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MAX038 Evaluation Kit
Evaluates: MAX038
_______________General Description ___________________________Features
The MAX038 evaluation kit (EV kit) is a high-frequency o 325kHz to 10MHz Operation
function generator capable of producing accurate tri- o Adjustable Duty Cycle
angle/sawtooth, sine, and square/pulse waveforms up
to 10MHz, using the supplied components. Output fre- o 2.5V Reference Output
quency and duty cycle are easily adjusted with on- o TTL-Compatible SYNC Output
board potentiometers. Removable jumpers select sine, o Fully Assembled and Tested
square, or triangle waveforms, or fix the duty cycle at
50%. The output is buffered with a MAX442 amplifier ____________________Component List
capable of driving a 50 coaxial cable. The MAX038 DESIGNATION QTY DESCRIPTION
EV kit is fully assembled and tested. U1 1 MAX038CPP
U2 1 MAX442CPA
______________Ordering Information C1 1 82pF capacitor
C2, C3, C5, C7,
C9, C10, C11, 8 0.1µF capacitors
PART TEMP. RANGE BOARD TYPE C12
MAX038EVKIT-DIP 0°C to +70°C Through-Hole C4, C6, C8 3 4.7µF capacitors
R1, R2 2 20k potentiometers
R3 1 50k potentiometer
______________________________EV Kit R4, R5 2 10k , 5% resistors
R6 1 51 , 5% resistor
R7, R8 2 270 , 5% resistors
R9, R10, R11 3 0 resistors
R12 1 3.3k , 5% resistor
JU1, JU2, JU5 3 2-pin headers
JU3, JU4 2 3-pin headers
None 5 Shunts
J1 1 BNC jack
_________________________Quick Start
The MAX038 EV kit is a fully assembled and tested
board. Follow these steps to verify board operation. Do
not turn on the power supply until all connections
are completed.
1) Connect a +5V supply to the pad marked +5V.
Connect a -5V supply to the pad marked -5V.
Connect ground(s) to the GND pad.
2) Connect an oscilloscope to the BNC jack marked
OUTPUT through a terminated 50 cable. The
MAX038 output prior to the amplifier stage may also
be monitored using an oscilloscope probe at the
OUT pad.
3) Place the shunt across pins 2 and 3 of JU4 for 50%
duty cycle. Place the shunt across pins 1 and 2 of
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAX038 Evaluation Kit
JU3 to allow the frequency to be adjusted. Verify Input Current Control
that there is a shunt on JU5. The current injected into the IIN pin acts as the primary
4) Verify the shunts on JU1 and JU2 for a square-wave frequency-adjustment control. The R3 potentiometer
output. Refer to Table 1 for alternate waveform varies the current to the MAX038's IIN pin. The input
selections. current can be easily monitored by removing the JU5
5) Apply power and verify the output waveform. shunt and placing a current meter across the JU5 pins.
The components supplied on the EV kit will allow an
_______________Detailed Description input current range of 50µA to 725µA. With the VADJ
Waveform Selection pin grounded, the fundamental output frequency (Fo) is
as follows:
To select the desired output waveform, place shunts
across JU1 and JU2 in the combinations shown in Fo (MHz) = IIN(µA) ÷ COSC (pF) [1]
Table 1. These jumpers set address pins A0 and A1 to where: IIN = current injected into IIN
TTL/CMOS-logic levels. External control may be initiat- = VREF ÷ (R3 + R12)
ed by connecting an external source to the A0 and
A1 pads and removing the shunts on JU1 and JU2. = 2.5V ÷ (0k to 50k + 3.3k )
Note that there are 10k pull-up resistors to +5V on the COSC = external oscillator capacitor (C1)
Evaluates: MAX038 A0 and A1 address lines. To use an external input current, connect the external
current source to the IIN pad and remove the JU5 shunt
Table 1. Waveform Jumper Select completely. Note that there is a 3.3k resistor in series
JU1 JU2 OUTPUT WAVEFORM with the device IIN pin.
Don't Care Open Sine Wave
Open Short Triangle Wave FADJ Control
Short Short Square Wave Varying the FADJ voltage will also vary the output fre-
quency. With a shunt across pins 1 and 2 of JU3, the
Table 2. Frequency and Duty-Cycle Jumper Select R2 potentiometer will vary the voltage applied to the
FADJ pin. With the JU3 shunt on pins 2 and 3, the FADJ
SHUNT pin is grounded. Grounding the FADJ pin sets the out-
JUMPER MAX038 OUTPUT
LOCATION put to the fundamental output frequency (Fo), as
1 & 2 Adjustable Frequency given by equation [1].
JU3 2 & 3 Pre-Set Frequency* To use an external FADJ voltage, connect the external
1 & 2 Adjustable Duty Cycle
JU4 source to the FADJ pad and remove the JU3 shunt
2 & 3 Fixed 50% Duty Cycle completely. Limit the external FADJ voltage to ±2.4V.
* Note: Frequency pre-set by oscillator capacitor (C1) and input
current (position of R3) as specified by formula [1]. Duty-Cycle Control
Output Frequency The voltage on the DADJ pin controls the duty cycle of
the output waveform. With the JU4 shunt on pins 1 and 2,
The output frequency is controlled by the oscillator the R1 potentiometer will vary the voltage applied to the
capacitor (C1), the current injected into the IIN pin, and DADJ pin, thus varying the duty cycle 15% to 85%. With
the voltage on the FADJ pin. The EV kit allows indepen- the JU4 shunt on pins 2 and 3, the DADJ pin is grounded.
dent adjustment of both input current (R3) and FADJ Grounding the DADJ pin fixes the duty cycle at 50%.
voltage (R2). Refer to the Detailed Description section
of the MAX038 data sheet for additional theory of oper- To use an external DADJ voltage, connect the external
ation. voltage source to the DADJ pad and remove the JU4
shunt completely. Limit the external DADJ voltage to
±2.3V.
