general description the max9647 evaluation kit (ev kit) provides a proven design to evaluate the max9647 single comparator. the ev kit circuit can be easily configured by installing shunts and changing a few components to support multiple configurations for comparator applications such as logic- level translation and relaxation oscillator. the ev kit provides 0603 component pcb pads for ease of evalu - ation. the ev kit operates from a +1.8v to +5.5v vdd supply. the ev kit comes with a max9647auk+ installed. contact the factory for samples of the pin-compatible max9648auk+. features accommodates multiple configurations for the comparator accommodates easy-to-use components proven pcb layout fully assembled and tested 19-6709; rev 0; 5/13 ordering information appears at end of data sheet. note: indicate that you are using the max9647 when contacting this component supplier. designation qty description c1 1 0.1f 10%, 16v x7r ceramic capacitor (0603) murata gcm188r71c104k c2 1 4.7f 10%, 16v x7r ceramic capacitor (0805) murata grm21br71c475k c3 0 not installed, ceramic capacitor (0603) ju1 1 2-pin header designation qty description in+, in-, out, vdd, vpull 5 red test points r1Cr3, r5 0 not installed, resistors (0603) r4 1 100k? 5% resistor (0603) vss 3 black multipurpose test points u1 1 comparator (5 sot23) maxim max9647auk+ 1 shunt 1 pcb: max9647 evkit supplier phone website murata americas 800-241-6574 www.murataamericas.com component list component supplier max9647 evaluation kit evaluates: max9647/max9648
maxim integrated 2 quick start required equipment max9647 ev kit three adjustable 0 to +5v dc power supplies oscilloscope procedure the ev kit is fully assembled and tested. follow the steps below to verify board operation. caution: do not turn on the power supplies until all connections are completed. 1) verify that a shunt is installed on jumper ju1. 2) set the first dc power supply to +3.3v and connect the positive terminal to vdd and the negative terminal to the gnd pcb pads. 3) set the second dc power supply to +1.5v and connect the positive terminal to in+ and the negative terminal to the gnd pcb pads. 4) set the third dc power supply to +1.0v and connect the positive terminal to in- and the negative terminal to the gnd pcb pads. 5) connect the oscilloscopes channel to the out pcb pad on the ev kit. 6) enable all three power supplies. 7) verify that the out signal is logic-high (3.3v). 8) increase the third dc power supply to +2.0v. 9) verify that the out signal is logic-low (0v). detailed description of hardware the max9647 ev kit is a fully assembled and tested pcb that evaluates the max9647 comparator. the ev kit requires a +1.8v to +5.5v input supply voltage at vdd for normal operation. the ev kit is configurable for different applications such as logic-level translation and relaxation oscillator by installing appropriate components on the pcb. comparator application circuits logic-level translation jumper ju1 is available to change the logic level of the comparators output. install a shunt on ju1 to set vdd as the comparator output logic level. remove the shunt from ju1 and apply the desired voltage at the vpull test point to set the comparator output logic level independent of the supply voltage. note that the out pins on the comparator have an absolute maximum of (vss - 0.3) to +6v. see table 1 for proper jumper ju1 configuration. relaxation oscillator the device can be configured to operate as a simple relaxation oscillator (figure 2), as follows: 1) add a suitable resistor and capacitor at the r3 and c3 pcb pads, respectively. 2) the trip thresholds are set by applying suitable exter - nal hysteresis using r1, r2, and r5 pcb pads. *default position. figure 1. logic-level translator circuit table 1. outa logic level (ju1) shunt position out_ pin logic-high voltage installed* pulled up to vdd through resistor r4 vdd not installed pulled up to vpull through resistor r4 external voltage applied at the vpull test point v dd v in v ref v pull r4 gnd out max9647 max9647 evaluation kit evaluates: max9647/max9648 www.maximintegrated.com
