  
Power-Down Time A = (1/Throughput A) − Conversion  
Time A = 10 μs − 4.7 μs = 5.3 μs (53% of the cycle time)  
The following examples show calculations for the information  
in this section.  
Conversion Time B = 16 × (1/SCLK) = 4.7 μs  
(23.5% of the cycle time for a throughput of 50 kSPS)  
Power Consumption Example 1  
Power-Down Time B = (1/Throughput B) − Conversion  
Time B = 20 μs − 4.7 μs = 15.3 μs (76.5% of the cycle time)  
This example shows that, for a fixed throughput rate, as the  
SCLK frequency increases, the average power consumption  
drops. From Figure 26, for SCLK A = 3.4 MHz, SCLK B =  
1.2 MHz, and a throughput rate of 50 kSPS, which gives a cycle  
time of 20 μs, the following values can be obtained:  
The average power consumption is calculated as explained in  
Power Consumption Example 1, considering the maximum  
current for a 3.4 MHz SCLK frequency for VDD = 1.8 V.  
Power Consumption A = ((4.7/10) × 186 μA + (5.3/10) ×  
100 nA) × 1.8 V= (87.42 + 0.053) μA × 1.8 V = 157.4 μW =  
0.157 mW  
Conversion Time A = 16 × (1/SCLK A) = 4.7 μs  
(23.5% of the cycle time)  
Power-Down Time A = (1/Throughput) − Conversion  
Time A = 20 μs − 4.7 μs = 15.3 μs (76.5% of the cycle time)  
Power Consumption B = ((4.7/20) × 186 μA + (15.3/20) ×  
100 nA) × 1.8 V = (43.7 + 0.076) μA × 1.8 V = 78.79 μW =  
0.078 mW  
Conversion Time B = 16 × (1/SCLK B) = 13 μs  
(65% of the cycle time)  
It can be concluded that for a fixed SCLK frequency, the average  
power consumption drops as the throughput rate decreases.  
Power-Down Time B = (1/Throughput) − Conversion  
Time B = 20 μs − 13 μs = 7 μs (35% of the cycle time)  
Rev. C | Page 21 of 28  
 
 
AD7466/AD7467/AD7468  
SERIAL INTERFACE  
Figure 29, Figure 30, and Figure 31 show the timing diagrams  
for serial interfacing to the AD7466/AD7467/AD7468. The  
serial clock provides the conversion clock and controls the  
transfer of information from the ADC during a conversion.  
CS  
occurs before 12 SCLKs elapse,  
down. If the rising edge of  
the conversion terminates, the SDATA line goes back into three-  
state, and the AD7468 enters power-down; otherwise SDATA  
returns to three-state on the 12th SCLK falling edge, as shown  
in Figure 31. Twelve serial clock cycles are required to perform  
the conversion process and to access data from the AD7468.  
CS  
The part begins to power up on the  
falling edge. The falling  
puts the track-and-hold into track mode and takes  
the bus out of three-state. The conversion is also initiated at this  
CS  
CS  
edge of  
CS  
going low provides the first leading zero to be read in by the  
microcontroller or DSP. The remaining data is then clocked out  
by subsequent SCLK falling edges, beginning with the second  
leading zero; thus, the first clock falling edge on the serial clock  
has the first leading zero provided and also clocks out the  
second leading zero. For the AD7466, the final bit in the data  
transfer is valid on the 16th SCLK falling edge, having been  
clocked out on the previous (15th) SCLK falling edge.  
point. On the third SCLK falling edge after the  
falling edge,  
the part should be powered up fully at Point B, as shown in  
Figure 29, and the track-and-hold returns to hold.  
For the AD7466, the SDATA line goes back into three-state and  
the part enters power-down on the 16th SCLK falling edge. If  
CS  
the rising edge of  
occurs before 16 SCLKs elapse, the  
conversion terminates, the SDATA line goes back into three-  
state, and the part enters power-down; otherwise SDATA  
returns to three-state on the 16th SCLK falling edge, as shown  
in Figure 29. Sixteen serial clock cycles are required to perform  
the conversion process and to access data from the AD7466.  
In applications with a slow SCLK, it is possible to read in data  
on each SCLK rising edge. In such a case, the first falling edge  
CS  
of SCLK after the  
zero and can be read in the following rising edge. If the first  
CS  
falling edge clocks out the second leading  
SCLK edge after the  
falling edge is a falling edge, the first  
CS  
For the AD7467, the 14th SCLK falling edge causes the SDATA  
line to go back into three-state, and the part enters power-down.  
leading zero that was clocked out when  
went low is missed,  
unless it is not read on the first SCLK falling edge. The 15th  
falling edge of SCLK clocks out the last bit, and it can be read in  
the following rising SCLK edge.  
CS  
If the rising edge of  
occurs before 14 SCLKs elapse, the con-  
version terminates, the SDATA line goes back into three-state,  
and the AD7467 enters power-down; otherwise SDATA returns  
to three-state on the 14th SCLK falling edge, as shown in Figure 30.  
Fourteen serial clock cycles are required to perform the  
conversion process and to access data from the AD7467.  
CS  
CS  
falling edge is a rising edge,  
If the first SCLK edge after the  
clocks out the first leading zero, and it can be read on the SCLK  
rising edge. The next SCLK falling edge clocks out the second  
leading zero, and it can be read on the following rising edge.  
For the AD7468, the 12th SCLK falling edge causes the SDATA  
line to go back into three-state, and the part enters power-  
t1  
CS  
tCONVERT  
t2  
t6  
B
SCLK  
1
2
3
4
5
13  
14  
t5  
15  
16  
t8  
t3  
t4  
t7  
tQUIET  
SDATA  
0
0
0
0
DB11  
DB10  
DB2  
DB1  
DB0  
THREE-STATE  
THREE-STATE  
4 LEADING ZEROS  
12 BITS OF DATA  
Figure 29. AD7466 Serial Interface Timing Diagram  
t1  
CS  
tCONVERT  
t6  
t2  
B
1
2
3
4
5
13  
t5  
14  
t8  
SCLK  
t7  
t3  
tQUIET  
t4  
DB9  
DB8  
10 BITS OF DATA  
DB0  
0
0
0
SDATA  
0
THREE-STATE  
THREE-STATE  
4 LEADING ZEROS  
Figure 30. AD7467 Serial Interface Timing Diagram  
Rev. C | Page 22 of 28  
 
