PA02 • PA02A
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OPERATING
CONSIDERATIONS
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GENERAL
Please read Application Note 1 "General Operating Considerations" which cov-
ers 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, internal power dissipation, current
limit; heat sink selection; Apex’s complete Application Notes library; Technical Seminar
Workbook; and Evaluation Kits.
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SAFE OPERATING AREA
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The SOA curves combine the
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effect of all limits for this Power
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Op Amp. For a given application,
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the direction and magnitude of
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the output current should be cal-
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culated or measured and checked
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against the SOA curves. This is
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simple for resistive loads but more
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complex for reactive and EMF
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generating loads. The following
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guidelines may save extensive
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analytical efforts:
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1. Under transient conditions,
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capacitive and dynamic* loads
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up to the following maximums
are safe:
CAPACITIVE LOAD
INDUCTIVE LOAD
±V
S
I
LIM
= 2A
I
LIM
= 5A
I
LIM
= 2A
I
LIM
= 5A
18V
2mF
0.7mF
.2H
10mH
15V
10mF
2.2mF
.7H
25mH
10V
25mF
10mF
5H
50mH
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* If the inductive load is driven near steady state conditions, allowing the output
voltage to drop more than 8V below the supply rail with I
LIM
= 5A, or 17V below the
supply rail with I
LIM
= 2A while the amplifier is current limiting, the inductor should
be capacitively coupled or the current limit must be lowered to meet SOA criteria.
2. The amplifier can handle any EMF generating or reactive load and short circuits
to the supply rails or shorts to common if the current limits are set as follows at
T
C
= 85°C.
SHORT TO ±V
S
SHORT TO
C, L OR EMF LOAD
COMMON
±V
S
18V
.5A
1.7A
15V
.7A
2.8A
10V
1.6A
4.2A
These simplified limits may be exceeded with further analysis using the operating
conditions for a specific application.
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CURRENT LIMIT
Proper operation requires the use of two current limit resistors, 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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DEVICE MOUNTING
The case (mounting flange) is electrically isolated and should be mounted directly to a
heatsink with thermal compound. Screws with Belville spring washers are recommended
to maintain positive clamping pressure on heatsink mounting surfaces. Long periods
of thermal cycling can loosen mounting screws and increase thermal resistance.
Since the case is electrically isolated (floating) with respect to the internal circuits it
is recommended to connect it to common or other convenient AC ground potential.
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This data sheet has been carefully checked and is believed to be reliable,
SHANNON ROAD •
is assumed
ARIZONA 85741
omissions. All specifications are subject
1 (800) 546-2739
APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH
however, no responsibility
TUCSON,
for possible inaccuracies
•
or
USA • APPLICATIONS HOTLINE:
to change without notice.
4
PA02U REV. L FEBRUARY 1998
© 1998 Apex Microtechnology Corp.
APEX [ CIRRUS LOGIC ]
