FOD2711A Optically Isolated Error Amplifier

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1 FODA Optically Isolated Error Amplifier Features Optocoupler, precision reference and error amplifier in single package.4v ± % reference CTR % to %,V RMS isolation UL approval E9, Volume Applications Power supplies regulation DC to DC converters Description June The FODA Optically Isolated Amplifier consists of the popular AZ4L precision programmable shunt reference and an optocoupler. The optocoupler is a gallium arsenide (GaAs) light emitting diode optically coupled to a silicon phototransistor. The reference voltage tolerance is %. The current transfer ratio (CTR) ranges from % to %. 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 FODA, 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 dip white package. Functional Bock Diagram Package Outlines NC LED C FB E COMP NC 4 GND FODA Rev...

2 Pin Definitions Pin Number Pin Name Pin Description 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 Voltage 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 V FAN4 PWM Control V O FODA R R FODA 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 Value Units T STG Storage Temperature -4 to + C T OPR Operating Temperature -4 to + C T SOL Lead Solder Temperature for sec. C V LED Input Voltage. V I LED Input DC Current ma V CEO Collector-Emitter Voltage V V ECO Emitter-Collector Voltage V I C Collector Current ma PD Input Power Dissipation () 4 mw PD Transistor Power Dissipation () mw PD Total Power Dissipation () 4 mw Notes:. Derate linearly from C at a rate of.4mw/ C. Derate linearly from C at a rate of.4mw/ C.. Derate linearly from C at a rate of.4mw/ C. FODA Rev...

4 Electrical Characteristics (T A = C unless otherwise specified) Input Characteristics Symbol Parameter Test Conditions Min. Typ.* Max. Unit T = -4 to + C 4 mv V F LED Forward Voltage I LED = ma, V COMP = V FB (Fig. ). V V REF Reference Voltage V COMP = V FB, I LED = ma (Fig.) -4 C to + C..9 V C..4. V REF (DEV) Deviation of V REF Over Temperature (4) A V REF / V COMP Ratio of Vref Variation to the Output of the Error Amplifier I LED = ma, V COMP = V REF to V (Fig. ) mv/v I REF Feedback Input Current I LED = ma, R = kω (Fig. ).. µa I REF (DEV) Deviation of I REF Over T A = -4 C to + C.. µa Temperature (4) I LED (MIN) Minimum Drive Current V COMP = V FB (Fig. ) µa I (OFF) Off-State Error Amplifier Current V LED = V, V FB = (Fig. 4).. µa Z OUT Error Amplifier Output Impedance () V COMP = V FB, I LED =.ma to ma, f< khz). Ω Output Characteristics Symbol Parameter Test Conditions Min. Typ. Max. Unit I CEO Collector Dark Current V CE = V (Fig. ) na BV ECO Emitter-Collector Voltage Breakdown I E = µa V BV CEO Collector-Emitter Voltage Breakdown I C =.ma V Transfer Characteristics Symbol Parameter Test Conditions Min. Typ. Max. Unit CTR Current Transfer Ratio I LED = ma, V COMP = V FB, V CE = V (Fig. ) V CE (SAT) Collector-Emitter Saturation I LED = ma, V COMP = V FB, Voltage I C =.ma (Fig. ) %.4 V Notes: 4. The deviation parameters V REF(DEV) and I REF(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, V REF, is defined as: V REF ( ppm/ C) { V REF( DEV) /V REF ( T A = C) } = T A where T A is the rated operating free-air temperature range of the device.. The dynamic impedance is defined as Z OUT = V 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 = V Z I OUT + R R FODA Rev... 4

5 Electrical Characteristics (Continued) (T A = C unless otherwise specified) 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,. µa V I-O = VDC () V ISO Withstand Insulation Voltage RH %, T A = C, t = min. () Vrms R I-O Resistance (Input to Output) V I-O = VDC () Ω Switching Characteristics Symbol Parameter Test Conditions Min. Typ. Max. Unit BW Bandwidth (Fig. ) khz CMH Common Mode Transient I LED = ma, Vcm = V PP,. kv/µs Immunity at Output HIGH R L =.kω () (Fig. ) CML Common Mode Transient Immunity at Output LOW I LED = ma, Vcm = V PP, R L =.kω () (Fig. ). kv/µs Notes:. Device is considered as a two terminal device: Pins,, and 4 are shorted together and Pins,, and are shorted together.. 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. FODA Rev...

6 Test Circuits I (LED) V F V V REF Figure. V REF, V F, I LED (min.) Test Circuit I (LED) V I (LED) R V COMP R V REF Figure. V REF / V COMP Test Circuit I (OFF) V I REF R V V (LED) Figure. I REF Test Circuit Figure 4. I (OFF) Test Circuit I CEO I (LED) I C V CE V CE V V COMP V REF Figure. I CEO Test Circuit Figure. CTR, V CE(sat) Test Circuit FODA Rev...

7 Test Circuits (Continued) V CC = +V DC R L V OUT 4 I F = ma µf. V PP Figure. Frequency Response Test Circuit 4Ω V IN.4V V CC = +V DC I F = ma (A) I F = ma (B) R.kΩ V OUT A B 4 _ VCM + V P-P Figure. CMH and CML Test Circuit FODA Rev...

