LT1207 Dual 250mA/60MHz Current Feedback Amplifier U DESCRIPTIO FEATURES The LT (R) 1207 is a dual version of the LT1206 high speed current feedback amplifier. Like the LT1206, each CFA in the dual has excellent video characteristics: 60MHz bandwidth, 250mA minimum output drive current, 400V/s minimum slew rate, low differential gain (0.02% typ) and low differential phase (0.17 typ). The LT1207 includes a pin for an optional compensation network which stabilizes the amplifier for heavy capacitive loads. Both amplifiers have thermal and current limit circuits which protect against fault conditions. These capabilities make the LT1207 well suited for driving difficult loads such as cables in video or digital communication systems. 250mA Minimum Output Drive Current 60MHz Bandwidth, AV = 2, RL = 100 900V/s Slew Rate, AV = 2, RL = 50 0.02% Differential Gain, AV = 2, RL = 30 0.17 Differential Phase, AV = 2, RL = 30 High Input Impedance: 10M Shutdown Mode: IS < 200A per Amplifier Stable with CL = 10,000pF U APPLICATIO S ADSL/HDSL Drivers Video Amplifiers Cable Drivers RGB Amplifiers Test Equipment Amplifiers Buffers Operation is fully specified from 5V to 15V supplies. Supply current is typically 20mA per amplifier. Two micropower shutdown controls place each amplifier in a high impedance low current mode, dropping supply current to 200A per amplifier. For reduced bandwidth applications, supply current can be lowered by adding a resistor in series with the Shutdown pin. The LT1207 is manufactured on Linear Technology's complementary bipolar process and is available in a low thermal resistance 16-lead SO package. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATION HDSL Driver 5V + 0.1F* 2.2F** + VIN SHDN A 1/2 LT1207 62 - L1 720 15k 720 240 720 - 15k * CERAMIC ** TANTALUM L1 = TRANSPOWER SMPT-308 OR SIMILAR DEVICE 62 1/2 LT1207 + -5V 0.1F* + SHDN B 2.2F** 1207 * TA01 1 LT1207 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO Supply Voltage ..................................................... 18V Input Current per Amplifier ............................... 15mA Output Short-Circuit Duration (Note 1) ....... Continuous Specified Temperature Range (Note 2) ...... 0C to 70C Operating Temperature Range ............... - 40C to 85C Junction Temperature ......................................... 150C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C ORDER PART NUMBER TOP VIEW V+ 16 1 V+ -IN A 2 15 OUT A +IN A 3 14 V - A LT1207CS 13 COMP A SHDN A 4 -IN B 5 12 OUT B +IN B 6 11 V - B 10 COMP B SHDN B 7 V+ 8 9 V+ S PACKAGE 16-LEAD PLASTIC SO JA = 40C/W (NOTE 3) Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS VCM = 0, 5V VS 15V, pulse tested, VSHDN A = 0V, VSHDN B = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage TA = 25C MIN TYP MAX UNITS 3 10 15 mV mV Input Offset Voltage Drift IIN+ Noninverting Input Current TA = 25C 2 5 20 A A 10 60 100 A A IIN- Inverting Input Current TA = 25C en Input