SM712_04 SEMTECH | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 6
Technical content
1 www.semtech.com PROTECTION PRODUCTS SM712 Asymmetrical TVS Diode for Extended Common-Mode RS-485 Description Features Circuit Diagram Schematic & PIN Configuration Revision 11/17/04 The SM712 transient voltage suppressor (TVS) diode is designed for asymmetrical (12V to -7V ) protection in multi-point data transmission standard RS-485 applica- tions. The SM712 may be used to protect devices from transient voltages resulting from electrostatic discharge (ESD), electrical fast transients (EFT), and lightning. The SM712 features 400 Watts (tp = 8/20µs) of power handling capability to accommodate the higher transient voltage levels which may be expected in extended common mode applications. This provides higher equipment reliability and eliminates the “guess work” required when using zener diodes that are not rated to handle such transient conditions. The SM712 replaces four discrete components by integrating two 12V and two 7V TVS diodes in a single package. The integrated design aids in reducing voltage over-shoot associated with trace inductance. The low clamping voltage of the SM712 minimizes the stress on the protected transceiver. The SOT23 package allows flexibility in the design of “crowded” circuit boards.
Applications
Mechanical Characteristics Protection of RS-485 transceivers with extended common-mode range Security systems Automatic Teller Machines HFC systems Networks 400 watts peak pulse power (t p = 8/20µs) Transient protection for asymmetrical data lines to IEC 61000-4-2 (ESD) ±15kV (air), ±8kV (contact) IEC 61000-4-4 (EFT) 40A (5/50ns) IEC 61000-4-5 (Lightning) 12A (8/20µs) Protects two +12V to -7V lines Low capacitance Low clamping voltage Solid-state silicon avalanche technology JEDEC SOT23 package Molding compound flammability rating: UL 94V-0 Marking : 712 Packaging : Tape and Reel per EIA 481 SOT23 (Top View)
2 2004 Semtech Corp. www.semtech.com PROTECTION PRODUCTSPROTECTION PRODUCTS SM712 Absolute Maximum Rating
Electrical Characteristics
)SVTV21( dna1ot3sniP 2ot3 )SVTV7( retemaraPl obmySs noitidnoCN IMP YTX AMN IMP YTX AMs tinU egatloVffO-dnatSesreveRV MWR 1ot2niPro1ot3niP2 17 V egatloVnwodkaerBesreveRV RB I TP Am1=3 .315 .7V tnerruCegakaeLesreveRI R V =R V MWR 10 2 µA egatloVgnipmalCV C I PP ,A5= sµ02/8=pt 020 1V egatloVgnipmalCV C I PP ,A71= sµ02/8=pt 622 1V ecnaticapaCnoitcnuJC j VR zHM1=f,V0=5 75 7F p VR V= MWR zHM1=f,5 45 4F p gnitaRl obmySe ulaVs tinU t(rewoPesluPkaeP p )sµ02/8=P kp 004s ttaW t(tnerruCesluPkaeP p )sµ02/8=I PP 71A erutarepmeTgniredloSdaeLT L ).ces01(062C ° erutarepmeTgnitarepOT J 521+ot55-C ° erutarepmeTegarotST GTS 051+ot55-C °
3 2004 Semtech Corp. www.semtech.com PROTECTION PRODUCTS SM712 Typical Characteristics Non-Repetitive Peak Pulse Power vs. Pulse Time Power Derating Curve Pulse Waveform Clamping Voltage vs. Peak Pulse Current 100 110 0 5 10 15 20 25 30 Time (µs) Percent of IPP e-t td = I PP /2 Wa v e f o r m Parameters: tr = 8µs td = 20µs Capacitance vs. Reverse Voltage 100 110 0 25 50 75 100 125 150 175 Ambient Temperature - T A (oC) % of Rated Power or IPP 0.01 0.1 0.1 1 10 100 1000 Pulse Duration - tp (µs) Peak Pulse Power - Ppk (kW) 02468 1 0 1 2 1 4 1 6 Peak Pulse Current - I PP (A) Clamping Voltage - VC (V) Pin 1 to 3 and 2 to 3 Pin 3 to 1 and 3 to Wavefor m Parameters: tr = 8µs td = 20µs 0123456789 1 0 1 1 1 2 1 3 Reverse Voltage - V R (V) Capacitance - Cj (pF) f = 1MHz
