Application in HDMI of PulseGuard ESD suppressor
High clear multimedia interface (HDMI) It is a kind of up-to-the-minute technology that can offer the high-level video quality, it is by the creation manufacturer (including many IC manufacturers) of HDMI A kind of digital interface specification of future generation suitable for the consumption electronic product jointly defined. A lot of large-scale film Co.s, satellite TVs, wired TV and Radio Corporations support HDMI norm. HDMI Licensing LLC is the authorized organization of a licence, responsible for managing HDMI normal licence to authorize specially, aim at promoting HDMI standard and in order to introduce the advantage of HDMI to the box consumers of a retailer and educate and popularize. However, HDMI is very apt to suffer danger of ESD, need extra protective device to prevent the port function from becoming abnormal. With HDMI constant improvement with width, the single chain bandwidth of HDMI 1.3 has already been improved to 10.2Gbps(340MHz) ,High to reveal and employ the demand while being clear in future in order to support. The higher the transfer rate is, mean the device requires lower electric capacity. USB2.0 bus line is very popular while consuming the electron in the walkie figure, its highest message transmission rate is 480Mbps, also demanding to press must have very low electric capacity to protect the component. Fig. 1: Adopt 0402 surfaces to stick to to capsulate PulseGuard PGB1010402 ESD suppressor. New PulseGuard PGB1010402 electrostatic release (ESD) of Littelfuse Company The suppressor, have low (0.06pF) self capacity , the leak current is low, low characteristic with quick speed of response of clamping the voltage, especially suitable for undervoltage, high-speed application, such as cellular telephone, MP3/MP4 player, PMP portable media player, GPS global positioning system. They can respond to the request that the application have low capacity very much to the protective device, can reduce the impact on completeness of intelligence signal to minimum. This text takes HDMI interface protection and USB2.0 interface protective circuit as examples, introduce PulseGuard (PGB) ESD suppressor consumes the application in the electron in the walkie figure. PulseGuard device adopts the polymer base usually used for making polymer PTC, has " variable active material (VVAM) of voltage of the patent " The characteristic that the low capacity exists, turn on fast, can offer for the fact that fast ESD protect low and clamp the coefficient. PulseGuard PGB1010402 accords with RoHS order, and 100% are unleaded, adopts 0402 surfaces to be stuck and capsulated. Fig. 2: Structure chart of PulseGuard. PulseGuard device formed by patent semiconductor material mixed in polymer. When ESD transient voltage is exerted on PulseGuard device, PulseGuard is touched off and clamped this transient voltage, in order to protect the postern electronic device. ESD transient voltage is changed fast, look on as the transient voltage is raised to certain extent, reach PGB clamp voltage, PGB device voltage, go on, inhibit to wink from, make it become " smooth " Stand up, turn magnitude of voltage into, equal to clamp level of suppressor wink at this moment, in order to dispel high to the impact on postern IC or or transceiver of voltage wink, purpose to achieve protective circuit. After turning into the passing of current of surging in wink, PGB resets automatically, returns to the normal high impedance state. Fig. 3: Operating principle of PulseGuard PGB1010402. HDMI port protective circuit needs 8 PGB devices to protect 8 circuits (Fig. 4a) of HDMI . Each circuit is protected by an earthy PGB. On the basis of the protected apparatus, PGB device should be put behind HDMI interface unit. In addition, should be as short as possible that PGB earthes PCB and routes, in order to bring the condensive load effect down to minimum. Fig. 4b is expicity to last two PGB device it last USB2.0 and last Ds oral + /circuit D. MLV V5.5MLA0603 (packed abrupt-wave absorber) And polymer positive temperature coefficient (PPTC) The resistance device is used for protecting Vbus power circuit. Fig. 4: (a) HDMI port of PulseGuard protects the circuit diagram; (b) USB2.0 port protects the circuit diagram. Littelfuse Company offers the abundant circuit protection products, including protecting and using the triode thyristor, transient voltage restraint (TVS) Diode, diode array, PulseGuard, PPTC, gas discharge tube, safety fuse, multi-layer rheostat (MLV) And metal-oxide varistor (MOV) . http://www.eefocus.com/article/09-03/68096s.html