Noise Voltage Density f = 10kHz, RF = 1k, RG = 10, RS = 0 + in Input Noise Current Density - in Input Noise Current Density RIN Input Resistance VIN = 12V, VS = 15V VIN = 2V, VS = 5V CIN Input Capacitance VS = 15V Input Voltage Range VS = 15V VS = 5V Common Mode Rejection Ratio VS = 15V, VCM = 12V VS = 5V, VCM = 2V Inverting Input Current Common Mode Rejection VS = 15V, VCM = 12V VS = 5V, VCM = 2V Power Supply Rejection Ratio VS = 5V to 15V CMRR PSRR 2 V/C 10 3.6 nV/Hz f = 10kHz, RF = 1k, RG = 10, RS = 10k 2 pA/Hz f = 10kHz, RF = 1k, RG = 10, RS = 10k 30 pA/Hz 10 5 M M 2 pF 12 2 13.5 3.5 V V 55 50 62 60 dB dB 1.5 0.5 0.1 0.1 60 77 10 10 A/V A/V dB LT1207 ELECTRICAL CHARACTERISTICS VCM = 0, 5V VS 15V, pulse tested, VSHDN A = 0V, VSHDN B = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS Noninverting Input Current Power Supply Rejection VS = 5V to 15V Inverting Input Current Power Supply Rejection AV MIN TYP MAX UNITS 30 500 nA/V VS = 5V to 15V 0.7 5 A/V Large-Signal Voltage Gain VS = 15V, VOUT = 10V, RL = 50 VS = 5V, VOUT = 2V, RL = 25 55 55 71 68 dB dB ROL Transresistance, VOUT/IIN- VS = 15V, VOUT = 10V, RL = 50 VS = 5V, VOUT = 2V, RL = 25 100 75 260 200 k k VOUT Maximum Output Voltage Swing VS = 15V, RL = 50, TA = 25C VS = 5V, RL = 25, TA = 25C 11.5 10.0 2.5 2.0 250 IOUT Maximum Output Current RL = 1 IS Supply Current per Amplifier VS = 15V, VSHDN = 0V, TA = 25C Supply Current per Amplifier, RSHDN = 51k (Note 4) VS = 15V, TA = 25C Positive Supply Current per Amplifier, Shutdown VS = 15V, VSHDN A = 15V, VSHDN B = 15V Output Leakage Current, Shutdown VS = 15V, VSHDN = 15V, VOUT = 0V Slew Rate (Note 5) AV = 2, TA = 25C 12.5 3.0 500 1200 mA 20 30 35 mA mA 12 17 mA 200 A SR BW V V V V 10 400 900 A V/s Differential Gain (Note 6) VS = 15V, RF = 560, RG = 560, RL = 30 0.02 % Differential Phase (Note 6) VS = 15V, RF = 560, RG = 560, RL = 30 0.17 DEG Small-Signal Bandwidth VS = 15V, Peaking 0.5dB RF = RG = 620, RL = 100 60 MHz VS = 15V, Peaking 0.5dB RF = RG = 649, RL = 50 52 MHz VS = 15V, Peaking 0.5dB RF = RG = 698, RL = 30 43 MHz VS = 15V, Peaking 0.5dB RF = RG = 825, RL = 10 27 MHz The denotes specifications which apply for 0C TA 70C. 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 - 40C to 85C but are neither tested nor guaranteed beyond 0C to 70C. Industrial grade parts tested over - 40C to 85C are available on special request. Consult factory. Note 3: Thermal resistance JA varies from 40C/W to 60C/W depending upon the amount of PC board metal attached to the device. JA is specified for a 2500mm2 test board covered with 2oz copper on both sides. Note 4: RSHDN 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 = 400. Note 6: NTSC composite video with an output level of 2V. 3 LT1207 U W U S ALL-SIG AL BA DWIDTH IS = 20mA per Amplifier Typical, Peaking 0.1dB AV RL RF VS = 5V, RSHDN = 0 -1 150 562 30 649 10 732 1 150 619 30 715 10 806 2 150 576 30 649 10 750 10 150 442 30 511 10 649 RG 