LIA120 Optically Isolated Linear Error Amplifier Features * 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 * UL approval pending Applications * Power supply feedback * Telecom central office supply * Telecom bricks * Modern transformer replacement * Digital telephone isolation The LIA120 is very well suited for high gain feedback amplifiers that require excellent linearity and low temperature variation, like 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. Ordering Information Block Diagram DS-LIA120-R01.0 Description The LIA120 Optically Isolated Reference Amplifier uses Clare's linear optical coupler technology and the IX431 precision programmable shunt regulator to provide very linear high gain signals with excellent temperature stability for a total gain error of less than 2dB. By using a linear optocoupler, the LIA120 essentially eliminates temperature and gain variations due to current transfer ratio (CTR) changes in the optocouplers, increases the bandwidth up to 10X, and eases engineering design constraints. Part # LIA120S LIA120STR NC 1 8 LED (Input) K 2 7 COMP A 3 6 FB NC 4 5 GND www.clare.com Description 8 Pin Surface Mount (50/Tube) Tape and Reel (1000/Reel) 1 LIA120 Absolute Maximum Ratings (@ 25 C) Parameter Storage Temperature Operating Temperature Input Voltage Input DC Current Photodiode Cathode-Anode Voltage Photodiode Anode-Cathode Voltage Total Power Dissipation (note 1) 1 Symbol Ratings Units T -40 to +125 C T -40 to +85 C VLED 9 V ILED 20 mA VKAO 20 V VAKO 0.5 V PD 145 mW 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. Derate linearly from 25C at a rate of 2.42 mW/ C. Electrical Characteristics: Parameter Input Characteristics @ 25C LED forward voltage Reference voltage Deviation of VREF over temperature - See Note 1 Transfer Characteristics @ 25C Current transfer ratio (IKA/ILED) Current Transfer Ratio in Feedback (IREF/ILED) Current Transfer Ratio Matching (IKA/IREF) Feedback input current Deviation of IREF over temperature - See Note 1 Minimum drive current Off-state error amplifier current Error amplifier output impedance - See Note 2 Output Characteristics @ 25C Cathode dark current Cathode-Anode voltage breakdown Isolation Characteristics @ 25C Withstand insulation voltage Resistance (input to output) AC Characteristics @ 25C Bandwidth (LED) - See Note 4 Common mode rejection ratio - See Note 5 Linearity Conditions Symbol Min Typ Max Units ILED = 5 mA, VCOMP = VFB (Fig.1) VCOMP = VFB, ILED = 10 mA (Fig.1) TA = -40 to +85C TA = 25C TA = -40 to +85C VF 0.8 1.2 1.4 V 1.210 1.228 - 1.24 32 1.265 1.252 - mV VREF VREF (DEV) V ILED = 5 mA, VCOMP = VFB, VKA = 5 V (Fig. 4) ILED = 5mA, VREF = 0.5V (Fig.2) ILED = 5mA, VKA = 5.0V ILED = 10 mA, R1 = 10 k (Fig.2) TA = -40 to +85C VCOMP = VFB (Fig.1) VIN = 6 V, VFB = 0 (Fig.3) VCOMP = VFB, ILED = 0.1 mA to 15 mA, f<1 kHz K1 K2 K3 IREF IREF (DEV) ILED (MIN) I (OFF) IZOUTI 1.0 1.0 85 1 - 2 2 100 226 110 0.001 0.21 3.0 3.0 115 0.1 - % % % A A mA A Ohm VIN = Open, VKA = 10V (Fig. 3) ID = 1A IKAO BVKA 20 0.3 - 100 - nA V RH 50%, TA = 25C, t = 1 min (Note 3) VI-O = 500 VDC (Note 3) VISO RI-O 3750 - 1012 - Vrms ILED = 1.0 mA, RL = 100 k, f = 100 Hz (Fig. 5) ILED = 5 mA, 100 mVPP BW CMRR THD - 100 70 70 - kHZ dB 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 25C)} 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 fig. 9, |Zout| = K2R1 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. 