Datasheet AD9725 Datasheet (Analog Devices)

14-Bit, 600+ MSPS

Preliminary Technical Data

FEATURES

600+ MSPS DAC update rate
16/14/12/10-bit resolution family
LVDS interface with built-in 100-termination resistors
Single data rate and double data rate capability
Excellent dynamic performance
SFDR = 63 dBc at 140 MHz
IMD = 73 dBc at 140 MHz
Differential current outputs: 2 mA to 20 mA
–40°C to +85°C temperature range operation
On-chip 1.20 V reference
Package: 80-lead thermally-enhanced TQFP
Versatile clock and data interface

APPLICATIONS

Instrumentation and test
Wideband communications systems
Point-to-point wireless
LMDS
PA linearization
High resolution displays

PRODUCT DESCRIPTION

The AD9725 is a 14-bit digital-to-analog converter (DAC) that
utilizes an LVDS interface to achieve conversion rates in excess
of 600 MSPS. It is in a family of pin compatible converters that
offers selection of 10-bit, 12-bit, 14-bit, and 16-bit resolution
grades. All of the devices share the same interface options, small
outline package, and pinout, providing an upward or downward
component selection path based on performance, resolution
and cost.

D/A Converter

AD9725

FUNCTIONAL BLOCK DIAGRAM

CALIBRATION REFERENCE

DB[13:0]+

DB[13:0]–

DDR

DATACLK_IN+

DATACLK_IN–

REXT

DATACLK_OUT+

DATACLK_OUT–

CLK+

CLK–

DATA

FORMATTER

DATA CLOCK
FORMATTER

DATA SYNC.

CLOCK DISTRIBUTIO N

AND CONTROL

14-BIT

DAC

SPI

Figure 1

PRODUCT HIGHLIGHTS

Ultralow noise and intermodulation distortion (IMD) enable
high quality waveform synthesis at intermediate frequencies up
to 200 MHz.

LVDS receivers support SDR or DDR modes, with the maxi­mum conversion rate exceeding 600 MSPS.

Manufactured on a CMOS process, the AD9725 uses a proprie­tary switching technique that enhances dynamic performance.

The current output of the AD9725 can be easily configured for
various single-ended or differential circuit topologies.

FSADJ

REFIO

IOUTA

IOUTB

SDIO

SDO/SYNC _ALRM

CSB

SCLK/SYN C_UPD

RESET

04540-0-001

Rev. PrA

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
registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

AD9725

TABLE OF CONTENTS

Preliminary Technical Data

Specifications..................................................................................... 3

DC Specifications ......................................................................... 3

AC Specifications.......................................................................... 4

Digital Specifications ................................................................... 5

Digital Timing Information........................................................ 5

Absolute Maximum Ratings............................................................ 6

Pin Configuration and Function Description .............................. 7

Serial Port Interface Register Maps................................................ 9

Definitions....................................................................................... 11

Typical Performance Curves......................................................... 12

Theory of Operation ...................................................................... 13

LVDS Inputs................................................................................ 13

Data Synchronization Circuitry............................................... 13

Internal Reference and Full-Scale Output Current................ 13

Analog Output............................................................................ 14

SPI Port Control......................................................................... 14

General Operation of the Serial Port Interface ...................... 14

Instruction Byte.......................................................................... 14

Serial Port Interface Pin Description....................................... 14

Notes on Serial Port Operation................................................ 15

Outline Dimension......................................................................... 16

Ordering Guide .......................................................................... 16

Rev. PrA | Page 2 of 16

Preliminary Technical Data

AD9725

SPECIFICATIONS

DC SPECIFICATIONS

Table 1. T
otherwise noted. Specifications subject to change without notice

Parameter Min Typ Max Unit

Resolution 14 Bits

DC Accuracy
Integral Nonlinearity ±1.5 LSB
Differential Nonlinearity ±0.75 LSB

Analog Output

Offset Error –1 1 %FSR
Gain Error %FSR
Full Scale Output Current 20 1.26 mA
Output Compliance Range 1.14 V
Output Resistance TBD 1.25 kW
Output Capacitance 0.1 TBD pF

Reference Output

Reference Voltage 1.2 V
Reference Output Current 100 nA

Reference Input

Reference Input Compliance Range V
Reference Input Resistance 5 kW
Small Signal Bandwidth 0.5 MHz

Temperature Coefficients

Offset Drift TBD ppm of FSR/ºC
Gain Drift (With Internal Reference) TBD ppm of FSR/ºC
Reference Voltage Drift TBD ppm/ºC

Power Supply1

AVDD1, AVDD2

Voltage Range 3.3 V
Analog Supply Current (I

ADVDD

Voltage Range 2.5 V

ACVDD mA

Voltage Range 2.5 V
Analog Supply Current ( I

CLKVDD

Voltage Range 2.5 V
Clock Supply Current (I

DVDD

Voltage Range 2.5 V
Digital Supply Current (I

DBVDD

Voltage Range 3.3 V
Digital Supply Current (I
Nominal Power Dissipation (P
Nominal Power Dissipation (P

