AD AD6644AST-65 14-bit, 40 msps/65 msps a/d converter Datasheet

a
14-Bit, 40 MSPS/65 MSPS
A/D Converter
AD6644
FEATURES
65 MSPS Guaranteed Sample Rate
40 MSPS Version Available
Sampling Jitter < 300 fs
100 dB Multitone SFDR
1.3 W Power Dissipation
Differential Analog Inputs
Digital Outputs
Two’s Complement Format
3.3 V CMOS-Compatible
Data Ready for Output Latching
Designed for multichannel, multimode receivers, the AD6644 is
part of ADI’s new SoftCell™ transceiver chipset. The AD6644
achieves 100 dB multitone, spurious-free dynamic range (SFDR)
through the Nyquist band. This breakthrough performance eases
the burden placed on multimode digital receivers (software radios)
which are typically limited by the ADC. Noise performance is
exceptional; typical signal-to-noise ratio is 74 dB.
The AD6644 is also useful in single channel digital receivers
designed for use in wide-channel bandwidth systems (CDMA,
W-CDMA). With oversampling, harmonics can be placed outside the analysis bandwidth. Oversampling also facilitates the use of
decimation receivers (such as the AD6620), allowing the noise
floor in the analysis bandwidth to be reduced. By replacing traditional analog filters with predictable digital components, modern
receivers can be built using fewer “RF” components, resulting
in decreased manufacturing costs, higher manufacturing yields,
and improved reliability.
APPLICATIONS
Multichannel, Multimode Receivers
AMPS, IS-136, CDMA, GSM, Third Generation
Single Channel Digital Receivers
Antenna Array Processing
Communications Instrumentation
Radar, Infrared Imaging
Instrumentation
The AD6644 is built on Analog Devices’ high-speed complementary bipolar process (XFCB) and uses an innovative, multipass
circuit architecture. Units are packaged in a 52-terminal LowProfile Quad Plastic Flatpack (LQFP) specified from –25°C
to +85°C.
PRODUCT DESCRIPTION
PRODUCT HIGHLIGHTS
The AD6644 is a high-speed, high-performance, monolithic
14-bit analog-to-digital converter. All necessary functions,
including track-and-hold (T/H) and reference, are included onchip to provide a complete conversion solution. The AD6644
provides CMOS-compatible digital outputs. It is the third generation in a wideband ADC family, preceded by the AD9042 (12-bit
41 MSPS) and the AD6640 (12-bit 65 MSPS, IF sampling.)
1. Guaranteed sample rate is 65 MSPS.
2. Fully differential analog input stage.
3. Digital outputs may be run on 3.3 V supply for easy interface
to digital ASICs.
4. Complete Solution: reference and track-and-hold.
5. Packaged in small, surface-mount, plastic, 52-terminal LQFP.
FUNCTIONAL BLOCK DIAGRAM
AVCC
DVCC
A1
TH1
AIN
TH2
A2
TH4
TH3
TH5
ADC3
AIN
VREF
ADC1
2.4V
DAC1
ADC2
5
ENCODE
ENCODE
6
DAC2
AD6644
5
DIGITAL ERROR CORRECTION LOGIC
INTERNAL
TIMING
MSB
GND
DMID OVR DRY
D13
D12
LSB
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
SoftCell is a trademark of Analog Devices, Inc.
REV. 0
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
AD6644–SPECIFICATIONS
DC SPECIFICATIONS (AV
CC
= 5 V, DVCC = 3.3 V; TMIN = –25ⴗC, TMAX = +85ⴗC)
Parameter
Temp
Test
Level
Min
AD6644AST-40
Typ
Max
RESOLUTION
AD6644AST-65
Typ
Max
Min
14
14
Unit
Bits
ACCURACY
No Missing Codes
Offset Error
Gain Error
Differential Nonlinearity (DNL)
Integral Nonlinearity (INL)
Full
Full
Full
Full
Full
II
II
II
II
V
TEMPERATURE DRIFT
Offset Error
Gain Error
Full
Full
V
V
10
95
10
95
ppm/°C
ppm/°C
–10
–10
–1.0
Guaranteed
3
–6
± 0.25
± 0.50
+10
+10
+1.5
Guaranteed
3
–6
± 0.25
± 0.50
–10
–10
–1.0
+10
+10
+1.5
mV
% FS
LSB
LSB
POWER SUPPLY REJECTION (PSRR)
Full
V
± 1.0
± 1.0
mV/V
REFERENCE OUT (VREF)
Full
V
2.4
2.4
V
ANALOG INPUTS (AIN, AIN)
Differential Input Voltage Range
Differential Input Resistance
Differential Input Capacitance
Full
Full
25°C
V
V
V
2.2
1
1.5
2.2
1
1.5
V p-p
kΩ
pF
Full
Full
II
II
Full
Full
Full
POWER SUPPLY
Supply Voltage
AVCC1
DVCC
Supply Current
IAVCC (AVCC = 5.0 V)
IDVCC (DVCC = 3.3 V)
POWER CONSUMPTION
4.85
3.0
5.0
3.3
5.25
3.6
II
II
245
30
II
1.3
4.85
3.0
5.0
3.3
5.25
3.6
V
V
276
36
245
30
276
36
mA
mA
1.5
1.3
1.5
W
NOTES
1
AVCC may be varied from 4.85 V to 5.25 V. However, rated ac (harmonics) performance is valid only over the range AVCC = 5.0 V to 5.25 V.
Specifications subject to change without notice.
DIGITAL SPECIFICATIONS
(AVCC = 5 V, DVCC = 3.3 V; TMIN = –25ⴗC, TMAX = +85ⴗC)
Parameter
Temp
Test
Level
ENCODE INPUTS (ENC, ENC)
Differential Input Voltage1
Differential Input Resistance
Differential Input Capacitance
Full
25°C
25°C
IV
V
V
Full
Full
V
V
Full
V
LOGIC OUTPUTS (D13–D0, DRY, OVR)
Logic Compatibility
Logic “1” Voltage2
Logic “0” Voltage2
Output Coding
DMID
Min
AD6644AST-40
Typ
Max
0.4
AD6644AST-65
Typ
Max
Min
0.4
10
2.5
V p-p
kΩ
pF
10
2.5
CMOS
2.5
0.4
Two’s Complement
DVCC/2
Unit
CMOS
2.5
0.4
Two’s Complement
DVCC/2
V
V
V
NOTES
1
All ac specifications tested by driving ENCODE and ENCODE differentially. Reference Figure 22 for performance versus encode power.
