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1 GSPS Direct Digital  

Synthesizer with 14-Bit DAC 

  

AD9912 

 

 

Rev. D 

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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: 781.329.4700 

Fax: 781.461.3113  ©2007–2009 Analog Devices, Inc. All rights reserved. 

FEATURES 

1 GSPS internal clock speed (up to 400 MHz output directly) 
Integrated 1 GSPS 14-bit DAC 
48-bit frequency tuning word with 4 µHz resolution 
Differential HSTL comparator 
Flexible system clock input accepts either crystal or external 

reference clock 

On-chip low noise PLL REFCLK multiplier 
2 SpurKiller channels 
Low jitter clock doubler for frequencies up to 750 MHz 
Single-ended CMOS comparator; frequencies of <150 MHz 
Programmable output divider for CMOS output 
Serial I/O control 
Excellent dynamic performance 
Software controlled power-down 
Available in two 64-lead LFCSP packages 
Residual phase noise @ 250 MHz  

10 Hz offset: −113 dBc/Hz 
1 kHz offset: −133 dBc/Hz 
100 kHz offset: −153 dBc/Hz 
40 MHz offset: −161 dBc/Hz 

APPLICATIONS 

Agile LO frequency synthesis 
Low jitter, fine tune clock generation 
Test and measurement equipment 
Wireless base stations and controllers 
Secure communications 
Fast frequency hopping 

GENERAL DESCRIPTION 

The AD9912 is a direct digital synthesizer (DDS) that features 
an integrated 14-bit digital-to-analog converter (DAC). The 
AD9912 features a 48-bit frequency tuning word (FTW) that 
can synthesize frequencies in step sizes no larger than 4 μHz. 
Absolute frequency accuracy can be achieved by adjusting the 
DAC system clock. 
The AD9912 also features an integrated system clock phase-
locked loop (PLL) that allows for system clock inputs as low 
as 25 MHz. 
The AD9912 operates over an industrial temperature range, 
spanning −40°C to +85°C.  

 

BASIC BLOCK DIAGRAM 

FDBK_IN

DAC_OUT

AD9912

S1 TO S4

OUT

OUT_CMOS

FILTER

SYSTEM CLOCK

MULTIPLIER

SERIAL PORT,

I/O LOGIC

CLOCK

OUTPUT

DRIVERS

DIGITAL

INTERFACE

06763-

001

DIRECT

DIGITAL

SYNTHESIS

CORE

STARTUP

CONFIGURATION

LOGIC

 

Figure 1. 

 

Содержание AD9912

Страница 1: ...MHz Programmable output divider for CMOS output Serial I O control Excellent dynamic performance Software controlled power down Available in two 64 lead LFCSP packages Residual phase noise 250 MHz 10...

Страница 2: ...S Divider Register 0x0100 to Register 0x0106 34 Frequency Tuning Word Register 0x01A0 to Register 0x01AD 34 Doubler and Output Drivers Register 0x0200 to Register 0x0201 36 Calibration User Accessibl...

Страница 3: ...pply with system clock PLL HSTL output driver and S divider enabled IAVDD Pin 53 40 48 mA DAC power supply IDVDD Pin 3 Pin 5 Pin 7 205 246 mA Digital core SpurKiller off IDVDD_I O Pin 1 Pin 141 2 3 mA...

Страница 4: ...ure 28 and Figure 29 for output swing vs frequency Output Voltage High VOH 2 7 V IOH 1 mA Pin 37 3 3 V Output Voltage Low VOL 0 4 V IOL 1 mA Pin 37 3 3 V Output Voltage High VOH 1 4 V IOH 1 mA Pin 37...

Страница 5: ...requency Range 6 100 MHz Multiplication Range 8 132 Integer multiples of 8 Input Duty Cycle 50 Deviating from 50 duty cycle may adversely affect spurious performance Minimum Differential Input Level 6...

Страница 6: ...utput 96 dBc 250 kHz 201 1 MHz Output 91 dBc 250 kHz 398 7 MHz Output 86 dBc 250 kHz DIGITAL TIMING SPECIFICATIONS Time Required to Enter Power Down 15 s Time Required to Leave Power Down 18 s Reset A...

Страница 7: ...s 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...

