INTEGRATED CIRCUITS DIVISION
www.ixysic.com
DS-LIA120-R04 1
LIA120
Optically Isolated
Linear Error Amplifier
Part # Description
LIA120S 8-Pin Surface Mount, Tubed (50/Tube)
LIA120STR 8-Pin Surface Mount, Tape and Reel (1000/Reel)
Applications
Features Description
Ordering Information
Block Diagram
• Power supply feedback
• Telecom central office supply
• Telecom bricks
• Modem transformer replacement
• Digital telephone isolation
• Optocoupler, precision reference and error amplifier
in single package
• Low voltage operation 2.7V
• 1.240V ± 2.5% reference
• CTR Matching 15%
• >70dB THD
• 70dB CMRR
• 3,750Vrms isolation
The LIA120 Optically Isolated Reference Amplifier
combines IXYS IC Division’s linear optical coupler
technology with an industry standard 431 type
precision programmable shunt regulator to provide
very linear high gain with excellent temperature
stability for a total gain error of less than 2dB. By using
optical feedback, the LIA120 essentially eliminates
temperature and gain variations due to current
transfer ratio (CTR) changes in optocouplers while
increasing the bandwidth up to 10X and easing
engineering design constraints.
The LIA120 is very well suited for high gain feedback
amplifiers that require excellent linearity and low
temperature variation such as isolated power
supply feedback stages, modem audio transformer
replacement, isolated industrial control signals, and
sensor feedback.
By using the LIA120, system designers can save
precious board space and reduce component count.
Available in an 8-pin surface mount package.
1
2
3
4 5
6
7
8 LED (Input)
FB
COMP
GND
NC
K
A
NC
Approvals
• UL 1577 Recognized Component: File E76270
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LIA120
Absolute Maximum Ratings are stress ratings. Stresses in
excess of these ratings can cause permanent damage to
the device. Functional operation of the device at conditions
beyond those indicated in the operational sections of this
data sheet is not implied.
Parameter Conditions Symbol Min Typ Max Units
Input Characteristics @ 25ºC
LED forward voltage ILED = 5 mA, VCOMP = VFB (Fig.1) VF0.8 1.2 1.4 V
Reference voltage ILED = 10 mA, VCOMP = VFB (Fig.1)
T
A = -40 to +85°C VREF
1.210 - 1.265 V
T
A = 25°C 1.228 1.24 1.252
Deviation of VREF over temperature - See Note 1 T
A = -40 to +85°C VREF (DEV) -32 - mV
Transfer Characteristics @ 25ºC
Current Transfer Ratio in Feedback (IREF/ILED)I
LED = 5mA, VREF = 0.5V (Fig.2) K11.0 2 3.0 %
Current transfer ratio (IKA/ILED)I
LED = 5 mA, VCOMP = VFB, VKA = 5 V (Fig. 4) K21.0 2 3.0 %
Current Transfer Ratio Matching (IKA/IREF)I
LED = 5mA, VKA = 5.0V K385 100 115 %
Feedback input current ILED = 10 mA, R1 = 10 kΩ (Fig.2) IREF - 226 - µA
Deviation of IREF over temperature - See Note 1 T
A = -40 to +85°C IREF (DEV) - 110 - µA
Minimum drive current VCOMP = VFB (Fig.1) ILED (MIN) 1- -mA
Off-state error amplifier current VIN = 6 V, VFB = 0 (Fig.3) IOFF - 0.001 0.1 µA
Error amplifier output impedance - See Note 2 ILED = 0.1 mA to 15 mA, VCOMP = VFB, f<1 kHz (Fig.1) IZOUTI - 0.21 -
Output Characteristics @ 25ºC
Cathode dark current VIN = Open, VKA = 10V (Fig. 3) IKAO - 0.3 100 nA
Cathode-Anode voltage breakdown IKA = 1µA BVKA 20 - - V
Isolation Characteristics @ 25ºC
Withstand insulation voltage RH ≤ 50%, T
A = 25°C, t = 1 min (Note 3) VISO 3750 - - Vrms
Resistance (input to output) VI-O = 500 VDC (Note 3) RI-O -10
12 -
AC Characteristics @ 25ºC
Bandwidth (LED) - See Note 4 -B
W- 100 - kHz
Common mode rejection ratio - See Note 5 ILED = 1.0 mA, RL=100 kΩ, f=100 Hz (Fig. 5) CMRR - 70 - dB
Linearity ILED = 5 mA, 100 mVPP THD - 70 - dB
1. The deviation parameters VREF(DEV) and IREF(DEV) are defined as the differences between the maximum and minimum values obtained over the rated temperature range. The average
full-range temperature coefficient of the reference input voltage, ∆VREF , is defined as:
|∆VREF| (ppm/°C) = {VREF (DEV)/VREF (TA 25°C)} X 106 / ∆TA
where ∆TA is the rated operating free-air temperature range of the device.
