4.5 GHz Direct Digital Synthesizer, DS878

DS878 – Direct Digital Synthesizer for High SpeedChirping
VCCLatch

32Switch

11DecoderLatch

Vi[0:31]

13Latch32

Accumulator

IQSL

Sine ROM

RST211OUT_P/N

CkP8

STRB_P/N

2
Latch

2

Pipeline
Clock

AVS

CkP1

MDSL
VCCO

SEL1
2

SEL0
SyncI_P/N
CK_P/N

SyncO_P/N

2
Divide by 8
2Clock Distribution

VTTVEEVEED

VEEA

KEY FEATURES••••••••••••••••32-bit frequency tuning word
13-bit ROM phase address resolution
On chip 11-bit DACClock rate up to 4.5 GHz
Analog outputs selectable between Normal-Hold format and Return-to-Zero format
Sine wave generation up to 2.25 GHz 1st Nyquist band for Normal-Hold mode or 6.75 GHz
3rd Nyquist band for Return-to-Zero mode.
Broadband worst SFDR near 50 dBc (DC to 2-GHz Bandwidth) at a 4 GHz clock rate
Complementary analog waveform outputs with 50 Ω back terminations
SyncI_P/N synchronizes multiple chip applications
SyncO_P/N provides reference for data loading and synchronizes STROBE signals.
LVTTL/CMOS digital pattern control input
Asynchronous Reset (RST) pin to initiate phase 0 (with IQSL = low) or 90 (with IQSL =high) starting state
Strobe inputs (STRB_P/N) to update the frequency word and DAC output frequency
Wide data loading window allow DS878 to be controlled by memory, micro-controller,
FPGA or DSP chips to update frequency word as fast as 8 clock cycles without clock
slipping or glitches during frequency transition
4.3 W power consumption with a single -5V power supply
64-pin QFN 9x9 package Euvis, Inc. 3319 Old Conejo Road, Newbury Park, CA 91320
Email: sales@euvis.com Web: www.euvis.com Tel.: (805) 498-8889

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4.5 GHz Direct Digital Synthesizer, DS878

Description
The DS878 is a high-speed Direct Digital Synthesizer (DDS) with a frequency tuning resolutionof 32 bits, ROM phase resolution of 13-bit and a DAC amplitude resolution of 11 bits. The

analog outputs of DAC can be selected between Normal-Hold mode (for the 1st Nyquistband ) and Return-to-Zero mode (for the 1st, 2nd and 3rd Nyquist band) operation. Sinewaves can be generated up to 1st Nyquist band near 1.8 GHz (at a 3.6-GHz clock rate) with
Normal-Hold mode of DAC or up to 3rd Nyquist band around 5.4 GHz with Return-to-Zero modeof DAC. The initial phase can be reset to zero degrees to start with. The chip has a pair ofcomplementary analog outputs with 50-∧ back terminations. The frequency of output waveforms
can be controlled by thirty-two frequency control bits, Vi[0:31]. The DS878 accepts either
differential clock inputs or a single-ended clock input and features 50-∧ on-chip backterminations with user-defined threshold. The frequency resolution bits accept LVTTL or CMOS
input levels. Differential synchronization input SyncI_P/N provides synchronization for multiple
chip applications and start each chip ready to accept frequency word inputs. The synchronous
Strobe inputs are latched by the transition edges of internal generated divide-by-8 clocks whichwere also sent to the output pins SyncO_P/N. SyncO_P/N. can be used as a reference tosynchronize the frequency word and strobe signal input timing alignment to the internal divideby8 clocks to latch properly. The Reset is asynchronous to minimize clock latencies ofeffectiveness on the analog outputs. The internal timing was optimized to avoid clock slipping
during frequency word transition or after reset. Only a single –5V power supply is required..

Spur Free Dynamic Range Performance

fclk = 3.5 GHz
70

SFDR (dBc)

60
50
4030
20
10000.5

1.0

1.5

2.0

2.5

Frequency (GHz) Euvis, Inc. 3319 Old Conejo Road, Newbury Park, CA 91320
Email: sales@euvis.com Web: www.euvis.com Tel.: (805) 498-8889

34.5 GHz Direct Digital Synthesizer, DS878

fclk = 4.0 GHz
70

SFDR (dBc)

605040302010000.5

1.0

1.5

2.0

2.5

Frequency (GHz)fclk = 4.5 GHz
70

SFDR (dBc)

60
50
40
30
20
1000

0.5

1.0

1.5

2.0

2.5

Frequency (GHz) Euvis, Inc. 3319 Old Conejo Road, Newbury Park, CA 91320
Email: sales@euvis.com Web: www.euvis.com Tel.: (805) 498-8889

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4.5 GHz Direct Digital Synthesizer, DS878

Representative Measured RF Spectrum

fclk = 3.5 GHz
fout = 5/64 * fclk

fout = 13/64 * fclk

10Power (dBm)

Power (dBm)

10-40-90-400900

Frequency (MHz)

1800-900fout = 21/64 * fclk

1800

fout = 29/64 * fclk

10Power (dBm)

Power (dBm)

10-40-90900

Frequency (MHz)-400900

Frequency (MHz)

1800-900900

1800

Frequency (MHz) Euvis, Inc. 3319 Old Conejo Road, Newbury Park, CA 91320
Email: sales@euvis.com Web: www.euvis.com Tel.: (805) 498-8889

5

4.5 GHz Direct Digital Synthesizer, DS878

fclk = 4.0 GHz
fout = 5/64 * fclk

fout = 13/64 * fclk

10Power (dBm)

Power (dBm)

10-40-90-4001000

Frequency (MHz)2000-900fout = 23/64 * fclk

2000

fout = 30/64 * fclk

10Power (dBm)

Power (dBm)

10-40-901000

Frequency (MHz)-4001000

Frequency (MHz)

2000-9001000

2000

Frequency (MHz) Euvis, Inc. 3319 Old Conejo Road, Newbury Park, CA 91320
Email: sales@euvis.com Web: www.euvis.com Tel.: (805) 498-8889

6

4.5 GHz Direct Digital Synthesizer, DS878

fclk = 4.5 GHz
fout = 7/64 * fclk

fout = 13/64 * fclk

10Power (dBm)

Power (dBm)

10-40-90-4001125

Frequency (MHz)

2250

-900

fout = 20/64 * fclk

2250

fout = 29/64 * fclk

10Power (dBm)

Power (dBm)

10-40-901125

Frequency (MHz)-4001125

Frequency (MHz)

2250-90011252250

Frequency (MHz) Euvis, Inc. 3319 Old Conejo Road, Newbury Park, CA 91320
Email: sales@euvis.com Web: www.euvis.com Tel.: (805) 498-8889

7