562 649 732 - - - 576 649 750 48.7 56.2 71.5 - 3dB BW (MHz) 48 34 22 54 36 22.4 48 35 22.4 40 31 20 - 0.1dB BW (MHz) 21.4 17 12.5 22.3 17.5 11.5 20.7 18.1 11.7 19.2 16.5 10.2 AV RL RF VS = 15V, RSHDN = 0 -1 150 681 30 768 10 887 1 150 768 30 909 10 1k 2 150 665 30 787 10 931 10 150 487 30 590 10 768 RG - 3dB BW (MHz) - 0.1dB BW (MHz) 681 768 887 - - - 665 787 931 536 64.9 84.5 50 35 24 66 37 23 55 36 22.5 44 33 20.7 19.2 17 12.3 22.4 17.5 12 23 18.5 11.8 20.7 17.5 10.8 RG - 3dB BW (MHz) - 0.1dB BW (MHz) 634 768 866 - - - 649 787 931 33.2 44.2 64.9 41 26.5 17 44 28 16.8 40 27 16.5 33 25 15.3 19.1 14 9.4 18.8 14.4 8.3 18.5 14.1 8.1 15.6 13.3 7.4 RG - 3dB BW (MHz) - 0.1dB BW (MHz) IS = 10mA per Amplifier Typical, Peaking 0.1dB AV RL RF VS = 5V, RSHDN = 10.2k -1 150 576 30 681 10 750 1 150 665 30 768 10 845 2 150 590 30 681 10 768 10 150 301 30 392 10 499 RG - 3dB BW (MHz) - 0.1dB BW (MHz) 576 681 750 - - - 590 681 768 33.2 43.2 54.9 35 25 16.4 37 25 16.5 35 25 16.2 31 23 15 17 12.5 8.7 17.5 12.6 8.2 16.8 13.4 8.1 15.6 11.9 7.8 AV RL RF VS = 15V, RSHDN = 60.4k -1 150 634 30 768 10 866 1 150 768 30 909 10 1k 2 150 649 30 787 10 931 10 150 301 30 402 10 590 IS = 5mA per Amplifier Typical, Peaking 0.1dB AV RL RF RG - 3dB BW (MHz) - 0.1dB BW (MHz) VS = 5V, RSHDN = 22.1k AV RL RF VS = 15V, RSHDN = 121k -1 150 30 10 604 715 681 604 715 681 21 14.6 10.5 10.5 7.4 6.0 -1 150 30 10 619 787 825 619 787 825 25 15.8 10.5 12.5 8.5 5.4 1 150 30 10 768 866 825 - - - 20 14.1 9.8 9.6 6.7 5.1 1 150 30 10 845 1k 1k - - - 23 15.3 10 10.6 7.6 5.2 2 150 30 10 634 750 732 634 750 732 20 14.1 9.6 9.6 7.2 5.1 2 150 30 10 681 845 866 681 845 866 23 15 10 10.2 7.7 5.4 10 150 30 10 100 100 100 11.1 11.1 11.1 16.2 13.4 9.5 5.8 7.0 4.7 10 150 30 10 100 100 100 11.1 11.1 11.1 15.9 13.6 9.6 4.5 6 4.5 4 LT1207 W U TYPICAL PERFOR A CE CHARACTERISTICS -3dB BANDWIDTH (MHz) 80 RF = 470 70 RF = 560 60 RF = 680 50 40 RF = 750 30 RF = 1k 20 10 AV = 2 RL = 10 40 RF = 560 30 RF = 750 20 RF = 1k RF = 2k 10 1k FEEDBACK RESISTOR AV = 2 RL = VS = 15V CCOMP = 0.01F 10 RF = 1.5k 100 0 0 4 14 12 10 8 SUPPLY VOLTAGE (V) 6 16 4 18 14 12 10 8 SUPPLY VOLTAGE (V) 6 16 1 18 Bandwidth vs Supply Voltage Bandwidth and Feedback Resistance vs Capacitive Load for 5dB Peak 50 70 RF =390 RF = 330 50 40 RF = 470 30 RF = 680 20 10 100 AV = 10 RL = 10 BANDWIDTH 40 30 RF = 560 20 RF = 680 RF = 1k 10 RF = 1.5k 1k 10 FEEDBACK RESISTOR RF = 1.5k 0 0 4 14 12 10 8 SUPPLY VOLTAGE (V) 6 16 0 100 4 18 14 12 10 8 SUPPLY VOLTAGE (V) 6 16 18 1 Differential Phase vs Supply Voltage Spot Noise Voltage and Current vs Frequency 100 0.10 RF = RG = 560 AV = 2 N PACKAGE 0.20 RL = 30 RL = 50 0.10 RL = 15 0.08 DIFFERENTIAL GAIN (%) 0.30 RF = RG = 560 AV = 2 N PACKAGE SPOT NOISE (nV/Hz OR pA/Hz) RL = 15 0.06 RL = 30 0.04 RL = 50 0.02 RL = 150 0 7 11 13 9 SUPPLY VOLTAGE (V) 15 LT1207 * TPC07 -in 10 en in RL = 150 0 5 1 10k LT1207 * TPC06 Differential Gain vs Supply Voltage 0.50 0.40 10 100 