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UM9989

Microsemi Corporation
Part Number UM9989
Manufacturer Microsemi Corporation
Description FAST MRI PROTECTION DIODES
Published Oct 23, 2007
Detailed Description www.DataSheet4U.com UM9989 FAST MRI PROTECTION DIODES DESCRIPTION KEY FEATURES WWW . Microsemi . C OM The UM9989 di...
Datasheet PDF File UM9989 PDF File

UM9989
UM9989

Overview
www.
DataSheet4U.
com UM9989 FAST MRI PROTECTION DIODES DESCRIPTION KEY FEATURES WWW .
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.
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 ƒ Available in surface mount package.
ƒ ƒ Metallurgical bond ƒ ƒ Planar passivated chip ƒ ƒ Non-magnetic construction ƒ ƒ Non cavity design ƒ ƒ Thermally matched configuration ƒ ƒ Low capacitance at 0 V bias ƒ ƒ Low conductance at 0 V bias ƒ ƒ Compatible with automatic insertion equipment 75 50 2.
5 -65 to +150 -65 to +150 V V A ºC ºC APPLICATIONS/BENEFITS ƒ MRI receiver protection ƒ ƒ Body coil isolation THERMAL CHARACTERISTICS (UNLESS OTHERWISE SPECIFIED) Thermal Resistance @ Lead length = 3/8 inches ROLA 100 ºC/Watt UM9989 Style “B” Style “SM” Copyright  2003...


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