Diode BurnoutAssembly Instructions Any Schottky junction, be it an RF diode or the gate of a SOT-3x3 PCB Footprint MESFET, is relatively delicate and can be burned out with Recommended PCB pad layouts for the miniature SOT‑ excessive RF power. Many crystal video receivers used 3x3 (SC‑70) packages are shown in Figures 26 and 27 (di‑ in RFID (tag) applications find themselves in poorly con‑ mensions are in inches). These layouts provide ample al‑ trolled environments where high power sources may lowance for package placement by automated assembly be present. Examples are the areas around airport and equipment without adding parasitics that could impair FAA radars, nearby ham radio operators, the vicinity of a the performance. broadcast band transmitter, etc. In such environments, the Schottky diodes of the receiver can be protected by a 0.026 device known as a limiter diode.[5] Formerly available only in radar warning receivers and other high cost electronic warfare applications, these diodes have been adapted to commercial and consumer circuits. 0.079 Avago offers a com plete line of surface mountable PIN 0.039 limiter diodes. Most notably, our HSMP‑4820 (SOT‑23) can act as a very fast (nanosecond) power‑sensitive switch when placed between the antenna and the Schottky di‑ 0.022 ode, shorting out the RF circuit temporarily and reflecting Dimensions in inches the excessive RF energy back out the antenna. Figure 26. Recommended PCB Pad Layout for Avago’s SC70 3L/SOT-323 Products.0.0260.0790.0390.018Dimensions in inchesFigure 27. Recommended PCB Pad Layout for Avago's SC70 6L/SOT-363 Products. 10