OPA547 ® High-Voltage, High-Current OPERATIONAL AMPLIFIER FEATURES DESCRIPTION ● WIDE SUPPLY RANGE Single Supply: +8V to +60V Dual Supply: ±4V to ±30V ● HIGH OUTPUT CURRENT: 500mA Continuous ● WIDE OUTPUT VOLTAGE SWING The OPA547 is a low cost, high-voltage/high-current operational amplifier ideal for driving a wide variety of loads. A laser-trimmed monolithic integrated circuit provides excellent low-level signal accuracy and high output voltage and current. The OPA547 operates from either single or dual supplies for design flexibility. In single supply operation, the input common-mode range extends below ground. ● FULLY PROTECTED: Thermal Shutdown Adjustable Current Limit ● OUTPUT DISABLE CONTROL ● THERMAL SHUTDOWN INDICATOR The OPA547 is internally protected against overtemperature conditions and current overloads. In addition, the OPA547 was designed to provide an accurate, user-selected current limit. Unlike other designs which use a “power” resistor in series with the output current path, the OPA547 senses the load indirectly. This allows the current limit to be adjusted from 0 to 750mA with a 0 to 150µA control signal. This is easily done with a resistor/potentiometer or controlled digitally with a voltage-out or current-out DAC. ● HIGH SLEW RATE: 6V/µs ● LOW QUIESCENT CURRENT ● PACKAGES: 7-Lead TO-220 7-Lead DDPAK Surface-Mount The Enable/Status (E/S) pin provides two functions. An input on the pin not only disables the output stage to effectively disconnect the load but also reduces the quiescent to conserve power. The E/S pin output can be monitored to determine if the OPA547 is in thermal shutdown. APPLICATIONS ● VALVE, ACTUATOR DRIVER ● SYNCHRO, SERVO DRIVER ● POWER SUPPLIES The OPA547 is available in an industry-standard 7-lead staggered TO-220 package and a 7-lead DDPAK surface-mount plastic power package. The copper tab allows easy mounting to a heat sink or circuit board for excellent thermal performance. It is specified for operation over the extended industrial temperature range, –40°C to +85°C. ● TEST EQUIPMENT ● TRANSDUCER EXCITATION ● AUDIO AMPLIFIER V+ – VIN OPA547 VO ILIM + VIN RCL (0.25W Signal Resistor) RCL sets the current limit value from 0 to 750mA. E/S V– International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111 Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 ® ©1997 Burr-Brown Corporation PDS-1326A 1 Printed in U.S.A. May, 1997 OPA547 SPECIFICATIONS At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted. OPA547T, F PARAMETER CONDITION OFFSET VOLTAGE Input Offset Voltage vs Temperature vs Power Supply INPUT BIAS CURRENT(1) Input Bias Current(2) vs Temperature Input Offset Current MIN TYP MAX UNITS VCM = 0, IO = 0 TA = –40°C to +85°C VS = ±4V to ±30V ±1 ±25 10 ±5 mV µV/°C µV/V VCM = 0V –100 ±0.5 ±5 VCM = 0V NOISE Input Voltage Noise Density, f = 1kHz Current Noise Density, f = 1kHz INPUT VOLTAGE RANGE Common-Mode Voltage Range: Positive Negative Common-Mode Rejection Linear Operation Linear Operation VCM = (V–) –0.1V to (V+) –3V (V+) –3 (V–) –0.1 80 INPUT IMPEDANCE Differential Common-Mode OPEN-LOOP GAIN Open-Loop Voltage Gain, f = 10Hz FREQUENCY RESPONSE Gain-Bandwidth Product Slew Rate Full Power Bandwidth Settling Time: ±0.1% Total Harmonic Distortion + Noise, f = 1kHz OUTPUT Voltage Output, Positive Negative Positive Negative Maximum Continuous Current Output: dc ac Leakage Current, Output Disabled, dc Output Current Limit Current Limit Range Current Limit Equation Current Limit Tolerance(1) VO = ±25V, RL = 1kΩ VO = ±25V, RL = 50Ω 100 RL = 50Ω G = 1, 50Vp-p, RL = 