LT1210

LT1210 1.1A, 35MHz Current Feedback Amplifier FEATURES s s s s s DESCRIPTIO s s s s 1.1A Minimum Output Drive Current 35MHz Bandwidth, AV = 2, RL = 10Ω 900V/µs Slew Rate, AV = 2, RL = 10Ω High Input Impedance: 10MΩ Wide Supply Range: ± 5V to ± 15V (TO-220 and DD Packages) Enhanced θJA SO-16 Package for ± 5V Operation Shutdown Mode: IS < 200µA Adjustable Supply Current Stable with CL = 10,000pF APPLICATIONS s s s s s Cable Drivers Buffers Test Equipment Amplifiers Video Amplifiers ADSL Drivers The LT ®1210 is a current feedback amplifier with high output current and excellent large-signal characteristics. The combination of high slew rate, 1.1A output drive and ±15V operation enables the device to deliver significant power at frequencies in the 1MHz to 2MHz range. Shortcircuit protection and thermal shutdown ensure the device’s ruggedness. The LT1210 is stable with large capacitive loads, and can easily supply the large currents required by the capacitive loading. A shutdown feature switches the device into a high impedance and low supply current mode, reducing dissipation when the device is not in use. For lower bandwidth applications, the supply current can be reduced with a single external resistor. The LT1210 is available in the TO-220 and DD packages for operation with supplies up to ± 15V. For ± 5V applications the device is also available in a low thermal resistance SO-16 package. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO S Twisted Pair Driver 15V Total Harmonic Distortion vs Frequency + –50 TOTAL HARMONIC DISTORTION (dB) 4.7µF* 100nF RT 11Ω 2.5W –60 VS = ± 15V VOUT = 20VP-P AV = 4 VIN + LT1210 SD T1** RL 100Ω 2.5W –70 RL = 12.5Ω –80 RL = 10Ω RL = 50Ω –90 – 4.7µF* –15V 100nF 1 3 845Ω * TANTALUM ** MIDCOM 671-7783 OR EQUIVALENT 1210 TA01 –100 1k 10k 100k FREQUENCY (Hz) 1M 1210 TA02 274Ω U U U + 1 LT1210 ABSOLUTE AXI U RATI GS Operating Temperature Range ............... –40°C to 85°C Junction Temperature ......................................... 150°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C Supply Voltage ..................................................... ± 18V Input Current .................................................... ± 15mA Output Short-Circuit Duration (Note 1) ....... Continuous Specified Temperature Range (Note 2) ...... 0°C to 70°C PACKAGE/ORDER INFORMATION TOP VIEW V+ 1 2 16 V + 15 NC 14 V – 13 COMP 12 SHUTDOWN 11 +IN 10 NC 9 V+ V+ FRONT VIEW 7 6 5 4 3 2 1 OUT V– COMP V+ SHUTDOWN +IN –IN OUT 3 V+ 4 NC 5 –IN 6 NC 7 V+ 8 TAB IS V + R PACKAGE 7-LEAD PLASTIC DD θJA ≈ 25°C/W S PACKAGE 16-LEAD PLASTIC SO θJA ≈ 40°C/W (Note 3) ORDER PART NUMBER LT1210CR Consult factory for Industrial and Military grade parts. ORDER PART NUMBER LT1210CS ELECTRICAL CHARACTERISTICS VCM = 0V, ± 5V ≤ VS ≤ ± 15V, pulse tested, VSD = 0V, unless otherwise noted. SYMBOL VOS PARAMETER Input Offset Voltage Input Offset Voltage Drift IIN+ IIN– en + in – in RIN CIN Noninverting Input Current Inverting Input Current Input Noise Voltage Density Input Noise Current Density Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range TA = 25°C q CONDITIONS TA = 25°C q q TA = 25°C q f = 10kHz, RF = 1k, RG = 10Ω, RS = 0Ω f = 10kHz, RF = 1k, RG = 10Ω, RS = 10k f = 10kHz, RF = 1k, RG = 10Ω, RS = 10k VIN = ± 12V, VS = ± 15V VIN = ± 2V, VS = ± 5V VS = ± 15V VS = ± 15V VS = ± 5V q q q q 2 U U W WW U W FRONT VIEW 7 6 5 4 3 2 1 T7 PACKAGE 7-LEAD TO-220 θJC = 5°C/W TAB IS V + OUT V– COMP V+ SHUTDOWN +IN –IN ORDER PART NUMBER LT1210CT7 MIN TYP ±3 10 ±2 ±10 3.0 2.0 40 MAX ±15 ± 20 ±5 ± 20 ± 60 ±100 UNITS mV mV µV/°C µA µA µA µA nV/√Hz pA/√Hz pA/√Hz MΩ MΩ pF V V 1.50 0.25 ±12 ±2 10 5 2 ± 13.5 ± 3.5 LT1210 ELECTRICAL CHARACTERISTICS VCM = 0V, ± 5V ≤ VS ≤ ± 15V, pulse tested, VSD = 0V, unless otherwise noted. SYMBOL CMRR PARAMETER Common