2 www.clare.com Rev. 1.0 LIA120 ILED ILED 8 8 2 VF IREF 7 3 7 3 6 V 6 V 2 R1 VREF VREF 5 5 FIG. 2. IREF TEST CIRCUIT FIG. 1. VREF, VF, ILED (min) TEST CIRCUIT ILED IOFF 8 2 IKAO 8 VKA 10V 7 VIN 7 3 6 V ID 2 3 6 V VCOMP VREF 5 5 FIG. 3. IOFF IKAO TEST CIRCUIT FIG. 4. CTR TEST CIRCUIT VCC = +5V DC ILED R1 100K VOUT 1 8 2 7 3 6 4 5 _ VCM + 10VP-P Fig. 5 CMRR Test Circuit Rev. 1.0 www.clare.com 3 LIA120 VC 100 RL 1 8 2 7 + R1 VOUT + V in CC RC VOUT 3 6 - R2 - 4 5 Fig. 6 Power Supply Feedback Application Circuit VCC 1 8 2 7 100 V DD RB1 CC RC VOUT 3 Ri 6 RL Vi RB2 4 5 Fig. 7 Non-inverting Linear Amplifier Circuit 4 www.clare.com Rev. 1.0 LIA120 PERFORMANCE DATA* LIA120 LED Current vs. Cathode Voltage 10 5 0 -5 -10 0.5 1.0 1.5 -0.5 I(OFF) - Off Current (nA) IREF - Reference Current (A) 2.5 ILED = 10mA R1 = 10 k 300 250 200 150 100 50 -20 0 20 40 60 1.0 1.5 1.21 1.18 -40 -20 0 20 40 60 80 80 LIA120 LED Forward Current vs. Forward Voltage LIA120 Off Current vs. Ambient Temperature 20 VIN = 10V VFB = 0 2.0 1.5 1.0 0.5 0 -40 0.5 1.24 VCOMP - Cathode Voltage (V) LIA120 Reference Current vs. Ambient Temperature 350 0.0 1.37 100 -40 -20 0 20 40 60 80 100 85C 25C 0.0 VCOMP - Cathode Voltage (V) ILED = 10mA 55C -0.5 1.30 ILED - Forward Current (mA) -15 -1.0 150 120 90 60 30 0 -30 -60 -90 -120 -150 -1.0 VREF - Reference Voltage (V) ILED - Supply Current (A) ILED - Supply Current (mA) 15 LIA120 Reference Voltage vs. Ambient Temperature LIA120 LED Current vs. Cathode Voltage -5C 15 10 5 0 1.0 1.1 1.2 1.3 1.4 1.5 LIA120 Dark Current vs. Temperature LIA120 Cathode Current vs. Ambient Temperature 1400 VKA = 10V IK - Cathode Current (A) IKAO - Dark Current (nA) 50 ILED = 20mA 1000 30 20 10 0 -10 VKA = 5V 1200 40 -40 -20 0 20 40 60 80 800 600 ILED = 5mA 200 0 100 ILED = 10mA 400 ILED = 1mA -40 -20 0 20 40 60 80 100 (IKA/IF) - Current Transfer Ratio (%) VF - Forward-Voltage (V) 3.5 3.0 LIA120 Current Transfer Ratio vs LED Current VKA = 5V 2.5 2.0 1.5 1.0 0.5 0 0 10 20 30 40 50 ILED - Forward Current (mA) LIA120 Bandwidth vs. Temperature for High Frequency Applications ILED = 20mA ILED = 10mA ILED = 5mA 40 30 20 10 ILED = 1mA 0 1 2 3 4 5 6 7 8 9 10 0 0 10 20 30 40 50 60 VKA (V) 70 80 LIA120 Voltage Gain vs. Frequency 60 50 Voltage Gain, A(Vo/Vin) dB 500 450 400 350 300 250 200 150 100 50 0 Frequency (kHz) IK - Cathode Current (A) LIA120 Cathode Current vs. Photodiode Voltage 90 40 20 0 10 100 1000 Frenquency kHz *The Performance data shown in the graphs above is typical of device performance. For guaranteed parameters not indicated in the written specifications, please contact our application department. Rev. 1.0 www.clare.com 5 LIA120 PERFORMANCE DATA* LIA120 Noise Spectrum for 40dB Gain Setup (220K/2.2K Gain) 0.00E+00 -1.00E+01 -2.00E+01 -3.00E+01 -4.00E+01 -5.00E+01 -6.00E+01 -7.00E+01 -8.00E+01 -9.00E+01 -1.00E+02 1.0E+ 2.0E+ 3.0E+ 4.0E+ 5.0E+ 6.0E+ 7.0E+ 8.0E+ 9.0E+ 03 03 03 03 03 03 03 03 03 0 -20 E n ( dB m / H z ) Power (dB) LIA120 Output Linearity THD for 40dB Setup -40 -60 -80 -100 -120 -140 1.000E+02 1.000E+03 1.000E+04 1.000E+05 Frequency (Hz) Frequency (Hz) Input Spectrum at FB Output Spectrum *The Performance data shown in the graphs above is typical of device performance. For guaranteed parameters not indicated in the written specifications, please contact our application department. 