FOD2742A, FOD2742B, FOD2742C Optically Isolated Error Amplifier

Transcription

1 FOD4A, FOD4B, FOD4C Optically Isolated Error Amplifier Features Optocoupler, precision reference and error amplifier in single package. reference CTR 100% to 00%,00 RMS isolation UL approval E9000, olume BSI approval 1, DE approval 11 CSA approval 1114 Low temperature coefficient 0 ppm/ C max. FOD4A: tolerance 0.% FOD4B: tolerance 1% FOD4C: tolerance % Applications Power supplies regulation DC to DC converters Schematic Description April 009 The FOD4 Optically Isolated Amplifier consists of the popular KA41 precision programmable shunt reference and an optocoupler. The optocoupler is a gallium arsenide (GaAs) light emitting diode optically coupled to a silicon phototransistor. It comes in grades of reference voltage tolerance = %, 1%, and 0.%. The Current Transfer Ratio (CTR) ranges from 100% to 00%. It also has an outstanding temperature coefficient of 0 ppm/ C. It is primarily intended for use as the error amplifier/reference voltage/optocoupler function in isolated ac to dc power supplies and dc/dc converters. When using the FOD4, power supply designers can reduce the component count and save space in tightly packaged designs. The tight tolerance reference eliminates the need for adjustments in many applications. The device comes in a -pin small outline package. Package Outline NC 1 LED C FB E COMP NC 4 GND FOD4A, FOD4B, FOD4C Rev

2 Pin Definitions Pin Number Pin Name Functional Description 1 NC Not connected C Phototransistor Collector E Phototransistor Emitter 4 NC Not connected GND Ground COMP Error Amplifier Compensation. This pin is the output of the error amplifier.* FB oltage Feedback. This pin is the inverting input to the error amplifier LED Anode LED. This pin is the input to the light emitting diode. *The compensation network must be attached between pins and. Typical Application 1 FAN40 PWM Control FOD4 R1 O R FOD4A, FOD4B, FOD4C Rev

3 Absolute Maximum Ratings (T A = C unless otherwise specified) Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Symbol Parameter alue Units T STG Storage Temperature -40 to +1 C T OPR Operating Temperature - to + C Reflow Temperature Profile (refer to 1) LED Input oltage I LED Input DC Current 0 ma CEO Collector-Emitter oltage 0 ECO Emitter-Collector oltage I C Collector Current 0 ma PD1 Input Power Dissipation (1) 14 mw PD Transistor Power Dissipation () mw PD Total Power Dissipation () 14 mw Notes: 1. Derate linearly from C at a rate of.4mw/ C. Derate linearly from C at a rate of 1.4mW/ C.. Derate linearly from C at a rate of.4mw/ C. FOD4A, FOD4B, FOD4C Rev

4 Electrical Characteristics (T A = C unless otherwise specified) Input Characteristics Symbol Parameter Test Conditions Device Min. Typ. Max. Unit F LED Forward oltage I LED = 10mA, COMP = FB (Fig. 1) All REF Reference oltage I LED = 10mA, COMP = FB (Fig. 1) A B C REF (DE) Deviation of REF Over Temperature T A = - C to + C (Fig. 1) All. 1 m RE COMP Ratio of REF ariation to the Output of the Error Amplifier I LED = 10mA (Fig. ) COMP = 10 to REF All m/ COMP = to I REF Feedback Input Current I LED = 10mA, R 1 = 10KΩ (Fig. ) All. 4 µa I REF (DE) Deviation of I REF Over T A = - C to + C (Fig. ) All µa Temperature I LED (MIN) Minimum Drive Current COMP = FB (Fig. 1) All ma I (OFF) Off-state Error Amplifier Current LED =, FB = 0 (Fig. 4) All µa Z OUT Error Amplifier Output Impedance (see note ) COMP = REF, I LED = 1mA to 0mA, f 1.0kHz All Ω Notes: 1. The deviation parameters REF(DE) and I REF(DE) 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, REF, is defined as: REF ( ppm/ C) { REF( DE) / REF ( T A = C) } 10 = T A where T A is the rated operating free-air temperature range of the device.. The dynamic impedance is defined as Z OUT = COMP / I LED. When the device is operating with two external resistors (see Figure ), the total dynamic impedance of the circuit is given by: Z OUT, TOT = Z I OUT 1 + R R FOD4A, FOD4B, FOD4C Rev