 
 
 
AD7466/AD7467/AD7468  
t1  
CS  
tCONVERT  
t6  
t2  
B
1
2
3
4
11  
12  
SCLK  
t8  
t5  
t7  
tQUIET  
t3  
t4  
0
0
0
0
DB7  
DB0  
8 BITS OF DATA  
SDATA  
THREE-STATE  
THREE-STATE  
4 LEADING ZEROS  
Figure 31. AD7468 Serial Interface Timing Diagram  
Figure 32 shows the connection diagram. For signal processing  
applications, it is imperative that the frame synchronization  
signal from the TMS320C541 provide equidistant sampling.  
MICROPROCESSOR INTERFACING  
The serial interface on the AD7466/AD7467/AD7468 allows  
the parts to be connected directly to many different micro-  
processors. This section explains how to interface the AD7466/  
AD7467/AD7468 with some of the more common microcontroller  
and DSP serial interface protocols.  
AD7466/  
AD7467/  
AD74681  
TMS320C5411  
SCLK  
CLKX  
AD7466/AD7467/AD7468 to TMS320C541 Interface  
CLKR  
DR  
SDATA  
CS  
The serial interface on the TMS320C541 uses a continuous  
serial clock and frame synchronization signals to synchronize  
the data transfer operations with peripheral devices like the  
FSX  
FSR  
CS  
AD7466/AD7467/AD7468. The  
input allows easy inter-  
1
ADDITIONAL PINS OMITTED FOR CLARITY.  
facing between the TMS320C541 and the AD74xx devices,  
without requiring any glue logic. The serial port of the  
TMS320C541 is set up to operate in burst mode (FSM = 1  
in the serial port control register, SPC) with internal CLKX  
(MCM = 1 in the SPC register) and internal frame signal  
(TXM = 1 in the SPC register), so both pins are configured as  
outputs. For the AD7466, the word length should be set to  
16 bits (FO = 0 in the SPC register). The standard synchronous  
serial port interface in this DSP allows only frames with a word  
length of 16 bits or 8 bits. Therefore, for the AD7467 and  
AD7468 where 14 and 12 bits are required, the FO bit also  
would be set up to 16 bits. In these cases, the user should keep  
in mind that the last 2 bits and 4 bits for the AD7467 and  
AD7468, respectively, are invalid data as the SDATA line goes  
back into three-state on the 14th and 12th SCLK falling edge.  
Figure 32. Interfacing to the TMS320C541  
AD7466/AD7467/AD7468 to ADSP-218x Interface  
The ADSP-218x family of DSPs is interfaced directly to the  
AD7466/AD7467/AD7468 without any glue logic. The SPORT  
control register must be set up as described in Table 9.  
Table 9. SPORT Control Register Setup  
Setting  
Description  
TFSW = RFSW = 1  
INVRFS = INVTFS = 1  
DTYPE = 00  
ISCLK = 1  
TFSR = RFSR = 1  
IRFS = 0  
Alternate framing  
Active low frame signal  
Right-justify data  
Internal serial clock  
Frame every word  
Sets up RFS as an input  
Sets up TFS as an output  
16 bits for the AD7466  
14 bits for the AD7467  
12 bits for the AD7468  
ITFS = 1  
To summarize, the values in the SPC register are FO = 0,  
FSM = 1, MCM = 1, and TXM = 1.  
SLEN = 1111  
SLEN = 1101  
SLEN = 1011  
Rev. C | Page 23 of 28  
 