2
Digital output logic levels: DV CC = 3.3 V, CLOAD = 10 pF. Capacitive loads >10 pF will degrade performance.
Specifications subject to change without notice.
SWITCHING SPECIFICATIONS
(AVCC = 5 V, DVCC = 3.3 V; ENCODE and ENCODE = Maximum Conversion Rate MSPS; TMIN =
–25ⴗC, TMAX = +85ⴗC)
Parameter
Temp
Test
Level
Maximum Conversion Rate
Minimum Conversion Rate
ENCODE Pulsewidth High
ENCODE Pulsewidth Low
Full
Full
Full
Full
II
IV
IV
IV
Min
AD6644AST-40
Typ
Max
40
Min
AD6644AST-65
Typ
Max
65
15
10
10
15
6.5
6.5
Unit
MSPS
MSPS
ns
ns
Specifications subject to change without notice.
–2–
REV. 0
AD6644
AC SPECIFICATIONS1 (AV
CC
= 5 V, DVCC = 3.3 V; ENCODE and ENCODE = Maximum Conversion Rate MSPS; TMIN = –25ⴗC, TMAX = +85ⴗC)
Temp
Test
Level
2.2 MHz
15.5 MHz
30.5 MHz
25°C
25°C
25°C
II
II
II
74.5
74.0
73.5
72
72
72
74.5
74.0
73.5
dB
dB
dB
2.2 MHz
15.5 MHz
30.5 MHz
25°C
25°C
25°C
II
II
V
74.5
74.0
73.0
72
72
74.5
74.0
73.0
dB
dB
dB
WORST HARMONIC (2ND or 3RD)2
Analog Input
2.2 MHz
@ –1 dBFS
15.5 MHz
30.5 MHz
25°C
25°C
25°C
II
II
V
92
90
85
83
83
92
90
85
dBc
dBc
dBc
WORST HARMONIC (4TH or Higher)2
Analog Input
2.2 MHz
@ –1 dBFS
15.5 MHz
30.5 MHz
25°C
25°C
25°C
II
II
V
93
92
92
85
85
93
92
92
dBc
dBc
dBc
TWO-TONE SFDR2, 3, 4
Full
V
100
100
dBFS
Full
V
90
90
dBc
25°C
V
250
250
MHz
Parameter
SNR
Analog Input
@ –1 dBFS
SINAD2
Analog Input
@ –1 dBFS
TWO-TONE IMD REJECTION
F1, F2 @ –7 dBFS
AD6644AST-40
Typ
Max
Min
Min
AD6644AST-65
Typ
Max
Unit
2, 4
ANALOG INPUT BANDWIDTH
NOTES
1
All ac specifications tested by driving ENCODE and ENCODE differentially.
2
AVCC = 5 V to 5.25 V for rated ac performance.
3
Analog input signal power swept from –7 dBFS to –100 dBFS.
4
F1 = 15 MHz, F2 = 15.5 MHz.
Specifications subject to change without notice.
SWITCHING SPECIFICATIONS
Parameter
(AVCC = 5 V, DVCC = 3.3 V; ENCODE and ENCODE = Maximum Conversion Rate MSPS; TMIN =
–25ⴗC, TMAX = +85ⴗC, CLOAD = 10 pF)
Name
Temp
Test
Level
tENC
tENC
tENCH
tENCL
Full
Full
Full
Full
V
V
IV
IV
6.2
6.2
tDR
tE_DR
Full
IV
2.6
Full
Full
IV
IV
10.3
15.1
Full
Full
Full
IV
IV
IV
3.8
3.0
3.0
Full
Full
IV
IV
6.2
15.9
Min
AD6644AST-40/65
Typ
Max
Unit
1
ENCODE INPUT PARAMETERS
Encode Period1 @ 65 MSPS
Encode Period1 @ 40 MSPS
Encode Pulsewidth High2 @ 65 MSPS
Encode Pulsewidth Low @ 65 MSPS
ENCODE/DATA READY
Encode Rising to Data Ready Falling
Encode Rising to Data Ready Rising
@ 65 MSPS (50% Duty Cycle)
@ 40 MSPS (50% Duty Cycle)
ENCODE/DATA (D13:0), OVR
ENC to DATA Falling Low
ENC to DATA Rising Low
ENCODE to DATA Delay (Hold Time)3
ENCODE to DATA Delay (Setup Time)4
Encode = 65 MSPS (50% Duty Cycle)
Encode = 40 MSPS (50% Duty Cycle)
REV. 0
tE_FL
tE_RL
tH_E
tS_E
–3–
15.4
25
7.7
7.7
9.2
9.2
ns
ns
ns
ns
3.4
tENCH + tDR
11.1
15.9
4.6
ns
12.3
17.1
ns
ns
5.5
4.3
4.3
tENC – tE_FL
9.8
19.4
9.2
6.4
6.4
ns
ns
ns
11.6
21.2
ns
ns
AD6644–SPECIFICATIONS
Parameter
Name
DATA READY (DRY5)/DATA, OVR
Data Ready to DATA Delay (Hold Time)2
Encode = 65 MSPS (50% Duty Cycle)
Encode = 40 MSPS (50% Duty Cycle)
Data Ready to DATA Delay (Setup Time)2
@ 65 MSPS (50% Duty Cycle)
@ 40 MSPS (50% Duty Cycle)
Temp
Test
Level
Min
Full
Full
IV
IV
8.0
12.8
Full
Full
IV
IV
3.2
8.0
AD6644AST-40/65
Typ
Max
tH_DR
Note 6
8.6
13.4
Note 6
5.5
10.3
tS_DR
Unit
9.4
14.2
ns
ns
6.5
11.3
ns
ns
APERTURE DELAY
tA
25°C
V
100
ps
APERTURE UNCERTAINTY (JITTER)
tJ
25°C
V
0.2
ps rms
NOTES
1
Several timing parameters are a function of t ENC and tENCH.
2
To compensate for a change in duty cycle for t H_DR and tS_DR use the following equation:
NewtH_DR = (tH_DR – % Change(tENCH)) × tENC/2
NewtS_DR = (tS_DR – % Change(tENCH)) × tENC/2.
