OPERATING
CONSIDERATIONS
PA01 • PA73
1. For sine wave outputs, use Power Design
1
to plot a load
line. Make sure the load line does not cross the 0.5ms limit
and that excursions beyond any other second breakdown
line do not exceed the time label, and have a duty cycle of
no more than 10%.
For other waveform outputs, manual load line plotting
is recommended. Applications Note 22, SOA AND LOAD
LINES, will be helpful. A Spice type analysis can be very
useful in that a hardware setup often calls for instruments
or amplifiers with wide common mode rejection ranges.
2. EMF generating or reactive load and short circuits to the
supply rail or shorts to common are safe if the current limits
are set as follows at T
C
= 85°C.
±V
S
34V
30V
25V
20V
15V
SHORT TO ±V
S
C, L, OR EMF LOAD
.58A
.46A
.61A
.86A
1.3A
SHORT TO
COMMON
1.1A
1.4A
1.7A
2.1A
2.9A
GENERAL
Please read Application Note 1 "General Operating Con-
siderations" which covers stability, 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, in-
ternal power dissipation, current limit and heat sink selection.
The "Application Notes" and "Technical Seminar" sections
contain a wealth of information on specific types of applications.
Package outlines, heat sinks, mounting hardware and other
accessories are located in the "Packages and Accessories"
section. Evaluation Kits are available for most Apex product
models, consult the "Evaluation Kit" section for details. For
the most current version of all Apex product data sheets, visit
www.apexmicrotech.com.
SAFE OPERATING AREA (SOA)
The output stage of most power amplifiers has three distinct
limitations:
1. The current handling capability of the transistor geometry
and the wire bonds.
2. The second breakdown effect which occurs whenever the
simultaneous collector current and collector-emitter voltage
exceeds specified limits.
3. The junction temperature of the output transistors.
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3. The output stage is protected against occaisional transient
flyback. However, for protection against sustained, high
energy flyback, external fast-recovery diodes should be
used.
CURRENT LIMIT
Proper operation requires the use of two current limit resis-
tors, connected as shown, in the external connection diagram.
The minimum value for R
CL
is 0.12 ohm; however, for optimum
reliability it should be set as high as possible. Refer to the
“General Operating Considerations” section of the handbook
for current limit adjust details.
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The SOA curves combine the effect of these limits. For a
given application, the direction and magnitude of the output
current should be calculated or measured and checked against
the SOA curves. This is simple for resistive loads but more
complex for reactive and EMF generating loads.
1
Note 1. Power Design is a self-extracting Excel spreadsheet
available free from www.apexmicrotech.com
This data sheet has been carefully checked and is believed to be reliable,
SHANNON ROAD •
is assumed
ARIZONA 85741 • USA • APPLICATIONS
are subject
1 (800) 546-2739
APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH
however, no responsibility
TUCSON,
for possible inaccuracies or omissions. All specifications
HOTLINE:
to change without notice.
4
PA01-73U REV R MARCH 2005
© 2005 Apex Microtechnology Corp.
APEX [ CIRRUS LOGIC ]