 
 
 
AD7466/AD7467/AD7468  
The connection diagram in Figure 33 shows how the ADSP-218x  
has the TFS and RFS of the SPORT tied together, with TFS set  
as an output and RFS set as an input. The DSP operates in  
alternate framing mode, and the SPORT control register is set  
up as described. The frame synchronization signal generated on  
AD7466/AD7467/AD7468 to DSP563xx Interface  
The connection diagram in Figure 34 shows how the AD7466/  
AD7467/AD7468 can be connected to the synchronous serial  
interface (SSI) of the DSP563xx family of DSPs from Motorola.  
The SSI is operated in synchronous mode and normal mode  
(SYN = 1 and MOD = 0 in Control Register B, CRB) with an  
internally generated word frame sync for both Tx and Rx  
(Bit FSL1 = 0 and Bit FSL0 = 0 in the CRB register). Set the  
word length in Control Register A (CRA) to 16 by setting Bits  
WL2 = 0, WL1 = 1, and WL0 = 0 for the AD7466. The word  
length for the AD7468 can be set to 12 bits (WL2 = 0, WL1 = 0,  
and WL0 = 1). This DSP does not offer the option for a 14-bit  
word length, so the AD7467 word length is set up to 16 bits like  
the AD7466 word length. In this case, the user should keep in  
mind that the last two bits are invalid data because the SDATA  
goes back into three-state on the 14th SCLK falling edge.  
CS  
the TFS is tied to , and as with all signal processing applica-  
tions, equidistant sampling is necessary. However, in this example,  
the timer interrupt is used to control the sampling rate of the  
ADC and, under certain conditions, equidistant sampling might  
not be achieved.  
The timer registers, for example, are loaded with a value that  
provides an interrupt at the required sample interval. When an  
interrupt is received, a value is transmitted with TFS/DT (ADC  
control word). The TFS is used to control the RFS and, there-  
fore, the reading of data. The frequency of the serial clock is set  
in the SCLKDIV register. When the instruction to transmit with  
TFS is given (that is, AX0 = TX0), the state of the SCLK is  
checked. The DSP waits until the SCLK goes high, low, and high  
again before transmission starts. If the timer and SCLK values  
are chosen such that the instruction to transmit occurs on or  
near the rising edge of SCLK, the data can be transmitted, or it  
can wait until the next clock edge.  
The frame sync polarity bit (FSP) in the CRB register can be set  
to 1, which means the frame goes low and a conversion starts.  
Likewise, by means of Bits SCD2, SCKD, and SHFD in the CRB  
register, it is established that Pin SC2 (the frame sync signal)  
and Pin SCK in the serial port are configured as outputs, and  
the most significant bit (MSB) is shifted first. To summarize,  
For example, the ADSP-2181 has a master clock frequency of  
16 MHz. If the SCLKDIV register is loaded with the value 3, an  
SCLK of 2 MHz is obtained, and eight master clock periods  
elapse for every SCLK period. If the timer registers are loaded  
with the value 803, 100.5 SCLKs occur between interrupts and,  
subsequently, between transmit instructions. This situation  
results in nonequidistant sampling as the transmit instruction is  
occurring on an SCLK edge. If the number of SCLKs between  
interrupts is a whole integer figure of N, equidistant sampling is  
implemented by the DSP.  
MOD = 0  
SYN = 1  
WL2, WL1, WL0 depend on the word length  
FSL1 = 0, FSL0 = 0  
FSP = 1, negative frame sync  
SCD2 = 1  
SCKD = 1  
SHFD = 0  
For signal processing applications, it is imperative that the  
frame synchronization signal from the DSP563xx provides  
equidistant sampling.  
AD7466/  
AD7467/  
AD74681  
ADSP-218x1  
AD7466/  
AD7467/  
AD74681  
DSP563xx1  
SCLK  
SCLK  
DR  
SDATA  
CS  
SCLK  
SCK  
SRD  
SC2  
RFS  
TFS  
SDATA  
CS  
1
ADDITIONAL PINS OMITTED FOR CLARITY.  
Figure 33. Interfacing to the ADSP-218x  
1
ADDITIONAL PINS OMITTED FOR CLARITY.  
Figure 34. Interfacing to the DSP563xx  
Rev. C | Page 24 of 28  
 