3
ENCODE to DATA Delay (Hold Time) is the absolute minimum propagation delay through the analog-to-digital converter.
4
ENCODE to DATA Delay (Setup Time) is calculated relative to 65 MSPS (50% duty cycle). In order to calculate t S_E for a given encode use the following equation:
NewtS_E = tENC(NEW) – tENC + tS_E (i.e., for 40 MSPS: NewtS_E(TYP) = 25 × 10–9 – 15.38 × 10–9 + 9.8 × 10–9 = 19.4 × 10 –9).
5
DRY is an inverted and delayed version of the encode clock. Any change in the duty cycle of the clock will correspondingly change the duty cycle of DRY.
6
Data Ready to DATA Delay(t H_DR and tS_DR) is calculated relative to 65 MSPS (50% duty cycle) and is dependent on t ENC and duty cycle. In order to calculate t H_DR
and tS_DR for a given encode use the following equations:
NewtH_DR = tENC(NEW)/2 – tENCH + tH_DR (i.e., for 40 MSPS: Newt H_DR(TYP) = 12.5 × 10–9 – 7.69 × 10–9 + 8.6 × 10–9 = 13.4 × 10–9
NewtS_DR = tENC(NEW)/2 – tENCH + tS_DR (i.e., for 40 MSPS: NewtS_DR(TYP) = 12.5 × 10–9 – 7.69 × 10–9 + 5.5 × 10–9 = 10.3 × 10–9.
Specifications subject to change without notice.
tA
Nⴙ3
N
AIN
Nⴙ1
Nⴙ2
Nⴙ4
t ENC
ENC, ENC
t ENCH
t ENCL
Nⴙ1
N
Nⴙ2
t E_FL
t E_DR
t E_RL
D[13:0], OVR
Nⴙ3
N–3
t H_E
t S_E
N–2
N–1
t DR
Nⴙ4
t S_DR
N
t H_DR
DRY
Figure 1. Timing Diagram
–4–
REV. 0
AD6644
ABSOLUTE MAXIMUM RATINGS 1
Parameter
ELECTRICAL
AVCC Voltage
DVCC Voltage
Analog Input Voltage
Analog Input Current
Digital Input Voltage
Digital Output Current
Min
Max
Unit
0
0
0
7
7
AVCC
25
AVCC
4
V
V
V
mA
V
mA
+85
150
300
+150
°C
°C
°C
°C
0
ENVIRONMENTAL2
Operating Temperature Range
(Ambient)
–25
Maximum Junction Temperature
Lead Temperature (Soldering, 10 sec)
Storage Temperature Range (Ambient) –65
EXPLANATION OF TEST LEVELS
Test Level
I
II
100% production tested.
100% production tested at 25°C, and guaranteed by
design and characterization at temperature extremes.
III Sample tested only.
IV Parameter is guaranteed by design and characterization
testing.
V Parameter is a typical value only.
NOTES
1
Absolute maximum ratings are limiting values to be applied individually, and
beyond which the serviceability of the circuit may be impaired. Functional
operability is not necessarily implied. Exposure to absolute maximum rating
conditions for an extended period of time may affect device reliability.
2
Typical thermal impedances (52-terminal LQFP); θJA = 33°C/W; θJC = 11°C/W.
These measurements were taken on a 6 layer board in still air with a solid ground
plane.
ORDERING GUIDE
Model
Temperature Range
Package Description
Package Option
AD6644AST-40
AD6644AST-65
AD6644ST/PCB
–25°C to +85°C (Ambient)
–25°C to +85°C (Ambient)
52-Terminal LQFP (Low-Profile Quad Plastic Flatpack)
52-Terminal LQFP (Low-Profile Quad Plastic Flatpack)
Evaluation Board with AD6644AST–65
ST-52
ST-52
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 AD6644 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.
REV. 0
–5–
WARNING!
ESD SENSITIVE DEVICE
AD6644
PIN FUNCTION DESCRIPTIONS
Pin No.
Name
Function
1, 33, 43
2, 4, 7, 10, 13, 15, 17, 19, 21, 23,
25, 27, 29, 34, 42
3
DVCC
GND
3.3 V Power Supply (Digital) Output Stage Only.
Ground.
VREF
5
6
8, 9, 14, 16, 18, 22, 26, 28, 30
11
12
20
ENCODE
ENCODE
AVCC
AIN
AIN
C1
24
C2
31
32
35
36
37–41, 44–50
51
52
DNC
OVR
DMID
D0 (LSB)
D1–D5, D6–D12
D13 (MSB)
DRY
2.4 V (Analog Reference). Bypass to ground with 0.1 µF microwave
chip capacitor.
Encode Input; conversion initiated on rising edge.
Complement of ENCODE; differential input.
5 V Analog Power Supply.
Analog Input.
Complement of AIN; Differential Analog Input.
Internal Voltage Reference; bypass to ground with 0.1 µF microwave
chip capacitor.
Internal Voltage Reference; bypass to ground with 0.1 µF microwave
chip capacitor.
Do not connect this pin.
Overrange Bit; high indicates analog input exceeds ± FS.
Output Data Voltage Midpoint; approximately equal to (DVCC)/2.
Digital Output Bit (Least Significant Bit); Two’s Complement
Digital Output Bits in Two’s Complement.
Digital Output Bit (Most Significant Bit); Two’s Complement.
Data Ready Output.
D4
GND
D5
D6
DVCC
D8
D7
D10
D9
D12
D11
DRY
D13 (MSB)
PIN CONFIGURATION
52 51 50 49 48 47 46 45 44 43 42 41 40
DVCC 1
39
PIN 1
IDENTIFIER
GND 2
VREF 3
38
36
D1
D0 (LSB)
37
GND 4
ENCODE 5
ENCODE 6
GND 7
D3
D2
35
DMID
AD6644
34
TOP VIEW
(Not to Scale)
33
GND
DVCC
32
OVR
AVCC 9
GND 10
AIN 11
31
DNC
AVCC
AIN 12
GND 13
28
GND
AVCC
27
GND
AVCC 8
30
29
C2
GND
AVCC
GND
C1
GND
AVCC
GND
GND
AVCC
AVCC
GND
AVCC
14 15 16 17 18 19 20 21 22 23 24 25 26
DNC = DO NOT CONNECT
–6–
REV. 0
AD6644
DEFINITIONS OF SPECIFICATIONS
Analog Bandwidth
Minimum Conversion Rate
The analog input frequency at which the spectral power of the
fundamental frequency (as determined by the FFT analysis) is
reduced by 3 dB.