2. The dynamic impedance is defined as |ZOUT| = ∆VCOMP/∆ILED, for the application circuit in Figure 6, |Zout| = K1R1
3. Device is considered as a two terminal device: Pins 1, 2, 3 and 4 are shorted together and Pins 5, 6, 7 and 8 are shorted together.
4. See compensation section for calculating bandwidth of LIA120.
5. Common mode transient immunity at output high is the maximum tolerable (positive) dVcm/dt on the leading edge of the common mode impulse signal, Vcm, to assure that the output will
remain high. Common mode transient immunity at output low is the maximum tolerable (negative) dVcm/dt on the trailing edge of the common pulse signal,Vcm, to assure that the output will
remain low.
Electrical Characteristics:
Parameter Symbol Ratings Units
Photodiode Cathode-Anode Voltage VKAO 20 V
Photodiode Anode-Cathode Voltage VAKO 0.5 V
Input Voltage VLED 9V
Input DC Current ILED 20 mA
Total Power Dissipation (note 1) PD145 mW
Operating Temperature T -40 to +85 ºC
Storage Temperature T -40 to +125 ºC
Absolute Maximum Ratings (@ 25ºC)
1 Derate linearly from 25°C at a rate of 2.42 mW/ °C.
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LIA120
R1
FIG. 1. V
REF
, V
F
, I
LED
(MIN)
TEST CIRCUIT FIG. 2. I
REF
TEST CIRCUIT
FIG. 4. CTR TEST CIRCUIT
FIG. 3. I
OFF
, I
KAO
TEST CIRCUIT
V
CC
= +5VDC
V
OUT
VCM
10V
PP
R1
100K
+
_
Fig. 5. CMRR Test Circuit
I
LED
VF
2
3
5
6
7
8
V
VREF
ILED
2
3
5
6
7
8
V
VREF
ILED
IREF
VREF
VKA
VIN
2
3
5
6
7
8
V
10V
IOFF
IKAO
2
3
5
6
7
8
VCOMP
2
3
5
6
7
8
V
ILED
IKA
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LIA120
PERFORMANCE DATA*
*The Performance data shown in the graphs above is typical of device performance. For guaranteed parameters not indicated in the written specifi cations, please
contact our application department.
LED Current vs. Cathode Voltage
VCOMP - Cathode Voltage (V)
ILED - Supply Current (mA)
-1.0
15
10
5
0
-5
-10
-15 -0.5 0.0 0.5 1.0 1.5
TA=25ºC
VCOMP=VFB
LED Current vs. Cathode Voltage
VCOMP - Cathode Voltage (V)
ILED - Supply Current (PA)
-1.0
150
120
90
60
30
0
-30
-60
-90
-120
-150
-0.5 0.0 0.5 1.0 1.5
TA=25ºC
VCOMP=VFB
Reference Voltage vs.
Ambient Temperature
VREF - Reference Voltage (V)
-40
1.30
1.37
1.24
1.21
1.18
-20 0 20406080
ILED = 10mA
TA - Ambient Temperature (ºC)
Reference Current vs.
