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PDF PA21A Data sheet ( Hoja de datos )

Número de pieza PA21A
Descripción POWER DUAL OPERATIONAL AMPLIFIERS
Fabricantes ETC 
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MICROTECHNOLOGY
POWER DUAL OPERATIONAL AMPLIFIERS
PA21/25/26 • PA21A/25A
HTTP://WWW.APEXMICROTECH.COM (800) 546-APEX (800) 546-2739
FEATURES
• LOW COST
• WIDE COMMON MODE RANGE —
Includes negative supply
• WIDE SUPPLY VOLTAGE RANGE
Single supply: 5V to 40V
Split supplies: ±2.5V to ±20V
• HIGH EFFICIENCY — |Vs–2.2V| at 2.5A typ
• HIGH OUTPUT CURRENT — 3A min (PA21A)
• INTERNAL CURRENT LIMIT
• LOW DISTORTION
APPLICATIONS
• HALF & FULL BRIDGE MOTOR DRIVERS
• AUDIO POWER AMPLIFIER
STEREO — 18W RMS per channel
BRIDGE — 36W RMS per package
• IDEAL FOR SINGLE SUPPLY SYSTEMS
5V — Peripherals
12V — Automotive
28V — Avionic
DESCRIPTION
The amplifiers consist of a monolithic dual power op amp
in a 8-pin hermetic TO-3 package (PA21 and PA25) and a 12-
pin SIP package (PA26). Putting two power op amps in one
package and on one die results in an extremely cost effective
solution for applications requiring multiple amplifiers per
board or bridge mode configurations.
The wide common mode input range includes the negative
rail, facilitating single supply applications. It is possible to
have a “ground based” input driving a single supply amplifier
with ground acting as the “second” or “bottom” supply of the
amplifier.
The output stages are also well protected. They possess
internal current limit circuits. While the device is well pro-
tected, the Safe Operating Area (SOA) curve must be ob-
served. Proper heatsinking is required for maximum reliabil-
ity.
This hybrid integrated circuit utilizes thick film (cermet)
resistors, ceramic capacitors and semiconductor chips to
maximize reliability, minimize size and give top performance.
Ultrasonically bonded aluminum wires provide reliable inter-
connections at all operating temperatures. The 8-pin TO-3
package is hermetically sealed and electrically isolated. The
use of compressible isolation washers voids the warranty.
The tab of the SIP12 plastic package is tied to –VS.
R2 R3
9K
+28V
10K
R4
R1
10K
5K A M B
++
1/2 PA21
1/2 PA21
COMMAND
INPUT
0/10V
+28V
R5
10K
R6
10K
FIGURE 1: BIDIRECTIONAL SPEED CONTROL FROM
A SINGLE SUPPLY
The amplifiers are especially well-suited for this application.
The extended common mode range allows command inputs
as low as 0V. Its superior output swing abilities let it drive within
2V of supply at an output current of 2A. This means that a
command input that ranges from 0V to 10V will drive a 24V
motor from full scale CCW to full scale CW at up to ±2A. A
single power op amp with an output swing capability of Vs –6
would require ±30V supplies and would be required to swing
48V p-p at twice the speed to deliver an equivalent drive.
EXTERNAL CONNECTIONS
PA26
Connect pins
3 and 10 to pin 7
and connect pins
4 and 9 to pin 6
unless special
functions are re-
quired.
++
A
SUB B
1 2 3 4 5 6 7 8 9 10 11 12
TYPICAL APPLICATION
R1 and R2 set up amplifier A in a non-inverting gain of 2.8.
Amp B is set up as a unity gain inverter driven from the output
of amp A. Note that amp B inverts signals about the reference
node, which is set at mid-supply (14V) by R5 and R6. When the
command input is 5V, the output of amp A is 14V. Since this is
equal to the reference node voltage, the output of amp B is also
14V, resulting in 0V across the motor. Inputs more positive
than 5V result in motor current flow from left to right (see Figure
1). Inputs less positive than 5V drive the motor in the opposite
direction.
+IN, A
3
IN, A
+VS
2 OUT, B
1
4
+
AB
+
5
OUT, A TOP VIEW
8
VS 6
PA25
7
+IN, B
IN, B
IN, A 3
4
+IN, A
5
+IN, B
6
IN, B
PA21
+VS
2
A
B
7
VS
OUT, A
1
8
OUT, B
APEX MICROTECHNOLOGY CORPORATION • TELEPHONE (520) 690-8600 • FAX (520) 888-3329 • ORDERS (520) 690-8601 • EMAIL [email protected]