50Ω G = –10, 50V Step RL = 50Ω, G = +3V, 1W Power IO = 0.5A IO = –0.5A IO = 0.1A IO = –0.1A (V+) –2.2 (V–) +1.6 (V+) –1.8 (V–) +1.2 ±500 500 POWER SUPPLY Specified Voltage Operating Voltage Range Quiescent Current Quiescent Current, Shutdown Mode TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance, θJC 7-Lead DDPAK, 7-Lead TO-220 7-Lead DDPAK, 7-Lead TO-220 Thermal Resistance, θJA 7-Lead DDPAK, 7-Lead TO-220 –500 ±50 nA nA/°C nA 90 200 nV/√Hz fA/√Hz (V+) –2.3 (V–) –0.2 95 V V dB 107 || 6 109 || 4 Ω || pF Ω || pF 115 110 dB dB 1 6 See Typical Curve 18 0.004(3) MHz V/µs kHz µs % (V+) –1.9 (V–) +1.3 (V+) –1.5 (V–) +0.8 V V V V mA mArms See Typical Curve 0 to ±750 ILIM = (5000)(4.75)/(31600Ω + RCL) ±10 ±30 RCL = 31.6kΩ (ILIM = ±375mA), RL = 50Ω mA A mA See Typical Curve(4) Capacitive Load Drive OUTPUT ENABLE /STATUS (E/S) PIN Shutdown Input Mode VE/S High (output enabled) VE/S Low (output disabled) IE/S High (output enabled) IE/S Low (output disabled) Output Disable Time Output Enable Time Thermal Shutdown Status Output Normal Operation Thermally Shutdown Junction Temperature, Shutdown Reset from Shutdown 100 E/S Pin Open or Forced High E/S Pin Forced Low E/S Pin High E/S Pin Low (V–) +2.4 Sourcing 20µA Sinking 5µA, TJ > 160°C (V–) +2.4 (V–) +0.8 –60 –65 1 3 ±4 ILIM Connected to V–, IO = 0 ILIM Connected to V– (V–) +3.5 (V–) +0.35 +160 +140 ±30 ±10 ±4 –40 –40 –55 (V–) +0.8 V V µA µA µs ms V V °C °C ±30 ±15 V V mA mA +85 +125 +125 °C °C °C f > 50Hz dc 2 3 °C/W °C/W No Heat Sink 65 °C/W NOTES: (1) High-speed test at TJ = +25°C. (2) Positive conventional current flows into the input terminals. (3) See “Total Harmonic Distortion+Noise” in the Typical Performance Curves section for additional power levels. (4) See “Small-Signal Overshoot vs Load Capacitance” in the Typical Performance Curves section. ® OPA547 2 ELECTROSTATIC DISCHARGE SENSITIVITY CONNECTION DIAGRAMS Top Front View 7-Lead Stagger-Formed TO-220 This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. 7-Lead DDPAK Surface-Mount 1 2 3 4 5 6 7 ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. 1 2 3 4 5 6 7 + VIN ILIM V+ E/S – VIN V– VO + VIN ILIM V+ E/S – VIN V– VO NOTE: Tabs are electrically connected to V– supply. ABSOLUTE MAXIMUM RATINGS Output Current ................................................................. See SOA Curve Supply Voltage, V+ to V– ................................................................... 60V Input Voltage ....................................................... (V–)–0.5V to (V+)+0.5V Input Shutdown Voltage ........................................................................ V+ Operating Temperature ................................................. –40°C to +125°C Storage Temperature ..................................................... –55°C to +125°C Junction Temperature ...................................................................... 150°C Lead Temperature (soldering 10s)(2) ................................................................. 300°C NOTE: (1) Stresses above these ratings may cause permanent damage. (2) Vapor-phase or IR reflow techniques are recommended for soldering the OPA547F surface mount package. Wave soldering is not recommended due to excessive thermal shock and “shadowing” of nearby devices. ORDERING/PACKAGE INFORMATION PRODUCT PACKAGE PACKAGE DRAWING NUMBER(1) TEMPERATURE RANGE OPA547T 7-Lead Stagger-Formed TO-220 327 –40°C to +85°C 7-Lead DDPAK Surface-Mount 328 –40°C to +85°C OPA547F(2) NOTE: (1) For detailed drawing and dimension table, please see end of data sheet. (2) Available