1

Supply currents measured under the following conditions: f

2

Power dissipation measured under the following conditions: f

3

Power dissipation measured under the following conditions: f

MIN

to T

, AVDD1, AVDD2, DBVDD = 3.3 V, ADVDD, ACVDD, CLKVDD, DVDD = 2.5 V, I

MAX

+ I

AVDD1

ADVDD

) 20 mA

CLKVDD

) 69 mA

DVDD

DBVDD

) 51 mA

AVDD2

+ I

) 9 mA

ACVDD

) 20 mA

)2 479 mW

DIS

)3 1000 mW

DIS

= 200 MSPS, f

DAC

= 200 MSPS, f

DAC

= 600 MSPS, f

DAC

= 11 MHz, nominal power supply voltages

OUT

= 11 MHz, nominal power supply voltages

OUT

= 111 MHz, nominal power supply voltages

OUT

= 20 mA, unless

OUTFS

Rev. PrA | Page 3 of 16

AD9725

Preliminary Technical Data

AC SPECIFICATIONS

Table 2. T
otherwise noted. Specifications subject to change without notice.

Parameter Typ Unit

Dynamic Performance

Max DAC Output Update Rate (DDR) 600 MSPS
Max DAC Output Update Rate (SDR) 440 MSPS

AC Linearity

Spurious Free Dynamic Range (SFDR) to Nyquist (f

f
f
f
f
f
f
f
f
f

Two Tone IMD to Nyquist (f

f
f
f
f
f
f
f
f
f

Noise Spectral Density (NSD)

f
f
f
f

CDMA2000 Adjacent Channel Leakage Ratio (ACLR)

f
f
f

WCDMA Adjacent Channel Leakage Ratio (ACLR), Single Carrier

f
f
f
f

WCDMA Adjacent Channel Leakage Ratio (ACLR), Four Carrier

f
f

to T

MIN

= 260 MSPS, f

DATA

= 260 MSPS, f

DATA

= 260 MSPS, f

DATA

= 400 MSPS, f

DATA

= 400 MSPS, f

DATA

= 400 MSPS, f

DATA

= 600 MSPS, f

DATA

= 600 MSPS, f

DATA

= 600 MSPS, f

DATA

= 300 MSPS, f

DATA

= 300 MSPS, f

DATA

= 300 MSPS, f

DATA

= 500 MSPS, f

DATA

= 500 MSPS, f

DATA

= 500 MSPS, f

DATA

= 600 MSPS, f

DATA

= 600 MSPS, f

DATA

= 600 MSPS, f

DATA

= 500 MSPS, f

DATA

= 500 MSPS, f

DATA

= 500 MSPS, f

DATA

= 500 MSPS, f

DATA

= 245.76 MSPS, IF = 61.44 MHz TBD dBc

DATA

= 491.52 MSPS, IF = 122.88 MHz TBD dBc

DATA

= 491.52 MSPS, IF = 190 MHz TBD dBc

DATA

= 184.32 MSPS, IF = 61.44 MHz 79 dBc

DATA

= 245.76 MSPS, IF= 61.44 MHz 79 dBc

DATA

= 491.52 MSPS, IF = 122.88 MHz 76 dBc

DATA

= 491.52 MSPS, IF = 190 MHz 74 dBc

DATA

= 184.32 MSPS, IF = 61.44 MHz, 69 dBc

DATA

= 368.64 MSPS, IF = 92.16 MHz 67 dBc

DATA

, AVDD1, AVDD2, DBVDD = 3.3 V, ADVDD, ACVDD, CLKVDD, DVDD = 2.5 V, I

MAZ

= 0 dBFS)

OUT

= 20 MHz 71 dBc

OUT

= 70 MHz 68 dBc

OUT

= 120 MHz 68 dBc

OUT

= 20 MHz 72 dBc

OUT

= 70 MHz 66 dBc

OUT

= 140 MHz 60 dBc

OUT

= 20 MHz TBD dBc

OUT

= 125 MHz TBD dBc

OUT

= 250 MHz TBD dBc

OUT

= f

OUT1

= 26 MHz, f

OUT1

= 100 MHz, f

OUT1

= 126 MHz, f

OUT1

= 26 MHz, f

OUT1

= 100 MHz, f

OUT1

= 126 MHz, f

OUT1

= 26 MHz, f

OUT1

= 126 MHz, f

OUT1

= 250 MHz, f

OUT1

= 20 MHz, 0 dBFS –162 dBm/Hz

OUT

= 20 MHz, –12 dBFS –165 dBm/Hz

OUT

= 120 MHz, 0 dBFS –151 dBm/Hz

OUT

= 120 MHz, –12 dBFS –161 dBm/Hz

OUT

= –6 dBFS)

OUT2

= 27 MHz 89 dBc

OUT2

= 101 MHz 80 dBc

OUT2

= 127 MHz 80 dBc

OUT2

= 27 MHz 90 dBc

OUT2

= 101 MHz 78 dBc

OUT2

= 127 MHz 76 dBc

OUT2

= 27 MHz TBD dBc

OUT2

= 127 MHz TBD dBc

OUT2

= 251 MHz TBD dBc

OUT2

OUTFS

= 20 mA, unless

Rev. PrA | Page 4 of 16

Preliminary Technical Data

T

AD9725

DIGITAL SPECIFICATIONS

Table 3. T
otherwise noted. Specifications subject to change without notice.

