PA94
PA94
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High Voltage Power Operational Amplifiers
FEATURES
DESCRIPTION
The PA94 is a high voltage, MOSFET operational amplifier designed as a low cost solution for driving continuous output currents up to 100mA and pulse currents
up to 200mA into capacitive loads. The safe operating
area (SOA) has no second breakdown limitations and
can be observed for all load types by choosing an appropriate current limiting resistor. The MOSFET output
stage is biased AB for linear operation. External compensation provides flexibility in choosing bandwidth
and slew rate for the application. APEX’s Power SIP
package uses a minimum of board space allowing for
high density circuit boards.. The Power SIP package is
electrically isolated. Isolating thermal washers (TW13)
prevent arcing from pins to heatsink.
♦ HIGH VOLTAGE — 900V (±450V)
♦ HIGH SLEW RATE — 500V/µS
♦ HIGH OUTPUT CURRENT — 100mA ♦ PROGRAMMABLE CURRENT LIMIT
APPLICATIONS
♦ HIGH VOLTAGE INSTRUMENTATION
♦ PROGRAMMABLE POWER SUPPLIES UP
TO ±430V
♦ MASS SPECTROMETERS
♦ SEMICONDUCTOR MEASUREMENT EQUIPMENT
EQUIVALENT SCHEMATIC
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Copyright
© Cirrus Logic, Inc. 2008
(All Rights Reserved)
AUG 2008
APEX − PA94UREVK
PA94
P r o d u c t I n n o v a t i o nF r o m
EXTERNAL CONNECTIONS
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PATENTED
8-pin SIP
PACKAGE
STYLE DQ
'PSHSFBUFSDFSBNJDQPXFSTVQQMZCZQBTTJOHSFRVJSFE
Formed leads available
See package style EC
1. Characteristics and Specifications
Absolute Maximum Ratings
Parameter
Symbol
Min
Max
Units
SUPPLY VOLTAGE, +VS to –VS
900
V
OUTPUT CURRENT, source, sink, within SOA
200
mA
POWER DISSIPATION, continuous @ TC = 25°C
30
W
20
V
INPUT VOLTAGE, differential
-20
INPUT VOLTAGE, common mode (Note 3)
-VS
TEMPERATURE, pin solder, 10s max.
VS
V
260
°C
150
°C
TEMPERATURE RANGE, storage
−40
85
°C
OPERATING TEMPERATURE RANGE, case
−25
85
°C
TEMPERATURE, junction (Note 2)
CAUTION
The PA94 is constructed from MOSFET transistors. ESD handling procedures must be observed.
The exposed substrate contains beryllia (BeO). Do not crush, machine, or subject to temperatures
in excess of 850°C to avoid toxic fumes.
Specifications
Parameter
Test Conditions1
Min
Typ
Max
Units
0.5
5
mV
15
50
µV/°C
10
25
µV/V
INPUT
OFFSET VOLTAGE, initial
Full temperature range
OFFSET VOLTAGE vs. temperature
OFFSET VOLTAGE vs. supply
OFFSET VOLTAGE vs. time
75
BIAS CURRENT, initial
200
4
BIAS CURRENT vs. supply
INPUT IMPEDANCE, DC
INPUT CAPACITANCE
COMMON MODE VOLTAGE RANGE
(Note 3)
VS = ±450V
±VS Ŧ30
COMMON MODE REJECTION, DC
VCM = ±90V
80
NOISE
10KHz bandwidth, RS = 1KΩ
pA
pA/V
50
OFFSET CURRENT, initial
µV/kHz
2000
500
pA
1011
Ω
4
pF
V
98
dB
2
µV RMS
PA94U
PA94
P r o d u c t I n n o v a t i o nF r o m
Parameter
Test Conditions1
Min
Typ
Max
Units
GAIN
OPEN LOOP @ 15Hz
RL = 5KΩ
115
dB
GAIN BANDWIDTH PRODUCT @ 1MHz
RL = 5KΩ
94
140
MHz
POWER BANDWIDTH
RL = 5KΩ
300
kHz
PHASE MARGIN, A V = 100
Full temp range
60
°
OUTPUT
IO = 70mA
VOLTAGE SWING
±VS Ŧ 24
±VS Ŧ 20
V
100
CURRENT, continuous
SLEW RATE, A V = 100
CC =2.2pF
SETTLING TIME, to 0.1%
RESISTANCE
mA
500
700
V/µS
2V Step
1
µS
no load
100
Ω
POWER SUPPLY
±50
VOLTAGE (Note 5)
CURRENT, quiescent total
±300
±450
V
17
24
mA
120
µA
CURRENT, quiescent output stage only
THERMAL
RESISTANCE, AC, junction to case
(Note 4)
