PA73 Ver la hoja de datos (PDF) - Cirrus Logic

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PA73

Power Operational Amplifier

Cirrus Logic 

PA01 • PA73

Product Innova tionFrom

GENERAL

Please read Application Note 1 "General Operating Consider-

ations" which covers stability, supplies, heat sinking, mounting,

current limit, SOA interpretation, and specification interpretation.

Visit www.cirrus.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 informa-

tion 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 Precision Power product models,

consult the "Evaluation Kit" section for details. For the most

current version of all Apex Precision Power product data sheets,

visit www.cirrus.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.

5.0

4.0

3.0

2.0

1.5

1.0

Tc = 85°C steady

TTcH=ER12M5A°CL

state

t = 5ms

SECOND

t

=

t=

1ms

0.5ms

BREAKDOWN

.8

.6

.4

PA01 LIMIT

.3

10

15

20 25 30 35 40 50 60

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. 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.

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 TC = 85°C.

SHORT TO ±VS

SHORT TO

±VS

C, L, OR EMF LOAD COMMON

34V

.58A

30V

.46A

25V

.61A

20V

.86A

15V

1.3A

1.1A

1.4A

1.7A

2.1A

2.9A

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 RCL 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.

1 Note 1. Power Design is a self-extracting Excel spreadsheet

available free from www.cirrus.com

4

PA01-73U

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