LM6317 120 MHz, Fast Settling, Low Power, Voltage Feedback Amplifier General Description Features (Typical unless otherwise noted) The LM6317 is a high speed, unity-gain stable voltage feedback amplifier that consumes only 40 mW of quiescent power. Operating at g 5V power supply, the LM6317 provides excellent AC performance such as 120 MHz of unity-gain bandwidth, 1500V/ms of slew rate, and 80 dB of SFDR. The LM6317 has the slew characteristic of a current feedback amplifier; yet it can be used in all traditional amplifier configurations. The high output current and good stability with capacitive load of LM6317 makes it ideal for driving cables. With its unity-gain stability, fast settling time and low output impedance, the LM6317 can be used to buffer A/D converters. The LM6317 also has very low input voltage and current noise, high CMRR and PSRR, desirable in precision applications such as ATE systems. Y Y Y Y Y Y Y Y Y Y 120 MHz 1100V/ms 12 ns 18 ns 80 dB 60 mA 80 dB, 74 dB 4 mA Applications Y Y Y Y Y Y Y Typical Performance Easy to use voltage feedback topology Unity-gain stability Wide unity-gain bandwidth Fast slew rate Fast settling time Ð 0.1% Ð 0.01% Low SFDR @ 1 MHz Driving 100X High output current High CMRR and PSRR Low supply current Specified for g 5V operation Active filters A/D Converter buffers Video cable drivers Communication systems Portable systems Ultrasound equipment ATE systems Connection Diagram Settling Time vs Gain 8-Pin DIP/SO TL/H/12542 – 2 Top View TL/H/12542 – 14 Ordering Information Temperature Range Package Industrial b 40§ C to a 85§ C Transport Media NSC Drawing N08E 8-Pin DIP LM6317IN Rails 8-Pin Small Outline LM6317IM Rails LM6317IMX M08A 2.5k Tape and Reel TinyPakTM is a trademark of National Semiconductor Corp. C1996 National Semiconductor Corporation TL/H/12542 RRD-B30M76/Printed in U. S. A. http://www.national.com LM6317 120 MHz, Fast Settling, Low Power, Voltage Feedback Amplifier November 1995 Absolute Maximum Ratings (Note 1) Operating Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Supply Voltage Junction Temperature Range ESD Tolerance (Note 2) Human Body Model Machine Model Supply Voltage (V a – Vb) g 2.3V s VS s g 6V b 40§ C s TJ s a 85§ C Thermal Resistance (iJA) N Package, 8-Pin Molded DIP M Package, 8-Pin Surface Mount 1.5 kV 200V 110§ C/W 170§ C/W 12V Differentfial Input Voltage 10V g 60 mA Output Current (Note 3) b 65§ C to a 150§ C Storage Temperature Range Maximum Junction Temperature (Note 4) 150§ C g 5V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ e 25§ C, V a e a 5V, Vb e b5V, VCM e 0V, and RL e 100X. Boldface limits apply at the temperature extremes. Symbol Parameter VOS Input Offset Voltage TC VOS Input Offset Voltage Average Drift IB Input Bias Current IOS Input Offset Current RIN Input Resistance CIN Input Capacitance Conditions Typ (Note 5) Limit (Note 6) Units 0.3 5 7 mV max 8 mV/§ C 3 12 22 mA max 0.2 2 4 mA max Differential 2 Common 1 Differential 1 Common 1 MX pF RO Open Loop Output Resistance CMRR Common Mode Rejection Ratio VCM e g 1.5V 80 62 57 dB min PSRR Power Supply Rejection Ratio VS e g 5V to g 4.5V 74 60 52 dB min AV Large Signal Voltage Gain VOUT e g 1V RL e 1 kX 70 55 50 67 53 48 3.2 2.6 2.3 V min b 3.2 b 2.6 b 2.3 V max 0.02 VOUT e g 1V RL e 100X VCM http://www.national.com Input Common-Mode Voltage Range CMRR e 60 dB 2 X dB min g 5V DC Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for TJ e 25§ C, V a e a 5V, Vb e b5V, VCM e 0V, and RL e 100X. Boldface limits apply at the temperature extremes. Symbol VO Parameter Output Swing Conditions Typ (Note 5) Limit (Note 6) Units 3.5 3 2.6 V min b 3.5 b3 b 2.6 V max 3 2.5 2.3 V min b3 b 2.5 b 2.3 V max 4 6 7 mA max RL e 1 kX RL e 100X IS Supply Current g 5V AC Electrical Characteristics Unless otherwise specified, TJ e 25§ C, V a e a 5V, Vb e 5V, AV e 1, and RL e 100X Symbol SR Parameter Slew Rate Conditions Typ (Note 5) Units 5V Step 1100 5V Step, AV e b1, RL e 500X 750 Unity-Gain