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LT1311 Quad 12MHz, 145ns Settling Precision Current-to-Voltage Converter for Optical Disk Drives
FEATURES
s s s s s s s s s s
DESCRIPTION
The LT (R)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. 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Four Complete Current-to-Voltage Converters 14-Lead Small Outline Package Accurate Gain: 20mV/A, 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
APPLICATIONS
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Optical Disk Drive Photo Diode Amplifiers Focus and Tracking Summing Amplifiers Color Scanners RGB Amplifiers Selectable Gain Amplifiers Matched Inverting Amplifiers
TYPICAL APPLICATION
Photo Diode Current-to-Voltage Converter
VCC 10V 1 IN A 0.1F 2 3 IN B 4 BIAS 5 IN C 6 7 IN D + - OUT A 14
13 OUT B 12
CIN = 1pF
+ - LT1311 + -
CIN = 20pF
5V 11
OUT C
10 9
CIN = 50pF
+ -
OUT D
8
INPUT = 100A STEP VS = 5V
1311 TA01
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Transient Response
1311 TA02
1
LT1311
ABSOLUTE MAXIMUM RATINGS
Total Supply Voltage (V + to ............................. 36V Input Current ..................................................... 15mA Output Short-Circuit Duration (Note 1) ........ Continuous Operating Temperature Range ............... - 40C to 85C Specified Temperature Range ...................... 0C to 70C Junction Temperature.......................................... 150C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C V -)
PACKAGE/ORDER INFORMATION
TOP VIEW IN A 1
+ - +
14 OUT A
-
ORDER PART NUMBER LT1311CS
NC 2 IN B 3 BIAS 4 V - (CD)
13 V - (AB) 12 OUT B 11 NC
6
+ -
IN D 7 S PACKAGE 14-LEAD PLASTIC SO
TJMAX = 150C, JA = 160C/ W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL 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 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 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
VS = 10V, VBIAS = 5V, TA = 25C, unless otherwise noted.
q q q q q q q q q q
CONDITIONS VOUT = 2V to 8V, RL = 2k to 5V Between Amplifiers (G/20k) x 100% With Respect to VBIAS With Respect to VBIAS VS = 15V, VBIAS = 0V (A + B) - (C + D) Between Amplifiers Pin 4 f = 1kHz f = 1kHz f = 1kHz, AV = 40dB VOS /IIN, DC, VOUT = 2V to 8V (IIN = 150A) 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 = - 250A Output High, ISOURCE = 10mA, IIN = - 250A Output Low, No Load, IIN = 250A Output Low, ISINK = 10mA, IIN = 250A IOUT = 0mA, f = 10MHz IIN = 200A, VOUT = 5V IIN = 0 IIN = 150A, VOUT at 3V, 7V
VOS VOS /T
in en
PSRR
VOUT
IOUT IS SR
Output Impedance Maximum Output Current Supply Current Slew Rate
2
+
IN C 5
10 OUT C 9 V+ 8 OUT D
MIN 19.2
TYP 20 - 70 0.1 150 1 1.5 3 10 2 5 100 5 4.5 0.2 400
MAX 20.8 1.0 500 5 10 50 80 4 20
q q q q q q q q q q q q q
2 V + - 2V
V - + 2V 55 250 90 4 10 8.8 8.5
64 500 18 103 100 9.0 8.8 1.0 1.2 60 55 7 80
1.2 1.5
30
11
UNITS mV/A ppm/C % V V/C mV mV V/C V/C mV A nV/Hz pA/Hz nV/Hz V dB k pF dB V V/mV V V V V mA mA V/s
U
W
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-
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WW
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LT1311
ELECTRICAL CHARACTERISTICS
SYMBOL BW tr, tf OS tS THD PARAMETER Small-Signal Bandwidth Full Power Bandwidth Rise Time, Fall Time Overshoot Settling Time Total Harmonic Distortion Crosstalk CONDITIONS
VS = 10V, VBIAS = 5V, TA = 25C, unless otherwise noted.
MIN TYP 12 10 65 35 0 145 210 0.004 110 MAX UNITS MHz MHz ns ns % ns ns % dB
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 q denotes specifications which apply over the full specified temperature range of 0C to 70C.
Note 1: A heat sink may be required depending on the power supply voltage and the number of amplifiers that are shorted.
