PA44 Apex Microtechnology Corporation, PA44 Datasheet - Page 4

• Manufacturer Part Number: PA44
• Description: High Voltage Power Operational Amplifier
• Manufacturer: Apex Microtechnology Corporation

PA44
GENERAL
erations" which covers stability, supplies, heat sinking, mount-
ing, current limit, SOA interpretation, and specification inter-
pretation. 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 Work-
book; and Evaluation Kits.
CURRENT LIMIT
connected as shown in the external connection diagram. The
minimum value is 18 ohms, however for optimum reliability the
resistor value should be set as high as possible. The value can
be estimated as follows with the maximum practical value of
500 ohms.
variations in current limit value with a given R
over temperature. The selected value of R
the specified typical value of output resistance to calculate the
total output resistance. Since the load current passes through
R
according to:
signal spurious oscillation present during the current limited
portion of the negative half cycle. The frequency of the oscil-
lation is not predictable and depends on the compensation,
gain of the amplifier, and load. The oscillation will cease as the
amplifier comes out of current limit.
INPUT PROTECTION
voltages up the supply rails and differential voltages up to ±16
volts as well as static discharge. Differential voltages exceed-
ing 16 volts will be clipped by the protection circuitry. However,
if more than a few milliamps of current is available from the
overload source, the protection circuitry could be destroyed.
The protection circuitry includes 300 ohm current limiting
resistors at each input, but this may be insufficient for severe
overloads. It may be necessary to add external resistors to the
application circuit where severe overload conditions are ex-
pected. Limiting input current to 1mA will prevent damage.
STABILITY
for unity gain to be stable with capacitive loads of at least 10 nF.
However, the low pass circuit created by the sumpoint (–in)
capacitance and the feedback network may add phase shift
and cause instabilities. As a general rule, the sumpoint load
resistance (input and feedback resistors in parallel) should be
1K ohm or less at low gain settings (up to 10). Alternatively, use
APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH SHANNON ROAD • TUCSON, ARIZONA 85741 • USA • APPLICATIONS HOTLINE: [phone]
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.
CL
Please read Application Note 1 "General Operating Consid-
For proper operation the current limit resistor, R
Use the typical performance graphs as a guide for expected
When the amplifier is current limiting, there may be small
The PA44 inputs are protected against common mode
The PA44 has sufficient phase margin when compensated
the value selected also affects the output voltage swing
where V
R
is the voltage swing reduction.
R
CL
V
=
R
= I
I
3
LIM
O
*
R
CL
PA44U REV. E AUGUST 2001 © 2001 Apex Microtechnology Corp.
CL
must be added to
CL
and variations
CL
, must be
a bypass capacitor across the feedback resistor. The time
constant of the feedback resistor and bypass capacitor com-
bination should match the time constant of the sumpoint
resistance and sumpoint capacitance.
be tailored to the application. Use the graphs of small signal
gain and phase response as well as the graphs for slew rate
and power response as a guide. The compensation capacitor
C
capacitor and associated resistor R
to the amplifier pins to avoid spurious oscillation. An NPO
capacitor is recommended for compensation.
SAFE OPERATING AREA (SOA)
fier has two distinct limitations:
1. The current handling capability of the die metallization.
2. The temperature of the output MOSFETs.
flyback. However, for protection against sustained, high en-
ergy flyback, external fast-recovery diodes should be used.
HEATSINKING
heatslug to which the monolithic amplifier is directly attached.
The solder connection of the heatslug to a minimum 1 square
inch foil area of the printed circuit board will result in thermal
performance of 25°C/W junction to air rating of the PA44.
Solder connection to an area of 1 to 2 square inches of foil is
recommended. This may be adequate heatsinking but the
large number of variables involved suggest temperature mea-
surements be made on the top of the package. Do not allow the
temperature to exceed 85°C. The heatslug is tied internally to –Vs.
C
The PA44 is externally compensated and performance can
The MOSFET output stage of this power operational ampli-
NOTE: The output stage is protected against transient
The PA44 package has a large exposed integrated copper
must be rated at 350V working voltage. The compensation
200
120
100
50
40
30
20
10
5
4
3
2
10
PULSE CURVES @ 10% DUTY CYCLE MAX
SUPPLY TO OUTPUT DIFFERENTIAL, V
20
30
50
PA44 SOA
100
300mS
C
must be mounted closely
200 300
CONSIDERATIONS
S
-V
200mS
O
(V)
OPERATING
500