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features high efficiency to 89% power density up to 1.78w/cm 3 (28w/in 3 ) 1.5kv input to output isolation industry standard pinout ul 1950 recognised non latching current limit constant 350khz frequency versatile control options continuous rating to 30w at 60c without heatsink operation to zero load protected against all load faults internal over temperature protection uses no electrolytic capacitors ul 94v-0 package materials description the nph25s series of dc-dc converters combines ease of application with versatility. the pin pattern is based on the popular industry standard, but two additional pins may optionally be fitted to provide a variety of features not commonly found on units of this type. high efficiency enables full rating to be achieved in a small package without heatsinking, and a high surge capability will provide for start-up and transient loads, whilst being thermally protected against sustained overload. overload protection of the ?constant current? type ensures start-up into complex load conditions. the copper case achieves efficient heat transfer and screening. the product range has been recognised by underwriters laboratory (ul) to ul 1950 for operational insulation, file number e179522 applies. newport components nph25s series 1 nph25s series isolated 25w single output dc-dc converters single output type (top view) *optional pin connections preliminary notice : this is not a final specification. some parametric limits may be subject to change. ?v in 0v +v in adj* +v out ss* ul 1950 recognised file number e179522.
absolute maximum ratings input voltage, 24v input types ?0.5v to 40v input voltage, 48v input types ?0.5v to 80v output voltage ?0.3v to regulated voltage output trim control ?1vto +30v synchronisation/shutdown control 15v relative to input return electrical specifications specifications typical at t a =25c, nominal input voltage rated output current unless otherwise specified. order code 1 nominal input voltage output voltage output current efficiency (v) (v) (a) (%) nph25s2403i 24 3.4 7.3 81 nph25s2405i 24 5.1 5.0 84 nph25s2412i 24 12.1 2.1 86 nph25s2415i 24 15.1 1.7 87 nph25s4803i 48 3.4 7.3 83 nph25s4805i 48 5.1 5.0 85 nph25s4812i 48 12.1 2.1 88 nph25s4815i 48 15.1 1.7 89 2 newport components nph25s series isolated 25w single output dc-dc converters 1 if optional pins adj and ss are required (as indicated in the pin connections diagram) prefix the ending ?i? with an e when ordering, e.g. nph25s4803ei.
family characteristics - input specifications typical at t a =25c, nominal input voltage and rated output current unless otherwise specified. parameter conditions min nom max units voltage range continuous operation, 24v input types 18 24 36 v continuous operation, 48v input types 36 48 75 family characteristics - output specifications typical at t a =25c, nominal input voltage and rated output current unless otherwise specified. parameter conditions min typ max units voltage set point error 50% load 0.5 % overall voltage error case temperature ?40 to 110c load 0% - 100% input specified range 2.5 % temperature coefficient of output voltage (slope) 250 ppmc deviation of output voltage temperature min-max 0.5 1 % line regulation operating voltage range, 50% load 0.1 % load regulation 0% - 100% rated load 1 0.5 % ripple rms 70 mv family characteristics - isolation specifications typical at t a =25c, nominal input voltage and rated output current unless otherwise specified. parameter conditions min typ max units isolation voltage flash tested for 1 second 1500 vdc resistance viso=500vdc 1 4000 g ? newport components nph25s series 3 nph25s series isolated 25w single output dc-dc converters 1 a minimum load of 10% of rating is recommended for typical applications ; see application notes.
family characteristics - control specifications typical at t a =25c, nominal input voltage and rated output current unless otherwise specified. parameter conditions min typ max units voltage trimming range at rated load, trim control at either output 10 % remote switch input 1 (voltage relative to input negative) not operating ?15 0 1.5 v operating, open circuit voltage 9 10 11 start delay time from application of valid input voltage to output being in specification 25 50 ms synchronisation 1 specified drive signal 320 440 khz switching frequency 330 350 395 khz family characteristics - general specifications typical at t a =25c, nominal input voltage and rated output current unless otherwise specified. parameter conditions min typ max units package weight 45 g thermal protection operates at case temperature 110 c current limit continuous short circuit causes no damage family characteristics - environment parameter conditions min typ max units case temperature full load ?40 110 c storage absolute max internal temperature ?40 125 c relative humidity non-condensing 85c 85 % 4 newport components nph25s series isolated 25w single output dc-dc converters 1 optional - where fitted.