on Tape and Reel. The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. ® 3 OPA547 TYPICAL PERFORMANCE CURVES At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted. OPEN-LOOP GAIN AND PHASE vs FREQUENCY INPUT BIAS CURRENT vs TEMPERATURE –160 120 RL = 50Ω φ 60 –45 40 –90 20 –135 0 –180 Phase (°) Gain (dB) 0 Input Bias Current (nA) G 80 –120 10 100 1k 10k 100k 1M VS = ±30V –100 IB –80 –60 –40 –20 0 –75 –20 1 VS = ±5V –140 100 10M –50 –25 0 25 50 75 100 125 150 Temperature (°C) Frequency (Hz) CURRENT LIMIT vs TEMPERATURE CURRENT LIMIT vs SUPPLY VOLTAGE ±600 ±600 +ILIM ±550 RCL = 15.9kΩ Current Limit (mA) Current Limit (mA) ±500 RCL = 31.6kΩ ±400 ±300 RCL = 63.4kΩ ±450 +400 RCL = 31.6kΩ ±350 ±300 ±200 RCL = 63.4kΩ ±250 ±100 –75 –ILIM RCL = 15.9kΩ ±500 ±200 –50 –25 0 25 50 75 100 125 150 0 ±5 ±10 Temperature (°C) ±15 ±20 ±25 ±30 Supply Voltage (V) QUIESCENT CURRENT vs TEMPERATURE VOLTAGE NOISE DENSITY vs FREQUENCY ±12 400 VS = ±30V Quiescent Current (mA) Voltage Noise (nV/√Hz) IQ 300 200 100 ±10 ±8 VS = ±5V ±6 VS = ±30V IQ Shutdown ±4 VS = ±5V ±2 –75 0 1 10 100 1k 10k 100k 1M ® OPA547 –50 –25 0 25 50 75 Temperature (°C) Frequency (Hz) 4 100 125 150 TYPICAL PERFORMANCE CURVES (CONT) At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted. POWER SUPPLY REJECTION vs FREQUENCY COMMON-MODE REJECTION vs FREQUENCY 120 90 Power Supply Rejection (dB) 80 70 60 50 40 30 100 +PSRR 80 60 40 –PSRR 20 20 0 10 100 1k 10k 100k 1M 1 10 100 Frequency (Hz) 100k 1M 120 105 AOL 40 115 100 G = +1 3 CMRR (dB) Overshoot (%) 10k OPEN-LOOP GAIN, COMMON-MODE REJECTION, AND POWER SUPPLY REJECTION vs TEMPERATURE SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE 50 1k Frequency (Hz) G = –1 20 CMRR 100 95 PSRR PSRR, AOL (dB) Common-Mode Rejection (dB) 100 95 90 10 85 –75 0 0 2k 4k 6k 8k 10k 12k 14k 16k 18k 20k –50 –25 0 GAIN-BANDWIDTH PRODUCT AND SLEW RATE vs TEMPERATURE 90 150 7 6.5 0.5 6 SR– 1W THD+N (%) 0.75 –25 125 RL = 50Ω G = +3 GBW –50 100 0.1 Slew Rate (V/µs) Gain-Bandwidth Product (MHz) 7.5 SR+ 0 –75 75 TOTAL HARMONIC DISTORTION+NOISE vs FREQUENCY 1.25 0.25 50 Temperature (°C) Load Capacitance (pF) 1 25 0.01 0.1W 6.25W 0.001 5.5 0 25 50 75 100 125 0.0001 5 150 20 Temperature (°C) 100 1k 10k 20k Frequency (Hz) ® 5 OPA547 TYPICAL PERFORMANCE CURVES (CONT) At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted. OUTPUT VOLTAGE SWING vs TEMPERATURE OUTPUT VOLTAGE SWING vs OUTPUT CURRENT 2.5 3 IO = +500mA IO = +100mA 2 VSUPPLY – VOUT (V) VSUPPLY– VOUT (V) 2.5 (V+) –VO 1.5 1 (V–) –VO 0.5 1.5 1 IO = –500mA 0.5 IO = –100mA 0 0 100 200 300 400 500 0 –75 600 –50 –25 0 25 50 MAXIMUM OUTPUT VOLTAGE SWING vs FREQUENCY OUTPUT LEAKAGE CURRENT vs APPLIED OUTPUT VOLTAGE 150 Leakage Current (mA) RL = 10Ω VS = ±30V 15 10 0.5 RCL = 31.6kΩ RCL = ∞ 0 RCL = 0 –0.5 Output Disabled VE/S < (V–) + 0.8V 5 0 1k 10k 100k –1 –40 1M –30 –20 –10 0 10 Frequency (Hz) Output Voltage (V) OFFSET VOLTAGE PRODUCTION DISTRIBUTION OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION 25 20 Typical production distribution of packaged units. Percent of Amplifiers (%) Percent of Amplifiers (%) 125 1 Maximum Output Voltage Without Slew Rate Induced Distortion 20 16 100 Temperature (°C) 25 18 75 Output Current (mA) 30 Output Voltage (Vp) 2 14 12 10 8 6 4 20 30 Typical production distribution of packaged units. 