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08/14/03 www.irf.com 1 low voltage high efficiency radiation hardened dc/dc converter z-zeries description output voltages from 1.5 to 3.3 volts 20 amps output current synchronous rectification efficiency up to 88% nominal 28 volt input total ionizing dose > 100krad (si) no see to let > 80 mev ? cm 2 /mg -40c to +85c operating range short circuit protection remote sensing adjustable output voltage flexible mounting configuration high power density derating to mil-std-975, mil-std-1547, gsfc-ppl-21 fully isolated - input to output and to case complimentary emi filter available base plate conduction cooling features 28v input, single output the z-series of dc/dc converter modules has been specifically designed in response to the need for low voltage at moderate current levels supplied with the high efficiency and tight regulation dictated by modern digital processing applications. these converters are designed specifically for operation in radiation environ- ments that are presented to commercial communica- tion satellites operating in long term geo and leo or- bits. they have been created to complement the spec- trum of electrical and radiation performance available in the advanced analog art2815t and m3g-series converters. requirements occurring in space vehicles operating in geostationary orbits, launch boosters, sci- entific space probes and similar applications requiring a low voltage, high efficiency converter with well char- acterized radiation hardness performance will be opti- mally satisfied by the z-series converters. an additional benefit of the z-series is high power den- sity. this is facilitated by utilizing the best features of chip and wire hybrid technology and surface mount fab- rication techniques. the hybrid portion is fabricated in a facility fully qualified to mil-prf-38534 and pro- cessed to class k requirements. the standard process- ing adopted for the z-series module has been created to assure with margin the reliability required for space applications. applicable generic lot qualification test data including radiation performance will be made avail- able on request. variations to the standard screening may be accommodated. consult ir santa clara for special requirements. pd- 94693a
2 www.irf.com z-series circuit description the z-series converters utilize a single ended forward topology with resonant reset. the nominal 250khz switch- ing frequency has been selected to optimize magnetic element size and switching loss. electrical isolation be- tween the primary and secondary sides of the converter is assured through exclusive use of magnetic coupling for all signals crossing the primary/secondary barrier. volt- age feed-forward is utilized to provide high line rejection. an under-voltage lockout circuit prohibits the converter from operating when the line voltage is too low to maintain the output voltage. the converter will not start until the line voltage rises to approximately 16.5 volts and will shut down when the input voltage drops below 15.5 volts. this hys- teresis voltage reduces the possibility of line noise inter- fering with the converter?s start-up and shut down. an input overvoltage circuit is also in place that will shut down the converter if the input voltage exceeds approximately 60 v, thereby precluding the possibility of exceeding the voltage rating of the synchronous rectifiers. a voltage of 0.8v or less will cause the converter to shut- down. the pin may be left open for normal operation and has a nominal open circuit voltage of 4.0v. to achieve the high efficiencies characterizing these con- verters, synchronous rectifiers have been used in place of rectifying diodes thus minimizing the conduction losses associated with those elements. an internal emi filter reduces the conducted emissions on the input power leads. a two-stage output filter reduces the typical output fundamental ripple to less than 20mv peak-to-peak. output current is limited under any load fault condition to approximately 125% of rated. an overload condition causes the converter output to behave like a constant current source with the output voltage dropping below nominal. the converter will resume normal operation when the load current is reduced below the current limit point. this pro- tects the converter from both overload and short circuit conditions. the current limit point exhibits a slightly nega- tive temperature coefficient to reduce the possibility of thermal runaway. a synchronization input is provided allowing operation of the converter synchronously with a user provided fre- quency source. this input permits synchronization of the converter to any compatible external frequency source operating in the band of 225 to 300 khz and is edge triggered with synchronization initiated on the negative transition. this signal should be a negative going pulse referenced to the input return and have a 20% to 80% duty cycle. compatibility requires the negative transition time to be less than 100 ns with minimum pulse amplitude of +4.25 volts referred to the input return. in the event of failure of an external synchronization source, the con- verter will revert to its own internally set frequency. when external synchronization is not desired, the sync input may be left open (unconnected) permitting the converter to operate at its? own internally set frequency. an output adjust pin is provided permitting the user to adjust the output voltage by approximately 5%. adjust- ment is accomplished by connecting a resistor brtween the adjust pin (pin 10) and +sense (pin 9) or ?sense (pin 11). the direction of the output change is opposite the sign of the sense pin to which it is connected, that is connecting to the ? sense pin causes an increase and connecting to the +sense pin causes a decrease in output voltage. remote sense is provided to compensate for conduction losses in the connections between the converter outputs and the load. the use of this sense feature permits com- pensating for as much as 250 mv in both the output and return lines. (500 mv each leg, round trip) an external inhibit port is provided to control converter oper ation. the nominal threshold relative to the input re- turn (pin 2) is 1.4v. if 2.0 volts or greater are applied to the inhibit pin (pin 3) then the converter will operate normally. design methodology the z-series was developed using a proven conserva- tive design methodology that includes selecting radiation tolerant and established reliability components and fully derating to the requirements of gsfc ppl-21, mil-std- 975 and mil-std-1547. heavy derating of the radiation- hardened power mosfet virtually eliminates the possi- bility of segr and seb. a magnetic feedback circuit is utilized instead of opto-couplers to minimize temperature, radiation and aging sensitivity. pspice was used exten- sively to predict and optimize circuit performance for both beginning and end-of-life. thorough design analyses in- clude worst case, stress , thermal and reliability (mtbf) .
www.irf.com 3 z-series for notes to specifications, refer to page 4

electrical characteristics - 40c t base +85c, v in =28 v dc 5%, c l =0, unless otherwise specified.

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www.irf.com 5 z-series flight screening for z-series typical mtbf for z-series mtbf vs temperature 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0 102030405060708090 base plate tem p erature mtbf (10e6) hr s . ( ! !6c c ,af /b 1&a$ 0
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6 www.irf.com z-series single output functional block diagram synchronous rectifier output filter power switch current sense rectifier gate drive circuit secondary bias regulator error am plifier voltage conditioner remote sense sample hold input emi filter 1 2 4 3 5 7 6 8 9 11 primary bias regulator /switchover under/over voltage inhibit 12 pulse-width modulator /controller drive cs drive fb sync shutdown 10 . ( . ( ! 4 ( 1 " ( % 0 @ $ # $ ! ( /g ( !! $ 5 ( !1 pin designation part numbering z 28 01r5 s /em model input volta g e 28 = 28v nominal outputs s = sin g le output volta g e 01r5 = 1.5v 02r5 = 2.5v 03r3 = 3.3v screening /em = en g ineerin g model blank = fli g ht model
www.irf.com 7 z-series world headquarters: 233 kansas st., el segundo, california 90245, tel: (310) 252-7105 ir santa clara: 2270 martin av., santa clara, california 95050, tel: (408) 727-0500 visit us at www.irf.com for sales contact information . data and specifications subject to change without notice. 08/03 mechanical diagram 2.410 max 3.060 3.510 max 1.960 0.50 ? 0.143 thru 5 places 0.060d 0.240 l max 6 pins mountin g plane +.004 -.003 0.767 1.425 3 = spaces @ 0.454 = 1.362 5678 2 1 11 10 9 12 3 4 0.30 0.40 0.44 0.220 0.220 0.375 0.125 0.34 0.40 0.20 0.133 0.133 0.740 max 0.015 0.031d 0.220 l max 6 pins 0.473 0.725 max hi g hest component tolerance unless otherwise specified: x.xx 0.010 x.xxx 0.005

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