1k CAPACITIVE LOAD (pF) LT1207 * TPC05 LT1207 * TPC04 AV = +2 RL = VS = 15V CCOMP = 0.01F -3dB BANDWIDTH (MHz) - 3dB BANDWIDTH (MHz) 80 60 10k PEAKING 0.5dB PEAKING 5dB AV = 10 RL = 100 FEEDBACK RESISTOR () PEAKING 0.5dB PEAKING 5dB 1 10000 LT1207 * TPC03 Bandwidth vs Supply Voltage 100 90 100 10 1000 CAPACITIVE LOAD (pF) LT1207 * TPC02 LT1207 * TPC01 -3dB BANDWIDTH (MHz) BANDWIDTH -3dB BANDWIDTH (MHz) - 3dB BANDWIDTH (MHz) 90 PEAKING 0.5dB PEAKING 5dB AV = 2 RL = 100 FEEDBACK RESISTOR () PEAKING 0.5dB PEAKING 5dB 100 10k 50 100 DIFFERENTIAL PHASE (DEG) Bandwidth and Feedback Resistance vs Capacitive Load for 0.5dB Peak Bandwidth vs Supply Voltage Bandwidth vs Supply Voltage 5 7 11 13 9 SUPPLY VOLTAGE (V) 15 LT1207 * TPC08 1 10 100 1k 10k FREQUENCY (Hz) 100k LT1207 * TPC09 5 LT1207 W U TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Ambient Temperature, VS = 5V Supply Current vs Supply Voltage 25 25 22 TJ = -40C 20 TJ = 25C 18 16 TJ = 85C 14 TJ = 125C 12 10 4 16 14 12 10 8 SUPPLY VOLTAGE (V) 6 RSD = 0 20 15 RSD = 10.2k 10 RSD = 22.1k 5 0 -50 -25 18 AV = 1 RL = 50 25 0 75 TEMPERATURE (C) 10 8 6 4 -1.0 -1.5 -2.0 2.0 1.5 1.0 0.5 2 100 300 400 200 SHUTDOWN PIN CURRENT (A) V- -50 500 -25 4 RL = 50 RL = 2k 1 V- -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 LT1207 * TPC16 6 0.6 SINKING 0.5 0.4 50 25 75 0 TEMPERATURE (C) 60 50 125 Supply Current vs Large-Signal Output Frequency (No Load) 60 NEGATIVE RL = 50 VS = 15V RF = RG = 1k POSITIVE 40 30 20 10 0 10k 100 LT1207 * TPC15 100k 1M 10M FREQUENCY (Hz) 100M LT1207 * TPC17 SUPPLY CURRENT PER AMPLIFIER (mA) POWER SUPPLY REJECTION (dB) OUTPUT SATURATION VOLTAGE (V) -4 2 SOURCING 0.7 0.3 -50 -25 125 70 RL = 2k -3 125 0.8 Power Supply Rejection Ratio vs Frequency RL = 50 100 0.9 LT1207 * TPC14 Output Saturation Voltage vs Junction Temperature 3 100 0 25 50 75 TEMPERATURE (C) LT1207 * TPC13 -2 50 25 0 75 TEMPERATURE (C) 1.0 OUTPUT SHORT-CIRCUIT CURRENT (A) COMMON MODE RANGE (V) SUPPLY CURRENT PER AMPLIFIER (mA) 12 -1 RSD = 121k 5 Output Short-Circuit Current vs Junction Temperature - 0.5 14 VS = 15V RSD = 60.4k 10 LT1207 * TPC12 V+ VS = 15V 16 V+ 15 Input Common Mode Limit vs Junction Temperature 20 0 20 LT1207 * TPC11 Supply Current vs Shutdown Pin Current 18 AV = 1 RL = RSD = 0 0 -50 -25 125 100 LT1207 * TPC10 0 SUPPLY CURRENT PER AMPLIFIER (mA) VSHDN = 0V SUPPLY CURRENT PER AMPLIFIER (mA) SUPPLY CURRENT PER AMPLIFIER (mA) 24 Supply Current vs Ambient Temperature, VS = 15V 50 AV = 2 RL = VS = 15V VOUT = 20VP-P 40 30 20 10 10k 100k 1M 10M FREQUENCY (Hz) LT1207 * TPC18 LT1207 W U TYPICAL PERFOR A CE CHARACTERISTICS Output Impedance in Shutdown vs Frequency Output Impedance vs Frequency AV = 1 RF = 1k VS = 15V RSHDN = 121k RSHDN = 0 1 0.1 VS = 15V VO = 2VP-P -40 2nd RL = 10 10k DISTORTION (dBc) 10 -30 100k VS = 15V IO = 0mA OUTPUT IMPEDANCE () OUTPUT IMPEDANCE () 100 2nd and 3rd Harmonic Distortion vs Frequency 1k -50 3rd 2nd -60 -70 RL = 30 3rd 100 -80 1M 10M 100M -90 10 100k 1M FREQUENCY (Hz) 10M 100M 3 2 4 5 FREQUENCY (MHz) 1 FREQUENCY (Hz) LT1207 * TPC19 Test Circuit for 3rd Order Intercept VS = 15V RL = 50 RF = 590 RG = 64.9 50 6 7 8 9 10 LT1207 * TPC21 LT1207 * TPC20 3rd Order Intercept vs Frequency 60 3rd ORDER INTERCEPT (dBm) 0.01 100k + PO 1/2 LT1207 - 40 590 30 50 65 MEASURE INTERCEPT AT PO LT1207 * TPC23 20 10 0 5 10 15 20 FREQUENCY (MHz) 25 30 LT1207 * TPC22 7 LT1207 W W SI PLIFIED SCHE ATIC V+ TO ALL CURRENT SOURCES Q5 Q10 Q2 Q18 D1 Q6 Q1 Q17 Q11 Q15 Q9 V- 1.25k +IN CC -IN V- 50 COMP RC OUTPUT V+ SHUTDOWN V+ Q12 Q3 Q8 Q16 Q14 D2 Q4 Q7 Q13 V- 1/2 LT1207 CURRENT FEEDBACK AMPLIFIER U W U UO APPLICATI LT1207 * SS S I FOR ATIO The LT1207 is a dual 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. line when the response has 0.5dB 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 section on capacitive loads). Capacitive Loads 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 the highest 0.1dB and 0.5dB bandwidths 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 0.5dB of peaking and a dashed 8 Each amplifier in the LT1207 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 5dB peak at 40MHz caused by the effect of the capacitance on the output stage. Adding a 0.01F bypass capacitor between the output and the COMP pins connects the compensation and completely eliminates the peaking. A lower value feedback resistor can now be used, resulting in a response which is flat to 0.35dB to 30MHz. LT1207 U UO S I FOR ATIO VS = 15V 10 RF = 1.2k COMPENSATION 8 VOLTAGE GAIN (dB) W 12 U APPLICATI 6 4 RF = 2k NO COMPENSATION 2 0 RF = 2k COMPENSATION -2 -4 -6 -8 1 10 FREQUENCY (MHz) 100 LT1207 * F01 Figure 1. typically 100A. Each 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 LT1207. The switching time between the active and shutdown states is less than 1s. A 24k pull-up resistor speeds up the turn-off time and insures that the amplifier 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 500A. Figure 3 shows the resulting waveforms. The network has the greatest effect for CL in the range of 0pF to 1000pF. The graph of Maximum Capacitive Load vs Feedback Resistor can be used to select the appropriate value of the feedback resistor. The values shown are for 0.5dB 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 capacitance. Also shown is the -3dB bandwidth with the suggested feedback resistor vs the load capacitance. 15V VOUT 1/2 LT1207 SHDN - -15V RF 15V 5V RG 24k ENABLE 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 30 load, the bandwidth drops from 55MHz to 35MHz when the compensation is connected. Hence, the compensation was made optional. To disconnect the optional compensation, leave the COMP pin open. 74C906 LT1207 * F02 Figure 2. Shutdown Interface VOUT Shutdown/Current Set + VIN Each amplifier has a separate Shutdown pin which can be used to either turn off the amplifier, which reduces the amplifier supply