5 Electrical Characteristics (T A = C unless otherwise specified) (Continued) Output Characteristics Symbol Parameter Test Conditions Min. Typ. Max. Unit I CEO Collector Dark Current CE = 10 (Fig. ) 1 0 na B ECO Emitter-Collector oltage I E = 100µA 10 Breakdown B CEO Collector-Emitter oltage Breakdown I C = 1.0mA 0 10 Transfer Characteristics Symbol Parameter Test Conditions Min. Typ. Max. Unit CTR Current Transfer Ratio I LED = 10mA, COMP = FB, CE = (Fig. ) CE (SAT) Collector-Emitter I LED = 10mA, COMP = FB, Saturation oltage I C =.ma (Fig. ) Isolation Characteristics % Symbol Parameter Test Conditions Min. Typ. Max. Unit I I-O Input-Output Insulation Leakage Current RH = 4%, T A = C, t = s, I-O = 000 DC (Note 1) 1.0 µa ISO Withstand Insulation oltage RH 0%, T A = C, 00 rms t = 1 min. (Note 1) R I-O Resistance (Input to Output) I-O = 00 DC (Note 1) 10 1 Ω Switching Characteristics Symbol Parameter Test Conditions Min. Typ. Max. Unit B W Bandwidth Fig. 0 khz CMH Common Mode Transient I LED = 0mA, cm = 10 PP 1.0 k/µs Immunity at Output HIGH RL =.kω (Fig. ) (Note ) CML Common Mode Transient Immunity at Output LOW I LED = 10mA, cm = 10 PP RL =.kω (Fig. ) (Note ) 1.0 k/µs Notes: 1. Device is considered as a two terminal device: Pins 1,, and 4 are shorted together and Pins,, and are shorted together.. Common mode transient immunity at output high is the maximum tolerable (positive) dcm/dt on the leading edge of the common mode impulse signal, cm, to assure that the output will remain high. Common mode transient immunity at output low is the maximum tolerable (negative) dcm/dt on the trailing edge of the common pulse signal,cm, to assure that the output will remain low. FOD4A, FOD4B, FOD4C Rev

6 Test Circuits I (LED) F REF Figure 1. REF, F, I LED (min) Test Circuit I (LED) I REF R1 Figure. I REF Test Circuit I (LED) R1 COMP R REF Figure. REF/ COMP Test Circuit I (OFF) (LED) Figure 4. I (OFF) Test Circuit I CEO I (LED) I (C) CE CE COMP REF Figure. I CEO Test Circuit Figure. CTR, CE(sat) Test Circuit FOD4A, FOD4B, FOD4C Rev

7 Test Circuits (Continued) OUT CC = + DC R L CC = + DC R1.kΩ I F = 10 ma 0.1 PP Figure. Frequency Response Test Circuit 1µf I F = 0 ma (A) I F = 10 ma (B) 4Ω IN 0.4 OUT A B 4 _ CM + 10 P-P Figure. CMH and CML Test Circuit FOD4A, FOD4B, FOD4C Rev

8 Typical Performance Curves REF REFERENCE OLTAGE () ILED SUPPLY CURRENT (ma) Fig. 9a LED Current vs. Cathode oltage COMP CATHODE OLTAGE () T A = C COMP = FB Fig. 10 Reference oltage vs. Ambient Temperature I LED = 10mA T A AMBIENT TEMPERATURE ( C) ILED SUPPLY CURRENT (ma) IREF REFERENCE CURRENT (µa) T A = C COMP = FB Fig. 9b LED Current vs. Cathode oltage COMP CATHODE OLTAGE () Fig. 11 Reference Current vs Ambient Temperature I LED = 10mA R1 = 10kΩ T A AMBIENT TEMPERATURE( C) IOFF OFF-STATE CURRENT (na) Fig. 1 Off-State Current vs. Ambient Temperature LED = IF FORWARD CURRENT (ma) Fig. 1 Forward Current vs. Forward oltage C 0 C 0 C T A AMBIENT TEMPERATURE ( C) F FORWARD OLTAGE () FOD4A, FOD4B, FOD4C Rev

9 Typical Performance Curves (Continued) (IC/IF) CURRENT TRANSFER RATIO (%) ICEO DARK CURRENT (na) Fig. 14 Dark Current vs. Ambient Temperature 1000 CE = T A AMBIENT TEMPERATURE ( C) Fig. 1 Current Transfer Ratio vs. LED Current 10 CE = C C 10 0 C I LED FORWARD CURRENT (ma) IC COLLECTOR CURRENT (ma) CE(sat) SATURATION OLTAGE () Fig. 1 Collector Current vs. Ambient Temperature CE = I LED = 1mA T A AMBIENT TEMPERATURE ( C) I LED = 10mA I C =.ma I LED = 0mA I LED = 10mA I LED = ma Fig. 1 Saturation oltage vs. Ambient Temperature T A AMBIENT TEMPERATURE ( C) IC COLLECTOR CURRENT (ma) Fig. 1 Collector Current vs. Collector oltage T A = C 0 I LED = 0mA 0 I LED = 10mA 1 10 I LED = ma I LED = 1mA CE COLLECTOR-EMITTER OLTAGE () ref / out ( m/) Fig. 19 Rate of Change ref to out vs. Temperature TEMPERATURE ( C) FOD4A, FOD4B, FOD4C Rev

10 Typical Performance Curves (Continued) OLTAGE GAIN (db) CC = 10 I F = 10mA Fig. 0 oltage Gain vs. Frequency RL = 1kΩ RL = 100Ω RL = 00Ω FREQUENCY (khz) FOD4A, FOD4B, FOD4C Rev

