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1
LT1311
s
Four Complete Current-to-Voltage Converters
s
14-Lead Small Outline Package
s
Accurate Gain: 20mV/
A,
4%
s
Low Offset Error: 250nA Max
s
Low Offset Drift: 2.5nA/
C Max
s
Fast Settling: 145ns to 0.1% for a 2V Step
s
Wide Bandwidth: 12MHz
s
Low Noise: 5pA/
Hz
s
Low Quiescent Current: 11mA Max
s
Wide Supply Range:
2V to
18V or 4V to 36V
The LT
1311 is a quad current-to-voltage converter de-
signed for the demanding requirements of photo diode
amplification. A new approach to current-to-voltage con-
version provides excellent DC and AC performance with-
out external DC trims or AC frequency compensation. The
LT1311 is ideal for converting multiple photo diode cur-
rents to voltages and for general purpose matched invert-
ing 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 oper-
ate 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.
Quad 12MHz, 145ns Settling
Precision Current-to-Voltage
Converter for Optical Disk Drives
FEATURES
DESCRIPTIO
N
U
TYPICAL APPLICATIO
N
U
APPLICATIO
N
S
U
s
Optical Disk Drive
Photo Diode Amplifiers
Focus and Tracking Summing Amplifiers
s
Color Scanners
RGB Amplifiers
Selectable Gain Amplifiers
s
Matched Inverting Amplifiers
, LTC and LT are registered trademarks of Linear Technology Corporation.
C
IN
= 1pF
C
IN
= 20pF
C
IN
= 50pF
INPUT = 100
A STEP
V
S
=
5V
1311 TA02
1
2
3
4
5
6
7
14
13
12
10
9
8
1311 TA01
11
+
+
+
+
5V
IN A
IN B
BIAS
IN C
IN D
OUT A
OUT B
OUT C
V
CC
10V
OUT D
LT1311
0.1
F
Transient Response
Photo Diode Current-to-Voltage Converter
2
LT1311
Total Supply Voltage (V
+
to V
) ............................. 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
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
T
JMAX
= 150
C,
JA
= 160
C/ W
ORDER PART
NUMBER
LT1311CS
Consult factory for Industrial and Military grade parts.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Current to Voltage Gain
V
OUT
= 2V to 8V, R
L
= 2k to 5V
q
19.2
20
20.8
mV/
A
Current to Voltage Gain Drift
q
70
ppm/
C
Current to Voltage Gain Mismatch
Between Amplifiers (
G/20k)
100%
q
0.1
1.0
%
V
OS
Input Offset Voltage
With Respect to V
BIAS
q
150
500
V
V
OS
/
T
Input Offset Voltage Drift
1
V/
C
Output Offset Voltage
With Respect to V
BIAS
q
1.5
5
mV
V
S
=
15V, V
BIAS
= 0V
q
3
10
mV
Output Offset Voltage Drift
q
10
50
V/
C
(A + B) (C + D)
q
80
V/
C
Output Offset Voltage Mismatch
Between Amplifiers
q
2
4
mV
Bias Input Current
Pin 4
q
5
20
A
Output Noise Voltage Density
f = 1kHz
100
nV/
Hz
i
n
Input Noise Current Density
f = 1kHz
5
pA/
Hz
e
n
Input Noise Voltage Density
f = 1kHz, A
V
= 40dB
4.5
nV/
Hz
Input Impedance
V
OS
/
I
IN
, DC,
V
OUT
= 2V to 8V (I
IN
=
150
A)
q
0.2
2
V