20 15 10 5 2 0 0 0 –5 –4 –3 –2 –1 0 1 2 3 4 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Offset Voltage Drift (µV/°C) Offset Voltage (mV) ® OPA547 5 6 TYPICAL PERFORMANCE CURVES (CONT) At TCASE = +25°C, VS = ±35V and E/S pin open, unless otherwise noted. SMALL SIGNAL STEP RESPONSE G = 1, CL = 1000pF 50mV/div 50mV/div SMALL SIGNAL STEP RESPONSE G = 3, CL = 1000pF 2µs/div 2µs/div 10V/div LARGE SIGNAL STEP RESPONSE G = 3, CL = 100pF, RL = 50Ω 5µs/div ® 7 OPA547 APPLICATIONS INFORMATION With the OPA547, the simplest method for adjusting the current limit uses a resistor or potentiometer connected between the ILIM pin and V– according to the equation: Figure 1 shows the OPA547 connected as a basic noninverting amplifier. The OPA547 can be used in virtually any op amp configuration. R CL = Power supply terminals should be bypassed with low series impedance capacitors. The technique shown, using a ceramic and tantalum type in parallel is recommended. Power supply wiring should have low series impedance. The low level control signal (0 to 150µA) also allows the current limit to be digitally controlled with a current-out or voltage-out DAC reference to V– according to the equations given in Figure 3. Figure 3 shows a simplified schematic of the internal circuitry used to set the current limit. Leaving the ILIM pin open programs the output current to zero, while connecting ILIM directly to V– programs the maximum output current limit, typically 750mA. V+ 10µF + G = 1+ 0.1µF(2) R1 R2 R1 R2 SAFE OPERATING AREA 5 2 VIN (5000)(4. 75) – 31.6kΩ I LIM E/S 7 OPA547 6 3 1 ILIM(1) Stress on the output transistors is determined both by the output current and by the output voltage across the conducting output transistor, VS – VO. The power dissipated by the output transistor is equal to the product of the output current and the voltage across the conducting transistor, VS – VO. The Safe Operating Area (SOA curve, Figure 2) shows the permissible range of voltage and current. VO ZL 0.1µF(2) 10µF + V– SAFE OPERATING AREA 1k Output Current (mA) NOTE: (1) ILIM connected to V– gives the maximum current limit, 750mA (peak). (2) Connect 0.1µF capacitors directly to package power supply pins. FIGURE 1. Basic Circuit Connections. POWER SUPPLIES The OPA547 operates from single (+8V to +60V) or dual (±4V to ±30V) supplies with excellent performance. Most behavior remains unchanged throughout the full operating voltage range. Parameters which vary significantly with operating voltage are shown in the typical performance curves. TC = 25°C Output current may be limited to less than 500mA—see text. 100 TC = 85°C TC = 125°C Pulse Operation Only (<50% Duty-Cycle) 10 1 2 5 10 20 50 100 VS – VO (V) Some applications do not require equal positive and negative output voltage swing. Power supply voltages do not need to be equal. The OPA547 can operate with as little as 8V between the supplies and with up to 60V between the supplies. For example, the positive supply could be set to 55V with the negative supply at –5V, or vice-versa. FIGURE 2. Safe Operating Area. The safe output current decreases as VS – VO increases. Output short-circuits are a very demanding case for SOA. A short-circuit to ground forces the full power supply voltage (V+ or V–) across the conducting transistor. With TC = 25°C the maximum output current of 500mA can be achieved under most conditions. Increasing the case temperature reduces the safe output current that can be tolerated without activating the thermal shutdown circuit of the OPA547. For further insight on SOA, consult Application Bulletin AB-039. ADJUSTABLE CURRENT LIMIT The OPA547 features an accurate, user-selected current limit. Current limit is set from 0 to 750mA by controlling the input to the ILIM pin. Unlike other designs which use a power resistor in series with the