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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


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     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













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                      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.