PA07A(2001) データシートの表示（PDF） - Apex Microtechnology
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PA07A Datasheet PDF : 4 Pages
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PA07 • PA07A
OPERATING
CONSIDERATIONS
GENERAL
Please read Application Note 1 "General Operating Consid-
erations" which covers stability, supplies, heat sinking, mount-
ing, current limit, SOA interpretation, and specification inter-
pretation. 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 Work-
book; and Evaluation Kits.
SAFE OPERATING AREA (SOA)
The output stage of most power amplifiers has three distinct
limitations:
1. The current handling capability of the wire bonds.
2. The second breakdown effect which occurs whenever the
simultaneous collector current and collector-emitter volt-
age exceed specified limits.
3. The junction temperature of the output transistors.
5.0
4.0
3.0
2.0
1.5
1.0
.8
Tc = 85°C steady
TTcH=ER12M5A°CL
state
t = 5ms
SECOND
t
=
t=
1ms
0.5ms
BREAKDOWN
.6
.4
.3
.2
10
15 20 25 30 35 40 50 60 70 80 100
SUPPLY TO OUTPUT DIFFERENTIAL VOLTAGE VS – VO (V)
SAFE OPERATING AREA CURVES
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. However, the
following guidelines may save extensive analytical efforts.
2. The amplifier can handle any reactive or EMF generating
load and short circuits to the supply rail or common if the
current limits are set as follows at TC = 85°C:
SHORT TO ±VS
SHORT TO
±VS
C, L, OR EMF LOAD
COMMON
50V
.21A
40V
.3A
30V
.46A
20V
.87A
15V
1.4A
.61A
.87A
1.4A
2.5A
4.0A
These simplified limits may be exceeded with further analysis
using the operating conditions for a specific application.
3. The output stage is protected against transient flyback.
However, for protection against sustained, high energy
flyback, external fast-recovery diodes should be used.
THERMAL SHUTDOWN PROTECTION
The thermal protection circuit shuts off the amplifier when
the substrate temperature exceeds approximately 150°C. This
allows heatsink selection to be based on normal operating
conditions while protecting the amplifier against excessive
junction temperature during temporary fault conditions.
Thermal protection is a fairly slow-acting circuit and there-
fore does not protect the amplifier against transient SOA
violations (areas outside of the TC = 25°C boundary). It is
designed to protect against short-term fault conditions that
result in high power dissipation within the amplifier. If the
conditions that cause thermal shutdown are not removed, the
amplifier will oscillate in and out of shutdown. This will result in
high peak power stresses, will destroy signal integrity and
reduce the reliability of the device.
CURRENT LIMIT
Proper operation requires the use of two current limit resis-
tors, connected as shown in the external connections diagram.
The minimum value for RCL is .12Ω, 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.
1. For DC outputs, especially those resulting from fault condi-
tions, check worst case stress levels against the new SOA
graph.
For sine wave outputs, use Power Design1 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.
1 Note 1. Power Design is a self-extracting Excel spreadsheet
available free from www.apexmicrotech.com
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PA07U REV. L FEBRUARY 2001 © 2001 Apex Microtechnology Corp.
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