not recommended for new designs this product was manufactured for maxim by an outside wafer foundry using a process that is no longer available. it is not recommended for new designs. the data sheet remains available for existing users. a maxim replacement or an industry second-source may be available. please see the quickview data sheet fo r this part or contact technical support for assistance. for further information, contact maxims applications tech support . downloaded from: http:///
eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it ________________________________________________________________ maxim integrated products 1 _______________ge ne ra l de sc ript ion the max038 evaluation kit (ev kit) is a high-freque ncy function generator capable of producing accurate tr i- angle/sawtooth, sine, and square/pulse waveforms up to 10mhz, using the supplied components. output fre - quency and duty cycle are easily adjusted with on- board potentiometers. removable jumpers select sine , square, or triangle waveforms, or fix the duty cycl e at 50%. the output is buffered with a max442 amplifier capable of driving a 50 coaxial cable. the max038 ev kit is fully assembled and tested. ___________________________fe a t ure s ? 325khz to 10mhz operation ? adjustable duty cycle ? 2.5v reference output ? ttl-compatible sync output ? fully assembled and tested ____________________com pone nt list _________________________quic k st a rt 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 connectionsare 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 ______________orde ring i nform a t ion ______________________________ev k it designation qty description u1 1 max038cpp u2 1 max442cpa c1 1 82pf capacitor c2, c3, c5, c7, c9, c10, c11, c12 8 0.1f capacitors c4, c6, c8 3 4.7f capacitors r1, r2 2 20k potentiometers r3 1 50k potentiometer 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 part MAX038EVKIT-DIP 0c to +70c temp. range board type through-hole 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. downloaded from: http:///
ju3 to allow the frequency to be adjusted. verify that there is a shunt on ju5. 4) verify the shunts on ju1 and ju2 for a square-wave output. refer to table 1 for alternate waveform selections. 5) apply power and verify the output waveform. _______________de t a ile d de sc ript ion wa ve form se le c t ion to select the desired output waveform, place shunts across ju1 and ju2 in the combinations shown in table 1. these jumpers set address pins a0 and a1 t o ttl/cmos-logic levels. external control may be init iat- ed by connecting an external source to the a0 and a1 pads and removing the shunts on ju1 and ju2. note that there are 10k pull-up resistors to +5v on the a0 and a1 address lines. * note: frequency pre-set by oscillator capacitor (c1) and input current (position of r3) as specified by formula [1 ]. out put fre que nc y the output frequency is controlled by the oscillato r capacitor (c1), the current injected into the iin p in, and the voltage on the fadj pin. the ev kit allows inde pen- dent adjustment of both input current (r3) and fadj voltage (r2). refer to the detailed description section of the max038 data sheet for additional theory of o per- ation. i nput curre nt cont rol the current injected into the iin pin acts as the p rimary frequency-adjustment control. the r3 potentiometer varies the current to the max038s iin pin. the inp ut current can be easily monitored by removing the ju5 shunt and placing a current meter across the ju5 pi ns. the components supplied on the ev kit will allow an input current range of 50a to 725a. with the vadj pin grounded, the fundamental output frequency (f o ) is as follows: f o (mhz) = i in (a) ? c osc (pf) [1] where: i in = current injected into iin = v ref ? (r3 + r12) = 2.5v ? (0k to 50k + 3.3k ) c osc = external oscillator capacitor (c1) to use an external input current, connect the exter nal current source to the iin pad and remove the ju5 sh unt completely. note that there is a 3.3k resistor in series with the device iin pin. fadj cont rol varying the fadj voltage will also vary the output fre- quency. with a shunt across pins 1 and 2 of ju3, th e r2 potentiometer will vary the voltage applied to t he fadj pin. with the ju3 shunt on pins 2 and 3, the f adj pin is grounded. grounding the fadj pin sets the ou t- put to the fundamental output frequency (f o ), as given by equation [1]. to use an external fadj voltage, connect the extern al source to the fadj pad and remove the ju3 shunt completely. limit the external fadj voltage to 2.4 v. dut y-cyc le cont rol the voltage on the dadj pin controls the duty cycle of the output waveform. with the ju4 shunt on pins 1 a nd 2, the r1 potentiometer will vary the voltage applied to the dadj pin, thus varying the duty cycle 15% to 85%. w ith the ju4 shunt on pins 2 and 3, the dadj pin is grou nded. grounding the dadj pin fixes the duty cycle at 50%. to use an external dadj voltage, connect the extern al voltage source to the dadj pad and remove the ju4 shunt completely. limit the external dadj voltage t o 2.3v. eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it 2 _______________________________________________________________________________________ table 1. waveform jumper select table 2. frequency and duty-cycle jumper select fixed 50% duty cycle 2 & 3 ju4 adjustable duty cycle 1 & 2 pre-set frequency* 2 & 3 ju3 adjustable frequency 1 & 2 max038 output shunt location jumper square wave short short triangle wave short open sine wave open don't care output waveform ju2 ju1 downloaded from: http:///