 
AD7466/AD7467/AD7468  
APPLICATION HINTS  
component side of the board is dedicated to ground planes,  
while signals are placed on the solder side.  
GROUNDING AND LAYOUT  
The printed circuit board that houses the AD7466/AD7467/  
AD7468 should be designed such that the analog and digital  
sections are separated and confined to certain areas. This facili-  
tates the use of ground planes that can be separated easily. A  
minimum etch technique is generally best for ground planes  
because it gives the best shielding. Digital and analog ground  
planes should be joined at only one place. If the devices are in a  
system where multiple devices require an AGND to DGND  
connection, the connection should still be made at one point  
only, a star ground point, which should be established as close  
as possible to the AD7466/AD7467/AD7468.  
Good decoupling is also very important. All analog supplies  
should be decoupled with 10 μF tantalum in parallel with 0.1 μF  
capacitors to AGND. All digital supplies should have a 0.1 μF  
ceramic disc capacitor to DGND. To achieve the best perform-  
ance from these decoupling components, the user should keep  
the distance between the decoupling capacitor and the VDD and  
GND pins to a minimum, with short track lengths connecting  
the respective pins.  
EVALUATING THE PERFORMANCE  
OF THE AD7466 AND AD7467  
Avoid running digital lines under the device because these  
couple noise onto the die. The analog ground plane should be  
allowed to run under the AD7466/AD7467/AD7468 to avoid  
noise coupling. The power supply lines to the devices should  
use as large a trace as possible to provide low impedance paths  
and to reduce the effects of glitches on the power-supply line.  
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 crossover of digital and analog signals. Traces on  
opposite sides of the board should run at right angles to each  
other to reduce the effects of feedthrough on the board. A  
microstrip technique is the best choice, but is not always  
possible with a double-sided board. With this technique, the  
The evaluation board package includes a fully assembled and  
tested evaluation board, documentation, and software for  
controlling the board from the PC via an evaluation board  
controller. To evaluate the ac and dc performance of the  
AD7466 and AD7467, the evaluation board controller can be  
used in conjunction with the AD7466/AD7467CB evaluation  
board and other Analog Devices evaluation boards ending in  
the CB designator.  
The software allows the user to perform ac tests (fast Fourier  
transform) and dc tests (histogram of codes) on the AD7466  
and AD7467. See the data sheet in the evaluation board package  
for more information.  
Rev. C | Page 25 of 28  
 
AD7466/AD7467/AD7468  
OUTLINE DIMENSIONS  
2.90 BSC  
6
1
5
2
4
3
2.80 BSC  
1.60 BSC  
PIN 1  
INDICATOR  
0.95 BSC  
1.90  
BSC  
1.30  
1.15  
0.90  
1.45 MAX  
0.22  
0.08  
10°  
4°  
0°  
0.60  
0.45  
0.30  
0.50  
0.30  
0.15 MAX  
SEATING  
PLANE  
COMPLIANT TO JEDEC STANDARDS MO-178-AB  
Figure 35. 6-Lead Small Outline Transistor Package [SOT-23]  
(RJ-6)  
Dimensions shown in millimeters  
3.20  
3.00  
2.80  
8
1
5
4
5.15  
4.90  
4.65  
3.20  
3.00  
2.80  
PIN 1  
0.65 BSC  
0.95  
0.85  
0.75  
1.10 MAX  
0.80  
0.60  
0.40  
8°  
0°  
0.15  
0.00  
0.38  
0.22  
0.23  
0.08  
SEATING  
PLANE  
COPLANARITY  
0.10  
COMPLIANT TO JEDEC STANDARDS MO-187-AA  
Figure 36. 8-Lead Mini Small Outline Package [MSOP]  
(RM-8)  
Dimensions shown in millimeters  
Rev. C | Page 26 of 28  
 