Parameter Conditions Min Typ Max Unit

Digital Inputs VCM = 0.875 V to 1.575 V

Differential Logic ‘1’

Differential Logic ‘0’ –0.6 –0.1 V
Logic ‘1’ current 3.5 mA
Logic ‘0’ current 3.5 mA
Differential Input Resistance 100 W
Differential Input Capacitance 3 pF
Data Setup Time (tDS) 0.9 ns
Data Hold Time (tDH) –0.3 ns
Data Clock Output Delay ( t

Serial Control Bus

Maximum SCLK Frequency (fSCLK) 15 MHz
Minimum Clock Pulse Width High (t
Minimum Clock Pulse Width Low (t
Maximum Clock Rise/Fall Time 1 ms
Minimum Data/Chip Select Set Up Time (tDS) 25 ns
Minimum Data Hold Time (tDH) 0 ns
Maximum Data Valid Time (tDV) 30 ns
RESET Pulse Width 1.5 ns

Inputs (SDI, SDIO, SCLK, CSB)

Logic ‘1’ Voltage 2.1 3 V
Logic ‘0’ Voltage 0 0.9 V
Logic ‘1’ Current –10 +10 µA
Logic ‘0’ Current –10 +10 µA
Input Capacitance 5 pF

SDIO Output

Logic ‘1’ Voltage DRVDD–0.6 V
Logic ‘0’ Voltage 0.4 V
Logic ‘1’ Current 30 50 mA
Logic ‘0’ Current 30 50 mA

MIN

to T

, AVDD1, AVDD2, DBVDD = 3.3 V, ADVDD, ACVDD, CLKVDD, DVDD = 2.5 V , I

MAX

(put into footnote, and delete

0.1 0.6 V

column?)

) 2.4 ns

DCO

) 30 ns

PWH

) 30 ns

PWL

= 20 mA, unless

OUTFS

DIGITAL TIMING INFORMATION

t

DCO

CLK

DATACLK_OU

DB[15:0]

DATACLK_IN

Figure 2. Single Datarate (SDR) Mode

t

DCO

CLK

DATACLK_OUT

DB[15:0]

DATACLK_IN

t

t

DH

DS

04540-0-002

Rev. PrA | Page 5 of 16

t

t

DS

Figure 3. Double Datarate (DDR) Mode

t

DH

DS

t

DH

04540-0-003

AD9725

Preliminary Technical Data

ABSOLUTE MAXIMUM RATINGS

Parameter With Respect to Min Max Unit

AVDD1, AVDD2, DBVDD ACOM1, ACOM2, DBCOM –0.3 TBD V
ADVDD, ACVDD, CLKVDD, DVDD

ACOM1, ACOM2, DBCOM ACOM1, ACOM2, DBCOM –0.3 +0.3 V
ADCOM, ACCOM, CLKCOM, DCOM

REFIO, FSDAJ ACOM1 –0.3 AVDD1 + 0.3 V
IOUTA, IOUTB ACOM1 –1 AVDD1 + 0.3 V
DB0-DB15, DB0-DB15 DBCOM –0.3 DBVDD + 0.3 V
DATACLKOUT, DATACLKOUT DBCOM –0.3 DBVDD + 0.3 V
REXT, CLK+, CLK- CLKCOM –0.3 CLKVDD + 0.3 V
SDO/SYNC_ALRM, SDIO, CSB DBCOM –0.3 DBVDD + 0.3 V
SCLK/SYNC, RESET DBCOM –0.3 DBVDD + 0.3 V
DDR, SPI_DIS ADCOM –0.3 ADVDD + 0.3 V

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only;
functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not
implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

ADCOM, ACCOM, CLKCOM,
DCOM

ADCOM, ACCOM, CLKCOM,
DCOM

–0.3 TBD V

–0.3 +0.3 V

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 this product 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. PrA | Page 6 of 16

Preliminary Technical Data

PIN CONFIGURATION AND FUNCTION DESCRIPTION

AD9725

CLKVDD

REXT
CLKVDD
CLKGND

CLK+

CLK–
CLKGND

DGND

DVDD
DB13+
DB13–
DB12+
DB12–
DB11+
DB11–
DB10+
DB10–
DB9+
DB9–

DBVDD

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

SPI_DIS

ADGND

ADVDD

PIN 1
IDENTIFIER

DB8–

DB8+

DBGND

ACGND

ACVDD

DB7–

DB7+

AVDD2

DB6+

IOUTA

AGND1

AVDD1

AGND2

AD9725

TOP VIEW

(Not to Scale)

DB6–

DBVDD

DATACLK_OUT–

DATACLK_OUT+

IOUTB

AGND1

AVDD1

DBGND

DATACLK_IN–

DATACLK_IN+

AGND2

AVDD2

DB5–

DB5+

ACGND

ACVDD

DB4–

DB4+

ADGND

ADVDD

6162636465666768697071727374757677787980

4039383736353433323130292827262524232221

DB3–

DB3+

DDR

FSADJ

60

REFIO

59

RESET

58

CSB

57

SCLK/SYNC_UPD

56

SDIO

55

SDO/SYNC_ALRM

54

DGND

53

DVDD

52

NC

51

NC

50

NC

49

NC

48

DB0–

47

DB0+

46

DB1–

45

DB1+

44

DB2–

43

DB2+

42

DBGND

41

DBVDD

04540-0-012

Figure 4. Pin Configuration

Table 4. Pin Function Description

Pin
No.