Mode Rejection Ratio Inverting Input Current Common Mode Rejection PSRR Power Supply Rejection Ratio Noninverting Input Current Power Supply Rejection Inverting Input Current Power Supply Rejection AV Large-Signal Voltage Gain CONDITIONS VS = ± 15V, VCM = ± 12V VS = ± 5V, VCM = ± 2V VS = ± 15V, VCM = ± 12V VS = ± 5V, VCM = ± 2V VS = ± 5V to ± 15V VS = ± 5V to ± 15V VS = ± 5V to ± 15V TA = 25°C, VS = ± 15V, VOUT = ± 10V, RL = 10Ω (Note 3) VS = ± 15V, VOUT = ± 8.5V, RL = 10Ω (Note 3) VS = ± 5V, VOUT = ± 2V, RL = 10Ω ROL Transresistance, ∆VOUT/∆IIN– TA = 25°C, VS = ± 15V, VOUT = ± 10V, RL = 10Ω (Note 3) VS = ± 15V, VOUT = ± 8.5V, RL = 10Ω (Note 3) VS = ± 5V, VOUT = ± 2V, RL = 10Ω VOUT Maximum Output Voltage Swing TA = 25°C, VS = ± 15V, RL = 10Ω (Note 3) q q q q q q q q q q q q MIN 55 50 TYP 62 60 0.1 0.1 MAX UNITS dB dB 10 10 500 5 µA/V µA/V dB nA/V µA/V dB dB dB kΩ kΩ kΩ V V V V A 60 77 30 0.7 55 55 55 100 75 75 ± 10.0 ± 8.5 ± 2.5 ± 2.0 1.1 71 68 68 260 200 200 ± 11.5 ± 3.0 2.0 35 50 65 30 200 10 TA = 25°C, VS = ± 5V, RL = 10Ω q IOUT IS Maximum Output Current (Note 3) Supply Current (Note 3) Supply Current, RSD = 51k (Notes 3, 4) Positive Supply Current, Shutdown Output Leakage Current, Shutdown VS = ± 15V, RL = 1Ω TA = 25°C, VS = ± 15V, VSD = 0V q q mA mA mA µA µA V/µs V/µs % DEG MHz MHz TA = 25°C, VS = ± 15V VS = ± 15V, VSD = 15V VS = ± 15V, VSD = 15V TA = 25°C, AV = 2, RL = 400Ω TA = 25°C, AV = 2, RL = 10Ω VS = ± 15V, RF = 750Ω, RG = 750Ω, RL = 15Ω VS = ± 15V, RF = 750Ω, RG = 750Ω, RL = 15Ω AV = 2, VS = ± 15V, Peaking ≤ 1dB, RF = RG = 680Ω, RL = 100Ω AV = 2, VS = ± 15V, Peaking ≤ 1dB, RF = RG = 576Ω, RL = 10Ω q q 15 SR Slew Rate (Note 5) Slew Rate (Note 3) Differential Gain (Notes 3, 6) Differential Phase (Notes 3, 6) 400 900 900 0.3 0.1 55 35 BW Small-Signal Bandwidth The q denotes specifications which apply for 0°C ≤ TA ≤ 70°C. Note 1: Applies to short circuits to ground only. A short circuit between the output and either supply may permanently damage the part when operated on supplies greater than ± 10V. Note 2: Commercial grade parts are designed to operate over the temperature range of – 40°C ≤ TA ≤ 85°C, but are neither tested nor guaranteed beyond 0°C ≤ TA ≤ 70°C. Industrial grade parts tested over – 40°C ≤ TA ≤ 85°C are available on special request. Consult factory. Note 3: SO package is recommended for ± 5V supplies only, as the power dissipation of the SO package limits performance on higher supplies. For supply voltages greater than ± 5V, use the TO-220 or DD package. See “Thermal Considerations” in the Applications Information section for details on calculating junction temperature. If the maximum dissipation of the package is exceeded, the device will go into thermal shutdown. Note 4: RSD is connected between the Shutdown pin and ground. Note 5: Slew rate is measured at ± 5V on a ± 10V output signal while operating on ± 15V supplies with RF = 1.5k, RG = 1.5k and RL = 400Ω. Note 6: NTSC composite video with an output level of 2V. 3 LT1210 SMALL-SIGNAL BANDWIDTH RSD = 0Ω, IS = 30mA, VS = ± 5V, Peaking ≤ 1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 549 590 619 604 649 619 562 590 576 392 383 215 RG 549 590 619 – – – 562 590 576 43.2 42.2 23.7 – 3dB BW (MHz) 52.5 39.7 26.5 53.5 39.7 27.4 51.8 38.8 27.4 48.4 40.3 36.0 1 2 10 RSD = 7.5k, IS = 15mA, VS = ± 5V, Peaking ≤ 1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 562 619 604 634 681 649 576 604 576 324 324 210 RG 562 619 604 – – – 576 604 576 35.7 35.7 23.2 – 3dB BW (MHz) 39.7 28.9 20.5 41.9 29.7 20.7 40.2 29.6 21.6 39.5 32.3 27.7 1 2 10 RSD = 15k, IS = 7.5mA, VS = ± 5V, Peaking ≤ 1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 536 549 464 619 634 511 536 549 412 150 118 100 RG 536 549 464 – – – 536 549 412 16.5 13.0 11.0 – 3dB BW (MHz) 28.2 