1 www.semtech.com protection products SRV08-4 railclamp ? ? ? ? ? low capacitance tvs diode array description features circuit diagram schematic & pin configuration revision 06/25/2002 railclamps are surge rated diode arrays designed to protect high speed data interfaces. the sr series has been specifically designed to protect sensitive compo- nents which are connected to data and transmission lines from overvoltage caused by esd (electrostatic discharge), eft (electrical fast transients), and light- ning. the unique design of the SRV08-4 integrates eight surge rated, low capacitance steering diodes with a tvs diode in a sot23- 6l package. during transient conditions, the steering diodes direct the transient to either the positive side of the power supply line or to ground. the internal tvs diode prevents over-voltage on the power line, protecting any downstream compo- nents. the low capacitance array configuration allows the user to protect four high-speed data or transmission lines. the low inductance construction minimizes voltage overshoot during high current surges. applications mechanical characteristics ? usb ports ? video graphics cards ? monitors and flat panel displays ? digital video interface (dvi) ? cellular handsets ? notebook computers ? portable electronics ? microcontroller input protection ? esd protection to iec 61000-4-2, level 4 ? array of surge rated diodes with internal tvs diode ? small package saves board space ? protects four i/o lines ? low capacitance (<5pf) for high-speed interfaces ? low clamping voltage ? low operating voltage: 5.0v ? solid-state silicon-avalanche technology ? jedec sot-23 6l package ? molding compound flammability rating: ul 94v-0 ? marking : v08 ? packaging : tape and reel per eia 481 sot-23 6l (top view) 2 13 4 6 5
2 ? 2002 semtech corp. www.semtech.com protection products SRV08-4 absolute maximum rating electrical characteristics (t=25 o c) g n i t a rl o b m y se u l a vs t i n u ) s 0 2 / 8 = p t ( r e w o p e s l u p k a e pp k p 0 5 1s t t a w ) s 0 2 / 8 = p t ( t n e r r u c e s l u p k a e pi p p 6a t n e r r u c d r a w r o f s u o u n i t n o ci f 0 0 2a m ) r i a ( 2 - 4 - 0 0 0 1 6 c e i r e p d s e ) t c a t n o c ( 2 - 4 - 0 0 0 1 6 c e i r e p d s e v d s e 5 1 8 v k e r u t a r e p m e t g n i r e d l o s d a e lt l ) . c e s 0 1 ( 0 6 2c e r u t a r e p m e t g n i t a r e p ot j 5 2 1 + o t 5 5 -c e r u t a r e p m e t e g a r o t st g t s 0 5 1 + o t 5 5 -c 4 - 8 0 v r s r e t e m a r a pl o b m y ss n o i t i d n o cm u m i n i ml a c i p y tm u m i x a ms t i n u e g a t l o v f f o - d n a t s e s r e v e rv m w r 5 o t 2 n i p5v e g a t l o v n w o d k a e r b e s r e v e rv r b i t a m 1 = 5 o t 2 n i p 6v t n e r r u c e g a k a e l e s r e v e ri r v m w r c 5 2 = t , v 5 = 5 o t 2 n i p 5a e g a t l o v d r a w r o fv f i f a m 5 1 =2 . 1v e g a t l o v g n i p m a l cv c i p p s 0 2 / 8 = p t , a 1 = d n u o r g o t n i p o / i y n a 5 . 2 1v e g a t l o v g n i p m a l cv c i p p s 0 2 / 8 = p t , a 5 = d n u o r g o t n i p o / i y n a 5 . 7 1v e c n a t i c a p a c n o i t c n u jc j v r z h m 1 = f , v 0 = d n u o r g o t n i p o / i y n a 35f p v r z h m 1 = f , v 0 = s n i p o / i n e e w t e b 1f p
3 ? 2002 semtech corp. www.semtech.com protection products SRV08-4 typical characteristics non-repetitive peak forward current vs. pulse time power derating curve 0 10 20 30 40 50 60 70 80 90 100 110 0 25 50 75 100 125 150 ambient temperature - t a ( o c) % of rated power or i pp variation of capacitance vs. reverse voltage 0 10 20 30 40 50 60 70 80 90 100 110 0 5 10 15 20 25 30 time ( s) percent of i pp e -t td = i pp /2 waveform parameters: tr = 8 s td = 20 s pulse waveform forward clamping voltage vs. peak pulse current current 0.01 0.1 1 10 0.1 1 10 100 1000 pulse duration - tp ( s) peak pulse power - p pp (kw) 0.00 5.00 10.00 15.00 20.00 25.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 forward current - i f (a) forward voltage -v f (v) waveform parameters: tr = 8 s td = 20 s 0 1 2 3 4 5 012345 reverse voltage (v) capacitance - (pf ) i/o to gnd f = 1mhz insertion loss s21 ch1 s21 log 3 db/ ref 0 db start . 030 000 mhz stop 3 000 . 000 000 mhz cor smo
4 ? 2002 semtech corp. www.semtech.com protection products SRV08-4 device connection options for protection of four high-speed data lines the SRV08-4 tvs is designed to protect four data lines from transient over-voltages by clamping them to a fixed reference. when the voltage on the protected line exceeds the reference voltage (plus diode v f ) 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. the negative reference is connected at pin 5. this pin should be connected directly to a ground plane on the board for best results. the path length is kept as short as possible to minimize parasitic inductance. the positive reference is connected at pin 2. in this configuration the data lines are referenced to the supply voltage. video interface protection video interfaces are susceptible to transient voltages resulting from electrostatic discharge (esd) and ?hot plugging? cables. if left unprotected, the video interface ic may be damaged or even destroyed. protecting a high-speed video port presents some unique challenges. first, any added protection device must have extremely low