Страница 8: ...configured under program control and do not have internal pull up pull down resistors 11 19 23 to 26 29 30 36 42 44 45 53 I Power AVDD Analog Supply Connect to a nominal 1 8 V supply 12 13 15 16 17 18...

Страница 9: ...nal should be filtered and sent back on chip through the FDBK_IN input This pin has an internal 50 pull down resistor 51 O Differential output DAC_OUTB Complementary DAC Output This signal should be f...

Страница 10: ...0 80 90 100 SIGNAL POWER dBm 20 1MHz 79dBc 500MHz 3kHz 10kHz CARRIER SFDR FREQ SPAN RESOLUTION BW VIDEO BW Figure 5 Wideband SFDR at 20 1 MHz SYSCLK 1 GHz SYSCLK PLL Bypassed 06763 006 0 100 200 300 4...

Страница 11: ...igure 11 Narrow Band SFDR at 398 7 MHz SYSCLK 1 GHz Wenzel Oscillator SYSCLK PLL Bypassed 06763 012 100 1k 10k 100k 1M 10M 100M FREQUENCY OFFSET Hz 80 90 100 110 120 130 140 150 160 PHASE NOISE dBc Hz...

Страница 12: ...790fs Figure 17 Absolute Phase Noise Using CMOS Driver at 1 8 V SYSCLK 1 GHz Wenzel Oscillator SYSCLK PLL Bypassed 06763 018 250 375 500 625 750 875 1000 SYSTEM CLOCK FREQUENCY MHz 800 700 600 500 40...

Страница 13: ...olute Phase Noise of Unfiltered DAC Output fOUT 171 MHz SYSCLK Driven by a 1 GHz Wenzel Oscillator SYSCLK PLL Bypassed 06763 054 100 1k 10k 100k 1M 10M 100M FREQUENCY OFFSET Hz 125 115 135 145 155 165...

Страница 14: ...gure 29 CMOS Output Driver Peak to Peak Amplitude vs Toggle Rate AVDD3 3 3 V with 20 pF Load 06763 024 0 0 5 1 0 1 5 2 0 2 5 TIME ns 0 4 0 6 0 2 0 0 2 0 4 0 6 AMPLITUDE V FREQUENCY 600MHz tRISE 20 80...

Страница 15: ...AD9912 SELF BIASING SYSCLK INPUT CRYSTAL MODE 10pF 06763 029 10pF REFER TO CRYSTAL DATA SHEET Figure 35 SYSCLK Input Xtal AD9912 SELF BIASING SYSCLK INPUT 0 1 F 0 1 F 100 06763 030 CLOCK SOURCE WITH...

Страница 16: ...ut frequency at 50 of fS where fS is the DAC sample rate but a practical limitation of 40 of fS is generally recommended to allow for the selectivity of the required off chip reconstruction filter The...

Страница 17: ...ram in Figure 41 The peak output current derives from a combination of two factors The first is a reference current IDAC_REF that is established at the DAC_RSET pin and the second is a scale factor th...

Страница 18: ...red output frequency plus 20 rolls off as steeply as possible and then maintains significant though not complete rejection of the remaining images Depending on how close unwanted spurs are to the desi...

Страница 19: ...input pins becomes the internal DAC sampling clock fS after passing through an internal buffer It is important to note that when bypassing the system clock PLL the LOOP_FILTER pin Pin 31 should be pul...

Страница 20: ...ng the range to 33 Care should be taken when choosing these values so as not to exceed the maximum input frequency of the SYSCLK PLL phase detector or SYSCLK PLL doubler These values can be found in t...

Страница 21: ...for frequencies up to 150 MHz The signal path for the CMOS clock driver can either include or bypass the CMOS output divider If the CMOS output divider is bypassed the HSTL and CMOS drivers are the s...

Страница 22: ...to Bit 3 of Register 0x0500 Register 0x0505 2 Turn off the fundamental by setting Bit 7 of Register 0x0013 and enable the SpurKiller channel by setting Bit 7 of Register 0x0500 Register 0x0505 3 Adjus...

Страница 23: ...51 2 still air 0 1 C W The AD9912 is specified for a case temperature TCASE To ensure that TCASE is not exceeded an airflow source can be used Use the following equation to determine the junction temp...

