UM9989 FAST MRI PROTECTION DIODES ® TM RoHS Compliant Versions Available KEY FEATURES DESCRIPTION Metallurgical bond Planar passivated chip Ultra Low magnetic construction Non cavity design Thermally matched configuration Low capacitance at 0 V bias IMPORTANT: For the most current data, visit our website: www.MICROSEMI.com ABSOLUTE MAXIMUM RATINGS AT 25º C (UNLESS OTHERWISE SPECIFIED) Low conductance at 0 V bias Rating Symbol Peak Repetitive Reverse Voltage Working Peak Reverse Voltage DC Blocking Voltage VRRM VRWM VR 75 V RMS Reverse Voltage Non-Repetitive Peak Forward Surge Current 8.3ms Single half sine wave Storage Temperature V R (RMS) 50 V IFSM 2.5 A TSTG -65 to +150 ºC Operating Temperature TOP -65 to +150 ºC Value Available in surface mount package. Unit www.MICROSEMI.com 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 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. Compatible with automatic insertion equipment RoHS Compliant Versions Available1 APPLICATIONS/BENEFITS MRI receiver protection Body coil isolation THERMAL CHARACTERISTICS (UNLESS OTHERWISE SPECIFIED) Thermal Resistance @ Lead length = 3/8 inches Copyright 2007 Rev: 2009-11-09 100 ºC/Watt UM9989 Style “B” ROLA Note 1: RoHS compliant versions are supplied with a matte Tin finish. RoHS part numbers are: UMX9989B UMX9989SM Style “SM” Microsemi Microwave Products 75 Technology Drive, Lowell, MA. 01851, 978-442-5600, Fax: 978-937-3748 Page 1 UM9989 FAST MRI PROTECTION DIODES ® TM RoHS Compliant Versions Available ELECTRICAL PARAMETERS @ 25C (unless otherwise specified) Symbol Forward Voltage (Note 1) VF Reverse Break Down Voltage (Note 1) Reverse Current (Note1) VBR IR Conditions Min Typ. Max Units IF = 10 mA , TJ = 25 ºC 1.0 V IF = 100 mA , TJ = 25 ºC 1.2 V IR = 100 uA 75 V VR = 20 V, TJ = 25 ºC 50 nA VR = 50 V, TJ = 25 ºC 500 nA 5 pF 40 uS Capacitance CT VR = 0V, F = 1 MHZ Conductance G VR = 0 V, F = 64 MHz 1.2 www.MICROSEMI.com Parameter Note: 1 Short duration test pulse used to minimize self heating effect. ELECTRICALS Copyright 2007 Rev: 2009-11-09 Microsemi Microwave Products 75 Technology Drive, Lowell, MA. 01851, 978-442-5600, Fax: 978-937-3748 Page 2 UM9989 FAST MRI PROTECTION DIODES ® TM RoHS Compliant Versions Available VF VS IF CONDUCTANCE VS FREQUENCY www.MICROSEMI.com CAPACITANCE VS FREQUENCY GRAPHS Copyright 2007 Rev: 2009-11-09 Microsemi Microwave Products 75 Technology Drive, Lowell, MA. 01851, 978-442-5600, Fax: 978-937-3748 Page 3 UM9989 FAST MRI PROTECTION DIODES ® TM RoHS Compliant Versions Available UM9989B UM9989SM www.MICROSEMI.com SM STYLE SOLDER FOOTPRINT MECHANICAL Copyright 2007 Rev: 2009-11-09 Microsemi Microwave Products 75 Technology Drive, Lowell, MA. 01851, 978-442-5600, Fax: 978-937-3748 Page 4