current to less than 200A, or to control the supply current in normal operation. The supply current in each amplifier is controlled by the current flowing out of the Shutdown pin. When the Shutdown pin is open or driven to the positive supply, the amplifier is shut down. In the shutdown mode, the output looks like a 40pF capacitor and the supply current is ENABLE If the shutdown feature is not used, the Shutdown pins must be connected to ground or V -. AV = 1 RF = 825 RL = 50 RPU = 24k VIN = 1VP-P LT1207 * F3 Figure 3. Shutdown Operation For applications where the full bandwidth of the amplifier is not required, the quiescent current may be reduced by connecting a resistor from the Shutdown pin to ground. 9 LT1207 U W U UO APPLICATI S I FOR ATIO The amplifier's supply current will be approximately 40 times the current in the Shutdown pin. The voltage across the resistor in this condition is V + - 3VBE. For example, a 60k resistor will set the amplifier's supply current to 10mA with VS = 15V. The photos (Figures 4a and 4b) show the effect of reducing the quiescent supply current on the large-signal response. The quiescent current can be reduced to 5mA in the inverting configuration without much change in response. In noninverting mode, however, the slew rate is reduced as the quiescent current is reduced. 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 the bandwidth is reduced. The photos (Figures 5a, 5b and 5c) show the large-signal response of the LT1207 or various gain configurations. The slew rate varies from 860V/s for a gain of 1, to 1400V/s for a gain of - 1. When the LT1207 is used to drive capacitive loads, the available output current can limit the overall slew rate. In the fastest configuration, the LT1207 is capable of a slew rate of over 1V/ns. The current required to slew a capacitor RF = 750 RL = 50 IQ = 5mA, 10mA, 20mA VS = 15V LT1207 * F04a Figure 4a. Large-Signal Response vs IQ, AV = -1 RF = 825 RL = 50 VS = 15V LT1207 * F05a Figure 5a. Large-Signal Response, AV = 1 RF = 750 RL = 50 IQ = 5mA, 10mA, 20mA VS = 15V LT1207 * 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, 10 RF = RG = 750 RL = 50 VS = 15V LT1207 * F05b Figure 5b. Large-Signal Response, AV = -1 LT1207 W U U UO APPLICATI S I FOR ATIO 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. Power Supplies LT1207 * F05c RF = 750 RL = 50 Figure 5c. Large-Signal Response, AV = 2 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 60V/s, determined by the current limit of 600mA. VS = 15V RF = RG = 3k RL = LT1207 * F06 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. The LT1207 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 500V per volt of supply mismatch. The inverting bias current can change as much as 5A per volt of supply mismatch, though typically the change is less than 0.5A per volt. Thermal Considerations Each amplifier in the LT1207 includes a separate thermal shutdown circuit which protects against excessive internal (junction) temperature. If the junction temperature exceeds the protection threshold, the amplifier 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. Heat flows away from the amplifier through the package's copper lead frame. 