20.0 15.0 28.6 19.8 14.9 28.3 19.9 15.7 31.5 27.1 19.4 1 2 10 4 U U W RSD = 0Ω, IS = 35mA, VS = ± 15V, Peaking ≤ 1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 604 649 665 750 866 845 665 715 576 453 432 221 RG 604 649 665 – – – 665 715 576 49.9 47.5 24.3 – 3dB BW (MHz) 66.2 48.4 46.5 56.8 35.4 24.7 52.5 38.9 35.0 61.5 43.1 45.5 1 2 10 RSD = 47.5k, IS = 18mA, VS = ± 15V, Peaking ≤ 1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 619 698 698 732 806 768 634 698 681 348 357 205 RG 619 698 698 – – – 634 698 681 38.3 39.2 22.6 – 3dB BW (MHz) 47.8 32.3 22.2 51.4 33.9 22.5 48.4 33.0 22.5 46.8 36.7 31.3 1 2 10 RSD = 82.5k, IS = 9mA, VS = ± 15V, Peaking ≤ 1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 590 649 576 715 768 649 590 665 549 182 182 100 RG 590 649 576 – – – 590 665 549 20.0 20.0 11.0 – 3dB BW (MHz) 34.8 22.5 16.3 35.5 22.5 16.1 35.3 22.5 16.8 37.2 28.9 22.5 1 2 10 LT1210 TYPICAL PERFOR A CE CHARACTERISTICS Bandwidth vs Supply Voltage 100 90 PEAKING ≤ 1dB PEAKING ≤ 5dB RF = 470Ω AV = 2 RL = 100Ω –3dB BANDWIDTH (MHz) FEEDBACK RESISTANCE (Ω) – 3dB BANDWIDTH (MHz) 80 70 60 50 40 30 20 10 0 4 6 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 RF = 1.5k RF = 680Ω RF = 1k RF = 560Ω RF = 750Ω Bandwidth vs Supply Voltage 100 90 –3dB BANDWIDTH (MHz) 50 PEAKING ≤ 1dB PEAKING ≤ 5dB AV = 10 RL = 100Ω – 3dB BANDWIDTH (MHz) 40 FEEDBACK RESISTANCE (Ω) 80 70 60 50 40 30 20 10 0 4 6 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 RF = 1.5k RF =390Ω RF = 330Ω RF = 470Ω RF = 680Ω Differential Phase vs Supply Voltage 0.6 0.5 0.4 0.3 0.2 0.1 0 RF = RG = 750Ω AV = 2 RL = 15Ω RL = 50Ω RL = 30Ω RL = 10Ω DIFFERENTIAL PHASE (DEG) 0.4 DIFFERENTIAL GAIN (%) RL = 10Ω 0.3 RL = 15Ω SPOT NOISE (nV/√Hz OR pA/√Hz) 5 7 11 13 9 SUPPLY VOLTAGE (±V) UW 1210 G01 Bandwidth vs Supply Voltage 50 PEAKING ≤ 1dB PEAKING ≤ 5dB 40 RF = 560Ω 30 RF = 750Ω RF = 1k AV = 2 RL = 10Ω 10k Bandwidth and Feedback Resistance vs Capacitive Load for Peaking ≤ 1dB 100 BANDWIDTH –3dB BANDWIDTH (MHz) 1k FEEDBACK RESISTANCE AV = 2 RL = ∞ VS = ± 15V CCOMP = 0.01µF 1 10 100 1000 CAPACITIVE LOAD (pF) 10 20 10 RF = 2k 0 4 6 14 12 10 8 SUPPLY VOLTAGE (± V) 16 18 100 1 10000 1210 G03 1210 G02 Bandwidth vs Supply Voltage 10k Bandwidth and Feedback Resistance vs Capacitive Load for Peaking ≤ 5dB 100 BANDWIDTH PEAKING ≤ 1dB AV = 10 RL = 10Ω –3dB BANDWIDTH (MHz) 30 RF = 680Ω RF = 560Ω RF = 1k RF = 1.5k 1k 20 FEEDBACK RESISTANCE AV = +2 RL = ∞ VS = ±15V CCOMP = 0.01µF 1 10 100 1000 CAPACITIVE LOAD (pF) 10 10 0 4 6 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 100 0 1 10000 1210 G06 1210 G04 1210 G05 Differential Gain vs Supply Voltage 0.5 RF = RG = 750Ω AV = 2 100 Spot Noise Voltage and Current vs Frequency – in 10 0.2 en +in 1 10 100 1k 10k FREQUENCY (Hz) 100k 1210 G09 0.1 RL = 50Ω RL = 30Ω 15 1210 G08 0 15 1210 G07 5 7 11 13 9 SUPPLY VOLTAGE (±V) 5 LT1210 TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Supply Voltage 40 38 36 SUPPLY CURRENT (mA) RSD = 0Ω TA = 25°C SUPPLY CURRENT (mA) 34 32 30 28 26 24 22 20 4 6 TA = 85°C 25 20 15 10 5 0 –50 –25 SUPPLY CURRENT (mA) TA = 125°C TA = – 40°C 12 14 8 10 SUPPLY VOLTAGE (±V) Supply Current vs Shutdown Pin Current 40 VS = ±15V 35 – 0.5 COMMON MODE RANGE (V) –1.0 –1.5 –2.0 2.0 1.5 1.0 0.5 OUTPUT SHORT-CIRCUIT CURRENT (A) SUPPLY CURRENT (mA) 30 25 20 15 10 5 0 0 100 300 400 200 SHUTDOWN PIN CURRENT (µA) 500 1210 G13 Output Saturation Voltage vs Junction Temperature V+ OUTPUT SATURATION VOLTAGE (V) –1 –2 –3 –4 VS = ±15V RL = 2k RL = 10Ω POWER SUPPLY REJECTION (dB) 60 NEGATIVE 50 40 30 20 10 0 10k POSITIVE SUPPLY CURRENT (mA) 4 3 2 1 V– –50 –25 RL = 10Ω RL = 2k 0 25 50 75 TEMPERATURE (°C) 6 UW 16 18 1210 G10 Supply Current vs Ambient Temperature, VS = ± 5V 40 35 30 RSD = 7.5k RSD = 0Ω AV = 1 RL = ∞ 40 35 30 25 20 15 