OS
/
I
IN
, f = 10MHz
400
Bias Voltage Range
q
V
+ 2V
V
+
2V
V
Bias Rejection Ratio
V
OUT
/
V
BIAS
, V
BIAS
= 2V to 8V
q
55
64
dB
Bias Input Resistance
V
BIAS
= 2V to 8V
q
250
500
k
Bias Input Capacitance
f = 100kHz
18
pF
PSRR
Power Supply Rejection Ratio
V
S
=
2V to
15V, V
BIAS
= 0V
q
90
103
dB
Minimum Supply Voltage
V
BIAS
= 2V
q
4
V
Voltage Gain
V
OUT
/
V
OS
, V
OUT
= 2V to 8V, R
L
= 2k to 5V
q
10
100
V/mV
V
OUT
Maximum Output Voltage Swing
Output High, No Load, I
IN
= 250
A
q
8.8
9.0
V
Output High, I
SOURCE
= 10mA, I
IN
= 250
A
q
8.5
8.8
V
Output Low, No Load, I
IN
= 250
A
q
1.0
1.2
V
Output Low, I
SINK
= 10mA, I
IN
= 250
A
q
1.2
1.5
V
Output Impedance
I
OUT
= 0mA, f = 10MHz
60
I
OUT
Maximum Output Current
I
IN
=
200
A, V
OUT
= 5V
q
30
55
mA
I
S
Supply Current
I
IN
= 0
q
7
11
mA
SR
Slew Rate
I
IN
=
150
A, V
OUT
at 3V, 7V
80
V/
s
V
S
= 10V, V
BIAS
= 5V, T
A
= 25
C, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
TOP VIEW
S PACKAGE
14-LEAD PLASTIC SO
1
2
3
4
5
6
7
14
13
12
11
10
9
8
IN A
NC
IN B
BIAS
IN C
V
(CD)
IN D
OUT A
V
(AB)
OUT B
NC
OUT C
V
+
OUT D
+
+
+
+
3
LT1311
V
S
= 10V, V
BIAS
= 5V, T
A
= 25
C, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BW
Small-Signal Bandwidth
12
MHz
Full Power Bandwidth
V
OUT
= 2.5V
P-P
, R
IN
= 20k
10
MHz
t
r
, t
f
Rise Time, Fall Time
10% to 90%, V
OUT
= 6V
P-P
, R
IN
= 20k
65
ns
10% to 90%, V
OUT
= 100mV
P-P
, R
IN
= 20k
35
ns
OS
Overshoot
V
OUT
= 100mV
P-P
, R
IN
= 20k
0
%
t
S
Settling Time
V
OUT
= 2V, 0.1%, R
IN
= 20k
145
ns
V
S
=
15V,
V
OUT
= 10V, 0.1%, R
IN
= 20k
210
ns
THD
Total Harmonic Distortion
V
OUT
= 2V
RMS
, 20Hz to 20kHz, R
IN
= 20k
0.004
%
Crosstalk
V
OUT
= 3V to 7V, R
L
= 2k to 5V, f = 100Hz,
110
dB
3 Channels Driven
The
q
denotes specifications which apply over the full specified
temperature range of 0
C to 70
C.
Note 1: A heat sink may be required depending on the power supply
voltage and the number of amplifiers that are shorted.
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
TEMPERATURE (
C)
50
SHORT-CIRCUIT CURRENT (mA)
90
80
70
60
50
40
30
25
75
1311 G04
25
0
50
100
125
V
S
=
15V
I
IN
= 750
A
V
S
=
5V
I
IN
= 250
A
Supply Current vs Supply Voltage
TOTAL SUPPLY VOLTAGE (V)
0
SUPPLY CURRENT (mA)
12
11
10
9
8
7
6
5
4
3
2
10
20
25
1311 G01
5
15
30
35
40
T
A
= 125
C
T
A
= 25
C
T
A
= 55
C
Short-Circuit Current
vs Temperature
FREQUENCY (Hz)
OUTPUT IMPEDANCE (
)
100
10
1
0.1
0.01
1k
100k
1M
1311 G06
10k
10M
R
IN
=
V
S
=
15V
V
S
=
5V
Output Impedance vs Frequency
3dB Bandwidth vs
Load Resistance
LOAD RESISTANCE (
)
100
3dB BANDWIDTH (MHz)
20
18
16
14
12
10
8
6
1k
10k
1131 G05
V
S
=
15V
R
IN
= 100k
V
S
=
5V
Bias Voltage Range vs
Temperature
TEMPERATURE (
C)
50
BIAS VOLTAGE RANGE (V)
V
+
V
+
1
