UM9989_09 Datasheet, PDF (1/4 Pages) Microsemi Corporation – FAST MRI PROTECTION DIODES

UM9989
TM
®
FAST MRI PROTECTION DIODES
RoHS Compliant 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 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, visit our website: www.MICROSEMI.com
ABSOLUTE MAXIMUM RATINGS AT 25º C
(UNLESS OTHERWISE SPECIFIED)
Rating
Symbol
Value
Unit
Peak Repetitive Reverse Voltage
V_RRM
Working Peak Reverse Voltage
V_RWM
75
V
DC Blocking Voltage
V_R
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
Available¹
APPLICATIONS/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”
Copyright  2007
Rev: 2009-11-09
Microsemi
Microwave Products
75 Technology Drive, Lowell, MA. 01851, 978-442-5600, Fax: [phone]
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