Supply Current vs Ambient Temperature, VS = ± 15V RSD = 0Ω RSD = 47.5k RSD = 15k RSD = 82.5k 10 5 AV = 1 RL = ∞ 50 25 0 75 TEMPERATURE (°C) 100 125 50 25 0 75 TEMPERATURE (°C) 100 125 0 –50 –25 1210 G11 1210 G12 Input Common Mode Limit vs Junction Temperature V+ Output Short-Circuit Current vs Junction Temperature 3.0 2.8 2.6 SINKING 2.4 2.2 2.0 1.8 1.6 –50 –25 SOURCING V– –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 50 25 75 0 TEMPERATURE (°C) 100 125 1210 G14 1210 G15 Power Supply Rejection Ratio vs Frequency 70 RL = 50Ω VS = ± 15V RF = RG = 1k Supply Current vs Large-Signal Output Frequency (No Load) 100 90 80 70 60 50 40 30 AV = 2 RL = ∞ VS = ± 15V VOUT = 20VP-P 100 125 100k 1M 10M FREQUENCY (Hz) 100M 1210 G17 20 10k 100k 1M FREQUENCY (Hz) 10M 1210 G18 1210 G16 LT1210 TYPICAL PERFOR A CE CHARACTERISTICS Output Impedance vs Frequency 100 VS = ±15V IO = 0mA OUTPUT IMPEDANCE (Ω) LARGE-SIGNAL VOLTAGE GAIN (dB) OUTPUT IMPEDANCE (Ω) 10 RSD = 82.5k 1 RSD = 0Ω 0.1 0.01 100k 10M 1M FREQUENCY (Hz) 3rd Order Intercept vs Frequency 56 54 3RD ORDER INTERCEPT (dBm) 52 50 48 46 44 42 40 0 2 UW 1210 G19 Output Impedance in Shutdown vs Frequency 10k 18 15 12 9 6 3 Large-Signal Voltage Gain vs Frequency AV = 4, RL = 10Ω RF = 680Ω, RG = 220Ω VS = ± 15V, VIN = 5VP-P 1k 100 10 100M 1 100k 10M 1M FREQUENCY (Hz) 100M 1210 G20 0 103 104 105 106 FREQUENCY (Hz) 107 108 1210 G21 Test Circuit for 3rd Order Intercept VS = ± 15V RL = 10Ω RF = 680Ω RG = 220Ω + LT1210 PO – 680Ω 220Ω MEASURE INTERCEPT AT PO 1210 TC01 10Ω 4 6 FREQUENCY (MHz) 8 10 1210 G22 7 LT1210 APPLICATI S I FOR ATIO The LT1210 is a current feedback amplifier with high output current drive capability. The device is stable with large capacitive loads and can easily supply the high currents required by capacitive loads. The amplifier will drive low impedance loads such as cables with excellent linearity at high frequencies. Feedback Resistor Selection The optimum value for the feedback resistors is a function of the operating conditions of the device, the load impedance and the desired flatness of response. The Typical AC Performance tables give the values which result in less than 1dB of peaking for various resistive loads and operating conditions. If this level of flatness is not required, a higher bandwidth can be obtained by use of a lower feedback resistor. The characteristic curves of Bandwidth vs Supply Voltage indicate feedback resistors for peaking up to 5dB. These curves use a solid line when the response has less than 1dB of peaking and a dashed line when the response has 1dB to 5dB of peaking. The curves stop where the response has more than 5dB of peaking. For resistive loads, the COMP pin should be left open (see Capacitive Loads section). Capacitive Loads The LT1210 includes an optional compensation network for driving capacitive loads. This network eliminates most of the output stage peaking associated with capacitive loads, allowing the frequency response to be flattened. Figure 1 shows the effect of the network on a 200pF load. Without the optional compensation, there is a 6dB peak at 40MHz caused by the effect of the capacitance on the output stage. Adding a 0.01µF bypass capacitor between the output and the COMP pins connects the compensation and greatly reduces the peaking. A lower value feedback resistor can now be used, resulting in a response which is flat to ± 1dB to 40MHz. The network has the greatest effect for CL in the range of 0pF to 1000pF. The graphs of Bandwidth and Feedback Resistance vs Capacitive Load can be used to select the appropriate value of feedback resistor. The values shown are for 1dB and 5dB peaking at a gain of 2 with no resistive load. This is a worst-case condition, as the amplifier is more stable at higher gains and with some resistive