Aperture Delay
The delay between the 50% point of the rising edge of the
ENCODE command and the instant at which the analog input
is sampled.
Aperture Uncertainty (Jitter)
The sample-to-sample variation in aperture delay.
The encode rate at which the SNR of the lowest analog signal
frequency drops by no more than 3 dB below the guaranteed limit.
Maximum Conversion Rate
The encode rate at which parametric testing is performed.
Output Propagation Delay
The delay between a differential crossing of ENCODE and
ENCODE and the time when all output data bits are within
valid logic levels.
Noise (For Any Range Within the ADC)
 FSdBm – SignaldBFS 


10

Differential Analog Input Resistance, Differential Analog Input
Capacitance, and Differential Analog Input Impedance
The real and complex impedances measured at each analog
input port. The resistance is measured statically and the capacitance and differential input impedances are measured with a
network analyzer.
Differential Analog Input Voltage Range
The peak-to-peak differential voltage that must be applied to the
converter to generate a full-scale response. Peak differential voltage
is computed by observing the voltage on a single pin and subtracting the voltage from the other pin, which is 180 degrees out
of phase. Peak-to-peak differential is computed by rotating the
inputs phase 180 degrees and taking the peak measurement again.
The difference is then computed between both peak measurements.
VNOISE = | Z | ×0.001 × 10
Where Z is the input impedance, FS is the full scale of the device
for the frequency in question, SNR is the value for the particular
input level and Signal is the signal level within the ADC reported
in dB below full scale. This value includes both thermal and
quantization noise.
Power Supply Rejection Ratio
The ratio of a change in input offset voltage to a change in power
supply voltage.
Signal-to-Noise-and-Distortion (SINAD)
Differential Nonlinearity
The ratio of the rms signal amplitude (set 1 dB below full scale)
to the rms value of the sum of all other spectral components,
including harmonics, but excluding dc.
The deviation of any code width from an ideal 1 LSB step.
Signal-to-Noise Ratio (Without Harmonics)
Encode Pulsewidth/Duty Cycle
The ratio of the rms signal amplitude (set at 1 dB below full scale)
to the rms value of the sum of all other spectral components,
excluding the first five harmonics and dc.
Pulsewidth high is the minimum amount of time that the
ENCODE pulse should be left in Logic 1 state to achieve rated
performance; pulsewidth low is the minimum time ENCODE
pulse should be left in low state. See timing implications of
changing tENCH in text. At a given clock rate, these specs define
an acceptable ENCODE duty cycle.
Full-Scale Input Power
Expressed in dBm. Computed using the following equation:
Spurious-Free Dynamic Range (SFDR)
The ratio of the rms signal amplitude to the rms value of the peak
spurious spectral component. The peak spurious component may
or may not be a harmonic. May be reported in dBc (i.e., degrades
as signal level is lowered), or dBFS (always related back to converter full scale).
Two-Tone Intermodulation Distortion Rejection
 V Full Scale rms

| Z |Input
= 10 log 
 0.001


2
PowerFull Scale






Harmonic Distortion, 2nd
The ratio of the rms signal amplitude to the rms value of the
second harmonic component, reported in dBc.
Harmonic Distortion, 3rd
The ratio of the rms signal amplitude to the rms value of the
third harmonic component, reported in dBc.
The ratio of the rms value of either input tone to the rms value
of the worst third order intermodulation product; reported in dBc.
Two-Tone SFDR
The ratio of the rms value of either input tone to the rms value
of the peak spurious component. The peak spurious component
may or may not be an IMD product. May be reported in dBc
(i.e., degrades as signal level is lowered), or in dBFS (always
related back to converter full scale).
Worst Other Spur
The ratio of the rms signal amplitude to the rms value of the worst
spurious component (excluding the 2nd and 3rd harmonic)
reported in dBc.
Integral Nonlinearity
The deviation of the transfer function from a reference line
measured in fractions of 1 LSB using a “best straight line”
determined by a least-square curve fit.
REV. 0
–7–
AD6644
EQUIVALENT CIRCUITS
DVCC
VCH AVCC
CURRENT
MIRROR
AIN
BUF
T/H
500⍀
VCL
VREF
BUF
VCH AVCC
DVCC
VREF
500⍀
AIN
D0–D13, OVR, DRY
T/H
BUF
VCL
Figure 2. Analog Input Stage
CURRENT
MIRROR
Figure 5. Digital Output Stage
LOADS
AVCC
AVCC
AVCC
