LIA120 CLARE | Alldatasheet
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www.clare.comDS-LIA120-R02.0 1 LIA120 Optically Isolated Linear Error Amplifier Part # Description LIA120S 8 Pin Surface Mount (50/Tube) LIA120STR Tape and Reel (1000/Reel)
Applications
Ordering Information
- 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
- UL approval pending The LIA120 Optically Isolated Reference Amplifier combines Clare’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. 4 5
8 LED (Input)
K A NC
www.clare.com2 LIA120 Rev. 2.0 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 @ 25°C LED forward voltage ILED = 5 mA, VCOMP = VFB (Fig.1) VF 0.8 1.2 1.4 V Reference voltage ILED = 10 mA, VCOMP = VFB (Fig.1) TATAT = -40 to +85°C VREF Deviation of VREF over temperature - See Note 1 TATAT = -40 to +85°C VREF (DEV)REF (DEV) - 32 - mV Transfer Characteristics @ 25°C Current Transfer Ratio in Feedback (IREF/IREF/IREF LED) ILED = 5mA, VREF = 0.5V (Fig.2) K1 1.0 2 3.0 % Current transfer ratio (IKA/IKA/IKA LED) ILED = 5 mA, VCOMP = VFB, VKA = 5 V (Fig. 4) K2 1.0 2 3.0 % Current Transfer Ratio Matching (IKA/IKA/IKA REF) ILED = 5mA, VKA = 5.0V K3 85 100 115 % Feedback input current ILED = 10 mA, R1 = 10 kΩ (Fig.2) IREF - 226 - µA Deviation of IREF over temperature - See Note 1 TATAT = -40 to +85°C IREF (DEV)REF (DEV) - 110 - µA Minimum drive current VCOMP = VFB (Fig.1) ILED (MIN)LED (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 - Ohm Output Characteristics @ 25°C 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 @ 25°C Withstand insulation voltage RH ≤ 50%, TA 50%, TA 50%, T = 25°C, t = 1 min (Note 3) VISO 3750 - - Vrms Resistance (input to output) VI-O = 500 VDC (Note 3) RI-O - 1012 - Ω AC Characteristics @ 25°C Bandwidth (LED) - See Note 4 BW - 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 (TA (T 25°C)} X 106 / ∆TATAT where ∆TATAT is the rated operating free-air temperature range of the device. 2. The dynamic impedance is defined as |Z OUT| = ∆VCOMP/∆ILED, for the application circuit in Figure 6, |Zout| = K 1R1 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 VAKOVAKOV 0.5 V Input Voltage VLED 9 V Input DC Current ILED 20 mA Total Power Dissipation (note 1) PD 145 mW Operating Temperature T -40 to +85 °C Storage Temperature T -40 to +125 °C Absolute Maximum Ratings (@ 25˚ C) 1 Derate linearly from 25°C at a rate of 2.42 mW/ °C. , for the application circuit in Figure 6, |Zout| = K˜, for the application circuit in Figure 6, |Zout| = K
www.clare.com 3Rev. 2.0 FIG. 1. VREF, VF, ILED (MIN) TEST CIRCUIT FIG. 2. IREF TEST CIRCUIT FIG. 4. CTR TEST CIRCUITFIG. 3. IOFF, IKAO TEST CIRCUIT VCC = +5VDC VOUT VCM 10VPP 100K Fig. 5. CMRR Test Circuit ILED VF V VREF ILED V VREF ILED IREF VREF VKAVIN V 10V IOFF IKAO VCOMP V ILED IKA
www.clare.com4 LIA120 Rev. 2.0 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. LIA120 LED Current vs. Cathode Voltage VCOMP - Cathode Voltage (V) ILED - Supply Current (mA) -1.0 -10 -15 LIA120 LED Current vs. Cathode Voltage VCOMP - Cathode Voltage (V) ILED - Supply Current (µA) -1.0 150 120 -30 -60 -90 -120 -150 LIA120 Reference Voltage vs. Ambient Temperature VREF - Reference Voltage (V) -40 1.30 1.37 1.24 1.21 1.18 -20 0 20 40 60 8 0 ILED = 10mA LIA120 Reference Current vs. Ambient Temperature IREF - Reference Current (µA) -40 350 300 250 200 150 100 -20 0 20 40 60 8 0 100 ILED = 10mA R1 = 10 kΩ LIA120 Off Current vs. Ambient Temperature I(OFF) - Off Current (nA) -40 2.5 