Name Description Pin

Name Description

No.

1 CLKVDD Clock Supply Voltage 41 DBGND Digital Data Supply Common
2 REXT

Bias Resistor. Sets DATACLK_OUT drive

42 DB2+

Digital Input Bit 2–True

strength. Nominally 1 kΩ to DBGND
3 CLKVDD Clock Supply Voltage 43 DB2– Digital Input Bit 2–Complement
4 CLKGND Clock Supply Common 44 DB1+ Digital Input Bit 1–True
5 CLK+ Clock Input–True 45 DB1– Digital Input Bit 1–Complement
6 CLK– Clock Input–Complement 46 DB0+ Digital Input Bit 0–True
7 CLKGND Clock Supply Common 47 DB0– Digital Input Bit 0–Complement
8 DGND Digital Common 48 NC No Connect
9 DVDD Digital Supply Voltage 49 NC No Connect
10 DB13+ Digital Input Bit 13–True 50 NC No Connect
11 DB13– Digital Input Bit 13–Complement 51 NC No Connect
12 DB12+ Digital Input Bit 12–True 52 DVDD Digital Supply Voltage
13 DB12– Digital Input Bit 12–Complement 53 DGND Digital Common
14 DB11+ Digital Input Bit 11–True 54 SDO/SYNC_ALRM

SPI_DIS = 1: Data/Clock

Synchronization Alarm
15 DB11– Digital Input Bit 11–Complement 55 SDIO SPI Serial Data Input/Output
16 DB10+ Digital Input Bit 10–True 56 SCLK/SYNC_UPD

SPI_DIS = 1: Data/Clock

Synchronization Update Required
17 DB10– Digital Input Bit 10–Complement 57 CSB SPI Chip Select (Active Low)
18 DB9+ Digital Input Bit 9–True 58 RESET Hardware Reset
19 DB9– Digital Input Bit 9–Complement 59 REFIO Reference Output, 1.2 V Nominal
20 DBVDD Digital Data Supply Voltage 60 FSADJ Full-Scale Current Adjust

Rev. PrA | Page 7 of 16

AD9725

Pin
No.

21 DBGND Digital Data Supply Common 61 DDR

22 DB8+ Digital Input Bit 8–True 62 ADVDD Analog Supply Voltage
23 DB8– Digital Input Bit 8–Complement 63 ADGND Analog Supply Common
24 DB7+ Digital Input Bit 7–True 64 ACVDD Analog Supply Voltage
25 DB7– Digital Input Bit 7–Complement 65 ACGND Analog Supply Common
26 DB6+ Digital Input Bit 6–True 66 AVDD2 Analog Supply Voltage
27 DB6– Digital Input Bit 6–Complement 67 AGND2 Analog Supply Common
28 DATACLK_OUT+ Data Clock Output–True 68 AVDD1 Analog Supply Voltage
29 DATACLK_OUT– Data Clock Output–Complement 69 AGND1 Analog Supply Common
30 DBVDD Digital Data Supply Voltage 70 IOUTB DAC Current Output–Complement
31 DBGND Digital Data Supply Common 71 IOUTA DAC Current Output–True
32 DATACLK_IN+ Data Clock Input–True 72 AGND1 Analog Supply Common
33 DATACLK_IN– Data Clock Input–Complement 73 AVDD1 Analog Supply Voltage
34 DB5+ Digital Input Bit 5–True 74 AGND2 Analog Supply Common
35 DB5– Digital Input Bit 5–Complement 75 AVDD2 Analog Supply Voltage
36 DB4+ Digital Input Bit 4–True 76 ACGND Analog Supply Common
37 DB4– Digital Input Bit 4–Complement 77 ACVDD Analog Supply Voltage
38 DB3+ Digital Input Bit 3–True 78 ADGND Analog Supply Common
39 DB3– Digital Input Bit 3–Complement 79 ADVDD Analog Supply Voltage
40 DBVDD Digital Data Supply Voltage 80 SPI_DIS SPI Disable (Active High)

Name Description Pin

No.

Name Description

Preliminary Technical Data

SPI_DIS = 1: Double Data Rate Mode
(Active High)