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
12 11 10
SUPPLY CURRENT (mA)
TA = 125C
BIAS VOLTAGE RANGE (V)
V+ -1 V
+ -2
OUTPUT SATURATION VOLTAGE (V)
9 8 7 6 5 4 3 2 0 5 10 15 20 25 30 TOTAL SUPPLY VOLTAGE (V) 35 40 TA = -55C TA = 25C
Short-Circuit Current vs Temperature
90
20 18
SHORT-CIRCUIT CURRENT (mA)
80
-3dB BANDWIDTH (MHz)
OUTPUT IMPEDANCE ()
70 60 50 40 30 -50 -25
VS = 15V IIN = 750A VS = 5V IIN = 250A
50 25 75 0 TEMPERATURE (C)
UW
1311 G01
Bias Voltage Range vs Temperature
V+
+
Output Saturation Voltage vs Load Current
V+ 125C V -1 V
+ -2
25C
-55C
V - +2 V - +1 V- -50 -25
V - +2 V - +1 V- 0.01 -55C 125C 25C 0.1 1 LOAD CURRENT (mA) 10
1311 G03
50 25 75 0 TEMPERATURE (C)
100
125
1311 G02
-3dB Bandwidth vs Load Resistance
VS = 15V
Output Impedance vs Frequency
100 RIN =
16 VS = 5V 14 12 10 8 RIN = 100k 6 100
10 VS = 5V 1 VS = 15V 0.1
100
125
1k LOAD RESISTANCE ()
10k
1131 G05
0.01
1k
10k
100k 1M FREQUENCY (Hz)
10M
1311 G06
1311 G04
3
LT1311 TYPICAL PERFORMANCE CHARACTERISTICS
Settling Time to 0.1%, 1mV,10mV vs Output Step
10 8 6 10mV 0.1% 1mV VS = 15V RIN = 20k RL = 1k AV = -1 350 VS = 5V VOUT = 2V STEP RIN = 100k RL = 1k
SETTLING TIME (ns)
OUTPUT STEP (V)
4 2 0 -2 -4 -6 -8 -10 0 100 200 300 10mV 0.1% 1mV
SETTLING TIME (ns)
SETTLING TIME (ns)
1311 G07
Gain and Phase vs Frequency
70 60 50 40 VS = 5V RL = 2k AV = 1 AV = 100 AV = 10 AV = 100, RIN = 200 AV = 10, RIN = 2k AV = 0.2 180 135 90 45 0 -8 -9 -10 -11
GAIN (dB)
GAIN (dB)
GAIN (dB)
30 20 10 0 -10 -20
AV = 1, RIN = 20k AV = 0.2, RIN = 100k 1M 10M FREQUENCY (Hz) 40M
1311 G10
-30 100k
Power Supply Rejection Ratio vs Frequency
90
POWER SUPPLY REJECTION RATIO (dB)
TOTAL HARMONIC DISTORTION (%)
VOLTAGE NOISE DENSITY (nV/Hz) CURRENT NOISE DENSITY (pA/Hz)
70
VS = 5V AV = 1 RL =
50 NEGATIVE 30 POSITIVE
10
-10 10k
100k 1M FREQUENCY (Hz)
4
UW
400
1311 G13
0.1% Settling Time vs Input Capacitance
240 230 220 210 200 190 180 170 160 150
0.1% Settling Time vs Capacitive Load
VS = 5V VOUT = 2V STEP RIN = 100k RL = 1k
300
250
200
150
100 500 0 10 30 40 20 INPUT CAPACITANCE (pF) 50
1311 G08
140
1
10 100 CAPACITIVE LOAD (pF)
1000
1311 G09
Frequency Response for Various Input Capacitance
VS = 5V RIN = 100k RL = 2k CIN = 50pF CIN = 20pF CIN = 10pF -8 -9 -10 -11 -12 -13 -14 -15 -16 -17 40M
1311 G11
Frequency Response for Various Capacitive Loads
VS = 5V RIN = 100k RL = 2k
CL = 500pF CL = 200pF
PHASE SHIFT (DEG)
-12 -13 -14 -15 -16 -17 -18 100k
CL = 100pF
CIN = 5pF CIN = 1pF CIN = 0pF 1M 10M FREQUENCY (Hz)
CL = 50pF CL = 0pF
-18 100k
1M 10M FREQUENCY (Hz)
40M
1311 G12
Total Harmonic Distortion vs Frequency
0.1
13 12 11 10 9 8 7 6 5 4 3
Noise Spectrum
0.01 VS = 15V VOUT = 6.5VRMS AV = -1 VS = 5V VOUT = 2VRMS AV = -1 10 100 10k 1k FREQUENCY (Hz) 100k
1311 G14
in
en
0.001 10M
10
1k 100 FREQUENCY (Hz)
10k
1311 G15
LT1311 TYPICAL PERFORMANCE CHARACTERISTICS