load in parallel with the capaci- VOLTAGE GAIN (dB) 8 U 14 12 10 8 6 4 2 0 –2 –4 –6 1 10 FREQUENCY (MHz) 100 1210 F01 W U UO VS = ±15V CL = 200pF RF = 3.4k NO COMPENSATION RF = 1.5k COMPENSATION RF = 3.4k COMPENSATION Figure 1 tance. Also shown is the – 3dB bandwidth with the suggested feedback resistor vs the load capacitance. Although the optional compensation works well with capacitive loads, it simply reduces the bandwidth when it is connected with resistive loads. For instance, with a 10Ω load, the bandwidth drops from 35MHz to 26MHz when the compensation is connected. Hence, the compensation was made optional. To disconnect the optional compensation, leave the COMP pin open. Shutdown/Current Set If the shutdown feature is not used, the SHUTDOWN pin must be connected to ground or V –. The Shutdown pin can be used to either turn off the biasing for the amplifier, reducing the quiescent current to less than 200µA, or to control the quiescent current in normal operation. The total bias current in the LT1210 is controlled by the current flowing out of the Shutdown pin. When the Shutdown pin is open or driven to the positive supply, the part is shut down. In the shutdown mode, the output looks like a 70pF capacitor and the supply current is typically less than 100µA. The Shutdown pin is referenced to the positive supply through an internal bias circuit (see the Simplified Schematic). An easy way to force shutdown is to use open-drain (collector) logic. The circuit shown in Figure 2 uses a 74C904 buffer to interface between 5V logic and the LT1210. The switching time between the active and shutdown states is about 1µs. A 24k pull-up resistor speeds LT1210 APPLICATI S I FOR ATIO 15V VIN + LT1210 VOUT RF –15V – SD 5V 74C906 ENABLE 24k 15V RG 1210 F02 Figure 2. Shutdown Interface up the turn-off time and ensures that the LT1210 is completely turned off. Because the pin is referenced to the positive supply, the logic used should have a breakdown voltage of greater than the positive supply voltage. No other circuitry is necessary as the internal circuit limits the Shutdown pin current to about 500µA. Figure 3 shows the resulting waveforms. ENABLE VOUT AV = 1 RF = 825Ω RL = 50Ω RPULL-UP = 24k VIN = 1V P-P VS = ±15V 1210 F03 Figure 3. Shutdown Operation For applications where the full bandwidth of the amplifier is not required, the quiescent current of the device may be reduced by connecting a resistor from the Shutdown pin to ground. The quiescent current will be approximately 65 times the current in the Shutdown pin. The voltage across the resistor in this condition is V + – 3VBE. For example, a 82k resistor will set the quiescent supply current to 9mA with VS = ±15V. The photos in Figures 4a and 4b show the effect of reducing the quiescent supply current on the large-signal U response. The quiescent current can be reduced to 9mA in the inverting configuration without much change in response. In noninverting mode, however, the slew rate is reduced as the quiescent current is reduced. RF = 750Ω RL = 10Ω IQ = 9mA, 18mA, 36mA VS = ±15V 1210 F04a W U UO Figure 4a. Large-Signal Response vs IQ, AV = – 1 RF = 750Ω RL = 10Ω IQ = 9mA, 18mA, 36mA VS = ±15V 1210 F04b Figure 4b. Large-Signal Response vs IQ, AV = 2 Slew Rate Unlike a traditional op amp, the slew rate of a current feedback amplifier is not independent of the amplifier gain configuration. There are slew rate limitations in both the input stage and the output stage. In the inverting mode, and for higher gains in the noninverting mode, the signal amplitude on the input pins is small and the overall slew rate is that of the output stage. The input stage slew rate is related to the quiescent current and will be reduced as the supply current is reduced. The output slew rate is set by the