4 2004 Semtech Corp. www.semtech.com PROTECTION PRODUCTSPROTECTION PRODUCTS SM712 RS-485 Common Mode VoltagesDevice Connection for Protection of Two RS-485 Data Lines EIA RS-485 specifies a ±7V ground difference between devices on the bus. This permits the bus voltage to range from +12V (5V + 7V) to -7V (0 - 7V). The SM712 is designed to protect two RS-485 data lines in extended common mode applications. The SM712 may be used to protect devices from transient voltages resulting from ESD, EFT, and lightning. The device is designed with asymmetrical operating volt- ages for optimum protection. The TVS diodes at pins 1 and 2 have a working voltage of 12 volts. These pins are connected to the differential data line pairs. The TVS diodes at pin 3 have a working voltage of 7 volts. Pin 3 is connected to ground. The internal TVS diodes of the SM712 will protect the transceiver input from positive transient voltage spikes greater than 12V and negative spikes greater than 7V. A series current limiting resistor may be added in applications requiring enhanced surge immunity. Circuit Board Layout Recommendations. Good circuit board layout is critical for the suppression of fast rise-time transients such as ESD. The following guidelines are recommended: z Place the SM712 near the input terminals or connectors to restrict electromagnetic coupling. z Minimize the path length between the SM712 and the protected line. This minimizes voltage over- shoot due to parasitic inductance of board traces. z Use ground planes whenever possible. z Long, single trace ground conductors should be avoided. The ground pin (Pin 3) should be con- nected directly to a ground plane on the circuit board for best results. z Minimize all conductive loops including power and ground loops. z Never run critical signals near board edges. RS-485 Protection Circuit Applications Information
5 2004 Semtech Corp. www.semtech.com PROTECTION PRODUCTS SM712 Land Pattern - SOT23 Outline Drawing - SOT23 e D E1 E bxN A2A 3X A bbb C A B B C SEATING PLANE aaa C 1.401.20 N3 3 0 - 8°0°8°0° - .055.047 bbb .008 0.20 aaa .004 0.10 INCHES .114 E D b e c .012 .003 .082 DIM A MIN .000 .035 0.51 0.18 2.64 0.30 0.08 2.10 .022 .075 .093 .020 .007 .104 (0.55)
1.90 BSC
2.37 2.90 MILLIMETERS MAX 0.10 1.12 MIN DIMENSIONS 0.01 MAXNOM - .004 .044 NOM 0.89 3.042.80.110 .120 e1 .037 0.95 BSC E1 .051 1.30 SEE DETAIL ASIDE VIEW DATUMS AND TO BE DETERMINED AT DATUM PLANE-A- -B-2. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). NOTES: OR GATE BURRS. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS3. -H- H DETAIL A 0.25C SEATING PLANE GAUGE PLANE 0 c L REFERENCE IPC-SM-782A.2. E .037 0.95 Y Y GZ C E X E1 .075 1.90 NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. DIM Y Z G X C MILLIMETERSINCHES (2.20) .055 .141 .039 .031 (.087) 1.40 3.60 1.00 0.80 DIMENSIONS
6 2004 Semtech Corp. www.semtech.com PROTECTION PRODUCTSPROTECTION PRODUCTS SM712 Contact Information Semtech Corporation Protection Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805)498-2111 FAX (805)498-3804
Ordering Information
rebmuNtraPh siniFdaeL repytQ leeR eziSleeR CT.217MSn SbP0 00,3h cnI7 TCT.217MS eerF-bP nSettaM 000,3h cnI7