capacitance and low leakage current so that the integrity of the video signal is not compromised. second, the protection component must be able to absorb high voltage transients without damage or degradation. as a minimum, the device should be rated to handle esd voltages per iec 61000-4-2, level 4 (15kv air, 8kv contact). the clamping voltage of the device (when conducting high current esd pulses) must be sufficiently low enough to protect the sensitive cmos ic. if the clamping voltage is too high, the ?protected? device may latch-up or be destroyed. finally, the device must take up a relatively small amount of board space, particularly in portable applications such as notebooks and handhelds. the SRV08-4 is designed to meet or exceed all of the above criteria. a typical video interface protection circuit is shown in figure 2. all exposed lines are protected including r, g, b, h-sync, v-sync , and the id lines for plug and play monitors. esd protection with railclamps railclamps are optimized for esd protection using the rail-to-rail topology. along with good board layout, figure 1 - data line and power supply protection using vcc as reference figure 2 - video interface protection applications information
5 ? 2002 semtech corp. www.semtech.com protection products SRV08-4 pin descriptions these devices virtually eliminate the disadvantages of using discrete components to implement this topology. consider the situation shown in figure 3 where dis- crete diodes or diode arrays are configured for rail-to- rail protection on a high speed line. during positive duration esd events, the top diode will be forward biased when the voltage on the protected line exceeds the reference voltage plus the v f drop of the diode. for negative events, the bottom diode will be biased when the voltage exceeds the v f of the diode. at first approximation, the clamping voltage due to the charac- teristics of the protection diodes is given by: v c = v cc + v f (for positive duration pulses) v c = -v f (for negative duration pulses) however, for fast rise time transient events, the effects of parasitic inductance must also be consid- ered as shown in figure 4. therefore, the actual clamping voltage seen by the protected circuit will be: v c = v cc + v f + l p di esd /dt (for positive duration pulses) v c = -v f - l g di esd /dt (for negative duration pulses) esd current reaches a peak amplitude of 30a in 1ns for a level 4 esd contact discharge per iec 61000-4-2. therefore, the voltage overshoot due to 1nh of series inductance is: v = l p di esd /dt = 1x10 -9 (30 / 1x10 -9 ) = 30v example: consider a v cc = 5v, a typical v f of 30v (at 30a) for the steering diode and a series trace inductance of 10nh. the clamping voltage seen by the protected ic for a positive 8kv (30a) esd pulse will be: v c = 5v + 30v + (10nh x 30v/nh) = 335v note that it is not uncommon for the v f of discrete diodes to exceed the damage threshold of the pro- tected ic. this is due to the relatively small junction area of typical discrete components. it is also possible that the power dissipation capability of the discrete diode will be exceeded, thus destroying the device. the railclamp is designed to overcome the inherent disadvantages of using discrete signal diodes for esd suppression. figure 3 - ?rail- figure 3 - ?rail- figure 3 - ?rail- figure 3 - ?rail- figure 3 - ?rail- t t t t t o-rail? pr o-rail? pr o-rail? pr o-rail? pr o-rail? pr o o o o o t t t t t ection t ection t ection t ection t ection t opology opology opology opology opology (first approximation) (first approximation) (first approximation) (first approximation) (first approximation) figure 4 - the effects of parasitic inductance figure 4 - the effects of parasitic inductance figure 4 - the effects of parasitic inductance figure 4 - the effects of parasitic inductance figure 4 - the effects of parasitic inductance when using discrete components to implement when using discrete components to implement when using discrete components to implement when using discrete components to implement when using discrete components to implement rail- rail- rail- rail- rail- t t t t t o-rail pr o-rail pr o-rail pr o-rail pr o-rail pr o o o o o t t t t t ection ection ection ection ection applications information (continued) figure 5 - rail- figure 5 - rail- figure 5 - rail- figure 5 - rail- figure 5 - rail- t t t t t o-rail pr o-rail pr o-rail pr o-rail pr o-rail pr o o o o o t t t t t ection using ection using ection using ection using ection using railclam railclam railclam railclam railclam p t p t p t p t p t v v v v v s arra s arra s arra s arra s arra ys ys ys ys ys
6 ? 2002 semtech corp. www.semtech.com protection products SRV08-4 outline drawing - so-8 land pattern outline drawing
7 ? 2002 semtech corp. www.semtech.com protection products SRV08-4 contact information semtech corporation protection products division 200 flynn road, camarillo, ca 93012 phone: (805)498-2111 fax (805)498-3804 r e b m u n t r a p g n i k r o w e g a t l o v r e p y t q l e e r e z i s l e e r c t . 4 - 8 0 v r sv 8 . 50 0 0 , 3h c n i 7 g t . 4 - 8 0 v r sv 8 . 50 0 0 , 0 1h c n i 3 1 marking codes r e b m u n t r a p g n i k r a m e d o c 4 - 8 0 v r s8 0 v ordering information v08
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