rohs com p liant microsemi microwave products 75 technology drive, lowell, ma. 01851, 978-442-5600, fax: 978-937-3748 page 1 umx9989ap? dual ultra low magnetic moment fast diodes for mri applications description the umx9989ap is the first mri switchi ng diode module, designed to optimize performance and reduce assembly la bor, cost, and polarity errors. there are two principle applications for which the umx9989ap modules are intended: 1) mri receiver protection fr om high rf energy fields, including long rf pulses and rf spike pulses present in most mri machines. the umx9989ap acts as a passive protector (limiter) for the mri receiver?s lna. the diode assembly exhibits extremely low insertion loss, both in the ?on? state (high power present) and the ?off? state (receiver power present) so the receiver?s noise figure is not increased by the protector circuit. 2) passive switching of surface coil detuning and blocking circuits. in this case, the flow of loop current during transmitter pul se turns on the diodes, without a switch driver. if the umx9989ap is combined with a pin diode (um7201sm) the combination can be used to implement a semi-active detune or block circuit design. the umx9989ap?s turn on the pin diode (used for higher power switching) during the sinc(x) sidelobes, before the main pulse of the transmitter waveform, sinc(x) = [sin (x)]/x, occurs. the mechanical drawin g shows the structure of the diode pair. manufacture of dual anti-pa rallel pairs of umx9989?s ensures that the matched pair of diodes can be inserted in a coil with the correct diode polarities and with the minimum parasitic inductance and capacitance, thermal impedance and labor for the coil manufacturer. important: for the most current data, consult our website: www.microsemi.com absolute maximum ratings at 25o c (unless otherwise specified) rating symbol value unit non-repetitive peak forward surge current 8.3ms single half sine wave i fsm 2 a storage temperature t stg -65 to +150 oc operating temperature t op -65 to +150 oc key features ? ultra low magnetic construction ? rohs compliant ? matched pairs available ? surface mount package. ? metallurgical bond ? planar passivated chip ? non cavity design ? thermally matched configuration ? low capacitance at 0 v bias ? low conductance at 0 v bias ? compatible with automatic insertion equipment applicati ons/benefits ? mr passive receiver protection ? mr passive blocking circuits ? mr passive detuning circuits ? mr passive disable circuits u u m m x x 9 9 9 9 8 8 9 9 a a p p ? ? copyright ? 2007 rev: 2009-01-19
rohs com p liant microsemi microwave products 75 technology drive, lowell, ma. 01851, 978-442-5600, fax: 978-937-3748 page 2 umx9989ap? dual ultra low magnetic moment fast diodes for mri applications electrical parameters @ 25 ? c (unless otherwise specified) parameter symbol conditions min typ. max units forward voltage (note 1) v f i f = 10 a i f = 1 a 0.38 1.2 0.4 1.4 v v capacitance conductance c t g v r = 0v, f = 1 mh z v r = 0 v, f = 64 mhz v r = 0 v, f = 64 mhz 4 4 8 8 80 pf pf us parallel resistance r p v r = 0 v, f = 64 mhz 12 kohms note: 1 short duration test pulse used to minimize self ? heating effect . electrical copyright ? 2007 rev: 2009-01-19
rohs com p liant microsemi microwave products 75 technology drive, lowell, ma. 01851, 978-442-5600, fax: 978-937-3748 page 3 umx9989ap? dual ultra low magnetic moment fast diodes for mri applications style ?um9989ap? outline style ?um9989ap? footprint mechanical notes: 1. these dim ensions will match the term inals and provide for additional solder fillets at the outboard ends at l east as wide as the terminals themselves , assuming accuracy of device placement within .005 inches 2. if the mounting method chosen requires use of an a dhesive separate from th e solder compound, a round (or square) spot of cement as s hown should be centrally located. 3. dimensions shown are in inches. copyright ? 2007 rev: 2009-01-19
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