DATA SHEET • CLA SERIES DIODES

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

200100I • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • September 28, 2009

5

0.25

0.50

0.75

1.00

–50

0

+50

+100

+150

Case Temperature (°C)

Figure 5. Power Handling Capability vs Temperature

Technical Description

The CLA4603 and CLA4606 limiter diodes are constructed in a

passivated flat-chip configuration and are available in a basic chip

form or encapsulated in several Skyworks hermetic ceramic

packages.

Limiter diodes with lower capacitance values to 0.08 pF and

constructed with a passivated mesa configuration are available in

the CLA4601 and CLA4605 series. The mesa devices offer low

capacitance and, therefore, broader bandwidth, lower loss, and

faster response at reduced power. These diodes are also available

in chip package form and represent the ultimate in limiter

performance not approached by other manufacturers.

The CLA4607 diodes (highest power) are available in both planar

and mesa construction.

Figures 6 and 7 illustrate the fundamental structures of diodes

mounted in a 50

Ω microstrip circuit.

Additional bonding and handling methods are contained in the

Skyworks Application Notes, Waffle Pack Chip Carrier

Handling/Opening Procedure (document #200146) and Diode

Chips, Beam-Lead Diodes, Capacitors: Bonding Methods and

Packaging (document #200146).

Basic Applications

In microstrip limiters, the bonding wire length and diameter

together with the chip capacitance, form a low-pass filter (see

Figure 8). Line lengths (X1 and X2) are varied to provide

broadband matching and flat leakage characteristics. Typically,

X1 and X2 are on the order of 0.1 wavelength. In Figure 9, the

CLA4607 chip provides about 20 dB attenuation, reducing a 1 kW

input signal to a 10 W output signal. The CLA4606 reduces this to

100 mW and the CLA4603 to about 20 mW.

During the rise time of the incident pulse, the diodes behave in

the following manner. The CLA4603, due to its thin I region, is the

first to change to a low impedance. Experiments indicate that the

CLA4603 reaches the 10 dB isolation point in about 1 ns and

20 dB in 1.5 ns with an incident power of 10 W.

The CLA4606 takes about 4 ns and the CLA4607 about 50 ns to

achieve 10 dB isolation. Consequently, the CLA4603 provides

protection during the initial stages of pulse rise time with the

thicker diodes progressively “turning on” as the power increases.

With proper spacing (X1 and X2), the “on” diodes reflect high

impedances to the upstream diodes, reducing the turn-on time for

those diodes and ensuring that essentially all of the incident

power is reflected by the input diode, preventing burnout of the

thinner diodes.

At the end of the pulse the process reverses and the diodes

“recover” to their high impedance states; the free charge that

was injected into their I regions by the high-incident power signal

leaks off through the ground return and is also reduced by internal

recombination. With a ground return, recovery time is on the order

of 50 ns. With a high impedance return (for example, the circuit

shown in Figure 10), the Schottky diode (such as the CDF7621-000)

recovers or “opens” in practically zero time. Internal recombination

on the order of several diode lifetimes is the only available

mechanism for recovery of the limiter diodes. This recovery time

can be long – on the order of 1 ms for the CLA4607 series. The

approximately doubles the recovery time compared to a short circuit.

When the Schottky diode is directly coupled to the transmission

line in cascade after the coarse limiter, the leakage power is less

than if a 0

Ω ground return were used. If the Schottky is

decoupled too much, the leakage power increases due to the high

DC impedance of a Schottky. Similarly, a 3

Ω ground return

causes an increase of about 3 dB in leakage power compared to a

0

Ω return.