UM5204 Datasheet, PDF (4/8 Pages) Union Semiconductor, Inc. – Quad Channel Low Capacitance ESD Protection Array

UM5204EEXF
Applications Information
Device Connection Options for Protection of Four High-Speed Data Lines
This device is designed to protect data lines by clamping them to a fixed reference. When the voltage on the
protected line exceeds the reference voltage the steering diodes are forward biased, conducting the transient
current away from the sensitive circuitry. Data lines are connected at pins 1, 3, 4 and 6. Pin 2 should be
connected directly to a ground plane. The path length is kept as short as possible to minimize parasitic
inductance. The positive reference is connected at pin 5. The options for connecting the positive reference are as
follows:
1. To protect data lines and the power line, connect pin 5 directly to the positive supply rail (VCC). In this
configuration the data lines are referenced to the supply voltage. The internal TVS diode prevents over-voltage
on the supply rail.
2. In applications where the supply rail does not exit the system, the internal TVS may be used as the reference.
In this case, pin 5 is not connected. The steering diodes will begin to conduct when the voltage on the protected
line exceeds the working voltage of the TVS (plus one diode drop).
3. In applications where complete supply isolation is desired, the internal TVS is again used as the reference and
VCC is connected to one of the I/O inputs. An example of this configuration is the protection of a SIM port. The
Clock, Reset, I/O, and VCC lines are connected at pins 1, 3, 4, and 6. Pin 2 is connected to ground and pin 5 is
not connected.
Matte Tin Lead Finish
Matte tin has become the industry standard lead-free replacement for SnPb lead finishes. A matte tin finish is
composed of 100% tin solder with large grains. Since the solder volume on the leads is small compared to the
solder paste volume that is placed on the land pattern of the PCB, the reflow profile will be determined by the
requirements of the solder paste. Therefore, these devices are compatible with both lead-free and SnPb assembly
techniques. In addition, unlike other lead-free compositions, matte tin does not have any added alloys that can
cause degradation of the solder joint.
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http://www.union-ic.com Rev.03 May.2008
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