um9989 microsemi microwave products 75 technology drive, lowell, ma. 01851, 978-442-5600, fax: 978-937-3748 page 1 fast mri protection diodes tm ? www. microsemi .com copyright ? 2007 rev: 2009-11-09 rohs com p liant versions available description the um9989 diode series was designed to protect mri receivers from high rf energy fields including long rf pulses and rf spike pulses present in most mri machines. the um9989 acts as a passive protector (limiter) for the mri receiver. no forward bias voltage is required to turn on the diode. it is self-biased by the rf transmitter pulse power. a switch driver is not needed for this receiver protection application. receiver protector diodes appear directly across the input port of the receiver. they are connected in anti-parallel pairs to limit the rf carrier excursion in both polarities. they must, therefore, exhibit extremely low in sertion loss, both in the ?on? state (high power present) and the ?off? state (receiver power present) so as not to decrease the receiver?s sensitivity. the um9989 diodes are available in two package configurations for flexibility in design. important: for the most current data, visit our website: www.microsemi.com absolute maximum ratings at 25o c (unless otherwise specified) rating symbol value unit peak repetitive reverse voltage working peak reverse voltage dc blocking voltage v rrm v rwm v r 75 v rms reverse voltage v r (rms) 50 v non-repetitive peak forward surge current 8.3ms single half sine wave i fsm 2.5 a storage temperature t stg -65 to +150 oc operating temperature t op -65 to +150 oc thermal characteristics (unless otherwise specified) thermal resistance @ lead length = 3/8 inches r ola 100 oc/watt key features ? available in surface mount package. ? metallurgical bond ? planar passivated chip ? ultra low magnetic construction ? non cavity design ? thermally matched configuration ? low capacitance at 0 v bias ? low conductance at 0 v bias ? compatible with automatic insertion equipment ? rohs compliant versions available 1 applicati ons/benefits ? mri receiver protection ? body coil isolation note 1: rohs compliant versions are supplied with a matte tin finish. rohs part numbers are: umx9989b umx9989sm style ?b? style ?sm? u u m m 9 9 9 9 8 8 9 9
um9989 microsemi microwave products 75 technology drive, lowell, ma. 01851, 978-442-5600, fax: 978-937-3748 page 2 fast mri protection diodes tm ? www. microsemi .com copyright ? 2007 rev: 2009-11-09 rohs com p liant versions available note: 1 short duration test pulse used to minimize self heating effect. electrical parameters @ 25 ? c (unless otherwise specified) parameter symbol conditions min typ. max units i f = 10 ma , t j = 25 oc 1.0 v forward voltage (note 1) v f i f = 100 ma , t j = 25 oc 1.2 v reverse break down voltage (note 1) v br i r = 100 ua 75 v v r = 20 v, t j = 25 oc 50 na reverse current (note1) i r v r = 50 v, t j = 25 oc 500 na capacitance c t v r = 0v, f = 1 mh z 1.2 5 pf conductance g v r = 0 v, f = 64 mhz 40 us e e l l e e c c t t r r i i c c a a l l s s
um9989 microsemi microwave products 75 technology drive, lowell, ma. 01851, 978-442-5600, fax: 978-937-3748 page 3 fast mri protection diodes tm ? www. microsemi .com copyright ? 2007 rev: 2009-11-09 rohs com p liant versions available vf vs if conductance vs frequency capacitance vs frequency g g r r a a p p h h s s
um9989 microsemi microwave products 75 technology drive, lowell, ma. 01851, 978-442-5600, fax: 978-937-3748 page 4 fast mri protection diodes tm ? www. microsemi .com copyright ? 2007 rev: 2009-11-09 rohs com p liant versions available um9989b um9989sm sm style solder footprint m m e e c c h h a a n n i i c c a a l l
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