Rev. PrA | Page 8 of 16

Preliminary Technical Data

AD9725

SERIAL PORT INTERFACE REGISTER MAPS

Table 5. Mode Control via SPI Port

Address Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

COMMS 00 SDIODIR DATADIR SWRST SLEEP PDN RESERVED1 RESERVED EXREF
01 RESERVED
DATA 02 DATAFMT DDR DCLKPOLI DCLKPOLO DISDCLKO SYNCMAN SYNCUPD SYNCALRM
03 RESERVED
04 RESERVED
05 RESERVED
06 RESERVED
07 RESERVED
08 RESERVED
09 RESERVED
0A RESERVED
0B RESERVED
0C RESERVED
VERSION 0D RESERVED RESERVED RESERVED RESERVED VERSION[3] VERSION[2] VERSION[1] VERSION[0]
CALMEMCK 0E RESERVED RESERVED CALMEM[1] CALMEM[0] RESERVED CALCKDIV[2] CALCKDIV[1] CALCKDIV[0]
MEMRDWR 0F CALSTAT CALEN XFERSTAT XFEREN SMEMWR SMEMRD FMEMRD UNCAL
MEMADDR 10 MEMADDR[7] MEMADDR[6] MEMADDR[5] MEMADDR[4] MEMADDR[3] MEMADDR[2] MEMADDR[1] MEMADDR[0]
MEMDATA 11 RESERVED RESERVED MEMDATA[5] MEMDATA[4] MEMDATA[3] MEMDATA[2] MEMDATA[1] MEMDATA[0]

1

Reserved registers should be set to Logic 0 (low state) during a write operation, and masked (ignored) during a read operation.

Table 6. SPI Register Definitions

Register Bit Direction Default Description

COMMCTRL(00)

SDIODIR 7 1 0 0: SDIO pin configured for input only during data

DATADIR 6 1 0 0: Serial data uses MSB first format

SWRST 5 1 0 1: Default all serial register bits, except address 00h
SLEEP 4 1 0 1: DAC output current off
PDN 3 1 0 1: All analog and digital circuitry, except serial

RESERVED 2 0 0 RESERVED
RESERVED 1 0 0 RESERVED
EXREF 0 1 0 0: Internal bandgap reference

DATACTRL(02)

DATAFMT 7 1 0 0: Twos complement input data format

DDR 6 1 0 0: Single Data Rate mode

DCLKPOLI 5 1 0 0: Data latched on DATACLKIN rising edge

DCLKPOLO 4 1 0 0: Data latched on DATACLKOUT rising edge

DISDCLKO 3 1 0 0: DATACLKOUT enabled

SYNCMAN 2 1 0 0: Automatic synchronization initiated following a

transfer
1: SDIO pin configured for input or output during data

transfer

1: Serial data uses LSB first format

interface, off

1: Unsigned binary input data format

1: Double Data Rate mode

1: Data latched on DATACLKIN falling edge

1: Data latched on DATACLKOUT falling edge

1: DATACLKOUT disabled

SYNCALRM
1: Manual synchronization needed following a

SYNCALRM

Rev. PrA | Page 9 of 16

AD9725

SYNCUPD 1 1 0 0: Data synchronization complete

SYNCALRM 0 0 0 0: Data synchronizer does not require updating

VERSION(0D)

VERSION[3:0] [3:0] 0 – Hardware version identifier

CALMEMCK(0E)

CALMEM [5:4] 0 00 Calibration memory

CALCKDIV [2:0] 1 000 Calibration clock divide ratio from channel data rate

MEMRDWR(0F)

CALSTAT 7 0 0 0: Self Calibration cycle not complete

CALEN 6 1 0 1: Self Calibration in progress
XFERSTAT 5 0 0 0: Factory memory transfer not complete

XFEREN 4 1 0 1: Factory memory transfer in progress
SMEMWR 3 1 0 1: Write static memory data from external port
SMEMRD 2 1 0 1: Read static memory to external port
FMEMRD 1 1 0 1: Read factory memory data to external port
UNCAL 0 1 0 1: Use uncalibrated

MEMADDR(10)

MEMADDR [7:0] I/O 00000000 Address of factory or static memory to be accessed

MEMDATA(11)

MEMDATA [5:0] I/O 000000 Data for factory or static memory access

1: Initiate data synchronization

1: Data synchronizer requires updating

00: Uncalibrated
01: Self calibration
10: Factory calibration
11: User input

000:/32
001:/64
110:/2048
111:/4096

1: Self Calibration cycle complete

1: Factory memory transfer complete

Preliminary Technical Data

1: External reference

Rev. PrA | Page 10 of 16

Preliminary Technical Data

DEFINITIONS

Linearity Error (Also Called Integral Nonlinearity or INL)

Linearity error is defined as the maximum deviation of the
actual analog output from the ideal output, determined by a
straight line drawn from zero-scale to full-scale.

Differential Nonlinearity ( DNL)

DNL is the measure of the variation in analog value, normalized
to full-scale, and associated with a 1 LSB change in digital input
code.

Monotonicity

A D/A converter is monotonic if the output either increases or
remains constant as the digital input increases.

Offset Error

The deviation of the output current from the ideal of zero is
called offset error. For I
inputs are all 0s. For I
inputs are set to 1s.

Gain Error

The difference between the actual and ideal output span. The
actual span is determined by the output when all inputs are set
to 1s, minus the output when all inputs are set to 0s.

Output Compliance Range

The range of allowable voltage at the output of a current-output
DAC. Operation beyond the maximum compliance limits may
cause either output stage saturation or breakdown, resulting in
nonlinear performance.

Temperature Drift

Temperature drift is specified as the maximum change from the
ambient (25°C) value to the value at either T
offset and gain drift, the drift is reported in ppm of full-scale
range (FSR) per degree celsius. For reference drift, the drift is
reported in ppm per degree celsius.