out put buffe r the max038 output amplitude is fixed at 2v p-p . the max038 output is capable of driving a capacitive lo ad up to 90pf. the max442 amplifier buffers the max038 output to a 50 coaxial cable. the max442 is set at a gain of 2v/v, so that the output amplitude remains 1v/v after the 50 back termination. the ev kits out pad provides access to the output of the max038 prior t o the max442 buffer stage. the max442 output connects to the bnc connector through a 50 resistor to back terminate a 50 coaxial cable. when a terminated 50 cable is connected, this resistor forms a voltage d ivider with the load impedance, which attenuates the signa l by one-half. the max442 is operated with a 2v/v closed-loop gain to provide unity gain at the 50 cables output. the max442 is actually a 2-channel amplifier. a bui lt- in multiplexer allows either of two input signals t o be selected. ttl-level address pin a0 selects either i n0 or in1. the max038 output is connected to max442 input in0. in1 is unused and connected to ground; i t may be used by cutting the ju7 trace, thus discon- necting in1 from ground. likewise, the max442 address pin a0 can be disconnected from ground by cutting the ju8 trace. pull up a0 to +5v to select in1. see the max442 data sheet for additional operation details. re fe re nc e v olt a ge the max038 includes a 2.5v bandgap reference capa- ble of sourcing 4ma and sinking 100a. access to th e reference voltage is provided at the ref pad. the r ef- erence voltage is primarily used to provide stable cur- rent to iin and to bias dadj and fadj. ex t e nding t he out put fre que nc y ra nge the components supplied with the ev kit allow an ou t- put frequency range of 325khz to 10mhz. the frequen - cy range is controlled primarily by the oscillator capaci- tor (c1) and the input current, which is a function of the reference voltage and potentiometer r3. the resulti ng frequency range can be shifted up or down depending on the value of c1. refer to the output frequency v s. input current graph which appears in the typical operating characteristics of the max038 data sheet. the upper end of the range can be extended by reduc - ing c1. the lower end of the range can be reduced b y increasing the value of c1. take care when selectin g alternate capacitors if stable operation over tempe ra- ture is desired. ceramic capacitors with low temper a- ture coefficients give the best results. refer to t he selecting resistors and capacitors section of the max038 data sheet for further details. sync out put a nd pha se -de t e c t or i nput refer to the sync output and phase detector sections of the max038 data sheet for details of circuit syn chro- nization. access to the phase detector input (pdi) and sync is provided at pads pdi and sync. high-speed transient currents in dgnd and dv+ can cause a switching spike in the output waveform at t he zero-crossing point. a lowpass output filter, as sh own in figure 3 of the max038 data sheet, may be used to greatly reduce the spike. complete lc filter assemb lies (s3lp series) are available from coilcraft (phone: 708-639-6400). if the sync output is not required, dis- abling the sync circuit will eliminate the switchin g spike. cut the trace between the dv+ and +5v pads to disable the sync output. eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it _______________________________________________________________________________________ 3 downloaded from: http:///
eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it 4 _______________________________________________________________________________________ max038 u1 gnd ref a1 a0 gnd cosc fadj dadj iin fadj dadj a1 a0 +5v ref iin 3 2 1 gnd out v- v+ gnd max442 u2 gnd in0 in1 v+ a0 vout v- 7 8 6 5 c11 0.1 m f r9 0 w r10 0 w r11 0 w r2 20k r3 50k r1 20k r12 3.3k c12 0.1 m f c5 0.1 m f c9 0.1 m f c3 0.1 m f c7 0.1 m f c4 4.7 m f c6 4.7 m f c8 4.7 m f c2 0.1 m f c1 82pf 2 1 3 4 -5v in- dgnd dv+ pdi sync gnd pdo 2 1 4 3 6 5 8 7 10 9 19 20 17 18 15 16 13 14 11 12 pdo pdi sync gnd +5v dv+ out 5v +5v ju8 cut here ju7 cut here ju6 cut here ju1 ju2 ju5 ju4 ju3 r7 270 w r4 10k r5 10k r8 270 w r6 51 w j1 bnc output 3 2 1 c10 0.1 m f cut here to disable sync figure 1. max038 ev kit schematic downloaded from: http:///
eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it _______________________________________________________________________________________ 5 figure 2. max038 ev kit component placement guide component side downloaded from: http:///
eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it 6 _______________________________________________________________________________________ figure 3. max038 ev kit pc board layoutcomponent side downloaded from: http:///
eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it _______________________________________________________________________________________ 7 figure 4. max038 ev kit pc board layoutsolder sid e downloaded from: http:///
eva lua t e s: m ax 0 3 8 m ax 0 3 8 eva lua t ion k it notes maxim cannot assume responsibility for use of any c ircuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the cir cuitry and specifications without notice at any tim e. 8 _____________________m a x im i nt e gra t e d produc t s, 1 2 0 sa n ga brie l drive , sunnyva le , ca 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0 ? 1996 maxim integrated products printed usa is a reg istered trademark of maxim integrated products. downloaded from: http:///
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