Full temp range, F > 60Hz
2.5
°C/W
RESISTANCE, DC, junction to case
Full temp range, F < 60Hz
4.2
°C/W
RESISTANCE, junction to air
Full temp range
TEMPERATURE RANGE, case
Meets full range specifications
30
°C/W
-25
+85
°C
NOTES: 1. Unless otherwise noted: TC = 25°C, DC input specifications are ± value given. Power supply voltage
is typical rating. Cc= 4.7pF.
2. Long term operation at the maximum junction temperature will result in reduced product life. Derate
internal power dissipation to achieve high MTTF.
3. Although supply voltages can range up to ± 450V the input pins cannot swing over this range. The
input pins must be at least 30V from either supply rail but not more than 450V from either supply rail.
See text for a more complete description of the common mode voltage range.
4. Rating applies if the output current alternates between both output transistors at a rate faster than
60Hz.
5. Derate max supply rating 0.625 V/°C below 25°C case. No derating needed above 25°C case.
TYPICAL APPLICATION
3'
Piezo positioning may be applied to the focusing of segmented mirror systems. The composite mirror may be
composed of hundreds of elements, each requiring focusing under computer control. In such complex systems the
PA94 reduces the costs of power supplies and cooling
with its advantages of low cost and low quiescent power
consumption while increasing circuit density with the SIP
package.
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PHASE COMPENSATION
GAIN
CC ≥100 2.2pF
≥50 4.7pF
≥10 22pF
CC rated for full supply voltage.
.7
RLIM =
ILIM
PA94U
PA94
P r o d u c t I n n o v a t i o nF r o m
INTERNAL POWER DISSIPATION AND HEATSINK SELECTION
With the unique combination of high voltage and speed of the PA94, traditional formulas for heatsink selection will
falsely lower the apparent power handling capability of this amplifier. To more accurately predict operating temperatures use Power Design1 revision 10 or higher, or use the following procedure:
Find internal dissipation (PD) resulting from driving the load. Use Power Design or refer to Apex Applications Note
1, General Operating Considertaions, paragraph 7. Find total quiescent power (PDQ) by multiplying 0.024A by VSS
(total supply voltage). Find output stage quiescent power (PDQOUT) by multiplying 0.00012 by VSS.
Calculate a heatsink rating which will maintain the case at 85°C or lower.
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Where:TC = maximum case temperature allowed
TA = maximum ambient temperature encountered
Calculate a heatsink rating which will maintain output transistor junctions at 150°C or lower.
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Where: TJ = maximum junction temperature allowed.
RØJC = AC or DC thermal resistance from the specification table.
Use the larger heatsink of these two calculations.
Power Design is an Excel spreadsheet available free from www.cirrus.com
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.cirrus.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 Workbook; and Evaluation Kits.
CURRENT LIMIT
For proper operation, the current limit resistor (RLIM) must be connected as shown in the external connection diagram. The minimum value is 3.5 ohm, however for optimum reliability the resistor value
should be set as high as possible. The value is calculated as follows; with the maximum practical value
of 30 ohms.