, 0 mA output is expected when the

OUTA

, 0 mA output is expected when all

OUTB

or T

MIN

MAX

. For

AD9725

Power Supply Rejection

The maximum change in the full-scale output as the supplies
are varied from minimum to maximum specified voltages.

Settling Time

The time required for the output to reach and remain within a
specified error band about its final value, measured from the
start of the output transition.

Glitch Impulse

Asymmetrical switching times in a DAC give rise to undesired
output transients that are quantified by a glitch impulse. It is
specified as the net area of the glitch in pV-s.

Spurious-Free Dynamic Range

The difference, in decibels, between the rms amplitude of the
output signal and the peak spurious signal over the specified
bandwidth.

Total Harmonic Distortion

THD is the ratio of the rms sum of the first six harmonic com­ponents to the rms value of the measured fundamental. It is
expressed as a percentage or in decibels (dB).

Signal-to-Noise Ratio (SNR)

S/N is the ratio of the rms value of the measured output signal
to the rms sum of all other spectral components below the
Nyquist frequency, excluding the first six harmonics and dc. The
value for SNR is expressed in decibels.

Adjacent Channel Power Ratio (or ACPR)

A ratio in dBc between the measured power within a channel
relative to its adjacent channel.

LVDS

Low voltage differential signaling. A differential logic specifi­cation that defines logic levels as approximately ±350 mV
(differential) over a common mode range of 0.875 V to 1.575 V.
LVDS is designed to achieve clock rates of up to 840 MHz.

Rev. PrA | Page 11 of 16

AD9725

TYPICAL PERFORMANCE CURVES

at f

Figure 5. SFDR vs . f

Figure 6. IMD vs. f

OUT

OUT

at f

DAC

= 400 MSPS

DAC

= 500 MSPS

Preliminary Technical Data

Figure 7. Noise Spectral Density vs. f

Figure 8. WCDMA ACLR at Select Intermediate Frequencies

and Sample Rates

OUT

at f

DAC

= 500 MSPS

Rev. PrA | Page 12 of 16

Preliminary Technical Data

THEORY OF OPERATION

LVDS INPUTS

The AD9725 uses LVDS (Low Voltage Differential Signaling)
digital inputs to enable high speed digital signaling. LVDS
allows the use of a differential signal for optimum noise reject­tion, and has small signal amplitude for fast speed and lower
power dissipation. Each differential digital input on the AD9725
has an internal 100 Ω resistor for proper load termination. The
LVDS digital data inputs on the AD9725 meet the IEEE reduced
range (RR) specs for common mode input range (875 mV to
1575 mV) with an input differential threshold of ±350 mV.

DATA SYNCHRONIZATION CIRCUITRY

The high speeds at which the LVDS digital interface is designed
to operate require maintaining synchronization of the data
(DB[15:0]+, DB[15:0]–) and data clock (DATACLK_IN+,
DATACLK_IN–) with the DAC clock (CLK+, CLK–). Since the
DAC clock input is not LVDS, the phase relationship between
that clock and the data can vary, and, unless precautions are
taken, data can be corrupted.

The input data must be provided at the same frequency as the
DAC clock from an LVDS source with an accompanying LVDS
data clock. Since the DAC and data clocks are different types,
their phase relationship is difficult to specify.

The AD9725 provides internal circuitry to keep the data from
being corrupted over a wide variation in relative phase. Once
the DAC and data clocks have been established and synchron­ization has been initiated, the phase between the two clocks can
vary by at least one full clock cycle without loss of data. If the
phase relationship between the clocks varies enough to cause a
possible loss of data, the AD9725 can be resynchronized in
several different ways.

The internal synchronization circuitry in the AD9725 eases this
problem by allowing the phase to vary by at least one full clock
cycle, once synchronization has been established. It does this by
demultiplexing the incoming data stream into four channels,
each containing every fourth data word. Each of these words is
present for four DAC clock cycles. The data is then remulti­plexed by sampling each channel with the appropriate DAC
clock cycle.

Initial synchronization is established in one of the following
ways:

1. When the RESET pin is asserted, the synchronization logic

is initiated to provide optimal internal timing.

2. If SPI_DIS is not asserted, the synchronization is optimized

by writing setting SYNC_UPD (02h[1]) high.

3. If SPI_DIS is asserted, the synchronization is optimized by

asserting the SYNC_UPD pin.

AD9725

Once synchronization is established, the AD9725 needs to be
reoptimized only if operating conditions change enough to
affect the relative phase of the DAC and data clocks by more
than one clock cycle. The AD9725 detects when a synchroni­zation update is necessary, and indicates this need by asserting
SYNCALRM (02h[0]) or SYNC_ALRM high. If SYNCALRM
(02h[0]) or SYNC_ALRM have been asserted, resynchroni­zation can be accomplished as follows:

1. If the synchronization logic is in automatic mode

(SYNCMAN (02h[2]) = 0), the synchronization logic will
optimize the internal timing as necessary. Two data words
will typically be lost or repeated when an optimization
occurs. If that possibility could cause s erious problems,
manual operation may be required.

