LT1311
Quad 12MHz, 145ns Settling
Precision Current-to-Voltage
Converter for Optical Disk Drives
FEATURES
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DESCRIPTION
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Four Complete Current-to-Voltage Converters
14-Lead Small Outline Package
Accurate Gain: 20mV/
µ
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
V
CC
10V
1 IN A
0.1µF
2
3 IN B
4 BIAS
5 IN C
6
7 IN D
+
–
OUT A
14
13
OUT B
12
C
IN
= 1pF
+
–
LT1311
+
–
C
IN
= 20pF
5V
11
OUT C
10
9
C
IN
= 50pF
+
–
OUT D
8
INPUT = 100µA STEP
V
S
=
±5V
1311 TA01
U
U
U
Transient Response
1311 TA02
1
LT1311
ABSOLUTE
MAXIMUM
RATINGS
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
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
T
JMAX
= 150°C,
θ
JA
= 160°C/ 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
V
S
= 10V, V
BIAS
= 5V, T
A
= 25°C, unless otherwise noted.
q
q
q
q
q
q
q
q
q
q
CONDITIONS
V
OUT
= 2V to 8V, R
L
= 2k to 5V
Between Amplifiers (∆G/20k)
×
100%
With Respect to V
BIAS
With Respect to V
BIAS
V
S
=
±15V,
V
BIAS
= 0V
(A + B) – (C + D)
Between Amplifiers
Pin 4
f = 1kHz
f = 1kHz
f = 1kHz, A
V
= 40dB
∆V
OS
/∆I
IN
, DC,
∆V
OUT
= 2V to 8V (I
IN
=
±150µA)
∆V
OS
/∆I
IN
, f = 10MHz
∆V
OUT
/∆V
BIAS
, V
BIAS
= 2V to 8V
V
BIAS
= 2V to 8V
f = 100kHz
V
S
=
±2V
to
±15V,
V
BIAS
= 0V
V
BIAS
= 2V
∆V
OUT
/∆V
OS
, V
OUT
= 2V to 8V, R
L
= 2k to 5V
Output High, No Load, I
IN
= – 250µA
Output High, I
SOURCE
= 10mA, I
IN
= – 250µA
Output Low, No Load, I
IN
= 250µA
Output Low, I
SINK
= 10mA, I
IN
= 250µA
I
OUT
= 0mA, f = 10MHz
I
IN
=
±200µA,
V
OUT
= 5V
I
IN
= 0
I
IN
=
±150µA,
V
OUT
at 3V, 7V
V
OS
∆V
OS
/∆T
i
n
e
n
PSRR
V
OUT
I
OUT
I
S
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/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
U
W
U
–
U
W W
W
LT1311
ELECTRICAL CHARACTERISTICS
SYMBOL
BW
t
r
, t
f
OS
t
S
THD
PARAMETER
Small-Signal Bandwidth
Full Power Bandwidth
Rise Time, Fall Time
Overshoot
Settling Time
Total Harmonic Distortion
Crosstalk
CONDITIONS
V
S
= 10V, V
BIAS
= 5V, T
A
= 25°C, unless otherwise noted.