maxim integrated 3 use the following equations to determine the optimum component values: the selection of r3 should be much larger than r4 (r4 << r3). if r4 and r3 are in comparable ranges, the v oh can drastically change, which eventually changes the trip points and hence the desired oscillating frequency. assuming r1 = 78.7k; r2 = r5 = 40.2k; c3 = 10nf; r3 = 100k; r4 = 1k; v pull_up = v dd = 5v. then: dd pp v r2 r = r5 r2 and v = r5 r2 + ? t_rise p p p dd p (r1) (r4) vv (r1 r4 r ) (r ) v 3.003 v (r1 r4 r ) + = ++ += ++ p t_fall p ol pp (r ) (r1) v v v 2.01 v (r r1) (r r1) =+= ++ v t_ris e and v t_fall values also vary with v dd used. using the basic time-domain equation for charging and discharging the respective comparator rc circuit, the comparator oscillator frequency can be calculated using the following equation: during charging phase: t 1/ c( t1) dd t_fall dd v v (v v )e ? =+? where t1 is the time required for the capacitor to charge to v c(t1) = v t_rise. during discharging phase: t2/ c(t2) ol t_rise ol v v (v v )e ? =+? where t2 is the time required for the capacitor to charge to v c(t2) = v t_fall. hence, for the above-mentioned case of component values: dd t_fall rise dd t_rise t_rise ol fall t_fall ol (v v ) t r3 c3 ln and (v v ) (v v ) t r3 c3 ln (v v ) ?? ? = ?? ? ?? ?? ? ?? = ?? ? ?? ?? 3 12 33 t ln( ) and t ln( ); r3 c3 1 10 22 ? = = = = ideally, because t1 = t2. the output square waveform has 50% duty cycle; however, because v oh and v ol are subject to changes, the waveform becomes asymmetric. hence the total time would be: t t1 t2 = + or osc dd t_fall dd t_rise t_rise ol t_fall ol 1 f (v v ) r3c3 ln (v v ) (v v ) r3c3 ln (v v ) 1 1.25khz ( 436 364)s ?? ?? ?? ?? ?? ?? ?? = ?? ?? ? ?? + ?? ?? ? ?? ?? ?? ?? ? ?? ?? ?? ?? ? ?? ?? ?? = = + figure 2. relaxation oscillator circuit v dd r1 r5 in+ in- r2 r3 c3 r4 gnd out max9647 v dd max9647 evaluation kit evaluates: max9647/max9648 www.maximintegrated.com
maxim integrated 4 component selection: choice of r4 (pullup resistor) should be within 500 to few k because r4 affects the time constant, v oh , v t_rise of the circuit. this eventually changes the frequency of oscillation. also ensure that r pull-up is small compared to the feedback resistors and particularly to r3. this way, it does not limit the current in that part of the circuit, but when r4 and r3 are in comparable ranges, the charging phase can take a longer period of time to charge the capacitor, which ultimately affects the oscillating frequency and also makes the duty cycle asymmetrical. other characteristics such as the offset voltage, the input bias current, propagation delay, and temperature also have an effect on the trip points and oscillation frequency. for instance, when c3 = 100pf and r3 = 10k, the capacitance used is in the vicinity of the input capaci - tance of the comparator (~3.5pf). the effective equiva - lent capacitance would be 103.5pf and produce a 3.5% error in the time constant. the board capacitance is not included in this case, which includes more errors. also, the duty cycle is asymmetrical because of r3 being 10 times that of r4. max9647 evaluation kit evaluates: max9647/max9648 www.maximintegrated.com
maxim integrated 5 figure 3. max9647 ev kit schematic max9647 evaluation kit evaluates: max9647/max9648 www.maximintegrated.com
maxim integrated 6 figure 4. max9647 ev kit component placement guide component side figure 6. max9647 ev kit pcb layoutsolder side figure 5. max9647 ev kit pcb layoutcomponent side 1.0? 1.0? 1.0? max9647 evaluation kit evaluates: max9647/max9648 www.maximintegrated.com
maxim integrated 7 #denotes rohs compliant. part type MAX9647EVKIT# ev kit ordering information max9647 evaluation kit evaluates: max9647/max9648 www.maximintegrated.com
? 2013 maxim integrated products, inc. 8 revision number revision date description pages changed 0 5/13 initial release revision history maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifcations without notice at any time. max9647 evaluation kit evaluates: max9647/max9648 maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.
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