AD7466/AD7467/AD7468  
ORDERING GUIDE  
Model  
AD7466BRT-REEL7  
AD7466BRT-R2  
AD7466BRTZ-REEL2  
AD7466BRTZ-REEL72  
AD7466BRTZ-R22  
AD7466BRM  
AD7466BRM-REEL  
AD7466BRM-REEL7  
AD7466BRMZ2  
AD7466BRMZ-REEL2  
AD7466BRMZ-REEL72  
AD7467BRT-REEL  
AD7467BRT-REEL7  
AD7467BRT-R2  
AD7467BRTZ-REEL2  
AD7467BRTZ-REEL72  
AD7467BRTZ-R22  
AD7467BRM  
Temperature Range  
−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 +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 +85°C  
−40°C to +85°C  
−40°C to +85°C  
−40°C to +85°C  
Linearity Error (LSB)1  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
1.5 max  
0.5 max  
0.5 max  
0.5 max  
0.5 max  
0.5 max  
0.5 max  
0.5 max  
0.5 max  
0.5 max  
0.5 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
0.2 max  
Package Description  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
6-Lead SOT-23  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
8-Lead MSOP  
Evaluation Board  
Evaluation Board  
Control Board  
Package Option  
RJ-6  
RJ-6  
RJ-6  
RJ-6  
Branding  
CLB  
CLB  
C2T  
C2T  
C2T  
CLB  
CLB  
CLB  
CLB#  
CLB#  
CLB#  
CMB  
CMB  
CMB  
CMB#  
CMB#  
CMB#  
CMB  
CMB  
CMB  
CMU  
CNB  
CNB  
CNB  
CNU#  
CNU#  
CNB  
CNB  
CNB  
CNU#  
CNU#  
CNU#  
RJ-6  
RM-8  
RM-8  
RM-8  
RM-8  
RM-8  
RM-8  
RJ-6  
RJ-6  
RJ-6  
RJ-6  
RJ-6  
RJ-6  
RM-8  
RM-8  
RM-8  
RM-8  
RJ-6  
RJ-6  
RJ-6  
RJ-6  
RJ-6  
RM-8  
RM-8  
RM-8  
RM-8  
RM-8  
RM-8  
AD7467BRM-REEL  
AD7467BRM-REEL7  
AD7467BRMZ2  
AD7468BRT-REEL  
AD7468BRT-REEL7  
AD7468BRT-R2  
AD7468BRTZ-REEL2  
AD7468BRTZ-REEL72  
AD7468BRM  
AD7468BRM-REEL  
AD7468BRM-REEL7  
AD7468BRMZ2  
AD7468BRMZ-REEL2  
AD7468BRMZ-REEL72  
EVAL-AD7466CB3  
EVAL-AD7467CB3  
EVAL-CONTROL BRD24  
1 Linearity error refers to integral nonlinearity.  
2 Z = RoHS Compliant Part, # denotes lead-free product may be top or bottom marked.  
3 This can be used as a standalone evaluation board or in conjunction with the EVAL-CONTROL BRD2 for evaluation/demonstration purposes.  
4 This board is a complete unit that allows a PC to control and communicate with all Analog Devices evaluation boards ending in the CB designator. For a complete  
evaluation kit, order a particular ADC evaluation board (such as EVAL-AD7466CB), the EVAL-CONTROL BRD2, and a 12 V ac transformer. See relevant evaluation board  
data sheets for more information.  
Rev. C | Page 27 of 28  
 
AD7466/AD7467/AD7468  
NOTES  
©2003–2007 Analog Devices, Inc. All rights reserved. Trademarks and  
registered trademarks are the property of their respective owners.  
C02643-0-5/07(C)  
Rev. C | Page 28 of 28  

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