LT1311 Quad 12MHz, 145ns Settling Precision Current-to-Voltage Converter for Optical Disk Drives U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT ®1311 is a quad current-to-voltage converter designed for the demanding requirements of photo diode amplification. A new approach to current-to-voltage conversion provides excellent DC and AC performance without external DC trims or AC frequency compensation. The LT1311 is ideal for converting multiple photo diode currents to voltages and for general purpose matched inverting amplifier applications. Four Complete Current-to-Voltage Converters 14-Lead Small Outline Package Accurate Gain: 20mV/µA, ±4% Low Offset Error: 250nA Max Low Offset Drift: 2.5nA/°C Max Fast Settling: 145ns to 0.1% for a 2V Step Wide Bandwidth: 12MHz Low Noise: 5pA/√Hz Low Quiescent Current: 11mA Max Wide Supply Range: ±2V to ±18V or 4V to 36V The LT1311 contains four current feedback amplifiers, each with an internal 20k feedback resistor. A supply bypass capacitor is the only external component required to convert four signal currents to voltages. Unlike voltage feedback-based current-to-voltage converters that operate with only a specified value of input capacitance, the current feedback LT1311 settles cleanly with any input capacitance up to 50pF. Only in the most demanding applications will the LT1311 need to be mounted close to the photo diodes. U APPLICATIONS ■ ■ Optical Disk Drive Photo Diode Amplifiers Focus and Tracking Summing Amplifiers Color Scanners RGB Amplifiers Selectable Gain Amplifiers Matched Inverting Amplifiers , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ TYPICAL APPLICATION Transient Response Photo Diode Current-to-Voltage Converter VCC 10V 1 IN A 0.1µF 2 3 IN B OUT A – + + – 14 CIN = 1pF 13 OUT B 12 CIN = 20pF 5V 4 BIAS 5 IN C 11 LT1311 – + OUT C CIN = 50pF 10 6 9 7 IN D + – OUT D INPUT = 100µA STEP VS = ±5V 8 1311 TA02 1311 TA01 1 LT1311 U PACKAGE/ORDER INFORMATION U W W V –) W to ............................. 36V Input Current ..................................................... ±15mA Output Short-Circuit Duration (Note 1) ........ Continuous Operating Temperature Range ............... – 40°C to 85°C Specified Temperature Range ...................... 0°C to 70°C Junction Temperature.......................................... 150°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C W Total Supply Voltage (V + U ABSOLUTE MAXIMUM RATINGS TOP VIEW IN A 1 14 OUT A – 13 V – (AB) + NC 2 + IN B 3 ORDER PART NUMBER LT1311CS 12 OUT B – 11 NC BIAS 4 – IN C 5 V – (CD) 10 OUT C + 6 9 V+ + – 8 OUT D IN D 7 S PACKAGE 14-LEAD PLASTIC SO TJMAX = 150°C, θJA = 160°C/ W Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL VOS ∆VOS /∆T PARAMETER Current to Voltage Gain Current to Voltage Gain Drift Current to Voltage Gain Mismatch Input Offset Voltage Input Offset Voltage Drift Output Offset Voltage VS = 10V, VBIAS = 5V, TA = 25°C, unless otherwise noted. CONDITIONS VOUT = 2V to 8V, RL = 2k to 5V in en PSRR VOUT IOUT IS SR 2 Bias Voltage Range Bias Rejection Ratio Bias Input Resistance Bias Input Capacitance Power Supply Rejection Ratio Minimum Supply Voltage Voltage Gain Maximum Output Voltage Swing Output Impedance Maximum Output Current Supply Current Slew Rate MIN 19.2 ● Between Amplifiers (∆G/20k) × 100% With Respect to VBIAS ● With Respect to VBIAS VS = ±15V, VBIAS = 0V ● ● Output Offset Voltage Drift Output Offset Voltage Mismatch Bias Input Current Output Noise Voltage Density Input Noise Current Density Input Noise Voltage Density Input Impedance ● (A + B) – (C + D) Between Amplifiers Pin 4 f = 1kHz f = 1kHz f = 1kHz, AV = 40dB ∆VOS /∆IIN, DC, ∆VOUT = 2V to 8V (IIN = ±150µA) ∆VOS /∆IIN, f = 10MHz ● ● ● ∆VOUT/∆VBIAS, VBIAS = 2V to 8V VBIAS = 2V to 8V f = 100kHz VS = ±2V to ±15V, VBIAS = 0V VBIAS = 2V ∆VOUT/∆VOS, VOUT = 2V to 8V, RL = 2k to 5V Output High, No Load, IIN = – 250µA Output High, ISOURCE = 10mA, IIN = – 250µA Output Low, No Load, IIN = 250µA Output Low, ISINK = 10mA, IIN = 250µA IOUT = 0mA, f = 10MHz IIN = ±200µA, VOUT = 5V IIN = 0 IIN = ±150µA, VOUT at 3V, 7V ±2 ±5 100 5 4.5 0.2 400 ● ● ● ● ● ● ● ● ● ● ● V – + 2V 55 250 90 4 10 8.8 8.5 ● ● ● ● TYP 20 – 70 0.1 ±150 ±1 ±1.5 ±3 ±10 ±30 MAX 20.8 1.0 ±500 ±5 ±10 ±50 ±80 ±4 ±20 2 V + – 2V 64 500 18 103 100 9.0 8.8 1.0 1.2 60 ±55 7 80 1.2 1.5 11 UNITS mV/µA ppm/°C % µV µV/°C mV mV µV/°C µV/°C mV µA nV/√Hz pA/√Hz nV/√Hz Ω Ω V dB kΩ pF dB V V/mV V V V V Ω mA mA V/µs LT1311 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER BW tr, tf Small-Signal Bandwidth Full Power Bandwidth Rise Time, Fall Time OS tS Overshoot Settling Time THD Total Harmonic Distortion Crosstalk VS = 10V, VBIAS = 5V, TA = 25°C, unless otherwise noted. CONDITIONS MIN TYP VOUT = 2.5VP-P, RIN = 20k 10% to 90%, VOUT = 6VP-P, RIN = 20k 10% to 90%, VOUT = 100mVP-P, RIN = 20k VOUT = 100mVP-P, RIN = 20k ∆VOUT = 2V, 0.1%, RIN = 20k VS = ±15V, ∆VOUT = 10V, 0.1%, RIN = 20k VOUT = 2VRMS, 20Hz to 20kHz, RIN = 20k VOUT = 3V to 7V, RL = 2k to 5V, f = 100Hz, 3 Channels Driven The ● denotes specifications which apply over the full specified temperature range of 0°C to 70°C. MAX UNITS 12 10 65 35 0 145 210 0.004 110 MHz MHz ns ns % ns ns % dB Note 1: A heat sink may be required depending on the power supply voltage and the number of amplifiers that are shorted. U W TYPICAL PERFORMANCE CHARACTERISTICS Bias Voltage Range vs Temperature Supply Current vs Supply Voltage V+ 11 TA = 125°C V+ –1 BIAS VOLTAGE RANGE (V) 10 9 TA = 25°C 8 7 6 V+ OUTPUT SATURATION VOLTAGE (V) 12 SUPPLY CURRENT (mA) Output Saturation Voltage vs Load Current TA = –55°C 5 4 V + –2 V – +2 V – +1 V –1 V –55°C + –2 V – +2 –55°C V – +1 3 125°C V– –50 –25 2 0 5 10 15 20 25 30 TOTAL SUPPLY VOLTAGE (V) 35 40 50 25 75 0 TEMPERATURE (°C) 100 V– 0.01 125 Output Impedance vs Frequency 20 100 VS = ±15V RIN = ∞ –3dB BANDWIDTH (MHz) VS = ±15V IIN = 750µA 60 VS = ± 5V IIN = 250µA OUTPUT IMPEDANCE (Ω) 18 80 50 10 1311 G03 –3dB Bandwidth vs Load Resistance 90 70 25°C 0.1 1 LOAD CURRENT (mA) 1311 G02 1311 G01 Short-Circuit Current vs Temperature SHORT-CIRCUIT CURRENT (mA) 25°C 125°C + 16 VS = ±5V 14 12 10 40 8 30 –50 –25 6 100 10 VS = ±5V 1 VS = ±15V 0.1 RIN = 100k 50 25 75 0 TEMPERATURE (°C) 100 125 1311 G04 1k LOAD RESISTANCE (Ω) 10k 1131 G05 0.01 1k 10k 100k 1M FREQUENCY (Hz) 10M 1311 G06 3 LT1311 U W TYPICAL PERFORMANCE CHARACTERISTICS Settling Time to 0.1%, 1mV,10mV vs Output Step 10 0.1% 1mV 300 2 0 –2 10mV –4 240 VS = ±5V VOUT = 2V STEP RIN = 100k RL = 1k 1mV 0.1% 220 250 200 150 –6 200 300 500 400 10 30 40 20 INPUT CAPACITANCE (pF) 0 180 170 50 AV = 100 AV = 0.2 AV = 10 AV = 100, RIN = 200Ω 30 20 –8 135 –9 90 –10 45 –11 0 AV = 10, RIN = 2k 10 0 PHASE SHIFT (DEG) 40 180 GAIN (dB) VS = ±5V RL = 2k AV = 1 AV = 1, RIN = 20k CIN = 5pF TOTAL HARMONIC DISTORTION (%) 50 NEGATIVE POSITIVE 10 –10 10k –14 10M 1311 G13 CL = 0pF –17 1M 10M FREQUENCY (Hz) 40M –18 100k 1M 10M FREQUENCY (Hz) 1311 G12 Noise Spectrum 0.01 VS = ±15V VOUT = 6.5VRMS AV = –1 VS = ±5V VOUT = 2VRMS AV = –1 10 40M 13 0.001 100k 1M FREQUENCY (Hz) CL = 50pF –16 CIN = 0pF 0.1 70 CL = 100pF –13 Total Harmonic Distortion vs Frequency VS = ±5V AV = 1 RL = ∞ CL = 200pF –12 1311 G11 Power Supply Rejection Ratio vs Frequency 90 