www.irf.com 1 features operates down to 1.0v dropout @ max current 0.015% line regulation 0.01% load regulation 1% reference voltage hermetic to-257aa (isolated tab) package electrically equivalent to lm1085 this part is also available in to-257aa package as om185st 06/24/08 description adjustable low dropout positive voltage regulator OM185SR v adj , 3.0a these three terminal positive adjustable voltage regulators are designed to provide 3.0a with higher efficiency than conventional voltage regulators. the devices are designed to operate to 1.5v input to output differential and the dropout voltage is specified as a function of load current. devices are pin compatible with older three terminal regulators and are supplied in the easy-to-use hermetic metal d2 package. these devices are ideally suited for military applications where small size, hermeticity and high reliability are required. d2 absolute maximum ratings @ t c = 25c parameter symbol value units output current i o 3.0 a differential voltage v diff 29 v thermal resistance, junction to case r jc 4.2 c/w operating junction temperature range t j -55 to +150 storage temperature range t stg -65 to +150 c product summary part number output voltage output current package OM185SR adjustable 3.0a d2 pd-97329
2 www.irf.com OM185SR 1. load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing. 2. line and load regulation are guaranteed up to the maximum power dissipation. power dissipation is determined by the input/output differential voltage and output current. guaranteed maximum power dissipation will not be available over the full input/output voltage range. 3. i full load curve is defined as the minimum value of current limit as a function of input to output voltage. note that power dissipation is only achievable over a limited range of input to output voltage. 4. dropout voltage is specified over the full output current range of the device. notes electrical characteristics t j = 25c (unless otherwise specified) parameter test conditions min. typ. max. units i out = 10ma, (v in - v out ) = 3.0v 1.238 1.250 1.262 10ma i out i full load , 1.5v (v in - v out ) 25v 1.220 1.250 1.270 i load = 10ma, 1.5v (v in - v out ) 15v -0.0150.2 -0.0350.2 (v in - v out ) = 3.0v, 10ma i out i full load -0.50.8 -0.81.0 dropout voltage v ref = 1%, i out = i full load -1.31.5v (v in - v out ) = 5.0v 3.0 - - (v in - v out ) = 25v 0.2 - - minimum load current (v in - v out ) = 25v - 5.0 10 ma thermal regulation 30ms pulse width (guaranteed by design) - 0.004 0.02 %/w f = 120hz, c adj = 25 f tantalum i out - i full load (v in - v out ) = 3.0v adjust pin current - 55 - 10ma i out i full load 1.5v (v in - v out ) 25v temperature stability -55c t j +150c -0.5- long term stability t j = 125c, t = 1000hrs - 0.3 1.0 a -0.25.0 60 75 - db adjust pin current change % v reference voltage % load regulation line regulation current limit a ripple rejection
www.irf.com 3 OM185SR fig 1: typical minimum input/output differential vs output current fig 2: typical short circuit current vs input/output differential fig 3: typical output voltage deviation vs temperature load regulation short circuit current dropout voltage
4 www.irf.com OM185SR the OM185SR series requires the use of an output capacitor as part of the device frequency compensation. for all operating conditions, the addition of 150 f aluminum electrolytic or a 22 f solid tantalum on the output will ensure stability. normally, capacitors much smaller than this can be used. many different types of capacitors with widely varying characteristics are available. these capacitors differ in capacitor tolerance (sometimes ranging up to 100%), equivalent series resistance, and capacitance temperature coefficient. the 150 f or 22 f values given will ensure stability. when the adjustment terminal is bypassed to improve the ripple rejection, the requirement for an output capacitor increases. the values of 22 f tantalum or 150 f aluminum cover all cases of bypassing the adjustment terminal. without bypassing the adjustment terminal, smaller capacitors can be used with equally good results and the table below shows approximately what size capacitors are needed to ensure stability. application notes: stability normally, capacitor values on the order of 100 f are used in the output of many regulators to ensure good transient response with heavy load current changes. output capacitance can be increased without limit and larger values of output capacitor further improve stability and transient response of the regulators. output voltage - adjustable regulators the OM185SR devices develop a 1.25v reference voltage between the output and the adjust terminal (see fig 4). by placing a resistor, r1 between these two terminals, a constant current is caused to flow through r1 and down through r2 to set the overall output voltage. normally this current is the specified minimum load current of 10ma. because i adj is very small and constant when compared with the current through r1, it represents a small error and can usually be ignored. recommended capacitor values input output adjustment 10 f10 f tantalum, 50 f aluminum none 10 f22 f tantalum, 150 f aluminum 20 f fig 4. basic adjustable regulator v out v in r 1 i adj OM185SR v adj 50 a in out adj r 2 v out = v ref 1+ r 2 + i adj r 2 r 1
www.irf.com 5 OM185SR ir world headquarters: 233 kansas st., el segundo, california 90245, usa tel: (310) 252-7105 ir leominster : 205 crawford st., leominster, massachusetts 01453, usa tel: (978) 534-5776 data and specifications subject to change without notice. 06/2008 om 185 s r m device number isolated / non-isolated s = isolated package code r = d2 screening level part numbering nomenclature case outline and dimensions - d2 package notes: 1. dimensioning & tolerancing per asme y14.5m-1994. 2. all dimensions are shown in millimeters (inches). 3. controlling dimension: inch. 4. this outline is a modified to-257aa jedec outline. 5. available with either glass or ceramic seals. pin assignments pin 1 - adjust pin 2 - v out pin 3 - v in
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