2. If the synchronization logic is in manual mode

(SYNCMAN (02h[2]) = 1), the logic will indicate the need
for an update by asserting SYNCALRM (02h[0]) high. In
normal operation, a logic high on SYNCALRM (02h[0])
does not mean that data is being lost, but that conditions
are close to the point where data may be lost. Optimization
should be initiated by setting SYNCUPD (02h[1]) high at a
convenient time.

3. Monitoring the synchronization logic state and initiating

an update can be done via package pins by setting SPI_DIS
high and using the SYNC_ALRM and SYNC_UPD pins in
the same way the manual synchronization operation is
described in step 2.

Note that SYNCUPD (02h[1]) or SYNC_UPD can be asserted
at any time to optimize the synchronization, even if
SYNCALRM (02h[0]) or SYNC_ALRM have not indicated that
it is necessary.

If either the data clock or the DAC clock is interrupted for any
reason, a SYNCUPD or SYNC_UPD should be executed to
insure that no subsequent data is lost.

INTERNAL REFERENCE AND FULL-SCALE OUTPUT
CURRENT

The AD9725 contains an internal band gap reference of 1.2 V.
The reference voltage is applied to an external resistor at FSADJ,
and the resultant current is amplified by the reference buffer to
provide the full-scale current for the DAC output. The gain
equation from the internal reference to the DAC output
(assuming the digital inputs are at full scale) is as follows:

= 1.2 × 32/FSADJ

I

OUTFS

Taking into account the state of the digital inputs, the output
current of I

I

OUTA

I

OUTB

= I
= I

OUTA

OUTFS

OUTFS

and I

at any instant in time is:

OUTB

× (DB15:DB0)/65536
× (1 − DB15:DB0)/65536

Rev. PrA | Page 13 of 16

AD9725

ANALOG OUTPUT

The analog output of the AD9725 is based around a high dyna­mic range CMOS DAC core. The output consists of a different­tial current source capable of up to 20 mA full-scale. The output
devices are PMOS and are capable of sourcing current into an
output termination within a compliance voltage range of ±1 V.
Excellent distortion, noise, and ACLR perfor-mance is achie­vable to Nyquist at sample rates of 600 MSPS+.

SPI PORT CONTROL

The AD9725 serial port is a flexible, synchronous serial com­munications port allowing easy interface to many industry
standard microcontrollers and microprocessors. The serial I/O
is compatible with most synchronous transfer formats, inclu­ding both the Motorola SPI and Intel SSR protocols. The inter­face allows read/write access to all registers that configure the
AD9725. Single or multiple byte transfers are supported as well
as MSB first or LSB first transfer formats. The AD9725 serial
interface port can be configured as a single pin I/O (SDIO) or
two unidirectional pins for in/out (SDIO/SDO).

GENERAL OPERATION OF THE SERIAL PORT
INTERFACE

There are two phases to a communication cycle with the
AD9725. Phase 1 is the instruction cycle, which is the writing of
an instruction byte into the AD9725, and coincident with the
first eight SCLK rising edges. The instruction byte provides the
AD9725 serial port controller with information regarding the
data transfer cycle, which is Phase 2 of the communication
cycle. The Phase 1 instruction byte defines the number of bytes
in the data transfer, the starting register address for the first byte
of the data transfer, and whether the upcoming data transfer is
read or write. The first eight SCLK rising edges of each com­munication cycle are used to write the instruction byte into the
AD9725.

A Logic 1 on the CS pin followed by a Logic 0 will reset the SPI
port timing to the initial state of the instruction cycle. This is
true regardless of the present state of the internal registers or
the other signal levels present at the inputs to the SPI port. If the
SPI port is in the midst of an instruction cycle or a data transfer
cycle, none of the present data will be written.

The remaining SCLK edges are for Phase 2 of the communi­cation cycle. Phase 2 is the actual data transfer between the
AD9777 and the system controller. Phase 2 of the communi­cation cycle is a transfer of 1, 2, 3, or 4 data bytes as determined
by the instruction byte. Normally, using one multibyte transfer
is the preferred method. However, single byte data transfers are
useful to reduce CPU overhead when register access requires
1 byte only. Registers change immediately upon writing to the
last bit of each transfer byte.

Preliminary Technical Data

INSTRUCTION BYTE

The instruction byte contains the information shown in Table 7

Table 7

N1 N0 Description

0 0 Transfer 1 byte
0 1 Transfer 2 byte
1 0 Transfer 3 byte
1 1 Transfer 4 byte

R/W

Bit 7 of the instruction byte determines whether a read or a
write data transfer will occur after the instruction byte write.
Logic high indicates a read operation. Logic 0 indicates a write
operation. N1, N0 -Bits 6 and 5 of the instruction byte
determine the number of bytes to be transferred during the data
transfer cycle. The bit decodes are shown in the following table:

Table 8

MSB LSB

I7 I6 I5 I4 I3 I2 I1 I0
R/W N1 N0 A4 A3 A2 A1 A0

A4, A3, A2, A1, A0

Bits 4, 3, 2, 1, 0 of the instruction byte determine which register
is accessed during the data transfer portion of the communi­cations cycle. For multibyte transfers, this address is the starting
byte address. The remaining register addresses are generated by
the AD9725.