AVCC
10k⍀
AVCC
AVCC
10k⍀
ENCODE
ENCODE
2.4V
VREF
10k⍀
10k⍀
100␮A
LOADS
Figure 3. ENCODE Inputs
Figure 6. 2.4 V Reference
AVCC
DVCC
VREF
AVCC
10k⍀
AVCC
DMID
CURRENT
MIRROR
10k⍀
C1 OR C2
Figure 4. Compensation Pin, C1 or C2
Figure 7. DMID Reference
–8–
REV. 0
Typical Performance Characteristics– AD6644
0
75.0
ENCODE = 65MSPS
AIN = 2.2MHz @ –1dBFS
SNR = 74.5dB
SFDR = 92dBc
–10
–20
–30
ENCODE = 65MSPS, AIN = –1dBFS
TEMP = –25 C, ⴙ25 C, ⴙ85 C
74.5
T = –25 C
–40
74.0
SNR – dB
–50
–60
–70
–80
T = ⴙ85 C
T = ⴙ25 C
73.5
73.0
–90
–100
72.5
–110
–120
–130
0
5
10
15
20
FREQUENCY – MHz
25
72.0
30
5
0
Figure 8. Single Tone at 2.2 MHz
10
15
20
FREQUENCY – MHz
25
30
Figure 11. Noise vs. Analog Frequency (Nyquist)
94
0
ENCODE = 65MSPS
AIN = 15.5MHz @ –1dBFS
SNR = 74dB
SFDR = 90dBc
–20
–30
ENCODE = 65MSPS, AIN = –1dBFS
WORST-CASE HARMONIC – dBc
–10
–40
–50
–60
–70
–80
–90
–100
–110
TEMP = ⴚ25 C, ⴙ25 C, ⴙ85 C
92
90
T = ⴙ25 C
T = ⴚ25 C, ⴙ85 C
88
86
84
82
–120
–130
0
5
10
15
20
FREQUENCY – MHz
25
80
30
5
0
Figure 9. Single Tone at 15.5 MHz
10
15
20
25
ANALOG INPUT FREQUENCY – MHz
30
Figure 12. Harmonics vs. Analog Frequency (Nyquist)
75
0
ENCODE = 65MSPS
AIN = 30MHz @ –1dBFS
SNR = 73.5dB
SFDR = 85dBc
–10
–20
–30
LOW NOISE ANALOG SOURCE
74
73
–40
SNR – dB
–50
–60
–70
–80
–90
72
PHASE NOISE OF ANALOG SOURCE
DEGRADES PERFORMANCE
71
70
–100
–110
69
AIN = –1dBFS
ENCODE = 65MSPS
–120
–130
0
5
10
15
20
FREQUENCY – MHz
25
68
30
0
Figure 10. Single Tone at 30 MHz
REV. 0
10
20
30
40
50
60
70
80
ANALOG FREQUENCY – MHz
90
100
Figure 13. Noise vs. Analog Frequency (IF)
–9–
AD6644
100
0
95
WORST OTHER SPUR
–10
ENCODE = 65MSPS
AIN = –1dBFS
90
HARMONICS – dBc
ENCODE = 65MSPS
AIN = 15MHz,
15.5MHz @ –7dBFS
NO DITHER
–20
–30
–40
85
–50
80
–60
75
–70
–80
70
–90
HARMONICS (2nd, 3rd)
–100
65
–110
60
–120
55
0
10
20
30
40
60
50
70
80
ANALOG FREQUENCY – MHz
90
–130
100
Figure 14. Harmonics vs. Analog Frequency (IF)
10
15
20
FREQUENCY – MHz
25
30
Figure 17. Two Tones at 15 MHz and 15.5 MHz
120
110
WORST-CASE SPURIOUS – dBFS and dBc
WORST-CASE SPURIOUS – dBFS and dBc
5
0
110
dBFS
100
ENCODE = 65MSPS
AIN = 15.5MHz
90
80
dBc
70
60
SFDR = 90dB
REFERENCE LINE
50
40
30
20
10
0
–80
–70
–20
–10
–60
–50
–30
–40
ANALOG INPUT POWER LEVEL – dBFS
dBFS
100
ENCODE = 65MSPS
F1 = 15MHz
F2 = 15.5MHz
90
80
60
SFDR = 90dB
REFERENCE LINE
50
40
30
20
10
0
–77
0
dBc
70
Figure 15. Single Tone SFDR
–57
–47
–37
–67
–27
–17
INPUT POWER LEVEL – (F1 = F2) dBFS
–7
Figure 18. Two-Tone SFDR
100
0
ENCODE = 65MSPS
AIN = 19MHz,
19.5MHz @ –7dBFS
NO DITHER
–20
AIN = 2.2MHz @ –1dBFS
SNR, WORST SPURIOUS – dB and dBc
–10
–30
–40
–50
–60
–70
–80
–90
–100
–110
95
WORST SPUR
90
85
80
75
SNR
70
65
–120
60
–130
0
5
10
15
20
FREQUENCY – MHz
25
30
Figure 16. Two Tones at 19 MHz and 19.5 MHz
0
10
20
40
50
60
70
30
ENCODE FREQUENCY – MHz
80
90
Figure 19. SNR, Worst Spurious vs. Encode
–10–
REV. 0
AD6644
0
0
ENCODE = 65MSPS
AIN = 15.5MHz @ –29.5dBFS
NO DITHER
–10
–20
–20
–30
–30
–40
–40
–50
–50
–60
–60
–70
–70
–80
–80
–90
–90
–100
–100
–110
–110
–120
–120
–130
–130
0
5
10
ENCODE = 65MSPS
AIN = 15.5MHz @ –29.5dBFS
DITHER @ –19dBm
–10
15
20
FREQUENCY – MHz
25
30
0
Figure 20. 1M FFT Without Dither
90
70
60
50
40
SFDR = 90dB
REFERENCE LINE
30
20
10
0
–90
–80
–20 –10
–70 –60
–50
–40
–30
ANALOG INPUT POWER LEVEL – dBFS
SNR, WORST SPURIOUS – dB and dBc
30
ENCODE = 65MSPS
AIN = 15.5MHz
DITHER = –19dBm
70
60
50
SFDR = 100dB
REFERENCE LINE
40
30
SFDR = 90dB
REFERENCE LINE
20
WORST SPUR
ENCODE = 65MSPS
85
30.5MHz
80
SNR
2.2MHz
75
30.5MHz
70
–10.0
5.0
–5.0
10.0
0
ENCODE INPUT POWER – dBm
–80
–60
–20
–70
–50
–40
–30
–10
ANALOG INPUT POWER LEVEL – dBFS
Figure 24. SFDR with Dither
2.2MHz
15.0
Figure 22. SNR, Worst Spurious vs. Clamped Encode
Power (See Figure 25)
REV. 0
80
0
–90
0
95
65
–15.0
25
10
Figure 21. SFDR Without Dither
90
15
20
FREQUENCY – MHz
100
ENCODE = 65MSPS
AIN = 15.5MHz
NO DITHER
WORST-CASE SPURIOUS – dBc
WORST-CASE SPURIOUS – dBc
80
10
Figure 23. 1M FFT with Dither
100
90
5
–11–
0
AD6644
THEORY OF OPERATION
0.1␮F
The AD6644 analog-to-digital converter (ADC) employs a three
stage subrange architecture. This design approach achieves the
required accuracy and speed while maintaining low power and
small die size.
CLOCK
SOURCE
T1–4T
ENCODE
100⍀
AD6644
ENCODE
As shown in the functional block diagram, the AD6644 has
complementary analog input pins, AIN and AIN . Each analog
input is centered at 2.4 V and should swing ± 0.55 V around
this reference (Figure 2). Since AIN and AIN are 180 degrees
out of phase, the differential analog input signal is 2.2 V peakto-peak.