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 11 LT1207 W U U UO APPLICATI S I FOR ATIO 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. Table 1 lists thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with 2oz 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. Fused 16-Lead SO Package COPPER AREA (2oz) TOPSIDE TOTAL THERMAL RESISTANCE COPPER AREA (JUNCTION-TO-AMBIENT) BACKSIDE 2500 sq. mm 2500 sq. mm 5000 sq. mm 40C/W 1000 sq. mm 2500 sq. mm 3500 sq. mm 46C/W 600 sq. mm 2500 sq. mm 3100 sq. mm 48C/W 180 sq. mm 2500 sq. mm 2680 sq. mm 49C/W 180 sq. mm 1000 sq. mm 1180 sq. mm 56C/W 180 sq. mm 600 sq. mm 780 sq. mm 58C/W 180 sq. mm 300 sq. mm 480 sq. mm 59C/W 180 sq. mm 100 sq. mm 280 sq. mm 60C/W 180 sq. mm 0 sq. mm 180 sq. mm 61C/W THERMAL RESISTANCE (C/W) TJ = Junction Temperature TA = Ambient Temperature PD = Device Dissipation JA = Thermal Resistance (Junction-to-Ambient) As an example, calculate the junction temperature for the circuit in Figure 8 assuming a 70C 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. 15V I 37.5mA + 330 12V 1/2 LT1207 SHDN - 1k -15V -12V f = 2MHz 0.01F 200pF 1k LT1206 * F07 Figure 8. Thermal Calculation Example The dissipation for each amplifier is: 70 PD = (37.5mA)(30V) - (12V)2/(1k||1k) = 0.837W 60 The total dissipation is PD = 1.674W. When a 2500 sq mm PC board with 2oz copper on top and bottom is used, the thermal resistance is 40C/W. The junction temperature TJ is: 50 40 30 TJ = (1.674W)(40C/W) + 70C = 137C 20 10 0 0 1000 3000 4000 2000 COPPER AREA (mm2) 5000 LT1207 * F07 Figure 7. Thermal Resistance vs Total Copper Area (Top + Bottom) Calculating Junction Temperature The junction temperature can be calculated from the equation: TJ = (PD)(JA) + TA 12 where: The maximum junction temperature for the LT1207 is 150C, so the heat sinking capability of the board is adequate for the application. If the copper area on the PC board is reduced to 280mm2 the thermal resistance increases to 60C/W and the junction temperature becomes: TJ = (1.674W)(60C/W) + 70C = 170C Which is above the maximum junction temperature indicating that the heat sinking capability of the board is inadequate and should be increased. LT1207 U TYPICAL APPLICATIO S Gain of Eleven High Current Amplifier + 1/2 LT1207 + LT1097 - - OUT COMP SHDN 0.01F 500pF 330 3k 10k LT1207 * TA02 OUTPUT OFFSET: < 500V SLEW RATE: 2V/s BANDWIDTH: 4MHz STABLE WITH CL < 10nF 1k Gain of Ten Buffered Line Driver 15V 1F 15V 1F + + + + LT1115 - 1F 1/2 LT1207 SHDN + - OUTPUT 0.01F RL -15V 1F 68pF + VIN -15V 560 560 909 LT1207 * TA03 100 RL = 32 VO = 5VRMS THD + NOISE = 0.0009% AT 1kHz = 0.004% AT 20kHz SMALL-SIGNAL 0.1dB BANDWIDTH = 600kHz 13 