2.0 1.5 1.0 0.5 -20 0 20 40 60 8 0 100 VIN = 10V VFB = 0 LIA120 LED Forward Current vs. Forward Voltage ILED - Forward Current (mA) VF - Forward-Voltage (V) 85ºC 55ºC 25ºC -5ºC LIA120 Dark Current vs. Temperature IKAO - Dark Current (nA) VKA = 10V -40 -10 -20 0 2 0 4 0 6 0 8 0 100 LIA120 Cathode Current vs. Ambient Temperature IK - Cathode Current (µA) VKA = 5V ILED = 20mA ILED = 10mA ILED = 5mA ILED = 1mA -40 1400 1200 1000 800 600 400 200 -20 0 2 0 4 0 6 0 8 0 100 LIA120 Current Transfer Ratio vs LED Current (IKA/IF) - Current Transfer Ratio (%) ILED - Forward Current (mA) VKA = 5V 3.5 3.0 2.5 2.0 1.5 1.0 0.5 10 20 30 40 50 LIA120 Cathode Current vs. Photodiode Voltage IK - Cathode Current (µA) VKA (V) 500 450 400 350 300 250 200 150 100 1 2 3 4 5 6 7 8 9 1 0 ILED = 20mA ILED = 10mA ILED = 5mA ILED = 1mA LIA120 Bandwidth vs. Temperature for High Frequency Applications Frequency (kHz) 10 20 30 40 50 60 70 80 90 LIA120 Voltage Gain vs. Frequency Voltage Gain, A(Vo/Vin) dB Frenquency kHz 100 1000
www.clare.com 5Rev. 2.0 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. LIA120 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+ 2.0E+ 3.0E+ 4.0E+ 5.0E+ 6.0E+ 7.0E+ 8.0E+ 9.0E+ Frequency (Hz) )Bd( rewoP LIA120 Noise Spectrum for 40dB Gain Setup (220K/2.2K Gain) -140 -120 -100 -80 -60 -40 -20 1.000E+02 1.000E+03 1.000E+04 1.000E+05 Frequency (Hz) )zH/mBd( nE Input Spectrum at FB Output Spectrum
www.clare.com6 LIA120 Rev. 2.0 VC VCC Vin 100Ω VOUT VOUT VOUT RL RC CC Fig. 6. Power Supply Feedback Application Circuit Fig. 7. Non-inverting Linear Amplifier Circuit Vi VDD Ri RC CC RL 100Ω
www.clare.com 7Rev. 2.0 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 devices. 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 it’s 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: K3 is taken from the datasheet as 1 nominally. The ac gain of the setup can be represented by: 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. 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. 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. m m RL • K1 R1 1 VOUT VIN R1 R2CTRFB RLED Cc R1 R2 R1 R2 Vout, biasILED m m RL • K1 R1 1 VOUT VIN R1 R2CTRFB RLED Cc R1 R2 R1 R2 Vout, biasILED m m RL • K1 R1 1 VOUT VIN R1 R2CTRFB RLED Cc R1 R2 R1 R2 Vout, biasILED m m RL • K1 R1 1 VOUT VIN R1 R2CTRFB RLED Cc R1 R2 R1 R2 Vout, biasILED m m RL • K1 R1 1 VOUT VIN R1 R2CTRFB RLED Cc R1 R2 R1 R2 Vout, biasILED Where:
- Gm = 1/ZOUT which is ~ 3 SiemensOUT which is ~ 3 SiemensOUT
- CTRFB is approximately CTRForward = 0.02 nominally CTRFB = K1, CTRFORWARD = K2, CTRFORWARD/CTRFB = K3
www.clare.com8 LIA120 Rev. 2.0 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 245ºC component body temperature for 10 seconds. Washing Clare does not recommend ultrasonic cleaning or the use of chlorinated solvents.
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-R02.0 ©Copyright 2005, Clare, Inc. All rights reserved. Printed in USA. 2/17/05 For additional information please visit our website at: www.clare.com MECHANICAL DIMENSIONS PC Board Pattern (Top View) Dimensions: mm (inches) Tape and Reel Packaging for 8 Pin Surface Mount Package K0 = 4.90 (0.193) K1 = 4.20 (0.165) Top Cover Tape P = 12.00 (0.472) User Direction of Feed NOTE: Tape dimensions not shown, comply with JEDEC Standard EIA-481-2 Embossment Embossed Carrier Top Cover Tape Thickness 0.102 MAX. (0.004) 330.2 DIA. (13.00) AO = 10.30 (0.406) BO = 10.30 (0.406) W = 16.30 max (0.642 max)