value of the feedback resistors and the internal capacitance. Larger feedback resistors will reduce the slew rate as will lower supply voltages, similar to the way 9 LT1210 APPLICATI S I FOR ATIO the bandwidth is reduced. The photos in Figures 5a, 5b and 5c show the large-signal response of the LT1210 for various gain configurations. The slew rate varies from 770V/µs for a gain of 1, to 1100V/µs for a gain of – 1. RF = 825Ω RL = 10Ω VS = ±15V 1210 F05a Figure 5a. Large-Signal Response, AV = 1 VS = ±15V RF = RG = 750Ω RL = 10Ω VS = ±15V 1210 F05b Figure 5b. Large-Signal Response, AV = – 1 RF = RG = 750Ω RL = 10Ω VS = ±15V 1210 F05c Figure 5c. Large-Signal Response, AV = 2 10 U When the LT1210 is used to drive capacitive loads, the available output current can limit the overall slew rate. In the fastest configuration, the LT1210 is capable of a slew rate of over 1V/ns. The current required to slew a capacitor at this rate is 1mA per picofarad of capacitance, so 10,000pF would require 10A! The photo (Figure 6) shows the large-signal behavior with CL = 10,000pF. The slew rate is about 150V/µs, determined by the current limit of 1.5A. RF = RG = 3k RL = ∞ 1210 F06 W U UO Figure 6. Large-Signal Response, CL = 10,000pF Differential Input Signal Swing The differential input swing is limited to about ± 6V by an ESD protection device connected between the inputs. In normal operation, the differential voltage between the input pins is small, so this clamp has no effect; however, in the shutdown mode the differential swing can be the same as the input swing. The clamp voltage will then set the maximum allowable input voltage. To allow for some margin, it is recommended that the input signal be less than ± 5V when the device is shut down. Capacitance on the Inverting Input Current feedback amplifiers require resistive feedback from the output to the inverting input for stable operation. Take care to minimize the stray capacitance between the output and the inverting input. Capacitance on the inverting input to ground will cause peaking in the frequency response (and overshoot in the transient response), but it does not degrade the stability of the amplifier. LT1210 APPLICATI Power Supplies The LT1210 will operate from single or split supplies from ± 5V (10V total) to ± 15V (30V total). It is not necessary to use equal value split supplies, however the offset voltage and inverting input bias current will change. The offset voltage changes about 500µV per volt of supply mismatch. The inverting bias current can change as much as 5µA per volt of supply mismatch, though typically the change is less than 0.5µA per volt. Power Supply Bypassing To obtain the maximum output and the minimum distortion from the LT1210, the power supply rails should be well bypassed. For example, with the output stage pouring 1A current peaks into the load, a 1Ω power supply impedance will cause a droop of 1V, reducing the available output swing by that amount. Surface mount tantalum and ceramic capacitors make excellent low ESR bypass elements when placed close to the chip. For frequencies above 100kHz, use 1µF and 100nF ceramic capacitors. If significant power must be delivered below 100kHz, capacitive reactance becomes the limiting factor. Larger ceramic or tantalum capacitors, such as 4.7µF, are recommended in place of the 1µF unit mentioned above. Inadequate bypassing is evidenced by reduced output swing and “distorted” clipping effects when the output is driven to the rails. If this is observed, check the supply pins of the device for ripple directly related to the output waveform. Significant supply modulation indicates poor bypassing. Thermal Considerations The LT1210 contains a thermal shutdown feature which protects against excessive internal (junction) temperature. If