description the qch28512t/rch28512t series of dc-dc convert- ers provides the ruggedness, reliability and features re- quired to meet the advanced challenges of today's hi-rel market. this family of converters uses all surface-mounted hybrid components including magnetics, all ceramic capaci- tors and ultrasonic wirebonds to give long life in full tempera- ture range and high acceleration environments. there is no power derating anywhere in the C55c to 125c operating range. this product family is tolerant of many types of faults including load short, load overload, loss of voltage feedback, large forward and reverse voltages applied to the synchroniza- tion pin and input overvoltage. this converter family will operate during input transients to 80 volts. the output voltages have little overshoot during the input voltage transient such that typical logic and linear parts on the outputs will stay well within data sheet absolute maximums. other operational features include low duty factor current limit and dynamic current limit threshold. the current limit operates in a cyclic on-off mode with an on time of about 2 milliseconds and an off time of 20 milliseconds for a duty factor of about 10 percent. this limits the converter dissipation to about 1 watt, so there is no danger of overheating during an output fault at 125 c. the dynamic current limit threshold allows over 50 percent more current to flow for a short time after power application, release from shutdown or recovery from previous current limit allowing large load capacitances to be charged during turn-on. this converter family is a push-pull 400 khz forward con- verter with full isolation between the input side, output side and case. this isolation is achieved without optocouplers for an even greater margin of reliability. the converter is housed in a power dip package and is hermetically sealed. the rch28512t has tabs for bolting the device down. external connections block diagram hi-rel design ? replaces apex dt28512t/f ? wave solderable package ? all ceramic capacitors ? no optocouplers ? surface mount magnetics ? withstands 3000 g y1 axis ? over-voltage protection (ovp) option other features ? triple output ? no derating ? ?55c to +125c ? wide supply range ? 16 to 40 volts ? high isolation ? 500v ? high power density ? 23 w/in 3 ? remote shutdown ? external synch input (fully ttl compat- ible option) 4707 dey road liverpool, n.y. 13088 m.s.kennedy corp. (315) 701-6751 qch28512t/ rch28512t iso-9001 certified by dscc 30w triple dc-dc converters preliminary rev. - 6/01 1 qch28512t rch28512t 1 2 3 4 5 positive input +5 out out common -12 out +12 out 10 9 8 7 6 input common synch inhibit case gnd case gnd
specifications input voltage v in no load 1, 2, 3 0 28 50 vdc normal to full load 16 40 operating 1 50 80 vpk transient uvlo v uvlo 1, 2, 3 10 12.5 14 vdc input current i in noload 1, 2, 3 0.12 adc full load 2 1.25 1.57 1.65 inhibited 0.0001 0.002 0.005 output current 3 i main 1 4.00 6.00 adc 2, 3 i +aux 1 0.42 0.83 2, 3 i -aux 1 -0.42 -0.83 2,3 output voltage 2,4 v main 1 4.95 5.0 5.05 vdc 2,3 v +aux 1 11.85 12.00 12.15 2, 3 v -aux 1 -11.85 -12.00 -12.15 2, 3 ovp 4 v ovp 1 5.3 5.6 5.9 vdc 2, 3 5.14 6.10 output power p out p main 1, 2, 3 0 20 30 w p aux 01020 p tot 030 p overload 30 35 65 (5) efficiency 2 h 163 % 2, 3 line regulation vr line v in 1 5 10 mv main 16-40v 2, 3 10 50 1 50 75 aux 2, 3 120 150 load regulation vr load i main 1 5 20 mv main 0 ? 4a 2, 3 20 50 i aux 1 50 75 aux 0 ? 0.42a 2, 3 150 250 input voltage range 0 to 50 vdc input voltage transient range 80v@50ms output withstand voltage 25 vdc storage temperature C65 to +150c operating temperature C55 to +125c temperature, pin soldering 10 seconds 300 c max absolute maximum ratings absolute maximum ratings specifications qch28512t/rch28512t test group a 12 parameter symbol conditions subgroup min typical max units comment unless noted: C55c t case 125c, 16vdc v in 40vdc, p main = 20w, p+ aux = p- aux = 5w. 2 preliminary rev. - 6/01
cross regulation vr cross i aux 1 5 20 mv main 0 ? 0.42a 2, 3 20 50 i main 1 50 75 aux 0 ? 4a 2, 3 150 250 current limit i lim 1 115 125 % 2, 3 load fault power p d overload 6 1, 2, 3 14 25 w short ckt. 6 inhibit pin voltage 7 v enh enabled 1, 2, 3 12 16.8 v dc v enl inhibited 0 5 inhibit pin current 7 i enh enabled 1, 2, 3 0 10 a dc i enl inhibited 650 1200 1800 isolation r iso 500v dc 1, 2, 3 100 meg w primary to secondary to case capacitive load c l 1, 2, 3 330 500 f main 10 22 aux input current ripple 2 i rip 4 100 ma rms 5, 6 120 250 output voltage ripple v rip 4 15 45 mv rms main 5, 6 30 90 4 12 36 aux 5 ,6 25 75 switching frequency f sw 4, 5, 6 350 400 450 khz sync. frequency f sync 4, 5, 6 300 650 khz sync. pin voltage 8 v hi 1, 2, 3 2.4 C v dc v lo C 0.4 sync. pin current i syn h 1, 2, 3 -400 a dc i syn l -500 -750 turn on time 9 t on 448ms turn on overshoot vt on c l =0 4 0 300 mvdc main 4 900 aux step load transient, vt load c l =0, i main =50 ? 100% 4 -800 +800 mvdc main response c l =0, i aux =50 ? 100% 4 500 750 aux specifications qch28512t/rch28512t test group a 12 parameter symbol conditions subgroup min typical max units comment unless noted: C55c t case 125c, 16vdc v in 40vdc, p main = 20w, p+ aux = p- aux = 5w. 3 preliminary rev. - 6/01
