APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH SHANNON ROAD • TUCSON, ARIZONA 85741 • USA • APPLICATIONS HOTLINE: 1 (800) 546-2739

4

PRELIMINARY

POWER SUPPLY BYPASSING

Bypass capacitors to power supply terminals +Vs and –Vs

must be connected physically close to the pins to prevent lo-

cal parasitic oscillation in the output stage of the PA69. Use

electrolytic capacitors at least 1μF. Bypass the electrolytic

capacitors with high quality ceramic capacitors (X7R) 0.1μF

or greater.

SUPPLY CURRENT

The PA69 features a class A/B driver stage to drive the output

MOSFETs and an innovative input stage to achieve very high

slew rates. The supply current drawn by the PA69, even with

no load, varies with the slew rate of the output signal.

STABILITY

The PA69 is externally compensated and performance

can be tailored to the application. Use the graphs of small

signal response and power response as a guide. Due to the

innovative design of the PA69, two compensation networks

are required. The values of these components should be the

same to provide symmetric slew rate characteristics. The

compensation capacitor Cc must be rated at 500V working

voltage. NPO capacitors are recommended. The compensa-

tion networks CcRc must be mounted closely to the amplifier

pins x & y and z & w to avoid spurious oscillation.

The PA69 may require an external 33 pF capacitor (mini-

mum breakdown of 200 V) between CC- (pin 3) and –Vs (pin

5) to prevent oscillations in the falling edge of the output. This

capacitor is provided with the evaluation kit. Please refer to

EK60 datasheet for details.

GENERAL

Please read Application Note 1 “General Operating Consid-

erations” which covers stability, power supplies, heat sinking,

mounting, current limit, SOA interpretation, and specification

interpretation. Visit www.apexmicrotech.com for design tools

that help automate tasks such as calculations for stability,

internal power dissipation, current limit, heat sink selection,

Apex’s complete Application Notes library, Technical Seminar

Workbook and Evaluation Kits.

SPECIAL CONSIDERATIONS

It is very important to realize that in order to achieve

high frequency performance the heat sink tab has to be

tied to a stable, low impedance reference, i.e. power sup-

ply or GND. An AC connection through a 0.1µF capacitor

is also sufficient. Internal to the PA69, the heatsink tab

is electrically isolated to more than 350V . This may help

allay some electrical isolation concerns in tying the heat

sink to Vs or GND.

CURRENT LIMIT

For proper operation, the current limit resistor, Rlim, must

be connected as shown in the external connections diagram.

For maximum reliability and protection, the resistor should

be set as high as possible. The value of the resistor is calcu-

lated as follows, with Ilim in A; the maximum practical value

is 1500Ω.

Rlim = 0.7 / Ilim

SAFE OPERATING AREA

The MOSFET output stage of the PA69 is not limited by

second breakdown considerations as in bipolar output stages.

Only thermal considerations and current handling capabilities

limit the SOA. The output stage is protected against transient

flyback by the parasitic body diodes of the output stage MOS-

FET structure. However, for protection against sustained high

energy flyback external fast-recovery diodes must be used.

OPERATING

CONSIDERATIONS

PA69

This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.

PA69U REV 3 FEBRUARY 2006 © 2006 Apex Microtechnology Corp.