Ambient Temperature
IREF - Reference Current (PA)
-40
350
300
250
200
150
100
50 -20 0 20406080100
TA - Ambient Temperature (ºC)
ILED=10mA
R1=10k:
Off Current vs. Ambient Temperature
I(OFF) - Off Current (nA)
-40
2.5
2.0
1.5
1.0
0.5
0
-20 0 20406080100
VIN=10V
VFB=0
TA - Ambient Temperature (ºC)
LED Forward Current
vs. Forward Voltage
ILED - Forward Current (mA)
VF - Forward-Voltage (V)
20
15
10
5
0
1.0 1.1 1.2 1.3 1.4 1.5
85ºC
55ºC
25ºC
-5ºC
Dark Current vs. Temperature
IKAO - Dark Current (nA)
VKA=10V
-40
50
40
30
20
10
0
-10 -20 0 20406080100
TA - Ambient Temperature (ºC)
Cathode Current
vs. Ambient Temperature
IK - Cathode Current (PA)
VKA=5V
ILED=20mA
-40
1400
1200
1000
800
600
400
200
0
-20 0 20406080100
TA - Ambient Temperature (ºC)
ILED=10mA
ILED=5mA
ILED=1mA
Current Transfer Ratio
vs LED Current
(IKA / IF) - Current Transfer Ratio (%)
ILED - Forward Current (mA)
VKA=5V
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
10 20 30 40 50
TA=-5ºC
TA=25ºC
TA=55ºC
TA=85ºC
Cathode Current
vs. Photodiode Voltage
IK - Cathode Current (PA)
VKA (V)
0
500
450
400
350
300
250
200
150
100
50
0
12345678910
ILED=20mA
ILED=10mA
ILED=5mA
ILED=1mA
TA=25ºC
Bandwidth vs. Temperature for
High Frequency Applications
Frequency (kHz)
0
50
40
30
20
10
0
10 20 30 40 50 60 70 80 90
Temperature (ºC)
Voltage Gain vs. Frequency
Voltage Gain, A(Vo/Vin) dB
Frequency (kHz)
10
60
40
20
0
100 1000
RL=100:
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LIA120
PERFORMANCE DATA*
*The Performance data shown in the graphs above is typical of device performance. For guaranteed parameters not indicated in the written specifi cations, please
contact our application department.
Output Linearity
THD for 40dB Setup
-1.00E+02
-9.00E+01
-8.00E+01
-7.00E+01
-6.00E+01
-5.00E+01
-4.00E+01
-3.00E+01
-2.00E+01
-1.00E+01
0.00E+00
1.0E+
03 2.0E+
03 3.0E+
03 4.0E+
03 5.0E+
03 6.0E+
03 7.0E+
03 8.0E+
03 9.0E+
03
Frequency (Hz)
)Bd ( rew oP
Noise Spectrum for 40dB Gain Setup
(220K/2.2K Gain)
-140
-120
-100
-80
-60
-40
-20
0
1.000E+02 1.000E+03 1.000E+04 1.000E+05
Frequency (Hz)
)zH /mBd( nE
Input Spectrum at FB
Output Spectrum
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6R04
LIA120
V
C
V
CC
V
in
100 Ω
V
OUT
+
V
OUT
V
OUT
R
L
R
1
R
C
C
C
R
2
Fig. 6. Power Supply Feedback Application Circuit
Fig. 7. Non-inverting Linear Amplifier Circuit
V
i
V
DD
R
i
R
2
R
1
R
C
C
C
R
L
+
–
–
100 Ω
2
3
5
6
7
8
2
3
5
6
7
8
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R04
LIA120
The LIA120
The LIA120 is an optically-coupled isolated linear error
amplifier. It integrates three of the most fundamental
elements necessary to make an isolated power supply:
a reference voltage, an error amplifier, and an isolated
coupling device. It is functionally equivalent to a 431
type shunt regulator plus a linear optical amplifier.
Powering the Isolated Input
The isolated input of the LIA120 is powered through
the LED pin (pin 8) via the part to its isolated
ground at pin 5. The typical operating current of
the device is determined by the output voltage and
current requirements as well as the CTR of the
linear optocoupler. For Figure 7, the LED current
requirement is set by the following equation.