step load transient 10 tr load c l =0 4 0.05 0.10 ms main recovery 4 3 5 aux step line transient, vt line c l =0 4 150 250 mvdc main response 4 100 250 aux step line transient 10 tr line c l =0 4 0.05 0.10 ms main recovery 4 3 5 aux load fault transient, vt flt c l =0 4 0 300 mvdc main response 4 900 aux load fault transient 10 ,tr flt c l =0 4 40 100 ms main response 4 tbd aux inhibit delay 11 td inh c l =0 4 0.1 0.2 ms main 4 tbd aux inhibit recovery 9 tr inh c l =0 4 4 8 ms main 4 tbd aux specifications qch28512t/rch28512t notes: 1. under voltage lock out (uvlo) is approx. 10.5-13.5 vdc. 2. vin = 281 v dc. nominal output power: p main = 20w, p+ aux = 5w, p- aux = 5w. 3. full power output must be equal to or less than 30 watts. short duration aux current is 2a peak. 4. over-voltage protection (ovp) guaranteed by design not to exceed 6v dc on main output under any static condition at room temperature. on models with ovp option, only. therefore this parameter is limited to <5.5v on these models. 5. short term over-load (stol). 6. continuous overload. auxiliary outputs are protected with thermal shutdown. 7. internal pull-up typically 22k ohms to v in . for 80-volt transients, input device must be able to sink at least 3.5 ma. 8. internal pull-up approximately 22k ohms to typically 12v. this is an open collector, ttl compatible, edge triggered active lo w input. a valid low must exist for 20% to 80% duty ratio. the converter takes approximately 2 ms to synchronize. for "ttl sync" option v max 55v. 9. time for outputs to reach 90% of final value. measured from valid inhibit high v enh or valid v in . 10. measured from start of transient to response within 90% of final value. 11. time for outputs to reach 50% of initial value. measured from valid inhibit low v enl or v in below uvlo. 12. as per mil-prf-38534. test group a 12 parameter symbol conditions subgroup min typical max units comment unless noted: C55c t case 125c, 16vdc v in 40vdc, p main = 20w, p+ aux = p- aux = 5w. 4 preliminary rev. - 6/01
qch28512t/rch28512t typical performance graphs 5 preliminary rev. - 6/01 -12v 12v 5v -12v 12v 5v -12v 12v 5v -12v 12v 5v
synchronization the synch pin allows the converter to be synchronized in frequency and phase with an external signal. this signal should be ttl compatable (0.8 max v inl and 2.0 v min v inh ). overdrive up to 10v is not harmful. transient voltage withstand is 50v with respect to input common. the frequency applied to this pin must be between 350 and 600 khz with duty factor anywhere from 20 to 80 percent. shutdown the shutdown pin turns off the power conversion circuits and puts the converter in standby mode. the shutdown pin is referenced to the input common pin. in standby mode the converter only draws 2.2 ma typical (5.0 ma maximum) input current from v in . for normal operation this pin should be open circuited and allowed to float. for shutdown pull this pin below 1 volt. the maximum open circuit voltage that will appear on this pin is 15 volts. see graphs for typical time response of the converter to assert and release shutdown. qch28512t/rch28512t application information load fault response the qch28512t/rch28512t family of dc-dc convert- ers use a common fault protection approach. load fault conditions include short-circuit and overload conditions. the qch28512t/rch28512t converters respond to load faults on the main output (+5v) by turning off all power conversion circuits for a period of time and then attempting to restart. the figure below shows the fault protection response to an output overload, the turn on plus detect fault time is typically two milliseconds and the off time is typically twenty milliseconds. the net "on" duty factor during a fault is only 10 percent, resulting in low converter dissipation and immunity from overheating at 125c. an added benefit to this method is that the amount of output current that defines a fault is pro- grammed to increase by 1.5x during the first few hundred microseconds of operation after power-up, load fault recov- ery or release of the shutdown pin. this allows qch28512t/ rch28512t converters to bring up capacitive and other difficult loads more reliably than some competing converters. normal time normal load fault v o i o the auxiliary outputs have individual overcurrent protection and independent fault protection. a rapid response thermal shutdown feature adds to the reliability of the converter by protecting each auxiliary output from load faults. substantial current may drawn from either auxiliary output but is limited to safe levels by independent current sensing circuitry on each. if the fault or overload continues for extended periods the thermal shut down circuitry will cycle the output to limit the maximum internal hotspot temperature to a safe level. 6 preliminary rev. - 6/01
the information contained herein is believed to be accurate at the time of printing. msk reserves the right to make changes to its products or specifications without notice, however, and assumes no liability for the use of its products. please visit our website for the most recent revision of this datasheet. m.s. kennedy corp. 4707 dey road, liverpool, new york 13088 phone (315) 701-6751 fax (315) 701-6752 www.mskennedy.com note: all dimensions are 0.010 inches unless otherwise labeled. esd triangle indicates pin 1. qch28512t the above example is an industrial grade 5v and 12v triple output converter without tabs ordering information screening blank= industrial; e= extended reliability; h= class h; k= class k triple output output voltages 512=5v and 12v nominal input voltage general part number (qch=no tabs; rch=tabs) 7 mechanical specifications preliminary rev. - 6/01 qch28512t rch28512t
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