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http://www.union-ic.com Rev.03 May.2016

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SM12/SM15

Electrical Characteristics (SM15)

Parameter

Symbol

Conditions

Min

Typ

Max

Unit

Reverse Stand-Off Voltage

15

V

Reverse Breakdown Voltage

16.7

18.7

V

Reverse Leakage Current

1

μA

Clamping Voltage

23

V

Peak Pulse Current

5.9

A

Junction Capacitance

Pin 1 to 3 and

Pin 2 to 3,

20

30

pF

Reverse Dynamic Resistance

1.12

Ω

Forward Dynamic Resistance

0.81

Reverse Dynamic Resistance

0.92

Ω

Forward Dynamic Resistance

0.42

Detailed Description

Device Connection Options

SM12/SM15 is designed to protect one bidirectional or two unidirectional data or I/O lines

operating at 12V/15V. Connection options are as follows: Bidirectional: Pin 1 is connected to the

data line and pin 2 is connected to ground (Since the device is symmetrical, these connections

may be reversed). The ground connection should be made directly to a ground plane. The path

length should be kept as short as possible to minimize parasitic inductance. Pin 3 is not connected.

Unidirectional: Data lines are connected to pin 1 and pin 2. Pin 3 is connected to ground. For best

results, this pin should be connected directly to a ground plane on the board. The path length

should be kept as short as possible to minimize parasitic inductance.

Circuit Board Layout Recommendations for Suppression of ESD

Good circuit board layout is critical for the suppression of fast rise-time transients such as ESD.

The following guidelines are recommended (Refer to application note SI99-01 for more detailed

information): Place the TVS near the input terminals or connectors to restrict transient coupling.

Minimize the path length between the TVS and the protected line. Minimize all conductive loops

including power and ground loops. The ESD transient return path to ground should be kept as

short as possible. Never run critical signals near board edges. Use ground planes whenever

possible.

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.