Both analog inputs are buffered prior to the first track-and-hold,
TH1. The high state of the ENCODE pulse places TH1 in hold
mode. The held value of TH1 is applied to the input of a 5-bit
coarse ADC1. The digital output of ADC1 drives a 5-bit digitalto-analog converter, DAC1. DAC1 requires 14 bits of precision
which is achieved through laser trimming. The output of DAC1
is subtracted from the delayed analog signal at the input of TH3
to generate a first residue signal. TH2 provides an analog pipeline delay to compensate for the digital delay of ADC1.
The first residue signal is applied to a second conversion stage
consisting of a 5-bit ADC2, 5-bit DAC2, and pipeline TH4.
The second DAC requires 10 bits of precision which is met by
the process with no trim. The input to TH5 is a second residue
signal generated by subtracting the quantized output of DAC2
from the first residue signal held by TH4. TH5 drives a final
6-bit ADC3.
HSMS2812
DIODES
Figure 25. Crystal Clock Oscillator – Differential Encode
If a low jitter ECL/PECL clock is available, another option is to
ac-couple a differential ECL/PECL signal to the encode input pins
as shown below. A device that offers excellent jitter performance
is the MC100LVEL16 (or same family) from Motorola.
VT
0.1␮F
ENCODE
ECL/
PECL
AD6644
0.1␮F
ENCODE
VT
Figure 26. Differential ECL for Encode
Analog Input
As with most new high-speed, high dynamic range analog-todigital converters, the analog input to the AD6644 is differential.
Differential inputs allow much improvement in performance
on-chip as signals are processed through the analog stages. Most
of the improvement is a result of differential analog stages having
high rejection of even order harmonics. There are also benefits
at the PCB level. First, differential inputs have high commonmode rejection to stray signals such as ground and power noise.
Also, they provide good rejection to common-mode signals such as
local oscillator feedthrough.
The digital outputs from ADC1, ADC2, and ADC3 are added
together and corrected in the digital error correction logic to
generate the final output data. The result is a 14-bit parallel
digital CMOS-compatible word, coded as two's complement.
APPLYING THE AD6644
Encoding the AD6644
The AD6644 encode signal must be a high quality, extremely low
phase noise source to prevent degradation of performance. Maintaining 14-bit accuracy places a premium on encode clock phase
noise. SNR performance can easily degrade by 3 dB to 4 dB
with 70 MHz input signals when using a high-jitter clock source.
See Analog Devices’ Application Note AN-501, “Aperture Uncertainty and ADC System Performance” for complete details.
For optimum performance, the AD6644 must be clocked
differentially. The encode signal is usually ac-coupled into the
ENCODE and ENCODE pins via a transformer or capacitors.
These pins are biased internally and require no additional bias.
Shown below is one preferred method for clocking the AD6644.
The clock source (low jitter) is converted from single-ended to
differential using an RF transformer. The back-to-back Schottky
diodes across the transformer secondary limit clock excursions
into the AD6644 to approximately 0.8 V p-p differential. This
helps prevent the large voltage swings of the clock from feeding
through to the other portions of the AD6644, and limits the noise
presented to the ENCODE inputs. A crystal clock oscillator can
also be used to drive the RF transformer if an appropriate limiting
resistor (typically 100 Ω) is placed in the series with the primary.
The AD6644 input voltage range is offset from ground by 2.4 V.
Each analog input connects through a 500 Ω resistor to a 2.4 V
bias voltage and to the input of a differential buffer (Figure 2). The
resistor network on the input properly biases the followers for maximum linearity and range. Therefore, the analog source driving the
AD6644 should be ac-coupled to the input pins. Since the differential input impedance of the AD6644 is 1 kΩ, the analog input
power requirement is only –2 dBm, simplifying the driver amplifier
in many cases. To take full advantage of this high-input impedance, a 20:1 transformer would be required. This is a large ratio
and could result in unsatisfactory performance. In this case, a
lower step-up ratio could be used. The recommended method for
driving the analog input of the AD6644 is to use a 4:1 RF transformer. For example, if RT were set to 60.4 Ω and RS were set
to 25 Ω, along with a 4:1 transformer, the input would match
to a 50 Ω source with a full-scale drive of 4.8 dBm. Series resistors (RS) on the secondary side of the transformer should be
used to isolate the transformer from A/D. This will limit the
amount of dynamic current from the A/D flowing back into
the secondary of the transformer. The terminating resistor (RT)
should be placed on the primary side of the transformer.
ANALOG INPUT
SIGNAL
T1–4T
RS
AIN
RT
AD6644
RS
AIN
0.1␮F
Figure 27. Transformer-Coupled Analog Input Circuit
–12–
REV. 0
AD6644
In applications where dc-coupling is required, a new differential
output op amp from Analog Devices, the AD8138, can be used
to drive the AD6644 (Figure 28). The AD8138 op amp provides
single-ended-to-differential conversion, which reduces overall
system cost and minimizes layout requirements.
CF
499⍀
VIN
0.1␮F
25⍀
VOCM
AD8138
499⍀
25⍀
AIN
AD6644
AIN
Care should be taken when routing the digital output traces.
To prevent coupling through the digital outputs into the analog
portion of the AD6644, minimal capacitive loading should be
placed on these outputs. It is recommended that a fan-out of
only one gate be used for all AD6644 digital outputs.
The layout of the Encode circuit is equally critical. Any noise
received on this circuitry will result in corruption in the digitization process and lower overall performance. The Encode clock
must be isolated from the digital outputs and the analog inputs.
5V
499⍀
tion of high frequency, high resolution design practices. All of
the digital outputs are segregated to two sides of the chip, with
the inputs on the opposite side for isolation purposes.
DIGITAL
OUTPUTS
VREF
Jitter Considerations
The signal-to-noise ratio (SNR) for an ADC can be predicted.
When normalized to ADC codes, Equation 1 accurately predicts
the SNR based on three terms. These are jitter, average DNL
error, and thermal noise. Each of these terms contributes to the
noise within the converter.
499⍀
CF
Figure 28. DC-Coupled Analog Input Circuit
Power Supplies
Care should be taken when selecting a power source. Linear
supplies are strongly recommended. Switching supplies tend to
have radiated components that may be “received” by the AD6644.
Each of the power supply pins should be decoupled as closely to
the package as possible using 0.1 µF chip capacitors.
1/ 2
2
2

 
V
(1 + ε ) 
SNR = –20 × log   N  + (2 × π × f ANALOG × t J RMS )2 +  NOISEN RMS  
 2 
2
 



Output Loading
Care must be taken when designing the data receivers for the
AD6644. It is recommended that the digital outputs drive a
series resistor (e.g. 100 Ω) followed by a gate like 74LCX574.
