UM9989

UM9989 FAST MRI PROTECTION DIODES DESCRIPTION KEY FEATURES W WW . Microsemi . C OM 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 selfbiased 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 insertion 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. Available in surface mount package. Metallurgical bond Planar passivated chip Non-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 IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com ABSOLUTE MAXIMUM RATINGS AT 25º C (UNLESS OTHERWISE SPECIFIED) Rating Peak Repetitive Reverse Voltage Working Peak Reverse Voltage DC Blocking Voltage RMS Reverse Voltage Non-Repetitive Peak Forward Surge Current 8.3ms Single half sine wave Storage Temperature Operating Temperature Symbol VRRM VRWM VR V R (RMS) IFSM T stg T op Value Unit 75 50 2.5 -65 to +150 -65 to +150 V V A ºC ºC APPLICATIONS/BENEFITS MRI receiver protection Body coil isolation THERMAL CHARACTERISTICS (UNLESS OTHERWISE SPECIFIED) Thermal Resistance @ Lead length = 3/8 inches ROLA 100 ºC/Watt UM9989 UM9989 Style “B” Style “SM” Copyright  2003 Rev. 0, 2004-10-26 Microsemi Page 1 UM9989 FAST MRI PROTECTION DIODES ELECTRICAL PARAMETERS @ 25°C (unless otherwise specified) W WW . Microsemi . C OM Parameter Forward Voltage (Note 1) Symbol VFm Conditions IF = 10 mA , Tj = 25 ºC IF = 100 mA , Tj = 25 ºC IR = 100 uA VR = 20 V, Tj = 25 ºC VR = 50 V, Tj = 25 ºC VR = 0V, F = 1 MHZ VR = 0 V, F = 64 MHz Min Typ. Max 1.0 1.2 Units V V V Reverse Break Down Voltage (Note 1) Reverse Current (Note1) VBR Irm 75 50 500 1.2 5 40 nA nA pF uS Capacitance Conductance CT G Note: 1 Short duration test pulse used to minimize self – heating effect. Copyright  2003 Rev. 0, 2004-10-26 Microsemi Page 2 UM9989 FAST MRI PROTECTION DIODES W WW . Microsemi . C OM ELECTRICALS ELECTRICALS Copyright  2003 Rev. 0, 2004-10-26 Microsemi Page 3 UM9989 FAST MRI PROTECTION DIODES W WW . Microsemi . C OM Copyright  2003 Rev. 0, 2004-10-26 Microsemi Page 4 UM9989 FAST MRI PROTECTION DIODES W WW . Microsemi . C OM STYLE “SM” STYLE “SM” FOOTPRINT MECHANICAL MECHANICAL PRODUCT PRELIMINARY DATA – Information contained in this document is pre-production data, and is proprietary to Microsemi Corp. It may not be modified in any way without the express written consent of Microsemi Corp. Product referred to herein is not guaranteed to achieve preliminary or production status and product specifications, configurations, and availability may change at any time. Copyright  2003 Rev. 0, 2004-10-26 Microsemi Page 5 UM9989 FAST MRI PROTECTION DIODES NOTES: W WW . Microsemi . C OM NOTES NOTES Copyright  2003 Rev. 0, 2004-10-26 Microsemi Page 6