PA94 PA94 P r o d u c t IInnnnoovvaa t i o n FFr roomm 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. Cirrus’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 12 +VS R1A R1B Q1 4 CC1 Q5 Q15A R7 R12 R20 Q4 ILIM 8 Q14 7 OUT Q29 Q21 R19 Q29 http://www.cirrus.com Q8 R10 2 +IN PA94U R4 6 CC2 Q15B R9 R11 –VS 10 R3 Q3 Q2 Q6 1 –IN C2 Q14 Q30 R27 Copyright © Cirrus Logic, Inc. 2009 (All Rights Reserved) JUN 20091 APEX − PA94UREVM PA94 P r o d u c t I n n o v a t i o nF r o m 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 INPUT VOLTAGE, differential -20 20 V INPUT VOLTAGE, common mode (Note 3) -VS VS V 260 °C TEMPERATURE, pin solder, 10s max. TEMPERATURE, junction (Note 2) 150 °C TEMPERATURE RANGE, storage −40 85 °C OPERATING TEMPERATURE RANGE, case −25 85 °C 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 INPUT OFFSET VOLTAGE, initial OFFSET VOLTAGE vs. temperature Full temperature range OFFSET VOLTAGE vs. supply 0.5 5 mV 15 50 µV/°C 10 25 µV/V OFFSET VOLTAGE vs. time 75 BIAS CURRENT, initial 200 BIAS CURRENT vs. supply µV/kHz 2000 4 OFFSET CURRENT, initial 50 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 500 pA 1011 Ω 4 pF V 98 dB 2 µV RMS 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 ° ±VS Ŧ 20 V 700 V/µS OUTPUT IO = 70mA ±VS Ŧ 24 SLEW RATE, A V = 100 CC =2.2pF 500 SETTLING TIME, to 0.1% 2V Step 1 µS RESISTANCE no load 100 Ω VOLTAGE SWING CURRENT, continuous 2 100 mA 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 ±50 ±300 ±450 V 17 24 mA 120 µA POWER SUPPLY VOLTAGE (Note 5) CURRENT, quiescent total 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 -25 °C/W +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. EXTERNAL CONNECTIONS –IN +IN CC1 1 2 4 CC2 OUT ILIM 6 7 8 CC RLIM –Vs +Vs 10 12 * * * 0.01µF or greater ceramic power supply bypassing required. PATENTED 8-pin SIP PACKAGE STYLE DQ Formed leads available See package style EC PHASE COMPENSATION GAIN CC ≥100 2.2pF ≥50 4.7pF ≥10 22pF CC rated for full supply voltage. .7 R = LIM ILIM PA94U 3 QUIESCENT CURRENT, I (X) PHASE, Ф (°) 20 1.04 -120 T = TC 1.00 -150 15 CC = 2.2pF 30 20 10 3 5 10 20 50 100 150 CURRENT LIMIT RESISTOR, RCL (Ω) OUTPUT VOLTAGE, VO (VP-P) C 5° 12 = 100 25 DC DC ,T ,T DC ,T C C C = 15 0m 20 = S 0m S = 85 25 12 °C °C 5° C 10 PULSE CURVES @ 10% DUTY CYCLE MAX 5 50 100 200 500 1K SUPPLY TO OUTPUT DIFFERENTIAL, VS –VO (V) 100 50 10K 100K 1M 2M FREQUENCY, F (Hz) INPUT NOISE 20 15 10 7 5 3 2 10 100 1K 10K FREQUENCY, F (Hz) TYPICAL APPLICATION 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. F 50 10 150 50 200 100 80 40 60 20 OUTPUT CURRENT, IO (mA) SAFE OPERATING AREA F 70 250 0 .2p 120 100 4 =2 CURRENT LIMIT 8 CC 100 1K 10K 100K 1M 10M 20M FREQUENCY, F (Hz) 5°C –5 TC = F 0 10 16 =2 .7p 20 TC 2p 40 CC = 22 pF 5°C 24 500 =2 CC = 4.7pF 60 TC 85 =4 80 POWER RESPONSE 1K °C = .92 .88 0 200 800 1000 400 600 TOTAL SUPPLY VOLTAGE, VS (V) 20M OUTPUT VOLTAGE SWING 32 .96 CC CC = 2.2pF 40 10M FREQUENCY, F (Hz) C SMALL SIGNAL RESPONSE -240 1M T 25 50 75 100 125 150 TEMPERATURE, T (°C) VOLTAGE DROP FROM SUPPLY, VS – VO (V) 0 100 200 CC = 4.7pF -210 5 0 CC = 22 pF -180 T = TA 10 QUIESCENT CURRENT 1.08 INPUT NOISE VOLTAGE, VN (nV/√Hz) 25 -90 CC OPEN LOOP GAIN, A (dB) PHASE RESPONSE POWER DERATING 30 120 CURRENT LIMIT, ILIM (mA) P r o d u c t I n n o v a t i o nF r o m OUTPUT CURRENT FROM +VS OR –VS, (mA) INTERNAL POWER DISSIPATION, P (W) PA94 1M RF +VS R IN 1 12 PIEZO DRIVE PA94 2 COMPUTER FOCUS COMMAND VOLTAGE 8 10 7 V OUT R CL –V S 4 PA94U P r o d u c t I n n o v a t i o nF r o m PA94 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 Cirrus 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. RØSA = TC - TA -0.1°C/W PD + PDQ 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. RØSA = TJ - TA - (PD + PDQOUT) * RØJC -0.1°C/W PD + PDQ 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; Cirrus’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 R = LIM 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 5 PA94 INPUT PROTECTION P r o d u c t I n n o v a t i o nF r o m 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. POWER SUPPLY PROTECTION FIGURE 1. OVERVOLTAGE PROTECTION A. +VS Z1 –IN D1 +IN 1 12 D2 PA94 2 10 +VS Z2 Z1 –VS B. –IN 1 12 Unidirectional zener diode transient suppressors are recommended Q1 Q2 PA94 as protection on the supply pins. The zeners clamp transients to +IN voltages within the power supply rating and also clamp power sup2 10 ply reversals to ground. Whether the zeners are used or not, the Z2 system power supply should be evaluated for transient performance –VS 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. 6 PA94U