11 The FOD4 The FOD4 is an optically isolated error amplifier. It incorporates three of the most common elements necessary to make an isolated power supply, a reference voltage, an error amplifier, and an optocoupler. It is functionally equivalent to the popular KA41 shunt voltage regulator plus the CNY1F-X optocoupler. Powering the Secondary Side The LED pin in the FOD4 powers the secondary side, and in particular provides the current to run the LED. The actual structure of the FOD4 dictates the minimum voltage that can be applied to the LED pin: The error amplifier output has a minimum of the reference voltage, and the LED is in series with that. Minimum voltage applied to the LED pin is thus = 4.0. This voltage can be generated either directly from the output of the converter, or else from a slaved secondary winding. The secondary winding will not affect regulation, as the input to the FB pin may still be taken from the output winding. The LED pin needs to be fed through a current limiting resistor. The value of the resistor sets the amount of current through the LED, and thus must be carefully selected in conjunction with the selection of the primary side resistor. Feedback Output voltage of a converter is determined by selecting a resistor divider from the regulated output to the FB pin. The FOD4 attempts to regulate its FB pin to the reference voltage,.. The ratio of the two resistors should thus be: R TOP = R BOTTOM OUT 1 REF The absolute value of the top resistor is set by the input offset current of.µa. To achieve 0.% accuracy, the resistance of R TOP should be: OUT > 1040µA R TOP Compensation The compensation pin of the FOD4 provides the opportunity for the designer to design the frequency response of the converter. A compensation network may be placed between the COMP pin and the FB pin. In typical low-bandwidth systems, a 0.1µF capacitor may be used. For converters with more stringent requirements, a network should be designed based on measurements of the system s loop. An excellent reference for this process may be found in Practical Design of Power Supplies by Ron Lenk, IEEE Press, 199. Secondary Ground The GND pin should be connected to the secondary ground of the converter. No Connect Pins The NC pins have no internal connection. They should not have any connection to the secondary side, as this may compromise the isolation structure. Photo-Transistor The Photo-transistor is the output of the FOD4. In a normal configuration the collector will be attached to a pull-up resistor and the emitter grounded. There is no base connection necessary. The value of the pull-up resistor, and the current limiting resistor feeding the LED, must be carefully selected to account for voltage range accepted by the PWM IC, and for the variation in current transfer ratio (CTR) of the opto-isolator itself. Example: The voltage feeding the LED pins is +1, the voltage feeding the collector pull-up is +10, and the PWM IC is the Fairchild KA1H00, which has a reference. If we select a 10K resistor for the LED, the maximum current the LED can see is: (1-4) /10KΩ = 00µA. The CTR of the opto-isolator is a minimum of 100%, so the minimum collector current of the photo-transistor when the diode is full on is also 00µA. The collector resistor must thus be such that: < 00 µa or R R COLLECTOR >.KΩ; COLLECTOR select 1KΩ to allow some margin. FOD4A, FOD4B, FOD4C Rev

12 Package Dimensions -pin SOIC Surface Mount SEATING PLANE 0.14 (.) 0.1 (.1) Recommended Pad Layout 0.01 (0.) (0.) 0.0 (.1) 0.1 (4.) Lead Coplanarity: (0.10) MAX (1.) Typ (4.1) (.) 0.00 (0.0) 0.00 (0.0) 0.04 (0.1) 0.44 (.19) 0.4 (.9) (0.) 0.00 (0.1) 0.00 (1.) 0. (.99) 0.1 (.94) 0.00 (1.) Dimensions in inches (mm). Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor s online packaging area for the most recent package drawings: FOD4A, FOD4B, FOD4C Rev

13 Ordering Information Option Order Entry Identifier Description DE 04 R R Tape and reel (00 units per reel) R R DE 04, Tape and reel (00 units per reel) Marking Information Definitions 1 X 4A YY 4 1 Fairchild logo Device number DE mark (Note: Only appears on parts ordered with DE option See order entry table) 4 One digit year code, e.g., Two digit work week ranging from 01 to Assembly package code S FOD4A, FOD4B, FOD4C Rev

14 Carrier Tape Specifications.0 ± ± ± MAX 4.0 ± ± MAX.40 ± 0.0 User Direction of Feed Dimensions in mm Ø1. MIN 1. ± ± ± 0..0 ± 0.0 Ø1. ± 0.1 FOD4A, FOD4B, FOD4C Rev

15 Reflow Profile Temperature ( C) TP TL Tsmax Tsmin Max. Ramp-up Rate = C/S Max. Ramp-down Rate = C/S Preheat Area Time C to Peak Time (seconds) Profile Freature Pb-Free Assembly Profile Temperature Min. (Tsmin) 10 C Temperature Max. (Tsmax) 00 C Time (t S ) from (Tsmin to Tsmax) 0 10 seconds Ramp-up Rate (t L to t P ) C/second max. Liquidous Temperature (T L ) 1 C Time (t L ) Maintained Above (T L ) 0 10 seconds ts tl tp Peak Body Package Temperature Time (t P ) within C of 0 C Ramp-down Rate (T P to T L ) Time C to Peak Temperature 0 C +0 C / C 0 seconds C/second max. minutes max. FOD4A, FOD4B, FOD4C Rev

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