CL = 500pF –15 CIN = 1pF 1311 G10 30 CIN = 10pF –14 –18 100k 40M –11 CIN = 20pF –13 VS = ±5V RIN = 100k RL = 2k –10 –17 1M 10M FREQUENCY (Hz) Frequency Response for Various Capacitive Loads –9 CIN = 50pF –12 1000 –8 –16 AV = 0.2, RIN = 100k –30 100k 10 100 CAPACITIVE LOAD (pF) 1311 G09 VS = ±5V RIN = 100k RL = 2k –15 –10 –20 1 1311 G08 Frequency Response for Various Input Capacitance 70 60 140 50 GAIN (dB) 100 Gain and Phase vs Frequency GAIN (dB) 190 VOLTAGE NOISE DENSITY (nV/√Hz) CURRENT NOISE DENSITY (pA/√Hz) 0 1311 G07 POWER SUPPLY REJECTION RATIO (dB) 200 150 100 SETTLING TIME (ns) 4 210 160 –8 –10 VS = ±5V VOUT = 2V STEP RIN = 100k RL = 1k 230 SETTLING TIME (ns) 10mV 4 SETTLING TIME (ns) OUTPUT STEP (V) 6 350 VS = ±15V RIN = 20k RL = 1k AV = –1 8 0.1% Settling Time vs Capacitive Load 0.1% Settling Time vs Input Capacitance 100 10k 1k FREQUENCY (Hz) 100k 1311 G14 12 11 10 9 8 in 7 6 en 5 4 3 10 1k 100 FREQUENCY (Hz) 10k 1311 G15 LT1311 U W TYPICAL PERFORMANCE CHARACTERISTICS Small-Signal Response Large-Signal Response VS = ±5V AV = –1 RL = 2k VS = ±15V AV = –1 RL = 2k 1311 G16 1311 G17 W W SI PLIFIED SCHE ATIC VCC R1 1k R2 2k Q3 Q1 R3 2k Q4 R4 2k Q5 R5 1k R6 4.5k R9 1.5k Q23 R10 1.5k Q24 Q6 Q28 Q25 Q29 C1 5pF Q26 Q33 Q27 Q17 Q32 Q18 + IBIAS PTAT BIAS Q19 R22 10Ω CC 2pF RFB 20k OUT IN Q20 R23 10Ω Q21 Q42 Q22 Q39 Q35 Q36 Q44 C2 5pF Q40 Q13 Q12 Q14 Q15 Q41 Q16 Q37 R11 1k R12 2k R13 2k R14 2k R15 1k R16 4.5k Q38 R19 1.5k R20 1.5k VEE 1311 SS 5 LT1311 U W U U APPLICATIONS INFORMATION Description Input Characteristics The LT1311 contains four identical current feedback amplifiers with their noninverting inputs tied together at pin 4. An external bias voltage is applied to this pin to set the quiescent output voltage of each amplifier. Each amplifier has an internal 20k feedback resistor between the output and the inverting input. The amplifiers are packaged in a 14-pin SO package with all four inverting inputs on one side and the outputs on the other. None of the inputs (or the outputs) are on adjacent pins for excellent channel separation. The inputs of the LT1311 are low impedance summing nodes. The current feedback amplifiers in the LT1311 have an open-loop input impedance of only a few hundred ohms and therefore the closed-loop response is fairly independent of stray capacitance on the inputs. This is a significant advantage over voltage feedback amplifiers that have to be set up for a particular input capacitance. The LT1311 settles cleanly with any input capacitance from zero to 50pF as shown in the characteristic curves. When the LT1311 is used to convert photo diode currents to signal voltages, the LT1311 does not have to be located close to the diodes. The feedback resistors in the LT1311 are laser-trimmed at wafer sort to set the current-to-voltage gain. The gain is set to 20mV/µA; the change with temperature is typically – 70ppm/°C. The gain matching of the four amplifiers is ten times better. The input offset voltage and bias current are trimmed as well. The trimming also minimizes the resulting output offset drift. For more detailed circuit information, please see the May 1995 (Volume 5, Number 2) issue of Linear Technology magazine. Supply Voltages The LT1311 can be operated on single or split supplies. The total supply voltage must be greater than 4V and less than 36V. The bias voltage applied to pin 4 can be any value from 2V above the negative supply to 2V below the positive supply. The outputs can swing to within 1V of either supply. The LT1311 is trimmed while operating on a single 10V supply with a bias voltage of 5V; this is the