output current path, the OPA547 senses the load indirectly. This allows the current limit to be set with a 0 to 150µA control signal. In contrast, other designs require a limiting resistor to handle the full output current (750mA in this case). POWER DISSIPATION Power dissipation depends on power supply, signal and load conditions. For dc signals, power dissipation is equal to the product of output current times the voltage across the con- ® OPA547 Current-Limited 8 ducting output transistor. Power dissipation can be minimized by using the lowest possible power supply voltage necessary to assure the required output voltage swing. heat sink required depends on the power dissipated and on ambient conditions. Consult Application Bulletin AB-038 for information on determining heat sink requirements. The internal protection circuitry was designed to protect against overload conditions. It does not activate until the junction temperature reaches approximately 160°C and was not intended to replace proper heat sinking. Continuously running the OPA547 into thermal shutdown will degrade reliability. For resistive loads, the maximum power dissipation occurs at a dc output voltage of one-half the power supply voltage. Dissipation with ac signals is lower. Application Bulletin AB-039 explains how to calculate or measure power dissipation with unusual signals and loads. The tab of the DDPAK surface-mount version should be soldered to a circuit board copper area for good heat dissipation. Figure 4 shows typical thermal resistance from junction to ambient as a function of the copper area. HEAT SINKING Most applications require a heat sink to assure that the maximum junction temperature (150°C) is not exceeded. The DAC METHOD (Current or Voltage) RESISTOR METHOD VO G = 5000 31.6kΩ 4.75V 7 RCL D/A 0.01µF (optional, for noisy environments) 6 V– V– RCL = 31.6kΩ 4.75V 7 6 VO G = 5000 5000 (4.75V) ILIM IDAC = ILIM/5000 – 31.6kΩ VDAC = (V–) + 4.75V – (31.6kΩ) (ILIM)/5000 OPA547 CURRENT LIMIT: 0 to 750mA DESIRED CURRENT LIMIT RESISTOR(1) (RCL) CURRENT DAC (IDAC) VOLTAGE DAC (VDAC) 0mA 100mA 375mA 500mA 750mA ILIM Open 205kΩ 31.6kΩ 15.8kΩ ILIM Shorted to V– 0µA 20µA 75µA 100µA 150µA (V–) + 4.75V (V–) + 4.12V (V–) + 2.38V (V–) + 1.59V (V–) + 0.01V NOTE: (1) Resistors are nearest standard 1% values. FIGURE 3. Adjustable Current Limit. THERMAL RESISTANCE vs CIRCUIT BOARD COPPER AREA Circuit Board Copper Area Thermal Resistance, θJA (°C/W) 50 OPA547F Surface Mount Package 1oz copper 40 30 20 10 0 0 1 2 3 4 OPA547 Surface Mount Package 5 Copper Area (inches2) FIGURE 4. Thermal Resistance vs. Circuit Board Copper Area. ® 9 OPA547 THERMAL PROTECTION The OPA547 has thermal shutdown that protects the amplifier from damage. Activation of the thermal shutdown circuit during normal operation is an indication of excessive power dissipation or an inadequate heat sink. Depending on load and signal conditions, the thermal protection circuit may cycle on and off. This limits the dissipation of the amplifier but may have an undesirable effect on the load. V+ 5V OPA547 E/S 1 6 5 (1) The thermal protection activates at a junction temperature of approximately 160°C. However, for reliable operation junction temperature should be limited to 150°C. To estimate the margin of safety in a complete design (including heat sink), increase the ambient temperature until the thermal protection is activated. Use worst-case load and signal conditions. For good reliability, the thermal protection should trigger more than 35°C above the maximum expected ambient condition of