Small-Signal Response Large-Signal Response
VS = 5V AV = -1 RL = 2k
SI PLIFIED SCHE ATIC
VCC R1 1k R2 2k R3 2k R4 2k R5 1k R6 4.5k R9 1.5k R10 1.5k
Q1
Q3
Q4
+
IBIAS PTAT
BIAS Q20
Q12
Q13
Q14
R11 1k
R12 2k
R13 2k
UW
W
Q5 Q15 R14 2k Q18
1311 G16
VS = 15V AV = -1 RL = 2k
1311 G17
W
Q23 Q6
Q24 Q28 C1 5pF Q29
Q25
Q26
Q17
Q27 Q32
Q33
Q19 IN Q21
RFB 20k
CC 2pF
R22 10 OUT R23 10 Q42
Q22 Q39 C2 5pF Q40 Q16 Q37 Q38 Q41 Q44
Q35
Q36
R15 1k
R16 4.5k
R19 1.5k
R20 1.5k VEE
1311 SS
5
LT1311
APPLICATIONS INFORMATION
Description 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 feedback resistors in the LT1311 are laser-trimmed at wafer sort to set the current-to-voltage gain. The gain is set to 20mV/A; 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 0.1F capacitor within an inch or two of the package works well. Input Characteristics 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. 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.
6
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LT1311
TYPICAL APPLICATIONS
Basic Optical System Focus and Tracking Signal Generation
8pF
0.1F
2 3 IN B 4 BIAS 5 IN C 6 V - (CD) 7 IN D
+ - LT1311
5V
+ -
WORST-CASE OUTPUT DRIFT IS 120V/C BANDWIDTH IS 7MHz 0.1% SETTLING IS LESS THAN 250ns
Wide Common-Mode Range Instrumentation Amplifier
100k -IN
1
100k +IN
7
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.
+ -
VCC 10V
1 IN A
+ -
U
OUT A V - (AB) OUT B
14
2k 2k
2k VCC 10V TRACKING SIGNAL (A + B) - (C + D)
13 12 2k 2k 2k 5V 2k
- +
1/2 LT1215
11
OUT C
10 9 8
VCC OUT D
2k 2k
+
1/2 LT1215
2k 2k
-
2k
FOCUS SIGNAL (A + C) - (B + D)
8pF
1311 TA04
TRIM FOR CMRR 20k 14
3
12
R2 2k
5 R2 2k
10
OUT
8
VS = 5V V CM = 18V VS = 15V V CM = 68V BW = 5MHz, AV = 20k/R2 = 10
1131 TA03
7
LT1311
PACKAGE DESCRIPTION
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0 - 8 TYP
0.016 - 0.050 0.406 - 1.270
*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 LT1113 LT1169 LT1213/LT1214 LT1215/LT1216 LT1222 DESCRIPTION Dual Low Noise, Precision, JFET Input Op Amp Dual Low Noise, Picoampere Bias Current, JFET Input Op Amp 28MHz, 12V/s, Single Supply, Dual and Quad Precision Op Amps 23MHz, 50V/s Single Supply, Dual and Quad Precision Op Amps Low Noise, Very High Speed Op Amp COMMENTS Lowest Voltage Noise FET Op Amp 5pA Input Bias Current Highest Bandwidth, Precision Single Supply Op Amps Fastest Settling, Precision Single Supply Op Amps External Compensation and Output Clamping
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
U
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
2
3
4
5
6
7
0.053 - 0.069 (1.346 - 1.752) 0.004 - 0.010 (0.101 - 0.254)
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) TYP
SO14 0294
LT/GP 0595 10K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1995

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