2 _______________________________________________________________________________________
MAX038 Evaluation Kit
Evaluates: MAX038
Output Buffer Extending the Output
The MAX038 output amplitude is fixed at 2Vp-p. The Frequency Range
MAX038 output is capable of driving a capacitive load The components supplied with the EV kit allow an out-
up to 90pF. The MAX442 amplifier buffers the MAX038 put frequency range of 325kHz to 10MHz. The frequen-
output to a 50 coaxial cable. The MAX442 is set at a cy range is controlled primarily by the oscillator capaci-
gain of 2V/V, so that the output amplitude remains 1V/V tor (C1) and the input current, which is a function of the
after the 50 back termination. The EV kit's OUT pad reference voltage and potentiometer R3. The resulting
provides access to the output of the MAX038 prior to frequency range can be shifted up or down depending
the MAX442 buffer stage. The MAX442 output connects on the value of C1. Refer to the Output Frequency vs.
to the BNC connector through a 50 resistor to back Input Current graph which appears in the Typical
terminate a 50 coaxial cable. When a terminated 50 Operating Characteristics of the MAX038 data sheet.
cable is connected, this resistor forms a voltage divider The upper end of the range can be extended by reduc-
with the load impedance, which attenuates the signal ing C1. The lower end of the range can be reduced by
by one-half. The MAX442 is operated with a 2V/V increasing the value of C1. Take care when selecting
closed-loop gain to provide unity gain at the 50 alternate capacitors if stable operation over tempera-
cable's output. ture is desired. Ceramic capacitors with low tempera-
The MAX442 is actually a 2-channel amplifier. A built- ture coefficients give the best results. Refer to the
in multiplexer allows either of two input signals to be Selecting Resistors and Capacitors section of the
selected. TTL-level address pin A0 selects either IN0 MAX038 data sheet for further details.
or IN1. The MAX038 output is connected to MAX442
input IN0. IN1 is unused and connected to ground; it Sync Output
may be used by cutting the JU7 trace, thus discon- and Phase-Detector Input
necting IN1 from ground. Likewise, the MAX442 Refer to the SYNC Output and Phase Detector sections
address pin A0 can be disconnected from ground by of the MAX038 data sheet for details of circuit synchro-
cutting the JU8 trace. Pull up A0 to +5V to select IN1. nization. Access to the Phase Detector Input (PDI) and
See the MAX442 data sheet for additional operation SYNC is provided at pads PDI and SYNC.
details. High-speed transient currents in DGND and DV+ can
Reference Voltage cause a switching spike in the output waveform at the
The MAX038 includes a 2.5V bandgap reference capa- zero-crossing point. A lowpass output filter, as shown in
ble of sourcing 4mA and sinking 100µA. Access to the Figure 3 of the MAX038 data sheet, may be used to
reference voltage is provided at the REF pad. The ref- greatly reduce the spike. Complete LC filter assemblies
erence voltage is primarily used to provide stable cur- (S3LP series) are available from Coilcraft (phone:
rent to IIN and to bias DADJ and FADJ. 708-639-6400). If the SYNC output is not required, dis-
abling the SYNC circuit will eliminate the switching
spike. Cut the trace between the DV+ and +5V pads to
disable the SYNC output.
_______________________________________________________________________________________ 3
MAX038 Evaluation Kit
1 8
IN0 A0
U2 JU8 C12
CUT HERE 0.1µF
2 MAX442 7
GND V+ +5V
JU7
CUT HERE J1
3 6 BNC
IN1 VOUT OUTPUT
R7 R6
4 5 270
-5V V- 51
IN-
C11
0.1µF R8
270
REF
+5V 5V
C2 C4 C5
Evaluates: MAX038 R4 R5 0.1µF
10k 10k 4.7µF 0.1µF
1 20
REF V-
R9
JU1 0
2 19
GND OUT OUT
18
JU2 GND
3
A0 A0 U1
17 +5V
4 MAX038 V+
A1 A1 C8 CUT HERE
C1 4.7µF TO DISABLE
C9
82pF SYNC
5 DV+ 16 0.1µF
COSC DV+
C6
4.7µF C7
0.1µF
6 15
GND DGND GND
JU6
R10 CUT HERE
0
DADJ 7 14
DADJ SYNC SYNC
R1
20k 1 2 3
8 13
JU4 FADJ PDI PDI
R11
C10 0
0.1µF R2 9 12
20k 1 2 3 GND PDO PDO
C3
JU3 0.1µF
R3 10 11
IIN GND
50k JU5 R12
3.3k
FADJ
IIN
Figure 1. MAX038 EV Kit Schematic
4 _______________________________________________________________________________________
MAX038 Evaluation Kit
Evaluates: MAX038
Figure 2. MAX038 EV Kit Component Placement Guide-Component Side
_______________________________________________________________________________________ 5
MAX038 Evaluation Kit
Evaluates: MAX038
Figure 3. MAX038 EV Kit PC Board Layout-Component Side
6 _______________________________________________________________________________________
MAX038 Evaluation Kit
Evaluates: MAX038
Figure 4. MAX038 EV Kit PC Board Layout-Solder Side
_______________________________________________________________________________________ 7
MAX038 Evaluation Kit
NOTES
Evaluates: MAX038
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.