typical characteristics ul 1950 recognition - max permissible loads for a given ambient temperature for any nph25s model temperature (c) power (w) temperature (c) power (w) 40 25.0 80 13.9 50 22.2 85 12.5 60 19.4 90 11.1 70 16.6 max power rating with case temperature maintained by external means (eg forced air cooling) part number case temperature units 100c 105c 110c nph25s2403 24 20 15 w nph25s2405 25 22 18 nph25s2412 30 24 21 nph25s2415 30 27 22 nph25s4803 25 20 16 w nph25s4805 25 24 20 nph25s4812 30 29 24 nph25s4815 30 30 26 newport components nph25s series 5 nph25s series isolated 25w single output dc-dc converters temperature ( c) temperature ( c) -40 -40 -20 -20 00 20 20 40 40 60 60 80 80 100 100 120 120 35 35 00 55 10 10 15 15 20 20 25 25 30 30 output power (w) output power (w) 2403 4803 4815 2415 2412 2405 4805 4812 thermal performance
application notes in a typical application, the nph series of dc-dc converters require nothing more than a dc supply of correct polarity and voltage to generate its specified output. these notes are intended to offer help in the use of other facilities offered by these converters, and to provide assistance in achieving their full potential. the product range includes optional control pins on each side of the isolation barrier. these can be programmed with external circuits to perform a variety of functions. voltage trimming the trimming (adjust) input on the secondary side allows output voltage adjustment within the capability of the power circuit. when open circuit, the trimming pin adj operates at near half the output voltage. a basic trimming arrangement consists of a potentiometer of 10k ? to 100k ? connected across the output, with its wiper connected to the adj pin (see figure 1). dependent on model, the output will be reduced by about 15% when the wiper is at the positive output, or increased by about 24% when at the negative rail. regulation will be maintained to at least 10% adjustment either way. if finer adjustment is required, a resistor may be included between the wiper and the pin. for example, 62k ? will restrict a 3.3v model to 5% adjustment range. the corresponding values for the other voltages are 5v:56k ? , 12v:100k ? and 15v:150k ? . set voltage the output voltage of all units is set to 100mv above nominal, to offset resistive losses and thus assist with worst case error calculations. for the ei versions, this allowance can be altered with a single fixed resistor, connected from the trimming pin to one of the output pins. other trimming functions the voltage applied to the trim pin need not be from a potentiometer. the trim facility may be driven electronically to provide ?margining?, remote sense, active load sharing, current control or remote programming (there is a minimum output voltage below which control is not possible). shutdown when the shutdown pin is shorted to the negative input, the converter will stop. its current consumption will then be less than 1ma at nominal supply voltage. the low voltage must be less than 1.5v to ensure that the unit stops, and must sink the above small input current. the unit will restart if the control pin is left open circuit or raised to a value close to its normal open circuit voltage. this is typically 10v. note however, that the unit will not meet specification while a significant current drain remains. if the shutdown pin is to be connected to a long wire, it is recommended that a capacitor decouples the pin to the supply common in order to avoid the risk of injecting noise into the converter circuit. a series resistor may also be helpful. values of 10nf and 1k ? may be used. many nph series converters may be switched together simply by linking the primary control pins. the primary common pins must also be linked. 6 newport components nph25s series isolated 25w single output dc-dc converters figure 1 : voltage trimming ?v in +v in dc +v out adj 0v 100k ? dc
frequency control if the primary side dc control voltage is pulled away from its open circuit voltage, the converter frequency will be changed, approximately in proportion to the voltage. with a 8.5vdc voltage to ss pin, the typical switching frequency will be 300khz. if this is raised to 15vdc, the switching frequency will typically be 510khz. the frequency may thus be moved away from a sensitive value or into a safe area. deviation of at least ?10% to 30% is achievable, though the efficiency will decline with significant changes. also note that if the frequency is lowered, the switching frequency component of output ripple will increase. since the design uses no large electrolytic capacitors, any use of a lower frequency must allow for the effects of increased ripple. additional external filtering may be required. synchronisation the converter frequency may be synchronised to an external frequency by connecting a negative going pulse the sync/shutdown pin. the drive signal is typically 8v to 12v amplitude and 100ns to 200ns duration. a suitable circuit consists of a cmos timer (7555 series or tlc555) connected as an oscillator or as a pulse shaper. its logic output (not the discharge output) should be connected via a 4.7nf capacitor to the converter pin. the synchronised frequency is above the free running value. however, the free running frequency can be lowered, so that sychronisation may include frequencies near or below the natural value. an example of a practical circuit is shown in figure 2, which uses a zener diode to lower the natural frequency. if the zener diode does not have a sufficiently sharp characteristic, it may be necessary to add a bias resistor. several converters of this family may be synchronised from the same reference provided the waveform can be maintained by the use of an adequate driver circuit. if the rise time is more than 20ns, for example, synchronisation may not be achieved over the specified frequency range. for best efficiency, set the frequency within the specified range of its natural state. filtering the module includes a basic level of filtering, sufficient for many applications. where lower noise levels are desired, filters can easily be added to achieve any required noise performance. a dc-dc converter generates noise in two principle forms: that which is radiated from its body and that conducted on its external connections. there are three separate modes of conducted noise: input differential, output differential and input-output. newport components nph25s series 7 nph25s series isolated 25w single output dc-dc converters figure 2 : synchronisation r2 (5k6) d1 (1n4148) 8 ss ic1 (tlc555c) 1 0v 5 6 +10v 4 2 3 c3 (4n7f, 25v) c4 (470nf, 16v) c2 (10nf, 16v) vr1 (8k2) r1 (470r) c1 (100pf, 16v) 7 set frequency 0v zd1 (bzx55c8v2)