To minimize capacitive loading, there should only be one gate
on each output pin. An example of this is shown in the evaluation
board schematic shown in Figure 30. The digital outputs of the
AD6644 have a constant output slew rate of 1 V/ns. A typical
CMOS gate combined with a PCB trace will have a load of
approximately 10 pF. Therefore, as each bit switches, 10 mA
(10 pF ⫻ 1 V ⫼ 1 ns) of dynamic current per bit will flow in or out
of the device. A full scale transition can cause up to 140 mA
(14 bits ⫻ 10 mA/bit) of current to flow through the output stages.
The series resistors should be placed as close to the AD6644 as
possible to limit the amount of current that can flow into the output stage. These switching currents are confined between ground
and the DVCC pin. Standard TTL gates should be avoided since
they can appreciably add to the dynamic switching currents of
the AD6644. It should also be noted that extra capacitive loading
will increase output timing and invalidate timing specifications.
Digital output timing is guaranteed with 10 pF loads.
fANALOG
= analog input frequency.
tJ RMS
= rms jitter of the encode (rms sum of encode
source and internal encode circuitry).
ε
= average DNL of the ADC (typically 0.41 LSB).
N
= Number of bits in the ADC.
VNOISE RMS = V rms thermal noise referred to the analog input
of the ADC (typically 2.5 LSB).
For a 14-bit analog-to-digital converter like the AD6644, aperture jitter can greatly affect the SNR performance as the analog
frequency is increased. The chart below shows a family of curves
that demonstrates the expected SNR performance of the AD6644
as jitter increases. The chart is derived from the above equation.
For a complete discussion of aperture jitter, please consult
Analog Devices’ Application Note AN-501, “Aperture
Uncertainty and ADC System Performance.”
Layout Information
The schematic of the evaluation board (Figure 30) represents a
typical implementation of the AD6644. A multilayer board is
recommended to achieve the best results. It is highly recommended that high-quality, ceramic chip capacitors be used to
decouple each supply pin to ground directly at the device. The
pinout of the AD6644 facilitates ease of use in the implementaREV. 0
80
AIN = 30MHz
AIN = 70MHz
75
SNR – dB
The AD6644 has separate digital and analog power supply pins.
The analog supplies are denoted AVCC and the digital supply
pins are denoted DVCC. AVCC and DVCC should be separate
power supplies. This is because the fast digital output swings
can couple switching current back into the analog supplies. Note
that AVCC must be held within 5% of 5 V. The AD6644 is specified for DVCC = 3.3 V as this is a common supply for digital ASICs.
(1)
70
AIN = 110MHz
65
AIN = 150MHz
60
AIN = 190MHz
55
0
0.1
0.2
0.3
0.4
JITTER – ps
Figure 29. SNR vs. Jitter
–13–
0.5
0.6
AD6644
EVALUATION BOARD
The evaluation board for the AD6644 is straightforward,
containing all required circuitry for evaluating the device. The
only external connections required are power supplies, clock,
and the analog inputs. The evaluation board includes the option
for an onboard clock oscillator for ENCODE.
Power to the analog supply pins of the AD6644 is connected via
the power terminal block (PCTB2). Power for the digital interface
is supplied via pin 1 of J6. The J2 connector mates directly with
SoftCell Receive Signal Processor (AD6620, AD6624) evaluation
boards, allowing complete evaluation of system performance.
The analog input is connected via a BNC connector AIN, which
is transformer-coupled to the AD6644 inputs. The transformer
has a turns ratio of 1:4 to reduce the amount of input power
required to drive the AD6644.
The Encode signal may be generated using an onboard crystal
oscillator, U5. The on-board oscillator may be replaced by an
external encode source via the SMA connector labeled OPT_CLK
or BNC connector labeled ENCODE. If an external source is
used, it must be a high-quality and very low-phase noise source.
The AD6644 output data is latched using 74LCX574 (U7, U2)
latches. The clock for these latches is determined by selecting
jumper E3–E4 or E4–E5. E3 to E5 is a just a gate delayed version of the clock, while connecting E4 to E5 utilizes the Data
Ready of the AD6644 to latch the output data. A clock is also
distributed with the output data (J2) that is labeled BUFLAT
(Pin 19 and 20, J2).
AD6644ST/PCB Bill of Material
Item
Quantity
Reference
