Atec DG535 User Manual

Digital Delay/Pulse Generator

DG535 — Digital delay and pulse generator (4-channel)

· Four independent delay channels

· Two fully-defined pulse channels

· 5 ps delay resolution

· <100 ps rms jitter

· Adjustable amplitude and offset

· Delays up to 1000 seconds

· 1 MHz maximum trigger rate

· Standard GPIB interface

· Optional ±32 V outputs

· DG535 ... $4195 (U.S. list)

DG535 Digital Delay/Pulse Generator

The DG535 Digital Delay/Pulse Generator provides four
precisely-timed logic transitions or two independent pulse
outputs. The delay resolution on all channels is 5 ps, and the
channel-to-channel jitter is typically 50 ps. Front-panel BNC
outputs deliver TTL, ECL, NIM or variable level (–3 to +4 V)

pulses into 50 Ω or high impedance loads. The high accuracy,

low jitter, and wide delay range make the DG535 ideal for
laser timing systems, automated testing, and precision
pulse

applications.

Delay Outputs

There are four delay output channels: A, B, C and D. The logic
transitions of these outputs can be delayed from an internal or
external trigger by up to 1000 seconds in 5 ps increments.
The T0 pulse, which marks the beginning of a timing cycle, is
generated by the trigger signal. The insertion delay between
an external trigger and the T0 pulse is about 85 ns.

Delays for each channel may be “linked” to T0 or any of the
other delay channels. For instance, you can specify the delays
of the four channels as:

A = T0 + 0.00125000
B = A + 0.00000005
C = T0 + 0.10000000
D = C + 0.00100000

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DG535 Digital Delay/Pulse Generator

In this case, when the A delay is changed, the B output will
move with it. This is useful, for instance, when A and B
specify a pulse and you want the pulse width to remain
constant as the delay of the pulse is changed. Regardless of
how the delay is specified, each delay output will stay asserted
until 800 ns after all delays have timed out. The delays will
then become unasserted, and the unit will be ready to begin a
new timing cycle.

Pulse Outputs

In addition to the four delay outputs, there are four pulse
output channels: AB, –AB, CD and –CD. The leading edge
of the AB pulse coincides with the leading edge of the earlier
of A or B, and the trailing edge of the AB pulse coincides
with the leading edge of the later of B or A. For instance, in
the previous example, a 50 ns pulse would appear at the AB
output and a 1 ms pulse at CD. Pulses as short as 4 ns (FWHM)
can be generated in this manner. The complementary outputs
(–AB and –CD) provide a pulse with identical timing and
inverted amplitude.

Output Amplitude Control

Each delay and pulse output has an independently adjustable
offset and amplitude which can be set between –3 V and +4 V
with 10 mV resolution. The maximum transition for each

output is limited to 4 V. In addition, you can also separately

select 50 Ω or high impedance termination for each output.

Preset levels, corresponding to standard logic families, can
also be selected. TTL, NIM and ECL levels can each be set
with a single key press.

Triggering

The DG535 can be triggered internally from 1 mHz to 1 MHz
with 4-digit frequency resolution. External, single-shot and
burst mode triggers are also supported. For power control
applications, the DG535 can be synchronized to the AC line.
An optional trigger inhibit input allows you to enable or
disable triggering with a TTL level input signal.

±32 Volt Outputs

For applications requiring higher voltages, a rear-panel high
voltage (±32 V) option is available. This option provides five
rear-panel BNCs which output 1 µs pulses at the transition
times of the front-panel T0, A, B, C and D outputs. The high
voltage option does not affect the function or the timing of the
front-panel outputs. The amplitude of the rear-panel outputs
is approximately 8× the corresponding front-panel output,

and the outputs are designed to drive 50 Ω loads. Since they

can only drive an average current of 0.8 mA, charging and
discharging the cable capacitance may be the most important

A timing cycle is initiated by an internal or external trig­ger. T0 is asserted approx. 85 ns after an external trigger.
Outputs A, B, C and D are asserted relative to T0 after
their programmed delays. All of the outputs return low
about 800 ns after the longest delay. The pulse outputs,
AB and CD, go high for the time interval between their
corresponding delay channels.

t

CYCLE

t

BUSY

t

D

TRIG

T0

A

B

C

D

AB

AB

CD

CD

t

TRIG

t

ID

t

A

t

B

t

>5 ns

trig

t

>1 µs + longest delay

cycle

tID <85 ns
t

<800 ns + longest delay

BUSY

t

0 to 999.999 999 999 995 s

A,B,C,D

t

C

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DG535 timing diagram

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DG535 Digital Delay/Pulse Generator

current limiting factor to consider when using them (assuming
a high impedance load). In this case, the average current is:
I = 2Vtf / Z, where V is the pulse step size, t is the length of
the cable in time (5 ns per meter for RG-58), f is the pulse
repetition rate, and Z is the cable’s characteristic impedance
(50 Ω for RG-58).