this last appears as common mode at the input and the output, and cannot therefore be removed by filtering at the input or output alone. the first level of filtering is to connect a capacitor between input and output returns, to reduce this form of noise. it typically contains high harmonics of the switching frequency, which tend to appear as spikes on surrounding circuits. the voltage rating of this capacitor must match the required isolation voltage. (due to the great variety in isolation voltage and required noise performance, this capacitor has not been included within the converter.) input ripple is a voltage developed across the internal input decoupling capacitor. it is therefore measured with a defined supply source impedance. although simple series inductance will provide filtering, on its own it can degrade the stability. a shunt capacitor is therefore recommended across the converter input terminals, so that it is fed from a low impedance. if no filtering is required, the inductance of long supply wiring could also cause a problem, requiring an input decoupling capacitor for stability. an electrolytic will perform well in these situations. see figure 3 for a recommended configuration to reduce all three conducted modes. the component values and ratings will depend on the converter rating and voltage, and the required noise performance, but the values quoted in figure 3 suit a 48v to 5v 25w converter. the input-output filtering is performed by the common-mode choke on the primary. this could be placed on the output, but would then degrade the regulation and produce less benefit for a given size, cost, and power loss. radiated noise is present in magnetic and electrostatic forms. the latter is suppressed by the metal case, which is connected to the output return, typically a zero-volt point. thanks to the small size of these units, neither form of noise will be radiated ?efficiently?, so will not normally cause a problem. any question of this kind usually better repays attention to conducted signals. mounting considerations the copper case is connected to the output (0v) pin. care is needed in the design of the circuit board on which the converter is mounted. top side tracks must not contact the edge of the case or the ferrite core, visible on the underside of the unit. protection the ?absolute maximum? ratings in the specification define conditions which may degrade life but will not result in immediate damage. this section of the application notes deals with those unavoidable or accidental occasions when the ratings are exceeded. 8 newport components nph25s series isolated 25w single output dc-dc converters figure 3 : recommended configuration to reduce noise 2.2 f 1mh 2.2 f 100 h dc dc 10nf, 250vac y rated 10nf, 250vac y rated 10 h 10 f 100 h
the unit will protect itself against a wide range of abnormal conditions. in others, where failure is inevitable, the consequent hazards have been minimised. if the supply polarity is reversed, the unit is unable to protect itself. the simple preventative measure of a series diode would add unacceptable power loss for the basic product, but it may be appropriate in some applications to fit this diode externally. with no polarity protection, tracks and components will safely fail to high impedance, disconnecting the power. a large fault current will occur in this process. newport components nph25s series 9 nph25s series isolated 25w single output dc-dc converters
? 1.75 1.60 2.54 2.54 20.32 14.84 14.96 5.08 20.32 4.50 3.70 ? 1.04 0.90 10.00 35.00 50.00 * * * * 0.1 x6 holes outline dimensions 1 recommended footprint details 10 newport components nph25s series isolated 25w single output dc-dc converters nph25s4803ei xyyww 1 all dimensions in mm 0.25mm. all pins on a 2.54mm pitch and within 0.25mm of true position. * optional pins (refer to pin connections diagram on page 1).
the following newport components publications are also available : the power components handbook (also in cd rom format) emc design guidelines please contact newport components or your local supplier for a copy of these data books. newport components limited reserve the right to alter or improve the specification, internal design or manufacturing process at any time, without notice. please check with your supplier or visit our web site to ensure that you have the current and complete specification for your product before use. for information and instructions on use, please consult the current power handbook. ? newport components limited 1999 no part of this publication may be copied, transmitted or stored in a retrieval system or reproduced in any way including, but not limited to, photography, photocopy, magnetic or other recording means, without prior written permission from newport components limited. information newport components limited newport components inc. 1 tanners drive, blakelands north 8917 glenwood avenue, raleigh milton keynes mk14 5bu, england nc 27612, usa tel: +44 (0)1908 615232 tel: +1 (919) 571-9405 fax: +44 (0)1908 617545 fax: +1 (919) 571-9262 email: info@newport-comps.com email: info@us.newport-comps.com www: http://www.newport-comps.com members of newport technology group 9000sanph25s issue 4 06/99 dcr 2308

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