LT1207 U TYPICAL APPLICATIO S CMOS Logic to Shutdown Interface Distribution Amplifier 15V + VIN 75 + 24k 1/2 LT1207 SHDN 75 1/2 LT1207 SHDN - 75 CABLE 75 RF 75 - LT1207 * TA05 LT1207 * TA04 5V RG -15V 75 10k 2N3904 Buffer AV = 1 VIN + - Differential Output Driver 1/2 LT1207 VIN *OPTIONAL, USE WITH CAPACITIVE LOADS **VALUE OF RF DEPENDS ON SUPPLY VOLTAGE AND LOADING. SELECT FROM TYPICAL AC PERFORMANCE TABLE OR DETERMINE EMPIRICALLY VOUT COMP SHDN 0.01F* + 1/2 LT1207 - + 0.01F 1k RF** LT1207 * TA06 500 VOUT 1k 1k Differential Input--Differential Output Power Amplifier (AV = 4) - 1/2 LT1207 - + 0.01F + + 1/2 LT1207 + - 1k VIN VOUT 1k 1k - 1/2 LT1207 - - + LT1207 * TA08 14 LT1207 * TA07 LT1207 U TYPICAL APPLICATIO S Paralleling Both CFAs for Guaranteed 500mA Output Drive Current + VIN 3 VOUT 1/2 LT1207 - 1k 1k + 3 1/2 LT1207 - 1k LT1207 * TA09 1k PACKAGE DESCRIPTIO U Dimensions in inches (millimeters) unless otherwise noted. 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 0.150 - 0.157** (3.810 - 3.988) 0.228 - 0.244 (5.791 - 6.197) 1 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 2 3 4 5 6 0.053 - 0.069 (1.346 - 1.752) 0.014 - 0.019 (0.355 - 0.483) 8 0.004 - 0.010 (0.101 - 0.254) 0 - 8 TYP 0.016 - 0.050 0.406 - 1.270 7 0.050 (1.270) TYP S16 0695 *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 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 circuits as described herein will not infringe on existing patent rights. 15 LT1207 U TYPICAL APPLICATION CCD Clock Driver. Two 3rd Order Gaussian Filters Produce Clean CCD Clock Signals 45pF CCD ARRAY LOAD 20V 1k CLOCK INPUT CLK 1k + Q 74HC74 D 1k 100pF 91pF Q 10 1/2 LT1207 3300pF - 1k 0.01F 510 45pF 1k 1k 1k 100pF CLOCK 5 INPUT 0 + 91pF 10 1/2 LT1207 - 3300pF 0.01F -10V 1k 15 LT1207 * TA10 DRIVER OUTPUT 510 0 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1206 Single 250mA/60MHz Current Feedback Amplifier Single Version of LT1207, 900V/s Slew Rate, 0.02% Differential Gain, 0.17 Differential Phase, with AV = 2 and RL = 30, Stable with CL = 10,000pF, Shutdown Control Reduces Supply Current to 200A LT1210 Single 1A/30MHz Current Feedback Amplifier Higher Output Current Version of LT1206 LT1229/LT1230 Dual/Quad 100MHz Current Feedback Amplifiers Low Cost CFA for Video Applications, 1000V/s Slew Rate, 30mA Output Drive Current, 0.04% Differential Gain, 0.1 Differential Phase, with AV = 2 and RL = 150, 9.5mA Max Supply Current per Op Amp, 2V to 15V Supply Range LT1360/LT1361/LT1362 Single/Dual/Quad 50MHz, 800V/s, C-LoadTM Op Amps Fast Settling Voltage Feedback Amplifier, 60ns Settling Time to 0.1%, 10V Step, 5mA Max Supply Current per Op Amp, 9nVHz Input Noise Voltage, Drives All Capacitive Loads, 1mV Max VOS, 0.2% Differential Gain, 0.3 Differential Phase with AV = 2 and RL = 150 C-Load is a trademark of Linear Technology Corporation 16 Linear Technology Corporation LT/GP 0196 10K * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1996