LINER LT1311 Quad 12mhz, 145ns settling precision current-to-voltage converter for optical disk drive Datasheet

LT1311
Quad 12MHz, 145ns Settling
Precision Current-to-Voltage
Converter for Optical Disk Drives
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DESCRIPTION
FEATURES
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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.
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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
, LTC and LT are registered trademarks of Linear Technology Corporation.
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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
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PACKAGE/ORDER INFORMATION
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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
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Total Supply Voltage (V +
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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
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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.
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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
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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
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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
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W
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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
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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
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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)
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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
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