PA05A(1997) Ver la hoja de datos (PDF) - Apex Microtechnology
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PA05A Datasheet PDF : 4 Pages
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PA05 • PA05A
OPERATING
CONSIDERATIONS
GENERAL
Please read the General Operating Considerations section,
which covers stability, supplies, heatsinking, mounting, cur-
rent limit, SOA interpretation, and specification interpretation.
Additional information can be found in the application notes.
For information on the package outline, heatsinks, and mount-
ing hardware, consult the Accessory and Package Mechanical
Data section of the handbook. The EK04 Evaluation Kit makes
prototype circuits a snap by providing an EK04PC proto circuit
board, MS05 mating socket, HS11 heatsink and hardware kit.
CURRENT LIMIT
The two current limit sense lines are to be connected directly
across the current limit sense resistor. For the current limit to
work correctly, pin 11 must be connected to the amplifier
output side and pin 10 connected to the load side of the current
limit resistor, RCL, as shown in Figure 1. This connection will
bypass any parasitic resistances, RP formed by sockets and
solder joints as well as internal amplifier losses. The current
limiting resistor may not be placed anywhere in the output
circuit except where shown in Figure 1. If current limiting is not
used, pins 10 and 11 must be tied to pin 7.
The value of the current limit resistor can be calculated as
follows:
Rf
SHUTDOWN OPERATION
To disable the output stage, pin 12 is connected to ground
via relay contacts or via an electronic switch. The switching
device must be capable of sinking 2mA to complete shutdown
and capable of standing off the supply voltage +VS. See Figure
2 for suggested circuits.
–LOGIC
K1
12 SHUTDOWN
A
–LOGIC
B
Q1
470Ω
12 SHUTDOWN
Ri
INPUT
10
1
11
CL
2 PA05 CL
7 RP
RCL
RL
ILIMIT = .7/RCL
FIGURE 1. CURRENT LIMIT
SAFE OPERATING AREA (SOA)
The MOSFET output stage of this power operational ampli-
fier has two distinct limitations:
1. The current handling capability of the MOSFET geometry
and the wire bonds.
2. The junction temperature of the output MOSFETs.
NOTE: The output stage is protected against transient flyback.
However, for protection against sustained, high energy
flyback, external fast-recovery diodes should be used.
30
15
12
t = 200ms
9
6
3
1.5
1.2
.9
.6
.3
1
2 3 4 5 10 20 30 40 50 100
SUPPLY TO OUTPUT DIFFERENTIAL (V)
FIGURE 2. SHUTDOWN OPERATION
From an internal circuitry standpoint, shutdown is just a
special case of current limit where the allowed output current
is zero. As with current limit, however, a small current does flow
in the output during shutdown. A load impedance of 100 ohms
or less is required to insure the output transistors are turned off.
Note that even though the output transistors are off the output
pin is not open circuited because of the shutdown operating
current.
BOOST OPERATION
With the VBOOST feature, the small signal stages of the
amplifier are operated at higher supply voltages than the
amplifier’s high current output stage. +VBOOST (pin 9), and
–VBOOST (pin 5) are connected to the small signal circuitry of
the amplifier. +VS (pin 8) and –VS (pin 6) are connected to the
high current output stage. An additional 5V on the VBOOST pins
is sufficient to allow the small signal stages to drive the output
transistors into saturation and improve the output voltage
swing for extra efficient operation when required. When close
swings to the supply rails is not required the +VBOOST and +VS
pins must be strapped together as well as the –VBOOST and –VS
pins. The boost voltage pins must not be at a voltage lower than
the VS pins.
COMPENSATION
The external compensation components CC and RC are
connected to pins 3 and 4. Unity gain stability can be achieved
at any compensation capacitance greater than 470 pF with at
least 60 degrees of phase margin. At higher gains, more phase
shift can be tolerated in most designs and the compensation
capacitance can accordingly be reduced, resulting in higher
bandwidth and slew rate. Use the typical operating curves as
a guide to select CC and RC for the application.
This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.
PA05U REV. F DECEMBER 1997 © 1997 Apex Microtechnology Corp.
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