The output voltage is typically constrained by the user
to satisfy the design requirements of the application
circuit. Design considerations must also take into
account that RL affects the total gain and that CTR
gains vary with process. Nominally the LED current
should be around 1-2mA but can be as high as
10-15mA if the user requires.
LED current is limited by the resistor in series with pin
8, the LED pin, to the supply and is typically 10-100
ohms for operating currents of 1-2mA. The minimum
operating voltage of 2.74V for the LIA120 from pin 8
to pin 5 is based on the sum of the voltage drop of the
LED and the operational voltage headroom of the 431.
Minimum operating voltage for the application circuit
is therefore the sum of the LIA120 minimum operating
voltage plus the voltage drop of the current limiting
resistor For a design with 1mA of LED current and
a current limiting resistor of 100 ohms, the minimum
operating voltage is calculated to be 2.74 + (0.001)
(100) = 2.84V.
Feedback
Setting the gain for the LIA120 is accomplished simply
by setting two resistors. The application circuit in
Figure 6 shows a resistor divider feeding the FB pin,
so the operating conditions for the gain are governed
by:
ILED = Vout,bias
RL K1
R1
R2
Vin
Vref Vref
Vout R1
RL
1
K3
-1
=
-
Compensation
The LIA120 is relatively easy to compensate but two
factors must be considered when analyzing the circuit.
The frequency response of the LIA120 can be as
high as 40kHz, but must be limited because of the
closed loop optical feedback to the input signal. In
the localized optical feedback there are two poles to
consider, the 431 dominant pole and the linear optical
coupler pole. The open loop gain of the optical loop
(for the application diagram) is:
The open loop gain is affected by the selection of R1
and R2, and without any compensation the circuit may
oscillate. The addition of a compensation network (Cc
and Rc) control the maximum bandwidth so that open
loop gain is rolling off long before the optical pole
causes the circuit to oscillate. The optical pole is at
~180kHz so the bandwidth is typically limited to less
than 40kHz.
While there is flexibility in the part to change the
compensation technique, the upper limit on frequency
response is generally desired to be such that the
circuit will not oscillate for a large selection of R1 and
R2. Therefore the compensation capacitor should not
be less than 100pF, which gives adequate bandwidth
for most designs.
This calculation provides a more accurate gain
calculation, but is only necessary when the voltage
divider resistor’s impedance is becoming close to the
optical output impedance of the shunt regulator.
K3 is taken from the datasheet as 1 nominally. The AC
gain of the setup can be represented by:
Where:
• Gm = 1/ZOUT which is ~ 3 Siemens
• CTRFB is approximately CTRForward = 0.02 nominally
CTRFB = K1, CTRFORWARD = K2, CTRFORWARD/CTRFB = K3
AVVOUT /VIN =RL
R1
R2R1GmCTRFB
1
GmCTRForward
1
Av, OPTICAL =Gm CTRFB
R1R2
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LIA120
Photodiode
The bandwidth through the part will be:
Where:
P1 max is 1kHz (6.28krad/s) due to the internal
compensation of the 431.
CTR is the current transfer ratio of the feedback
optocoupler (0.001-0.003).
RLED is the combined impedance of the limiting
resistor and the LED resistance (25 ohms) and Gm is
the transconductance of the 431 (3 Siemens).
However, since some of these elements vary over
operating conditions and temperature, the bandwidth
should be practically limited to less than 40kHz to
avoid oscillations, which is the value computed by
100pF.
BW Hz =Gm CTRFB
R1R2
*P5LED&C51 R2 + 1
P1
< BW Hz MAX
The output of the LIA120 is a photodiode capable or
withstanding high voltages. For the most accurate
results, attempt to bias the voltage across the cathode
anode the same as VREF . The load resistors can be
placed in series with the cathode or anode for desired
output polarity.
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LIA120
Manufacturing Information
Moisture Sensitivity
All plastic encapsulated semiconductor packages are susceptible to moisture ingression. IXYS Integrated
Circuits Division classified all of its plastic encapsulated devices for moisture sensitivity according to
the latest version of the joint industry standard, IPC/JEDEC J-STD-020, in force at the time of product
evaluation. We test all of our products to the maximum conditions set forth in the standard, and guarantee proper
operation of our devices when handled according to the limitations and information in that standard as well as to any
limitations set forth in the information or standards referenced below.