Bandwidth AV e b1, RL e 500X 120 MHz b 3 dB Frequency AV e a 2 80 MHz im Phase Margin AV e b1, RL e 500X 60 § ts Settling Time en Input-Referred Voltage Noise in Input-Referred Current Noise 0.1%, 2V Step 12 0.01%, 2V Step 18 f e 100 kHz 4.2 V/ms ns nV 0Hz f e 100 kHz pA 2 0Hz Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics. Note 2: Human body model, 1.5 kX in series with 100 pF. Machine model, 200X in series with 100 pF. Note 3: Applies to both single-supply and split-supply operation. Sourcing and sinking more than 60 mA at the output may adversely affect reliability. Note 4: The maximum power dissipation is a function of TJ(max), iJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD e (TJ(max) –TA)/iJA. All numbers apply for packages soldered directly into a PC board. Note 5: Typical values represent the most likely parametric norm. Note 6: All limits are guaranteed by testing or statistical analysis. 3 http://www.national.com Typical Performance Characteristics Supply Current vs Supply Voltage Unless otherwise noted, TA e 25§ C, VS e g 5V IB and IOS vs Common-Mode Voltage TL/H/12542 – 4 TL/H/12542–3 Open Loop Frequency Response Bandwidth vs Supply Voltage Inverting Frequency Response TL/H/12542–9 2nd and 3rd Harmonic Distortion TL/H/12542 – 10 Settling Time vs Capactive Load TL/H/12542–12 http://www.national.com TL/H/12542 – 8 Equivalent Input Noise TL/H/12542 – 11 Maximum Power Dissipation vs Ambient Temperature TL/H/12542 – 13 4 TL/H/12542 – 5 Bandwidth vs Capacitive Load TL/H/12542 – 7 Non-Inverting Frequency Response PSRR, CMRR, and Closed Loop Ro TL/H/12542 – 24 Typical Performance Characteristics Unless otherwise noted, TA e 25§ C, VS e g 5V (Continued) Large Signal Pulse Response (AV e a 1) Small Signal Pulse Response (AV e a 1) TL/H/12542 – 1 TL/H/12542 – 15 Large Signal Pulse Response (AV e b1) Small Signal Pulse Response (AV e b1) TL/H/12542 – 16 TL/H/12542 – 17 Large Signal Pulse Response (AV e a 2) Small Signal Pulse Response (AV e a 2) TL/H/12542 – 18 TL/H/12542 – 19 5 http://www.national.com Application Notes Using the LM6317 COMPONENTS SELECTION AND FEEDBACK RESISTOR It is important in high speed applications to keep all component leads short because wires are inductive at high frequency. For discrete components, choose carbon composition-type resistors and mica-type capacitors. Surface mount components are preferred over decrete components for minimum inductive effect. Large values of feedback resistors can couple with parasitic capacitance and cause undersirable effects such as ringing or oscillation in high speed amplifiers. Feedback resistor value around 1 kX is recommended. LIMITS AND PRECAUTIONS The absolute maximum supply voltage which may be applied to the LM6317 is 12V. Designers should not design for more than 10V nominal, and carefully check supply tolerances under all conditions so that the voltages do not exceed the maximum. DIFFERENTIAL INPUT VOLTAGE Differential input voltage is the difference in voltage between the non-inverting ( a ) input and the inverting (b) input of the op amp. The absolute maximum differential input for the LM6317 is 10V across the inputs. This limit also applies when there is no power supplied to the op amp. This may not be a problem in most conventional op amp designs, however, designers should avoid using the LM6317 as comparators or forcing the inputs to different voltages. In some designs, diodes protection may be needed between the inputs, as shown in Figure 1 . COMPENSATION FOR INPUT CAPACITANCE The combination of an amplifier’s input capacitance with the gain setting resistors adds a pole that can cause peaking or oscillation. To solve this problem, a feedback capacitor with a value CF l (RG c CIN)/RF can be used to cancel that pole. The value of CIN can be found in the DC Electrical Characteristics Table of the datasheet. Figure 2 illustrates the compensation circuit. TL/H/12542–20 FIGURE 1. Input Protection for LM6317 TL/H/12542 – 21 FIGURE 2. Compensating for Input Capacitance Layout Consideration Power Supply Bypassing PRINTED CIRCUIT BOARDS AND HIGH SPEED OP AMPS There are many things to consider when designing PC boards for high speed op amps. Without proper caution, it is very easy and frustrating to have excessive ringing, oscillation and other degraded AC performance in high speed circuits. As a rule, the signal traces should be short and wide to provide low inductance and low impedance paths. Any unused board space needs be grounded to reduce stray signal pickup. Critical components should also be grounded at a common point to eliminate voltage drop. Sockets add capacitance to the board and can affect frequency performance. It is better to solder the amplifier directly into the PC board without using any socket. Bypassing the power supply is necessary to maintain low power supply impedance across frequency. Both positive and negative power supplies should be bypassed individually by placing 0.01 mF creramic capacitors directly to power supply pins and 2.2 mF tantalum capacitors close to the power supply pins. USING PROBES Active (FET) probes are ideal for taking high frequency measurements because they have wide bandwidth, high input impedance and low input capacitance. However, the probe ground leads provide a long ground loop that will produce errors in measurement. Instead, the probes can be grounded directly by removing the ground leads and probe jackets and using scope probe jacks. TL/H/12542 – 22 FIGURE 3. Power Supply Bypassing http://www.national.com 6 Application Notes (Continued) Other High Speed and Video Amplifiers Termination National Semiconductor has an extensive line of high speed amplifiers, with a range of operating voltage from 3V single supply to g 15V, and a range of package types, such as the space saving SOT23-5 TinyPakTM (3.05mm c 3.00mm c 1.43mm - about the size of a grain of rice) and a wide SO-8 for better power dissipation. This op amp line includes LM6171 100 MHz low distortion amplifier with greater than 3000V/ms slew rate. Voltage feedback design draws only 2.5 mA. Specified at g 15V and g 5V supplies. LM7131 TinyPak (SOT23-5) video amplifier with 70 MHz gain bandwidth. Specified at 3V, 5V and g 5V supplies. LM7171 200 MHz voltage feedback amplifier with 100 mA output current and 4000V/ms slew rate. Supply current of 6.5 mA. Specified at g 15V and g 5V supplies. Information on these parts is available from your National Semiconductor representative. In high frequency applications, reflections occur if signals are not properly terminated. To minimize reflection, coaxial cable with matching characteristic impedance to the signal source should be used. The other end of the cable should be terminated with the same value terminator or resistor. For the commonly used cables. RG59 has 75X characteristics impedance, and RG58 has 50X characteristics impedance. Driving Capacitive Loads Amplifiers driving capacitive loads can oscillate or have ringing at the output. To eliminate oscillation or reduce ringing, an isolation resistor can be placed as shown below in Figure 4 . The combination of the isolation resistor and the load capacitor froms a pole to incease stability by adding more phase margin to the overall system. The desired performance depends on the value of the isolation resistor; the bigger the isolation resistor, the more damped the pulse response becomes. A 50X isolation resistor is recommended for initial evaluation. TL/H/12542 – 23 FIGURE 4. Driving Capacitive Load Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin Small Outline Order Number LM6317IM or LM6317IMX NSC Package Number M08A 7 http://www.national.com LM6317 120 MHz, Fast Settling, Low Power, Voltage Feedback Amplifier Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Pin DIP Order Number LM6317IN NSC Package Number N08E LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 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