ASCEL Electronic AE20125 Installation and operating instructions

Æ20125
10 MHz Sweep DDS
Function Generator
Assembly and
Operation Manual

REV 3.1 EN
© 2015 Ascel Electronic

Table of Contents
Safety Information.....................................................................ii
Handover of a evice Built From a Kit....................................iv
Intended Use.............................................................................iv
ES Warning.............................................................................v
AE20125 Sweep S Function Generator...............................1
Circuit escription.....................................................................2
Soldering....................................................................................4
Component Reference................................................................6
Assembly..................................................................................14
Calibration................................................................................17
Troubleshooting Checklist.......................................................18
Power Supply...........................................................................20
Case Mounting.........................................................................21
Operation..................................................................................23
Circuit iagram.......................................................................33
Bill of Materials.......................................................................35
Component Placement iagram..............................................38
ata Interface...........................................................................39
Specifications...........................................................................42
i

Warnin
Please read this manual before you assemble and use this kit.
Keep it accessible for all users at all times.
Safety Information
Know and follow the applicable regulations for
electric devices in your region. In Germany,
these are especially V E 0100, V E
0550/0551, V E 0700, V E 0711 and V E
0860. Pay attention to the following safety
advices:
• isconnect the power supply before opening the case.
• Work on devices only if you made sure that they are
disconnected from any power supply, and any possible charge
inside is discharged.
• evices must only be used if they are mounted in a case in a
way that prevents the user from touching any live wires or
parts. isconnect the device from its power supply during
assembly.
• Always check the power cords for breaks or damaged
insulation. Replace any defective parts immediately.
• Seek advice from a qualified expert if you are not sure about
any specific value of a part, an installation procedure, or how
to connect accessories.
ii

•Always check if the device is suitable for the intended purpose
before putting the unit in use. Seek assistance from a qualified
professional or the manufacturer if you are not sure.
• The manufacturer assumes no liability for errors made during
assembly or operation.
• evices that need a supply voltage greater that 24V may be
assembled by professionals only, to avoid hazards from
improper assembly.
• In schools, educational institutes or workshops, the use of this
unit must take place under the supervision of qualified staff.
• o not put this unit in use in an environment where the risk of
fire or explosion or explosive gas, vapor or dust is present.
• If the unit must be repaired, use original parts only. The use of
inappropriate parts may lead to a safety risk.
• Avoid working alone.
• Keep electronic parts away from children.
• o not replace parts with such that does not meet the required
parameters. For example: never replace a fuse with another one
with higher nominal current!
• Other regulations may apply. Please check the local safety
regulations for assembling electronic devices.
iii

Handover of a Device Built From a Kit
(in countries where applicable)
If you hand over a device built from a kit, you legally become
the manufacturer. This means you are responsible for
complying with the appropriate regulations for electronic
devices. All accompanying papers, in particular this manual,
must also be passed over. Where necessary (for example in the
European Union) you must also publish your identity to the
consignee.
Intended Use
(in countries where applicable)
The intended use of this device is the generation of waveform
signals for measuring purposes.
• Other uses are not approved!
iv

ESD Warnin
What is ESD?
ES (Electrostatic Dis-
charge) is the sudden flow
of electricity between two
objects caused by contact
or an electrical short. It
can reach very high voltages of many kV. In some cases even
over 100kV!
Causes of ESD
The main cause of ES events is static electricity. Static
electricity is usually generated through tribocharging, like
walking on a rug, ascending from a fabric seat, removing some
types of plastic packaging or using non-ES compliant tools.
Danger of ESD
The high voltage pulse can easily destroy electronic parts. ICs
and FETs are very sensitive to high voltage. Even a short,
single touch may destroy a part!
How do I prevent damage due to ESD?
Always ground yourself while working with electronic parts. A
grounded conducting wrist strap and proper anti-static work
surface mat will help prevent ES damage. Also make sure
that the soldering iron is grounded and ES -safe.
v
Warning symbol for an
electrostatic sensitive device

AE20125 Sweep DDS Function
Generator
The AE20125 Function Generator is capable of producing sine,
square and triangle signals with an output frequency from 0.1
Hz to 10 MHz1, continuously adjustable in 0.1 Hz step over the
entire range. The maximum amplitude is 5Vpp. The C offset
is adjustable from -5V to +5V.
Sweep and modulation capabilities: frequency (FSK) and phase
(PSK) shift keying. Internal or external modulation source.
Adjustable internal frequency, and calculation and display of
PLL frequency when used as a timebase for PLL, are some of
the advanced functions.
The USB interface2 allows remote control of the function
generator with the included software. The easy, plain text
command protocol allows simple integration with external
tools and systems. Every function of the device can be remote
controlled.
All SM (Surface Mounted evice) components are already
soldered, so the kit is also suitable for beginners in electronics.
The comprehensive manual should help answer all questions
that may arise during assembly.
Please read the complete manual (especially if you are not yet
experienced in electronic engineering) before building the kit.
1for sine, 2.5 MHz for s uare and triangle
2optional
1

Circuit Description
The AE20125 Function Generator is based upon a irect igi-
tal Synthesizer ( S). S uses a processor to calculate the
output waveform and a igital-to-Analog Converter ( AC) to
create the actual voltage needed to produce a waveform. S
has the advantage of high accuracy and resolution.
Note: for a comprehensive overview of DDS, an excellent
document is available from Analog Devices1.
The heart of the AE20125 is the A 9833 from Analog evices
(IC2). It is capable of producing sine, square, and triangle wa-
veforms. The 25 MHz crystal oscillator Q1 provides the master
clock for the S. The output signal of the S is discretely
constructed from a finite number of steps. This signal always
contains unwanted high frequency components. A reconstructi-
on filter is needed to remove these components from the signal.
The filter is composed of L1, C4, L2, C5, L3, C11 and R8. As
the square wave signal does not require filtering, the filter is di-
sabled with the relay K1 when switched to square wave. The
square wave produced by the A 9833 has a different amplitude
than the other waveforms, so the divider R14/P4 adjusts it to
match the amplitude of the sine and triangle wave.
IC1 is the microcontroller that controls the device. The keys
and the LC are connected to it. The FT I FT230XS UART-
to-USB-Bridge (IC6) provides USB connectivity to the
microcontroller.
1A Technical Tutorial on Digital Signal Synthesis, 1999,
http://www.analog.com/static/imported-
files/tutorials/450968421DDS_Tutorial_rev12-2-99.pdf
2

The reconstructed waveform from the A 9833 is fed into the
output amplifier. The high speed current feedback op amp
LM6181 (IC3) amplifies the signal to an amplitude of 5Vpp.
The high bandwidth of 100 MHz, 100mA output drive
capability and the very high slew rate of 2000V/µs makes the
LM6181 an ideal choice for this application. P1* and P2*
adjusts the output amplitude (0 to 5Vpp) and the C offset (-
5V to +5V). The offset symmetry can be trimmed with P3. C19
decouples the output signal of the A 9833, removing its own
C offset. Note: This causes a slight attenuation of signals
below 12 Hz.
The supply voltage of 14 to 18V C is fed through the
protection diode 1 and buffered by the electrolytic capacitor
C12. The 5V digital supply comes from the linear regulator
IC4. The inverter, built around T1-T4, provides the negative
supply, IC5 regulates the -5V rail.
A combined analog/digital circuit like this depends on good
supply bypassing, ensured by many ceramic and electrolytic
capacitors and ferrite beads.
The Sync output and the Mod-In input are respectively
protected against overvoltage/overcurrent by R15 and by R18,
2 and 3.
3