SERIAL PORT INTERFACE PIN DESCRIPTION

SCLK (Serial Clock)

The serial clock pin is used to synchronize data to and from the
AD9725, and to run the internal state machines. The SCLK
maximum frequency is 15 MHz. All data input to the AD9725 is
registered on the rising edge of SCLK. All data is driven out of
the AD9725 on the falling edge of SCLK.

CSB (Chip Select)

Active low input starts and gates a communication cycle. It
allows more than one device to be used on the same serial
communications line. The SDO and SDIO pins will go to a high
impedance state when this input is high. Chip select should stay
low during the entire communication cycle.

SDIO

Serial data I/O. Data is always written into the AD9725 on this
pin. This pin, however, can be used as a bidirectional data line.
The configuration of this pin is controlled by Bit 7 of register
address 00h. The default is Logic 0, which configures the SDIO
pin as unidirectional.

Rev. PrA | Page 14 of 16

Preliminary Technical Data

SDO

Serial data out. Data is read from this pin for protocols that use
separate lines for transmitting and receiving data. In the case
where the AD9725 operates in a single bidirectional I/O mode,
this pin does not output data and is set to a high impedance
state.

MSB/LSB Transfers

The AD9725 serial port can support both MSB first and LSB
first data formats. This functionality is controlled by register
address 00h Bit 6. The default is MSB first. When this bit is set
to active high, the AD9725 serial port is in LSB first format.
That is, if the AD9725 is in LSB first mode, the instruction byte
must be written from least significant bit to most significant bit.
Multibyte data transfers in MSB format can be completed by
writing an instruction byte that includes the register address of
the most significant byte. In MSB first mode, the serial port
internal byte address generator decrements for each byte
required of the multibyte communication cycle. Multibyte data
transfers in LSB first format can be completed by writing an
instruction byte that includes the register address of the least
significant byte. In LSB first mode, the serial port internal byte
address generator increments for each byte required of the
multibyte communication cycle.

The AD9725 serial port controller address will increment from
1Fh to 00h for multibyte I/O operations if the MSB first mode is
active. The serial port controller address will decrement from
00h to 1Fh for multibyte I/O operations if the LSB first mode is
active.

CS

SCLK

SDIO

SDO

INSTRUCTION CYCLE DATA TRANSFER CYCLE

R/W 16

14 13 12 11 10 D7nD6

(n)15(n)

D7nD6

n

n

Figure 9. Serial Register Interface Timing MSB First

D20D10D0

D20D10D0

0

0

04540-0-008

AD9725

NOTES ON SERIAL PORT OPERATION

The AD9725 serial port configuration bits reside in Bit 6 and
Bit 7 of register address 00h. It is important to note that the
configuration changes immediately upon writing to the last bit
of the register. For multibyte transfers, writing to this register
may occur during the middle of communication cycle. Care
must be taken to compensate for this new configuration for the
remaining bytes of the current communication cycle.

CS

SCLK

SDIO

SDO

CS

SCLK

SDIO

CS

SCLK

SDIO

SDO

The same considerations apply to setting the reset bit in register
address 00h. All other registers are set to their default values, but
the software reset doesn’t affect the bits in register address 00h.

It is recommended to use only single byte transfers when
changing serial port configurations or initiating a software
reset.

INSTRUCTION CYCLE DATA TRANSFER CYCLE

10 11 12 13 14 15

(n)16(n)

R/W D00D10D2

D00D10D2

0

0

D6nD7

D6nD7

Figure 10. Serial Register Interface Timing LSB First

t

DS

t

DS

INSTRUCTION BIT 7 INSTRUCTION BIT 6

t

SCLK

t

PWHtPWL

t

DH

Figure 11. Timing Diagram for Register Write to AD9725

t

DV

DATA BIT n DATA BIT n– 1

Figure 12. Timing Diagram for Register READ to AD9725

n

n

04540-0-009

04540-0-010

04540-0-011

Rev. PrA | Page 15 of 16

AD9725

OUTLINE DIMENSION

1.20

0.75

MAX

0.60

0.45

SEATING

PLANE

Preliminary Technical Data

14.00 SQ

12.00 SQ

80

1

PIN 1

TOP VIEW

(PINS DOWN)

61

60

61

60

BOTTOM

VIEW

80

1

6.00
SQ



0.15

0.05

COPLANARITY

0.20

0.09

0.08

20

21

1.05

1.00

0.95

0.50 BSC

0.27

0.22

0.17

COMPLIANT TO JEDEC STANDARDS MS-026-ADD-HD

41

40

GAGE PLANE

0.25

3.5°

41

40

7°

0°

20

21

Figure 13. 80-Lead Thin Plastic Quad Flat Package, Exposed Pad [TQFP/ED]

(SV-80)

Dimensions shown in millimeters

ORDERING GUIDE

Model Temperature Range Package Description Package Option

AD9725BSV -40°C to +85°C 80 Lead TQFP SV-80

THERMAL CHARACTERISTICS

Thermal Resistance

80-Lead Thermally Enhanced
TQFP Package θ

= 23.5°C/W*

JA

*With thermal pad soldered to PCB.

© 2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.

PR04682-0-1/04(PrA)

Rev. PrA | Page 16 of 16