Failure to adhere to the warnings or limitations as established by the listed specifications could result in reduced
product performance, reduction of operable life, and/or reduction of overall reliability.
This product carries a Moisture Sensitivity Level (MSL) rating as shown below, and should be handled according
to the requirements of the latest version of the joint industry standard IPC/JEDEC J-STD-033.
Device Moisture Sensitivity Level (MSL) Rating
LIA120S MSL 1
ESD Sensitivity
This product is ESD Sensitive, and should be handled according to the industry standard JESD-625.
Reflow Profile
This product has a maximum body temperature and time rating as shown below. All other guidelines of J-STD-020
must be observed.
Device Maximum Temperature x Time
LIA120S 250ºC for 30 seconds
Board Wash
IXYS Integrated Circuits Division recommends the use of no-clean flux formulations. However, board washing to
remove flux residue is acceptable. Since IXYS Integrated Circuits Division employs the use of silicone coating as
an optical waveguide in many of its optically isolated products, the use of a short drying bake could be necessary
if a wash is used after solder reflow processes. Chlorine- or Fluorine-based solvents or fluxes should not be used.
Cleaning methods that employ ultrasonic energy should not be used.
INTEGRATED CIRCUITS DIVISION
For additional information please visit our website at: www.ixysic.com
LIA120
10
IXYS Integrated Circuits Division makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication and reserves the right to make
changes to specifications and product descriptions at any time without notice. Neither circuit patent licenses nor indemnity are expressed or implied. Except as set forth in IXYS Integrated
Circuits Division’s Standard Terms and Conditions of Sale, IXYS Integrated Circuits Division assumes no liability whatsoever, and disclaims any express or implied warranty, relating to
its products including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or infringement of any intellectual property right.
The products described in this document are not designed, intended, authorized or warranted for use as components in systems intended for surgical implant into the body, or in other
applications intended to support or sustain life, or where malfunction of IXYS Integrated Circuits Division’s product may result in direct physical harm, injury, or death to a person or severe
property or environmental damage. IXYS Integrated Circuits Division reserves the right to discontinue or make changes to its products at any time without notice.
Specification: DS-LIA120-R04
©Copyright 2013, IXYS Integrated Circuits Division
All rights reserved. Printed in USA.
12/9/2013
LIA120S
LIA120STR Tape & Reel
Dimensions
mm
(inches)
PCB Land Pattern
2.540 ± 0.127
(0.100 ± 0.005)
9.652 ± 0.381
(0.380 ± 0.015)
6.350 ± 0.127
(0.250 ± 0.005)
9.525 ± 0.254
(0.375 ± 0.010)
0.457 ± 0.076
(0.018 ± 0.003)
0.813 ± 0.102
(0.032 ± 0.004)
4.445 ± 0.127
(0.175 ± 0.005)
7.620 ± 0.254
(0.300 ± 0.010)
0.635 ± 0.127
(0.025 ± 0.005)
0.254 ± 0.0127
(0.010 ± 0.0005)
2.54
(0.10)
8.90
(0.3503)
1.65
(0.0649)
0.65
(0.0255)
3.302 ± 0.051
(0.130 ± 0.002)
Pin 1
Dimensions
mm
(inches)
User Direction of Feed
NOTES:
1. Dimensions carry tolerances of EIA Standard 481-2
2. Tape complies with all “Notes” for constant dimensions listed on page 5 of EIA-481-2
Embossment
Embossed Carrier
Top Cover
Tape Thickness
0.102 MAX.
(0.004 MAX.)
330.2 DIA.
(13.00 DIA.)
K1
=4.20
(0.165)
0
K =4.90
(0.193)
P=12.00
(0.472)
W=16.00
(0.63)
Bo=10.30
(0.406)
Ao=10.30
(0.406)
Mechanical Dimensions
Mouser Electronics
Authorized Distributor
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