PA34 Просмотр технического описания (PDF) - Unspecified
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PA34 Datasheet PDF : 5 Pages
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PA34
OPERATING
CONSIDERATIONS
GENERAL
Please read Application Note 1 "General Operating
Considerations" 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,
internal 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.
CURRENT LIMIT
Current limit is internal to the amplifier, the typical value is
shown in the current limit specification.
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3
2
DC
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allowing the output voltage to drop more than 6V below the
supply rail while the amplifier is current limiting, the inductor
should be capacitively coupled or the supply voltage must be
lowered to meet SOA criteria.
NOTE: For protection against sustained, high energy flyback,
external fast-recovery diodes should be used.
MONOLITHIC AMPLIFIER
STABILITY CONSIDERATIONS
All monolithic power op amps use output stage topologies
that present special stability problems. This is primarily due
to non-complementary (both devices are NPN) output
stages with a mismatch in gain and phase response for
different polarities of output current. It is difficult for the
op amp manufacturer to optimize compensation for all
operating conditions.
The recommended R-C network of 1 ohm in series with
0.1µF from output to AC common (ground or a supply rail,
with adequate bypass capacitors) will prevent local output
stage oscillations.
The amplifiers are internally compensated for unity gain
stability, no additional compensation is required.
THERMAL CONSIDERATIONS
The PA34 may require a thermal washer which is electrically
insulating since the tab is tied to –VS.This can result in thermal
impedances for R θCS of up to 1°C/W or greater.
VBOOST
TC = 25°C
.1
1
2 3 4 56
10
20 30 40 50
SUPPLY TO OUTPUT DIFFERENTIAL VOLTAGE VS –VO (V)
– IN
+VS
+IN
OUT
SAFE OPERATING AREA (SOA)
The SOA curves combine the effect of all limits for this
power op amp. 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. The following guidelines may save
extensive analytical efforts.
Under transient conditions, capacitive and dynamic*
inductive loads up to the following maximum are safe:
±Vs
CAPACITIVE LOAD INDUCTIVE LOAD
20V
200µF
15V
500µF
10V
5mF
5V
50mF
7.5mH
25mH
35mH
150mH
* If the inductive load is driven near steady state conditions,
FIGURE 2. EQUIVALENT SCHEMATIC
ISENSE
RS
– VS
ADDITIONAL PA34 PIN FUNCTIONS
VBOOST
The VBOOST pin is the positive terminal for the load of the
second stage of the amplifier.When that terminal is connected
to a voltage greater than +VS it will provide more drive to the
upper output transistor, which is a darlington connected emitter
follower. This will better saturate the output transistor.
When VBOOST is about 5 Volts greater than +VS the
positive output can swing 0.5 Volts closer to the rail. This is
as much improvement as is possible.
APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH SHANNON ROAD • TUCSON, ARIZONA 85741 • USA • APPLICATIONS HOTLINE: 1 (800) 546-2739
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