Internal or External Timebase

Both internal and external references may be used as the
timebase for the DG535. The internal timebase can be either
the standard 25 ppm crystal oscillator timebase, or the optional
1 ppm temperature-compensated crystal oscillator (TCXO).
The internal timebase is available as a 1 Vpp square wave on a

rear-panel BNC. This output is capable of driving a 50 Ω load

and can be used to provide a master timebase to other delay
generators. Any external 10.0 MHz reference signal with a
1 Vpp amplitude can also be used as an external timebase.

Fast Rise and Fall Time Modules

External in-line modules are available to reduce the rise or fall
time of the DG535 outputs to 100 ps. These modules use step

individual digits. The backlit 20-character LCD display makes
it easy to view delay settings in all lighting conditions.

The DG535 comes standard with a GPIB (IEEE-488)
interface. All instrument functions can be queried and set
via the interface. You can even display the characters the
DG535 has received over the interface on the front-panel
LCD display. This can be valuable when debugging programs
which send commands to the instrument.

Ordering Information

DG535 Delay/pulse generator w/ GPIB $4195
Option 02 ±32 V rear panel outputs $650
Option 03 1 ppm TCXO timebase $350
Option 06 Trigger inhibit input $250

SRD1 100 ps rise time module $250

O4B 100 ps fall time module $250

O4C Bias Tee (for 02 & SRD1 or O4B) $100

O5 Dual rack mount tray $150

recovery diodes to speed up the rise time (option SRD1) or the

fall time (option O4B). A bias tee (option O4C) allows these
modules to be used with the optional rear-panel outputs to
produce steps up to 15 V. For step amplitudes of less than

2.0 V, the fast transition time units should be attached directly
to the front panel of the DG535.

Easy to Use, Easy to Program

All instrument functions can be accessed through a simple,
intuitive, menu-based interface. Delays can be entered with
the numeric keypad in either fixed-point or exponential
notation, or by using the cursor keys to select and change

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DG535 rear panel (with Opt. 02)

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DG535 Specifications

Delays

Channels Four independent delay outputs
Range 0 to 999.999,999,999,995 seconds
Resolution 5 ps
Accuracy 1500 ps + timebase error × delay

Timebase Standard: 25 ppm crystal oscillator

Optional: 1 ppm TCXO (opt. 03)
External: 10.0 MHz reference input

RMS jitter <100 ps + (10–8 × delay)

Trigger delay (typ.) 85 ns (ext. trigger to T0 output)

External Trigger

Rate DC to 1/(1 µs + longest delay)
Threshold ±2.56 VDC
Resolution 10 mV

Slope Trigger on rising or falling edge

Impedance 1 MΩ + 40 pF or 50 Ω

Internal Rate Generator

Rate Single shot, 0.001 Hz to

1.000 MHz, or line
Resolution Four digits, 0.001 Hz below 10 Hz

Accuracy Same as timebase

Jitter 1:10,000

Settling <2 seconds for any rate change

Burst mode 2 to 32766 pulses per burst at
integer multiples (4 to 32767) of the
trigger period

Outputs

Load 50 Ω or high impedance
Rise time 2 to 3 ns (typ.)

Slew rate 1 V/ns
Overshoot <100 mV + 10 % of pulse amplitude

Levels TTL: 0 to 4 VDC (normal or inverted)
ECL: –1.8 to –0.8 VDC
(normal or inverted)
NIM: –0.8 to 0.0 VDC
(normal or inverted)
VAR: Adjustable offset and
amplitude between –3 and +4 VDC
with 10 mV resolution.
4 V maximum transition.
Accuracy ±(50 mV + 3 % of pulse amplitude)
Option 02 Rear-panel 1 µs pulses corresponding
to T0, A, B, C, D outputs with
nominal amplitude of 8× the front­ panel outputs (1 kHz rep. rate).
Output level is reduced by 2 V/mA
of additional average output current.

Fast Rise Time (opt. SRD1)

Output amplitude +0.5 to 2.0 VDC
Output offset –0.8 VDC (typ.)
Transition time
Rise (20/80 %) 100 ps (max.)
Fall (20/80 %) 2000 ps (max.)
Pulse aberrations
Foot 4 % (typ.)
Ring ±5 % (typ.)

Fast Fall Time (opt. O4B)

Output amplitude –0.5 to –2.0 VDC
Output offset +0.8 VDC (typ.)
Transition time
Rise (20/80 %) 2500 ps (max.)
Fall (20/80 %) 100 ps (max.)
Pulse aberrations
Foot 4 % (typ.)
Ring ±5 % (typ.)

General

Display backlit 20-character LCD
Computer interface GPIB (IEEE-488). All instrument
functions and settings may be
controlled over the interface bus.
Interface queue can be viewed from
the front panel.
Dimensions 8.5" × 4.75" × 14" (WHD)
Weight 10 lbs.
Power 70 W, 100/120/220/240 VAC,
50/60 Hz
Warranty One year parts and labor on defects
in materials and workmanship

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