10

Diode Burnout

Any Schottky junction, be it an RF diode or the gate of a

MESFET, is relatively delicate and can be burned out with

excessive RF power. Many crystal video receivers used

in RFID (tag) applications find themselves in poorly con‑

trolled environments where high power sources may

be present. Examples are the areas around airport and

FAA radars, nearby ham radio operators, the vicinity of a

broadcast band transmitter, etc. In such environments,

the Schottky diodes of the receiver can be protected by a

in radar warning receivers and other high cost electronic

warfare applications, these diodes have been adapted to

commercial and consumer circuits.

Avago offers a complete line of surface mountable PIN

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‑

ode, shorting out the RF circuit temporarily and reflecting

the excessive RF energy back out the antenna.

Assembly Instructions

SOT-3x3 PCB Footprint

Recommended PCB pad layouts for the miniature SOT‑

3x3 (SC‑70) packages are shown in Figures 26 and 27 (di‑

mensions are in inches). These layouts provide ample al‑

lowance for package placement by automated assembly

equipment without adding parasitics that could impair

the performance.

Figure26. RecommendedPCBPadLayoutforAvago’s SC70 3L/SOT-323 Products.

Figure27. Recommended PCB Pad Layout for Avago's SC70 6L/SOT-363 Products.

0.026

0.039

0.079

0.022

Dimensions in inches

0.026

0.079

0.018

0.039

Dimensions in inches