your application. This produces a junction temperature of 125°C at the maximum expected ambient condition. HCT or TTL In 1 4 4N38 Optocoupler V– NOTE: (1) Optional—may be required to limit leakage current of optocoupler at high temperatures. FIGURE 6. Output Disable with Dual Supplies. Thermal Shutdown Status Internal thermal shutdown circuitry shuts down the output when the die temperature reaches approximately 160°C, resetting when the die has cooled to 140°C. The E/S pin can be monitored to determine if shutdown has occurred. During normal operation the voltage on the E/S pin is typically 3.5V above the negative rail. Once shutdown has occurred this voltage drops to approximately 350mV above the negative rail. ENABLE/STATUS (E/S) PIN The Enable/Status Pin provides two functions: forcing this pin low disables the output stage, or, E/S can be monitored to determine if the OPA547 is in thermal shutdown. One or both of these functions can be utilized on the same device using single or dual supplies. For normal operation (output enabled), the E/S pin can be left open or pulled high (at least +2.4V above the negative rail). Figure 7 gives an example of monitoring shutdown in a single supply application. Figure 8 provides a circuit for dual supplies. External logic circuitry or an LED could be used to indicate if the output has been thermally shutdown, see Figure 13. Output Disable A unique feature of the OPA547 is its output disable capability. This function not only conserves power during idle periods (quiescent current drops to approximately 4mA) but also allows multiplexing in low frequency (f<10kHz), multichannel applications. Signals that are greater than 10kHz may cause leakage current to increase in devices that are shutdown. Figure 15 shows the two OPA547s in a switched amplifier configuration. The on/off state of the two amplifiers is controlled by the voltage on the E/S pin. V+ 5V OPA547 2.49kΩ E/S TTL V– To disable the output, the E/S pin is pulled low, no greater than 0.8V above the negative rail. Typically the output is shutdown in 1µs. Figure 5 provides an example of how to implement this function using a single supply. Figure 6 gives a circuit for dual supply applications. To return the output to an enabled state, the E/S pin should be disconnected (open) or pulled to at least (V–) + 2.4V. It should be noted that pulling the E/S pin high (output enabled) does not disable internal thermal shutdown. Zetex ZVN3310 OR HCT FIGURE 7. Thermal Shutdown Status with a Single Supply. 5V V+ V+ 1kΩ OPA547 2N3906 E/S OPA547 22kΩ 470Ω E/S Zetex ZVN3310 V– CMOS or TTL V– FIGURE 5. Output Disable with a Single Supply. FIGURE 8. Thermal Shutdown Status with Dual Supplies. ® OPA547 10 Output Disable and Thermal Shutdown Status As mentioned earlier, the OPA547’s output can be disabled and the disable status can be monitored simultaneously. Figures 9 and 10 provide examples using a single supply and dual supplies, respectively. OUTPUT PROTECTION Reactive and EMF-generating loads can return load current to the amplifier, causing the output voltage to exceed the power supply voltage. This damaging condition can be avoided with clamp diodes from the output terminal to the power supplies as shown in Figure 11. Schottkey rectifier diodes with a 1A or greater continuous rating are recommended. OUTPUT STAGE COMPENSATION The complex load impedances common in power op amp applications can cause output stage instability. For normal operation output compensation circuitry is not typically required. However, if the OPA547 is intended to be