Description
1
2
2
19
Tantalum Chip Capacitor 10 µF
Ceramic Chip Capacitor 0508, 0.1 µF
3
4
5
6
7
8
9
10
11
12
13
8
1
1
4
2
1
1
2
1
1
4
C1, C2
C3, C7, C8, C9, C10, C11, C16, C30, C31,
C32, C4, C22, C23, C24, C25, C26, C27,
C28, C29
C12, C13, C14, C17, C18, C19, C20, C21
CR1
E3, E4, E5
F1, F2, F3, F4
J1, J6
J2
J3
J4, J5
R1
R2
R3, R4, R5, R8
14
15
16
17
18
2
1
1
1
30
19
20
21
22
2
1
2
1
R6, R7
R9
R10
R35
R36, R37, R38, R39, R40, R41, R42, R43,
R44, R45, R46, R47, R48, R49, R50, R51,
R52, R53, R54, R55, R56, R57, R58, R59,
R60, R61, R62, R63, R64, R65
T2, T3
U1
U2, U7
U3
23
24
2
1
U4, U6
U5
–14–
Ceramic Chip Capacitor 0508, 0.01 µF
HSMS2812 Surface Mount Diode
3-Pin Header
Ferrite (Optional)
PCTB2
50-Pin Double Row Header
SMA Connector
BNC Connector
Surface-Mount Resistor 1206, 100 Ω
Surface-Mount Resistor 1206, 60.4 Ω
Surface-Mount Resistor 0805, 499 Ω (Optional,
DC-Coupling Only)
Surface-Mount Resistor 0805, 25 Ω
Surface-Mount Resistor 0805, 348 Ω
Surface-Mount Resistor 0805, 615 Ω
Surface-Mount Resistor 0805, 49.9 Ω
Surface-Mount Resistor 0402, 100 Ω
Surface-Mount Transformer Mini-Circuits T4–1, 1:4 Ratio
AD6644AST 14-Bit 65 MSPS A/D Converter
74LCX574 Octal Latch
AD8138 Single-to-Differential Amplifier (Optional – DC
Coupling Only)
NC7SZ32 Two Input OR Gate
CTS Reeves Full-Size MX045 Crystal Clock Oscillator
REV. 0
K1115
2
AIN
J5
2
ENC
J4
1
1
8
Figure 30. AD6644ST/PCB Schematic (GS02357D Schematic)
R2
60.4⍀
R1
100⍀
C3
100nF
T2
6
4
1
3P3VD
R8
499⍀
DR_OUT
6
3
T1–4T
4
1
2
1:4
5
6
T3
4
5
C30
100nF
CR1
VREF
R4
499⍀
2
Vⴙ
3
V–
GND
1
8
2
U3
R5
499⍀
5VA
C27
100nF
1
3
ENC
ENC
E5
E3
R7
25⍀
VREF
E4
C32
100NF
OPT_LAT
NC7SZ32
4
HSMS2812
C28
100nF
GND
3
AD8138
R3
499⍀
C29
100nF
1:4
1
2
T1–4T 3
R9
348⍀
2
ⴙV
R10
615⍀ U4 5
3P3V
5VA
R6
25⍀
GND
5VA
5VA
GND
AIN
AIN
GND
13
12
11
10
9
8
7
6
5
GND 4
3
3P3V 1
GND 2
U1
BUFLAT
GND
AIN
AIN
AD6644ST
GND
GND
GND
AVCC
DNC
AVCC
OVR
DVCC
14 15 16 17 18 19 20 21 22 23 24 25 26
AVCC
GND
AVCC
GND
ENC
ENC
DMID
D1
D0
VREF
GND
D2
D3
GND
DVCC
52 51 50 49 48 47 46 45 44 43 42 41 40
NOTE: THE DOTTED LINE REPRESENTS AN OPTIONAL ANALOG DRIVE INPUT
C4
100nF
R35
49.9⍀
GND OUT
OPT_CLK
J3
7
SMA
2
DR_OUT
DRY
AVCC
1
D13
GND
C22
100nF
AVCC
14
GND
VCC
AVCC
NC
D12
D11
D10
D9
D8
GND
C1
5VA
GND
5VA
GND
5VA
GND
1
GND
AVCC
F3
FERRITE
GND
D5
U5
3P3V
GND
D7
D6
DVCC
GND
C2
GND
3P3V
PCTB2
1
2
J1
C8
100nF
GND
5VA
GND
BNC
BNC
D4
AVCC
–15–
30
5VA
29 GND
28 5VA
27 GND
31
32
PREF
34 GND
33 3P3V
35
36
37
38
39
1
C9
100nF
2
F1
FERRITE
C1
10␮F
GND
C7
100nF
GND
5VA
REV. 0
C10
100nF
C2
10␮F
R43
R42
R41
R40
R39
R38
R36
R45
R46
R47
R48
R49
R50
R51
R44
C11
100nF
C16
100nF
GND 1
100⍀ 2
100⍀ 3
100⍀ 4
100⍀ 5
100⍀ 6
100⍀ 7
100⍀ 8
GND 9
GND 10
GND 1
100⍀ 2
100⍀ 3
100⍀ 4
100⍀ 5
100⍀ 6
100⍀ 7
100⍀ 8
100⍀ 9
GND 10
U7
20
19
19
20
C12
10nF
C17
10nF
C13
10nF
C18
10nF
74LCX574
Q0
18
Q1
17
D2
Q2
16
Q3
D3
15
D4
Q4
14
D5
Q5
13
D6
Q6
12
D7
Q7
11
GND CLOCK
D0
D1
OUT_EN VCC
U2
GND
3
ⴙV
100⍀
100⍀
100⍀
100⍀
100⍀
100⍀
100⍀
H2
H3
H4
4
C20
10nF
C14
10nF
1
2
F4
FERRITE
C19
10nF
C23
100nF
B05
B04
B03
B02
B01
B00
GND
GND
GND
GND
GND
GND
OVR
GND
B13
B12
B11
B10
B09
B08
B07
B06
GND
20
28
30
27
29
38
37
48
50
C25
100nF
3P3V
C26
100nF
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
3P3VD
HEADR50
46
47
49
44
42
45
43
41
40
36
35
39
34
33
32
26
25
31
24
23
22
18
19
21
16
17
14
12
15
13
11
8
10
9
6
7
5
2
4
3
J2
2
1
1
F2
FERRITE
C24
100nF
5VA
PCTB2
1
C21
10nF
H1
MOUNTING HOLES
BUFLAT
3P3VD
R63
R62
R61
R60
R59
R58
R37
NC7SZ32
2
1
U6 5
3P3VD
3P3VD
R65
100⍀
100⍀
R52
R53
100⍀
R54
100⍀
100⍀
R55
100⍀
R56
100⍀
R57
R64
100⍀
BUFLAT
BUFLAT
74LCX574
Q0
18
Q1
17
D2
Q2
16
D3
Q3
15
D4
Q4
14
D5
Q5
13
D6
Q6
12
D7
Q7
11
GND CLOCK
D0
D1
OUT_EN VCC
J6
2
AD6644
AD6644
Figure 31. AD6644ST/PCB Top Side Silkscreen
Figure 32. AD6644ST/PCB Top Side Copper
–16–
REV. 0
AD6644
Figure 33. AD6644ST/PCB Bottom Side Silkscreen
Figure 34. AD6644ST/PCB Bottom Side Copper
REV. 0
–17–
AD6644
Figure 35. AD6644ST/PCB Ground Layer – Layers 2 and 5 (Negative)
Figure 36. AD6644ST/PCB “Split” Power Layer – Layers 3 and 4 (Negative)
–18–
REV. 0
AD6644
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
0.063 (1.60)
MAX
0.472 (12.00) SQ
0.030 (0.75)
0.018 (0.45)
39
27
40
26
SEATING
PLANE
0.394
(10.0)
SQ
TOP VIEW
(PINS DOWN)
14
52
0.006 (0.15)
0.002 (0.05)
1
13
0.026 (0.65)
BSC
0.015 (0.38)
0.009 (0.22)
PRINTED IN U.S.A.
0.057 (1.45)
0.053 (1.35)
C3812–5–4/00 (rev. 0)
52-Terminal Plastic Low Profile Quad Flatpack
(ST-52)
REV. 0
–19–