Страница 24: ...es that are used both to address an internal 8 16 ROM and to select the SYSCLK mode see Table 8 The ROM contains eight 16 bit DDS frequency tuning words FTWs one of which is selected by the state of t...

Страница 25: ...e about 25 mA At a minimum a ferrite bead should be used to isolate these from other 3 3 V supplies with a separate regulator being ideal 1 8 V SUPPLIES DVDD Pin 3 Pin 5 and Pin 7 These pins should be...

Страница 26: ...he serial control port state machine enters a wait state until all data has been sent If the system controller decides to abort the transfer before all of the data is sent the state machine must be re...

Страница 27: ...r map that is written to or read from during the data transfer portion of the communications cycle The AD9912 uses all of the 13 bit address space For multibyte transfers this address is the starting...

Страница 28: ...CARE DON T CARE DON T CARE DON T CARE D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 06763 057 Figure 52 Serial Control Port Read MSB First 16 Bit Inst...

Страница 29: ...rameter Description tCLK Period of SCLK tDV Read data valid time time from falling edge of SCLK to valid data on SDIO SDO tDS Setup time between data and rising edge of SCLK tDH Hold time between data...

Страница 30: ...Reserved 0x00 0x0012 M AC Reset DDS reset 0x00 0x0013 M PD fund DDS S div 2 reset S divider reset 0x00 System clock 0x0020 N divider N divider Bits 4 0 0x12 0x0021 Reserved 0x00 0x0022 PLL parameters...

Страница 31: ...x00 Harmonic spur reduction 0x0500 M Spur A HSR A enable Amplitude gain 2 Spur A harmonic Bits 3 0 0x00 0x0501 M Spur A magnitude Bits 7 0 0x00 0x0503 M Spur A phase Bits 7 0 0x00 0x0504 M Spur A phas...

Страница 32: ...ive registers instead of the buffer 1 reads the buffered values that take effect during the next I O update 0 reads values that are currently in effect Register 0x0005 Serial Options Self Clearing Tab...

Страница 33: ...scription 4 0 N divider These bits set the feedback divider for system clock PLL There is a fixed divide by 2 preceding this block as well as an offset of 2 added to this value Therefore setting this...

Страница 34: ...setting is greater than 65 536 or if the signal on FDBK_IN is greater than 400 MHz this bit must be set FREQUENCY TUNING WORD REGISTER 0x01A0 TO REGISTER 0x01AD Register 0x01A0 to Register 0x01A5 Rese...

Страница 35: ...y Register 0x01AB FTW0 Frequency Tuning Word Continued Table 29 Bits Bit Name Description 47 40 FTW0 These registers contain the FTW frequency tuning word for the DDS The FTW determines the ratio of t...

Страница 36: ...ed Register 0x040B DAC Full Scale Current Table 34 Bits Bit Name Description 7 0 DAC full scale current DAC full scale current Bits 7 0 See the Digital to Analog DAC Output section Register 0x040C DAC...

Страница 37: ...ting this bit doubles the gain of the cancelling circuit and also doubles the minimum step size 5 4 Reserved Reserved 3 0 Spur B harmonic Spur B Harmonic 1 to Spur B Harmonic 15 Allows user to choose...

Страница 38: ...T Figure 57 64 Lead Lead Frame Chip Scale Package LFCSP_VQ 9 mm 9 mm Body Very Thin Quad CP 64 1 Dimensions shown in millimeters COMPLIANT TO JEDEC STANDARDS MO 220 VMMD 4 062209 A 0 25 MIN 1 64 16 17...

Страница 39: ...CPZ REEL71 2 40 C to 85 C 64 Lead Lead Frame Chip Scale Package LFCSP_VQ CP 64 7 AD9912BCPZ1 40 C to 85 C 64 Lead Lead Frame Chip Scale Package LFCSP_VQ CP 64 1 AD9912BCPZ REEL71 40 C to 85 C 64 Lead...

Страница 40: ...AD9912 Rev D Page 40 of 40 NOTES 2007 2009 Analog Devices Inc All rights reserved Trademarks and registered trademarks are the property of their respective owners D06763 0 11 09 D...

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