equivalent of ±5V supplies with the bias at ground. Operation on a single 5V supply with a bias voltage of 2.5V results in very similar performance. Operation on ±15V supplies results in slightly more bandwidth and offset (see the electrical tables and the characteristic curves). Bypassing the supplies and bias voltage pins requires no special care. For accurate settling, a 0.1µF capacitor within an inch or two of the package works well. 6 Output Characteristics The outputs of the LT1311 are complementary emitter followers. The outputs will swing to within 1V of the supplies with no load, 1.2V delivering 10mA. The outputs are short-circuit protected with a 55mA current limit. Voltage Gain Applications When the LT1311 is used with external input resistors to make an inverting voltage gain amplifier, the bandwidth remains fairly constant for gains of 10 or less. At high gains the bandwidth is limited by a gain bandwidth product of about 250MHz. See the characteristic curves for details. The bandwidth is also influenced by any stray capacitance in parallel with the input resistor. The parallel stray capacitance results in a zero that pushes out the bandwidth. This is particularly noticeable with large input resistors that give gains less than one. For example, a single 100k input resistor results in a bandwidth of 14MHz but two 50k resistors in series result in only 10MHz bandwidth. Overload Recovery When one or more of the outputs is driven into the rail it will not affect the other amplifiers. However, the output that hit the rail will generate a glitch and take one to two microseconds to recover. Supply current will increase 2mA to 3mA for each amplifier while it is driven into the rail. LT1311 U TYPICAL APPLICATIONS Basic Optical System Focus and Tracking Signal Generation 8pF 1 IN A VCC 10V 0.1µF – + 2 + – 3 IN B 5V 4 BIAS 5 IN C OUT A 14 V – (AB) 13 OUT B 12 LT1311 – + OUT C 2k 11 2k 10 2k 5V + – 7 IN D OUT D VCC 10V – TRACKING SIGNAL (A + B) – (C + D) 1/2 LT1215 2k 6 V – (CD) VCC 2k 2k + 2k 9 8 2k 2k + WORST-CASE OUTPUT DRIFT IS 120µV/°C BANDWIDTH IS 7MHz 0.1% SETTLING IS LESS THAN 250ns FOCUS SIGNAL (A + C) – (B + D) 1/2 LT1215 2k – 2k 2k 8pF 1311 TA04 Wide Common-Mode Range Instrumentation Amplifier 100k –IN 1 TRIM FOR CMRR 20k 14 3 12 R2 2k 5 100k +IN 7 10 OUT R2′ 2k 8 VS = ±5V V CM = ±18V VS = ±15V V CM = ±68V BW = 5MHz, AV = 20k/R2 = 10 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. 1131 TA03 7 LT1311 U PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted. S Package 14-Lead Plastic SOIC 0.337 – 0.344* (8.560 – 8.738) 14 13 12 11 10 9 8 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157* (3.810 – 3.988) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 2 3 4 5 6 7 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0° – 8° TYP 0.016 – 0.050 0.406 – 1.270 0.050 (1.270) TYP 0.014 – 0.019 (0.355 – 0.483) SO14 0294 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm) RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1113 Dual Low Noise, Precision, JFET Input Op Amp Lowest Voltage Noise FET Op Amp LT1169 Dual Low Noise, Picoampere Bias Current, JFET Input Op Amp 5pA Input Bias Current LT1213/LT1214 28MHz, 12V/µs, Single Supply, Dual and Quad Precision Op Amps Highest Bandwidth, Precision Single Supply Op Amps LT1215/LT1216 23MHz, 50V/µs Single Supply, Dual and Quad Precision Op Amps Fastest Settling, Precision Single Supply Op Amps LT1222 Low Noise, Very High Speed Op Amp External Compensation and Output Clamping 8 Linear Technology Corporation LT/GP 0595 10K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1995