1 page




PA21A pdf
OPERATING
CONSIDERATIONS
PA21/25/26 PA21A/25A
ADDITIONAL PA26 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 emit-
ter 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.
VBOOST pin requires approximately 1012mA of current.
Dynamically it represents 1K impedance. The maximum
voltage that can be applied to VBOOST is 40 volts with respect to
VS. There is no limit to the difference between +VS and VBOOST.
+VS 20V
DB1
DB2
7 3 10
CB1
PA26A
5
CB2
SPEAKER
PA26B
8
FIGURE 3. SIMPLE BOOTSTRAPPING IMPROVES POSITIVE
OUTPUT SWING. CONNECT PINS 3 AND 10 TO VS IF NOT
USED. TYPICAL CURRENTS ARE 12mA EACH.
Figure 3 shows a bootstrap which dynamically couples the
output waveform onto the VBOOST pin. This causes VBOOST to
swing positive from it's initial value, which is equal to +VS -0.7 V
(one diode drop), an amount equal to the output. In other
words, if VBOOST was initially 19.3, and the output swings
positive 18 Volts, the voltage on the VBOOST pin will swing to 19.3
-0.7 + 18 or 36.6. The capacitor needs to be sized based on a
1K impedance and the lowest frequency required by the
circuit. For example, 20Hz will require > 8uF.
ISENSE
The ISENSE pin is in series with the negative half of the output
stage only. Current will flow through this pin only when nega-
tive current is being outputted. The current that flows in this pin
is the same current that flows in the output (if 1A flows in the
output, the ISENSE pin will have 1A of current flow, if +1A flows
in the output the ISENSE pin will have 0 current flow).
The resistor choice is arbitrary and is selected to provide
whatever voltage drop the engineer desires, up to a maximum
of 1.0 volt. However, any voltage dropped across the resistor
will subract from the swing to rail. For instance, assume a +/
12 volt power supply and a load that requires +/1A. With no
current sense resistor the output could swing +/10.2 volts. If
a 1 resistor is used for current sense (which will drop 1 Volt
at 1 Amp) then the output could swing +10.2, 9.2 Volts.
+VS
PA26
VBIAS
B
R
RL IL
VIN A
R
RFB
RIN
RS RS RIN RFB
VS OR GND
VREF
FIGURE 4. ISENSE TRANSCONDUCTANCE BRIDGING
AMPLIFIER
Figure 4 shows the PA26 ISENSE feature being used to obtain
a Transconductance function. In this example, amplifier "A" is
the master and amplifier "B" is the slave. Feedback from
sensing resistors RS is applied to the summing network and
scaled to the inverting input of amplifier "A" where it is com-
pared to the input voltage. The current sensing feedback
imparts a Transconductance feature to the amplifiers transfer
function. In other words, the voltage developed across the
sensing resistors is directly proportional to the output current.
Using this voltage as a feedback source allows expressing the
gain of the circuit in amperes vs input voltage. The transfer
funcion is approximately:
IL= (VIN VREF) *RIN/ RFB/ Rs
In the illustration, resistors RIN, RFB and RS determine gain.
VBIAS should be set midway between +Vs and -Vs, Vref is
usually ground in dual supply systems or used for level
translation in single supply systems.
MOUNTING PRECAUTIONS
1. Always use a heat sink. Even unloaded, the PA26 can
dissipate up to 3.6 watts. A thermal washer or thermal
grease should always be used.
2. Avoid bending the leads. Such action can lead to internal
damage.
3. Always fasten the tab to the heat sink before the leads are
soldered to fixed terminals.
4. Strain relief must be provided if there is any probability of
axial stress to the leads.
AThPisEXdatMa IsCheReOt hTaEsCbHeeNnOcaLreOfuGllYy cChOecRkPedOaRnAd TisIbOeNlievedTEtoLEbePrHelOiaNblEe,(h5o2w0ev)e6r,9n0o-r8es6p0on0sibilFitAyXis(a5ss2u0m)ed8f8o8r -p3os3s2ib9leinOacRcuDraEcRieSs (o5r o2m0i)ss6io9n0s.-A8l6l s0p1ecificEaMtioAnIsLarpersoudbjleictt@toacpheanxgmeiwcirtohotuetcnho.tcicoem.
PA21/25/26U REV. G FEBRUARY 2000 © 2000 Apex Microtechnology Corp.

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