MIN
TYP
12
10
65
35
0
145
210
0.004
110
MAX
UNITS
MHz
MHz
ns
ns
%
ns
ns
%
dB
V
OUT
= 2.5V
P-P
, R
IN
= 20k
10% to 90%, V
OUT
= 6V
P-P
, R
IN
= 20k
10% to 90%, V
OUT
= 100mV
P-P
, R
IN
= 20k
V
OUT
= 100mV
P-P
, R
IN
= 20k
∆V
OUT
= 2V, 0.1%, R
IN
= 20k
V
S
=
±15V, ∆V
OUT
= 10V, 0.1%, R
IN
= 20k
V
OUT
= 2V
RMS
, 20Hz to 20kHz, R
IN
= 20k
V
OUT
= 3V to 7V, R
L
= 2k to 5V, f = 100Hz,
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 PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
12
11
10
SUPPLY CURRENT (mA)
T
A
= 125°C
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 35
TOTAL SUPPLY VOLTAGE (V)
40
T
A
= –55°C
T
A
= 25°C
Short-Circuit Current
vs Temperature
90
20
18
SHORT-CIRCUIT CURRENT (mA)
80
–3dB BANDWIDTH (MHz)
OUTPUT IMPEDANCE (Ω)
70
60
50
40
30
–50 –25
V
S
=
±15V
I
IN
= 750µA
V
S
=
±
5V
I
IN
= 250µA
50
25
75
0
TEMPERATURE (°C)
U W
1311 G01
Bias Voltage Range vs
Temperature
V
+
Output Saturation Voltage
vs Load Current
V
+
125°C
V
+
–1
V
+
–2
–55°C
25°C
V
–
+2
V
–
+1
V
–
V
–
+2
V
–
+1
V
–
–55°C
125°C
25°C
0.1
1
LOAD CURRENT (mA)
10
1311 G03
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0.01
1311 G02
–3dB Bandwidth vs
Load Resistance
V
S
=
±15V
Output Impedance vs Frequency
100
R
IN
=
∞
16
V
S
=
±5V
14
12
10
8
R
IN
= 100k
6
100
10
V
S
=
±5V
1
V
S
=
±15V
0.1
100
125
1k
LOAD RESISTANCE (Ω)
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
V
S
=
±15V
R
IN
= 20k
R
L
= 1k
A
V
= –1
350
V
S
=
±5V
V
OUT
= 2V STEP
R
IN
= 100k
R
L
= 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
V
S
=
±5V
R
L
= 2k
A
V
= 1
A
V
= 100
A
V
= 10
A
V
= 100, R
IN
= 200Ω
A
V
= 10, R
IN
= 2k
A
V
= 0.2
180
135
90
45
0
–8
–9
–10
–11
GAIN (dB)
GAIN (dB)
GAIN (dB)
30
20
10
0
–10
–20
A
V
= 1, R
IN
= 20k
A
V
= 0.2, R
IN
= 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
V
S
=
±5V
A
V
= 1
R
L
=
∞
50
NEGATIVE
30
POSITIVE
10
–10
10k
100k
1M
FREQUENCY (Hz)
4
U W
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
V
S
=
±5V
V
OUT
= 2V STEP
R
IN
= 100k
R
L
= 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
V
S
=
±5V
R
IN
= 100k
R
L
= 2k
C
IN
= 50pF
C
IN
= 20pF
C
IN
= 10pF
–8
–9
–10
–11
–12
–13
–14
–15
–16
–17
40M
1311 G11
Frequency Response for Various
Capacitive Loads
V
S
=
±5V
R
IN
= 100k
R
L
= 2k
C
L
= 500pF
C
L
= 200pF
PHASE SHIFT (DEG)
–12
–13
–14
–15
–16
–17
–18
100k
C
L
= 100pF
C
IN
= 5pF
C
IN
= 1pF
C
IN
= 0pF
1M
10M
FREQUENCY (Hz)
C
L
= 50pF
C
L
= 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
V
S
=
±15V
V
OUT
= 6.5V
RMS
A
V
= –1
V
S
=
±5V
V
OUT
= 2V
RMS
A
V
= –1
10
100
10k
1k
FREQUENCY (Hz)
100k
1311 G14
i
n
e
n
0.001
10M
10
1k
100
FREQUENCY (Hz)
10k
1311 G15
LT1311
TYPICAL PERFORMANCE CHARACTERISTICS
Small-Signal Response
Large-Signal Response
V
S
=
±5V
A
V
= –1
R
L
= 2k
SI PLIFIED SCHE ATIC
V
CC
R1
1k
R2
2k
R3
2k
R4
2k
R5
1k
R6
4.5k
R9
1.5k
R10
1.5k
Q1
Q3
Q4
+
I
BIAS
PTAT
BIAS
Q20
Q12
Q13
Q14
R11
1k
R12
2k
R13
2k
U W
W
Q5
Q15
R14
2k
Q18
1311 G16
V
S
=
±15V
A
V
= –1
R
L
= 2k
1311 G17
W
Q23
Q6
Q24
Q28
C1
5pF
Q29
Q25
Q26
Q17
Q27
Q32
Q33
Q19
IN
Q21
R
FB
20k
C
C
2pF
R22
10Ω
OUT
R23
10Ω
Q42
Q22
Q39
C2
5pF
Q40
Q16
Q37
Q38
Q41
Q44
Q35
Q36
R15
1k
R16
4.5k
R19
1.5k
R20
1.5k
V
EE
1311 SS
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