the junction temperature of the device exceeds the protection threshold, the device will begin cycling between normal operation and an off state. The cycling is not harmful to the part. The thermal cycling occurs at a slow rate, typically 10ms to several seconds, which depends on the power dissipation and the thermal time constants of the package and heat sinking. Raising the ambient temperature until the device begins thermal shutdown gives a good indication of how much margin there is in the thermal design. S I FOR ATIO U For surface mount devices heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Experiments have shown that the heat spreading copper layer does not need to be electrically connected to the tab of the device. The PCB material can be very effective at transmitting heat between the pad area attached to the tab of the device, and a ground or power plane layer either inside or on the opposite side of the board. Although the actual thermal resistance of the PCB material is high, the length/area ratio of the thermal resistance between the layer is small. Copper board stiffeners and plated through holes can also be used to spread the heat generated by the device. Tables 1 and 2 list thermal resistance for each package. For the TO-220 package, thermal resistance is given for junction-to-case only since this package is usually mounted to a heat sink. Measured values of thermal resistance for several different board sizes and copper areas are listed for each surface mount package. All measurements were taken in still air on 3/32" FR-4 board with 2 oz copper. This data can be used as a rough guideline in estimating thermal resistance. The thermal resistance for each application will be affected by thermal interactions with other components as well as board size and shape. Table 1. R Package, 7-Lead DD COPPER AREA TOPSIDE* BACKSIDE 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 125 sq. mm 2500 sq. mm THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 25°C/W 27°C/W 35°C/W *Tab of device attached to topside copper W U UO Table 2. Fused 16-Lead SO Package COPPER AREA TOPSIDE BACKSIDE 2500 sq. mm 1000 sq. mm 600 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 2500 sq. mm 2500 sq. mm 2500 sq. mm 2500 sq. mm 1000 sq. mm 600 sq. mm 300 sq. mm 100 sq. mm 0 sq. mm BOARD AREA 5000 sq. mm 3500 sq. mm 3100 sq. mm 2680 sq. mm 1180 sq. mm 780 sq. mm 480 sq. mm 280 sq. mm 180 sq. mm THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 40°C/W 46°C/W 48°C/W 49°C/W 56°C/W 58°C/W 59°C/W 60°C/W 61°C/W 11 LT1210 APPLICATI S I FOR ATIO T7 Package, 7-Lead TO-220 Thermal Resistance (Junction-to-Case) = 5°C/W Calculating Junction Temperature The junction temperature can be calculated from the equation: TJ = (PD)(θJA) + TA where: TJ = Junction Temperature TA = Ambient Temperature PD = Device Dissipation θJA = Thermal Resistance (Junction-to-Ambient) As an example, calculate the junction temperature for the circuit in Figure 7 for the SO and R packages assuming a 70°C ambient temperature. The device dissipation can be found by measuring the supply currents, calculating the total dissipation and then subtracting the dissipation in the load and feedback network. PD = (76mA)(10V) – (1.4V)2/ 10 = 0.56W 220Ω –5V 680Ω 1210 F07 TYPICAL APPLICATIONS Precision × 10 High Current Amplifier + LT1097 VIN + LT1210 COMP – SD 500pF 330Ω 3k 5V 10k – 0.01µF 9.09k OUTPUT OFFSET: < 500µV SLEW RATE: 2V/µs BANDWIDTH: 4MHz STABLE WITH CL < 10nF 1k 1210 TA03 12 U 5V W U U UO A 76mA + LT1210 SD VO 10Ω – 2V 0V –2V VO = 1.4VRMS Figure 7 then: TJ = (0.56W)(46°C/W) + 70°C = 96°C for the SO package with 1000 sq. mm topside heat sinking TJ = (0.56W)(27°C/W) + 70°C = 85°C for the R package with 1000 sq. mm topside heat sinking Since the maximum junction