driven into current limit, a R/C network may be required. Figure 11 shows an output series R/C compensation (snubber) network (3Ω in series with 0.01µF) which generally provides excellent stability. Some variations in circuit values may be required with certain loads. V+ R1 5kΩ R2 20kΩ G=– R2 = –4 R1 VIN D1 OPA547 V+ 3Ω (Carbon) Motor D2 0.01µF V– OPA547 E/S D1, D2 : International Rectifier 11DQ06. V– Open Drain (Output Disable) HCT (Thermal Status Shutdown) FIGURE 11. Motor Drive Circuit. FIGURE 9. Output Disable and Thermal Shutdown Status with a Single Supply. V+ 5V 1 6 5V OPA547 E/S 5 7.5kΩ 1W 1 6 2 (1) Zetex ZVN3310 5 TTL Out 4 4N38 Optocoupler HCT or TTL In 2 4 4N38 Optocoupler V– NOTE: (1) Optional—may be required to limit leakage current of optocoupler at high temperatures. FIGURE 10. Output Disable and Thermal Shutdown Status with Dual Supplies. ® 11 OPA547 VOLTAGE SOURCE APPLICATION Figure 12 illustrates how to use the OPA547 to provide an accurate voltage source with only three external resistors. First, the current limit resistor, RCL, is chosen according to the desired output current. The resulting voltage at the ILIM pin is constant and stable over temperature. This voltage, VCL, is connected to the noninverting input of the op amp and used as a voltage reference, thus eliminating the need for an external reference. The feedback resistors are selected to gain VCL to the desired output voltage level. PROGRAMMABLE POWER SUPPLY A programmable power supply can easily be built using the OPA547. Both the output voltage and output current are user-controlled. Figure 13 shows a circuit using potentiometers to adjust the output voltage and current while Figure 14 uses digital-to-analog converters. An LED tied to the E/S pin through a logic gate indicates if the OPA547 is in thermal shutdown. R1 R2 V+ VO = VCL (1 + R2/R1) 4.75V 31.6kΩ IO = VCL ILIM For Example: V– RCL 0.01µF (Optional, for noisy environments) If ILIM = 375mA, RCL = 31.6kΩ VCL = 31.6kΩ • 4.75V (31.6kΩ + 31.6kΩ) Desired VO = 19V, G = 5000 (4.75V) 31.6kΩ + RCL = 2.375V 19 2.375 Uses voltage developed at ILIM pin as a moderately accurate reference voltage. =8 R1 = 1kΩ and R2 = 7kΩ FIGURE 12. Voltage Source. 1kΩ 9kΩ G=1+ +5V 9kΩ = 10 1kΩ +30V 14.7kΩ 5 2 V+ 6 Output Adjust 0.8V to 2.5V VO = 0.8V to 25V(1) OPA547 1 4 3 7 E/S 74HCT04 ILIM R ≥ 250Ω 4.7kΩ V– +5V 0V to 4.75V Thermal Shutdown Status (LED) 1kΩ Current Limit Adjust 20kΩ 0.01µF(2) FIGURE 13. Resistor-Controlled Programmable Power Supply. ® OPA547 12 NOTES: (1) For VO = 0V, V– = –1V. (2) Optional: Improves noise immunity. 1kΩ 9kΩ +10V OUTPUT ADJUST VREF +30V G = 10 +5V VREF A +5V RFB A 1/2 OPA2336 IOUT A 1/2 DAC7800/1/2(3) VO = 0.8 to 25V(1) OPA547 10pF 74HCT04 E/S DAC A AGND A ILIM IO = 0 to 750mA R ≥ 250Ω V– Thermal Shutdown Status (LED) VREF B RFB B 10pF 1/2 OPA2336 IOUT B 1/2 DAC7800/1/2(3) DAC B 0.01µF(2) DGND AGND B CURRENT LIMIT ADJUST NOTES: (1) For VO = 0V, V– = –1V. (2) Optional, improves noise immunity. (3) Chose DAC780X based on digital interface: DAC7800 - 12-bit interface, DAC7801 - 8-bit interface + 4 bits, DAC7802 - serial interface. (4) Can use OPA2237, IO = 100mA to 750mA. FIGURE 14. Digitally-Controlled Programmable Power Supply. R1 R2 VIN1 OPA547 ILIM AMP1 E/S RC1 R3 VE/S R4 RC2 Close for high current (Could be open drain output of a logic gate). VO VIN2 AMP2 V– E/S FIGURE 16. Multiple Current Limit Values. VE/S > (V–) +2.4V: Amp 1 is on, Amp 2 if off VO = –VIN1 R2 ( ) R1 VE/S < (V–) +2.4V: Amp 2 is on, Amp 1 if off VO = –VIN2 R4 ( ) R3 FIGURE 15. Swap Amplifier. ® 13 OPA547