V
+
2
V
+2
V
+1
V
25
75
1311 G02
25
0
50
100
125
LOAD CURRENT (mA)
0.01
OUTPUT SATURATION VOLTAGE (V)
0.1
1
10
1311 G03
125
C
125
C
55
C
55
C
V
+
V
+
1
V
+
2
V
+2
V
+1
V
25
C
25
C
Output Saturation Voltage
vs Load Current
4
LT1311
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
0.1% Settling Time vs
Input Capacitance
SETTLING TIME (ns)
0
OUTPUT STEP (V)
10
8
6
4
2
0
2
4
6
8
10
1311 G07
400
100
200
300
500
1mV
1mV
10mV
10mV
0.1%
0.1%
V
S
=
15V
R
IN
= 20k
R
L
= 1k
A
V
= 1
CAPACITIVE LOAD (pF)
1
SETTLING TIME (ns)
240
230
220
210
200
190
180
170
160
150
140
10
100
1000
1311 G09
V
S
=
5V
V
OUT
= 2V STEP
R
IN
= 100k
R
L
= 1k
Settling Time to 0.1%, 1mV,10mV
vs Output Step
INPUT CAPACITANCE (pF)
0
SETTLING TIME (ns)
350
300
250
200
150
100
40
1311 G08
10
20
30
50
V
S
=
5V
V
OUT
= 2V STEP
R
IN
= 100k
R
L
= 1k
0.1% Settling Time vs
Capacitive Load
FREQUENCY (Hz)
100k
GAIN (dB)
PHASE SHIFT (DEG)
70
60
50
40
30
20
10
0
10
20
30
180
135
90
45
0
1M
10M
40M
1311 G10
V
S
=
5V
R
L
= 2k
A
V
= 1
A
V
= 10
A
V
= 100
A
V
= 100, R
IN
= 200
A
V
= 10, R
IN
= 2k
A
V
= 1, R
IN
= 20k
A
V
= 0.2, R
IN
= 100k
A
V
= 0.2
Gain and Phase vs Frequency
FREQUENCY (Hz)
100k
GAIN (dB)
8
9
10
11
12
13
14
15
16
17
18
1M
10M
40M
1311 G12
V
S
=
5V
R
IN
= 100k
R
L
= 2k
C
L
= 500pF
C
L
= 200pF
C
L
= 0pF
C
L
= 100pF
C
L
= 100pF
C
L
= 50pF
FREQUENCY (Hz)
100k
GAIN (dB)
8
9
10
11
12
13
14
15
16
17
18
1M
10M
40M
1311 G11
V
S
=
5V
R
IN
= 100k
R
L
= 2k
C
IN
= 50pF
C
IN
= 20pF
C
IN
= 10pF
C
IN
= 0pF
C
IN
= 1pF
C
IN
= 5pF
Frequency Response for
Various Input Capacitance
Frequency Response for Various
Capacitive Loads
Power Supply Rejection Ratio
vs Frequency
FREQUENCY (Hz)
POWER SUPPLY REJECTION RATIO (dB)
90
70
50
30
10
10
100k
1M
10M
1311 G13
10k
V
S
=
5V
A
V
= 1
R
L
=
POSITIVE
NEGATIVE
FREQUENCY (Hz)
0.001
TOTAL HARMONIC DISTORTION (%)
0.01
0.1
100
10k
100k
1311 G14
10
1k
V
S
=
15V
V
OUT
= 6.5V
RMS
A
V
= 1
V
S
=
5V
V
OUT
= 2V
RMS
A
V
= 1
Total Harmonic Distortion
vs Frequency
FREQUENCY (Hz)
10
13
12
11
10
9
8
7
6
5
4
3
100
i
n
e
n
1k
10k
1311 G15
VOLTAGE NOISE DENSITY (nV/
Hz)
CURRENT NOISE DENSITY (pA/
Hz)
Noise Spectrum
5
LT1311
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
V
S
=
5V
A
V
= 1
R
L
= 2k
1311 G16
V
S
=
15V
A
V
= 1
R
L
= 2k
1311 G17
Small-Signal Response
Large-Signal Response
SI PLIFIED SCHE ATIC
W
W
R1
1k
R2
2k
R3
2k
R4
2k
Q1
Q3
Q4
Q5
R5
1k
R6
4.5k
R11
1k
R12
2k
R13
2k
R14
2k
R15
1k
R16
4.5k
R9
1.5k
R10
1.5k
R22
10
R23
10
R20
1.5k
R19
1.5k
V
CC
OUT
V
EE
Q13
Q14
Q15
R
FB
20k
C1
5pF
C
C
2pF
C2
5pF
IN
BIAS
I
BIAS
PTAT
Q28
Q33
Q44
Q41
Q39
Q40
Q17
1311 SS
Q12
Q16
Q38
Q37
Q35
Q36
Q21
Q19
Q22
Q18
Q20
Q6
Q23
Q26
Q24
Q25
Q29
Q32
Q42
Q27
+
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