temperature is 150°C, both packages are clearly acceptable. CMOS Logic to Shutdown Interface 15V OUT + – LT1210 SD 24k –15V 2N3904 1210 TA04 LT1210 TYPICAL APPLICATIONS Distribution Amplifier VIN 75Ω + – LT1210 SD RF RG 75Ω 1210 TA05 SI PLIFIED SCHE ATIC TO ALL CURRENT SOURCES Q2 Q18 Q17 1.25k +IN –IN Q1 SHUTDOWN V+ U Buffer AV = 1 + – LT1210 COMP SD VOUT 0.01µF* * OPTIONAL, USE WITH CAPACITIVE LOADS ** VALUE OF R F DEPENDS ON SUPPLY VOLTAGE AND LOADING. SELECT FROM TYPICAL AC PERFORMANCE TABLE OR DETERMINE EMPIRICALLY 1210 TA06 75Ω 75Ω CABLE VIN 75Ω 75Ω RF** W W V+ Q5 D1 Q6 Q9 V– RC Q15 Q10 Q11 V– CC 50Ω COMP OUTPUT V+ Q12 Q8 Q4 Q7 D2 Q13 Q16 Q14 Q3 V– 1210 SS 13 LT1210 PACKAGE DESCRIPTION 0.256 (6.502) 0.060 (1.524) 0.060 (1.524) 0.183 (4.648) 0.075 (1.905) 0.300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +0.012 0.143 –0.020 0.040 – 0.060 (1.016 – 1.524) 0.026 – 0.036 (0.660 – 0.914) 0.013 – 0.023 (0.330 – 0.584) S Package 16-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.386 – 0.394* (9.804 – 10.008) 16 15 14 13 12 11 10 9 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0° – 8° TYP 0.016 – 0.050 0.406 – 1.270 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 14 U Dimensions in inches (millimeters) unless otherwise noted. R Package 7-Lead Plastic DD Pak (LTC DWG # 05-08-1462) 0.060 (1.524) TYP 0.390 – 0.415 (9.906 – 10.541) 15° TYP 0.165 – 0.180 (4.191 – 4.572) 0.045 – 0.055 (1.143 – 1.397) +0.008 0.004 –0.004 0.330 – 0.370 (8.382 – 9.398) 0.059 (1.499) TYP ( +0.203 0.102 –0.102 ) 0.095 – 0.115 (2.413 – 2.921) 0.050 ± 0.012 (1.270 ± 0.305) ( +0.305 3.632 –0.508 ) R (DD7) 0396 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) 1 0.053 – 0.069 (1.346 – 1.752) 2 3 4 5 6 7 8 0.004 – 0.010 (0.101 – 0.254) 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) TYP S16 0695 LT1210 PACKAGE DESCRIPTION 0.390 – 0.415 (9.906 – 10.541) 0.460 – 0.500 (11.684 – 12.700) 0.040 – 0.060 (1.016 – 1.524) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. U Dimensions in inches (millimeters) unless otherwise noted. T7 Package 7-Lead Plastic TO-220 (Standard) (LTC DWG # 05-08-1422) 0.147 – 0.155 (3.734 – 3.937) DIA 0.230 – 0.270 (5.842 – 6.858) 0.570 – 0.620 (14.478 – 15.748) 0.330 – 0.370 (8.382 – 9.398) 0.165 – 0.180 (4.293 – 4.572) 0.045 – 0.055 (1.143 – 1.397) 0.620 (15.75) TYP 0.700 – 0.728 (17.780 – 18.491) 0.152 – 0.202 0.260 – 0.320 (3.860 – 5.130) (6.604 – 8.128) 0.026 – 0.036 (0.660 – 0.914) 0.135 – 0.165 (3.429 – 4.191) 0.095 – 0.115 (2.413 – 2.921) 0.013 – 0.023 (0.330 – 0.584) 0.155 – 0.195 (3.937 – 4.953) T7 (TO-220) (FORMED) 0695 15 LT1210 TYPICAL APPLICATION Wideband 9W Bridge Amplifier 15V INPUT 5VP-P + – LT1210 SD 10nF 1 –15V 680Ω 100nF 220Ω 1 15V 910Ω 1 1 T1* 1 GAIN (dB) + – LT1210 SD 10nF –15V * COILTRONICS Versa-PacTM CTX-01-13033-X2 OR EQUIVALENT 1210 TA07 RELATED PARTS PART NUMBER LT1010 LT1166 LT1206 LT1207 LT1227 LT1360 LT1363 DESCRIPTION Fast ±150mA Power Buffer Power Output Stage Automatic Bias System Single 250mA, 60MHz Current Feedback Amplifier Dual 250mA, 60MHz Current Feedback Amplifier Single 140MHz Current Feedback Amplifier Single 50MHz, 800V/µs Op Amp Single 70MHz, 1000V/µs Op Amp COMMENTS 20MHz Bandwidth, 75V/µs Slew Rate Sets Class AB Bias Currents for High Voltage/High Power Output Stages Shutdown Function, Stable with CL = 10,000pF, 900V/µs Slew Rate Dual Version of LT1206 Shutdown Function, 1100V/µs Slew Rate Voltage Feedback, Stable with CL = 10,000pF Voltage Feedback, Stable with CL = 10,000pF 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 U Frequency Response PO 9W 26 RL 50Ω 9W 23 20 17 14 11 8 5 1 2 –1 –4 10k 100k 1M 10M FREQUENCY (Hz) 100M 1210 TA08 Versa-Pac is a trademark of Coiltronics, Inc. LT/GP 0796 7K • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 1996