6 www.clare.com Rev. 1.0 LIA120 The LIA120 The LIA120 is an optically isolated error amplifier. It incorporates three of the most common elements necessary to make an isolated power supply: a reference voltage, and error amplifier, and a linear optocoupler. It is functionally equivalent to the IX431 shunt regulator plus a linear optocoupler. Powering the isolated input The isolated input of the LIA120 is powered through the LED pin (pin 8) through the part to it's isolated ground. The typical operating current in the device is dictated by the output voltage and output current requirements, and the CTR of the linear optocoupler. The output voltage is typically constrained by the user, RL also affects the total gain, and CTR varies with process, but the nominal LED current should be around 1-2mA, and can be as high as 10mA-15mA if the user requires. The LED current is limited by a resistor in series with the LED pin to the supply and m is typically 10-100 ohms for operating currents of 1-2mA. The current limiting resistor, in conjunction with the LED voltage, and voltage headroommof the IX431 sets the minimum operating voltage of the isolated input to 2.74V plus the drop of the limiting resistor. Feedback Setting the gain for the LIA120 is accomplished simply by setting two resistors. The application circuit shows a resistor divider feeding the FB pin, so the operating conditions for the gain are governed by: K3 is taken from the datasheet as 1 nominally. The ac gain of the setup can be represented by: m m m Where: m * Gm = 1/ZKA which is ~ 3 Siemens * CTRFB is approximately CTRForward = 0.02 nominally CTRFB/CTRForward = K3 Rev. 1.0 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. 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 signals. In the localized optical feedback there are two poles m to consider, the IX431 dominant pole and the linear optical coupler pole. The open loop gain of the optical loop (for the application m 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 limited to typically <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 mlarge selection of R1 and R2. Therefore the compensation capacitor should not be less than 100pF which gives adequate bandwidth m for most designs. The bandwidth through the part will be: Where: P1 max is 1KHz (= 6.28Krad/s), due to the internal compensation of the IX431 CTR is the current transfer ratio of the feedback optocoupler (0.025 - 0.005) RLED is the combined impedance of the limiting resistor and the LED resistance (25 Ohms) Gm is transconductance of the IX431 (3 Siemens) However, since some of these elements vary over operating conditions and temperature, the bandwidth should be practically limited to <40KHz to avoid oscillations, which is the value computed by 100pF. www.clare.com 7 LIA120 Photodiode 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. Manufaturing Information Soldering Recommended soldering processes are limited to 245C component body temperature for 10 seconds. Washing Clare does not recommend ultrasonic cleaning or the use of chlorinated solvents. 8 www.clare.com Rev. 1.0 MECHANICAL DIMENSIONS PC Board Pattern (Top View) 8 Pin Surface Mount ("S" Suffix) Tape and Reel Packaging for 8 Pin Surface Mount Package 330.2 DIA. (13.00) Top Cover Tape Thickness 0.102 MAX. (0.004) W = 16.30 max (0.642 max) BO = 10.30 (0.406) Top Cover Tape Embossed Carrier Embossment K1 = 4.20 (0.165) K0 = 4.90 (0.193) P = 12.00 (0.472) AO = 10.30 (0.406) User Direction of Feed NOTE: Tape dimensions not shown, comply with JEDEC Standard EIA-481-2 Dimensions: mm (inches) For additional information please visit our website at: www.clare.com Clare, Inc. 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 Clare's Standard Terms and Conditions of Sale, Clare, Inc. 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 Clare's product may result in direct physical harm, injury, or death to a person or severe property or environmental damage. Clare, Inc. reserves the right to discontinue or make changes to its products at any time without notice. Specification: DS-LIA120-R01.0 (c)Copyright 2004, Clare, Inc. All rights reserved. Printed in USA. 11/15/04