2
DDS9m Manual
1.0
DESCRIPTION
1.1 The Model DDS9m is a four-channel Direct
Digital Synthesizer (DDS) on a small printed wiring
module with RS232 serial control. The DDS9m pro-
vides four independent sine wave and LVCMOS
output signals, which can be set from 0.1Hz to
171MHz in 0.1Hz steps when using the internal
VCTCXO clock (LVCMOS is optimized for outputs
greater than 1MHz and less 125MHz).
1.2 The DDS9m can also be used with an External
Clock input. An on-board programmable frequency
multiplier generates the master clock allowing user
configured frequency ranges. The multiplier can be
disabled for direct inputs up to 500MHz for opti-
mum phase noise performance. When used with the
same external clock source, multiple DDS9m are
phase synchronous.
2.0
SPECIFICATIONS
2.1 OUTPUTS
TYPES: Four Sine and LVCMOS simultaneously (four
frequencies.)
IMPEDANCE: Sine: 50
Ω;
LVCMOS: 50
Ω.
RANGE: 0.1Hz to 171MHz in 0.1Hz steps (Sine out, int.
clock).
SINE AMPLITUDE: approximately 1V
pp
(+4dBm @
35MHz) into 50
Ω.
Programmable from 0/1024 to 1023/
1024 of Full Scale (10-bits).
PHASE: Each channel 14-bits programmable.
FLATNESS: ±3dB from 1kHz to 150MHz referenced to
amplitude at 35MHz, full scale.
2.2 LVCMOS AMPLITUDE
V
oh
>=2.4V and V
ol
<=0.4V when series terminated. Rise
and fall times <1.5ns. (1MHz< F
out
<125MHz)
2.3 CONTROL
Output frequencies, amplitudes (10-bits) and phases (14-
bits) are controlled by an RS232 serial port at 19.2kbaud.
All settings (except table mode data) can be saved in
non-volatile (EEPROM) memory via the RS232 port.
2.4 ACCURACY AND STABILITY
Accuracy: <±1.5ppm at 10 to 40
o
C. Stable to an addi-
tional ±1ppm per year, 18 to 28
o
C. (Internal Clock)
2.5 EXTERNAL CLOCK IN
LEVEL: 0.2 to 0.5Vrms Sine or Square Wave. 50
Ω.
FREQUENCY: 10MHz to 125MHz with multiplier of 4 to
NOVATECH INSTRUMENTS
20 enabled. Direct input of 1MHz to 500MHz.
2.6 SPECTRAL PURITY
(Typ. 50
Ω
load, internal
clock, full-scale output)
Phase Noise: <-120dBc, 10kHz offset, 5MHz out.
Spurious:
<-60dBc below 10MHz (typ. 300MHz span)
<-60dBc below 40MHz
<-55dBc below 80MHz
<-50dBc below 160MHz
Harmonic: <-65dBc below 1MHz
<-55dBc below 20MHz
<-45dBc below 80MHz
<-35dBc below 160MHz
(channel-channel isolation: <-60dBc)
2.7 TABLE MODE
On-board 4Mb static ram holds up to 32,768 profile
points in table mode allowing a different output in 100
µ
s
increments. Channels 0 and 1 only.
2.8 POWER REQUIREMENTS
+3.14V to +3.46VDC@<750mA. Battery back-up 3.0V
nominal at <400
µ
A (2-AA, LR6, typical).
2.9 SIZE
82.6mm by 88.9mm circuit board. Max. height 10mm.
2.10 CONNECTORS
MCX for Sine Outputs and EXT CLK IN. 2-pin header for
+3.3V power and external back-up battery. 24-pin header
for high speed control. DE9 for Serial Control. 2-pin wire-
points for LVCMOS outputs.
3.0
HARDWARE INSTALLATION
WARNING:
The DDS9m contains static sensitive components.
Before opening the package, follow appropriate
static precautions. Failure to follow static
precautions may damage the DDS9m.
3.1 Power Connection. Figure 1, Connection
Placement Diagram, shows a top view of the
DDS9m module. The required power of +3.3Volts
DC is applied through a 2-pin connector (mates with
Amp 640621-2). If you are using a Novatech Instru-
ments supplied connector, Red is +3.3VDC and
Black is the common return.
3.2 The quality of your power supply may affect the
performance of the DDS9m. The supply should be
free of ripple and noise (<50mV). Even though