.7 RLIM = ILIM
COMMON MODE INPUT RANGE
Operational amplifiers are usually designed to have a common mode input voltage range that approximates the
power supply voltage range. However, to keep the cost as low as possible and still meet the requirements of most
applications the common mode input voltage range of the PA94 is restricted. The input pins must always be a least
30V from either supply voltage but never more than 450V. This means that the PA94 cannot be used in applications
where the supply voltages are extremely unbalanced. For example, supply voltages of +800V and –100V would not
be allowed in an application where the non-inverting pin is grounded because in normal operation both input pins
would be at 0V and the difference voltage between the positive supply and the input pins would be 800V. In this
kind of application, however, supply voltages +450V and -100V does meet the input common mode voltage range
requirements since the maximum difference voltage between the inputs pins and the supply voltage is 450V (the
maximum allowed). The output has no such restrictions on its voltage swing. The output can swing within 24V of
either supply voltage regardless of value so long as the total supply voltage does not exceed 900V.
PA94U PA94
P r o d u c t I n n o v a t i o nF r o m
INPUT PROTECTION
FIGURE 1. OVERVOLTAGE PROTECTION
Although the PA94 can withstand differential input voltages up to
±20V, additional external protection is recommended. In most applications 1N4148 or 1N914 signal diodes are sufficient (D1, D2 in
Figure 1a). In more demanding applications where low leakage or
low capacitance are of concern 2N4416 or 2N5457-2N5459 JFETs
connected as diodes will be required (Q1, Q2 in Figure 1b). In either case the input differential voltage will be clamped to ±.7V. This
is sufficient overdrive to produce maximum power bandwidth. Note
that this protection does not automatically protect the amplifier from
excessive common mode input voltages.
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POWER SUPPLY PROTECTION
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Unidirectional zener diode transient suppressors are recommended
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as protection on the supply pins. The zeners clamp transients to
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ply reversals to ground. Whether the zeners are used or not, the
;
system power supply should be evaluated for transient performance
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including power-on overshoot and power-off polarity reversal as well
as line regulation.
Conditions which can cause open circuits or polarity reversals on either power supply rail should be avoided or protected against. Reversals or opens on the negative supply rail is known to induce input stage failure. Unidirectional
transzorbs prevent this, and it is desirable that they be both electrically and physically as close to the amplifier as
possible.
STABILITY
The PA94 is stable at gains of 100 or more with a NPO (COG) compensation capacitor of 2.2pF. The compensation
capacitor, Cc, in the external connections diagram must be rated at 1000V working voltage and mounted closely to
pins 4 and 6 to prevent spurious oscillation. A compensation capacitor less than 2.2pF is not recommended.
EXTERNAL COMPONENTS
The compensation capacitor Cc must be rated for the total supply voltage. An NPO (COG) capacitor rated a 1kV is
recommended.
Of equal importance are the voltage rating and voltage coefficient of the gain setting feedback resistor. Typical voltage ratings of low wattage resistors are 150 to 250V. Up to 500 V can appear across the feedback resistor. High
voltage rated resistors can be obtained. However a 1 megohm feedback resistor composed of five 200k resistors in
series will produce the proper voltage rating.
CAUTIONS
The operating voltages of the PA94 are potentially lethal. During circuit design develop a functioning circuit at the
lowest possible voltages. Clip test leads should be used for "hands off" measurements while troubleshooting.
PA94U
PA94
P r o d u c t I n n o v a t i o nF r o m
Contacting Cirrus Logic Support
For all Apex Precision Power product questions and inquiries, call toll free 800-546-2739 in North America.
For inquiries via email, please contact [email protected].
International customers can also request support by contacting their local Cirrus Logic Sales Representative.
To find the one nearest to you, go to www.cirrus.com
IMPORTANT NOTICE
Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
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does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.
CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL APPLICATIONS”). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED TO BE
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PA94U