8 Typical Performance Curves VREF REFERENCE VOLTAGE (V) ILED SUPPLY CURRENT (ma) - - Fig. Reference Voltage vs. Ambient Temperature.44 ILED = ma Fig. 9a LED Current vs. Cathode Voltage T A = C V COMP = VFB V COMP CATHODE VOLTAGE (V) ILED SUPPLY CURRENT (ma) IREF REFERENCE CURRENT (na) - - Fig. 9b LED Current vs. Cathode Voltage T A = C VCOMP = VFB - - V COMP CATHODE VOLTAGE (V) Fig. Reference Current vs. Ambient Temperature 4 4 I LED = ma R = kω T A AMBIENT TEMPERATURE ( C) -4-4 T A AMBIENT TEMPERATURE ( C) Fig. Off-State Current vs. Ambient Temperature VCC =.V Fig. Forward Current vs. Forward Voltage IOFF OFF-STATE CURRENT (NA) IF FORWARD CURRENT (ma) C C C T A AMBIENT TEMPERATURE ( C) V F FORWARD VOLTAGE (V) FODA Rev...

9 Typical Performance Curves (Continued) ICEO DARK CURRENT (na) (IC/IF) CURRENT TRANSFER RATIO (%) Fig. 4 Dark Current vs. Ambient Temperature V CE = V T A AMBIENT TEMPERATURE ( C) Fig. Current Transfer Ratio vs. LED Current V CE = V C C C I LED FORWARD CURRENT (ma) VCE(SAT) SATURATION VOLTAGE (V) IC COLLECTOR CURRENT (ma) Fig. Collector Current vs. Ambient Temperature V CE = V I LED = ma I LED = ma I LED = ma I LED = ma 4 9 T A AMBIENT TEMPERATURE ( C) Fig. Saturation Voltage vs. Ambient Temperature T A AMBIENT TEMPERATURE ( C) Fig. Collector Current vs. Collector Voltage Fig. 9 Rate of Change Vref to Vcomp vs. Temperature IC COLLECTOR CURRENT (ma) T A = C I LED = ma I LED = ma I LED = ma I LED = ma 4 9 V CE COLLECTOR-EMITTER VOLTAGE (V) DELTA VREF / DELTA VCOMP ( mv/v) TEMPERATURE ( C) FODA Rev... 9

10 Typical Performance Curves (Continued) VOLTAGE GAIN (db) Fig. Voltage Gain vs. Frequency V CC = V I F = ma R L = kω R L = Ω R L = Ω. FREQUENCY (khz) FODA Rev...

11 The FODA The FODA 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 AZ4L shunt voltage regulator plus the CNYF- optocoupler. Powering the Secondary Side The LED pin in the FODA powers the secondary side, and in particular provides the current to run the LED. The actual structure of the FODA 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.4v +.V =.4V. 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 FODA attempts to regulate its FB pin to the reference voltage,.4v. The ratio of the two resistors should thus be: R TOP = R BOTTOM V OUT V REF The absolute value of the top resistor is set by the input offset current of.µa. To achieve % accuracy, the resistance of R TOP should be: V OUT > µa R TOP Compensation The compensation pin of the FODA 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.µf 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, 99. 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 FODA. 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 +V, the voltage feeding the collector pull-up is +V, and the PWM IC is the Fairchild KAH, which has a V reference. If we select a KΩ resistor for the LED, the maximum current the LED can see is: (V.4V) / kω = 9µA. The CTR of the opto-isolator is a minimum of %, and so the minimum collector current of the photo-transistor when the diode is full on is also 9µA. The collector resistor must thus be such that: V V < 9 µa or R R COLLECTOR >.4KΩ; COLLECTOR select kω to allow some margin. FODA Rev...

12 Package Dimensions Through Hole SEATING PLANE. (.).4 (.). (.). (.4) 4 Surface Mount.9 (9.9). (9.4). (.4) TYP PIN ID.. (.). (.). (.).4 (.4).4 (.9). (.). (.) MIN. (.4). (.) MAX. (.) TYP.4" Lead Spacing SEATING PLANE. (.).4 (.). (.). (.4) 4.9 (9.9). (9.4). (.4) TYP PIN ID. -Pin DIP Land Pattern. (.). (.). (.).4 (.4).4 (.9). (.).4 (.) MIN. (.4). (.) to.4 (.) TYP 4.9 (9.9). (9.4) PIN ID.. (.). (.). (.). (.). (.).4 (.4). (.) TYP.4 (.4).9 (.49). (.4). (.). (.) MIN. (.4). (.). (.). (.4). (.4) TYP Lead Coplanarity :.4 (.) MAX.4 (.4). (.) MIN.4 (.) MAX. Note: All dimensions are in inches (millimeters) FODA Rev...

13 Ordering Information Option Example Part Number Description No Option FODA Standard Through Hole S FODAS Surface Mount Lead Bend SD FODASD Surface Mount; Tape and Reel T FODAT.4" Lead Spacing V FODAV VDE4 TV FODATV VDE4;.4 Lead Spacing SV FODASV VDE4; Surface Mount SDV FODASDV VDE4; Surface Mount; Tape and Reel Marking Information A V XX YY B 4 Definitions Fairchild logo Device number VDE mark (Note: Only appears on parts ordered with VDE option See order entry table) 4 Two digit year code, e.g., Two digit work week ranging from to Assembly package code FODA Rev...

14 Carrier Tape Specifications D P P t K E F A W W B d User Direction of Feed P D Symbol Description Dimension in mm W Tape Width. ±. t Tape Thickness. ±. P Sprocket Hole Pitch 4. ±. D Sprocket Hole Diameter. ±. E Sprocket Hole Location. ±. F Pocket Location. ±. P 4. ±. P Pocket Pitch. ±. A Pocket Dimensions. ±. B. ±. K 4.9 ±. W Cover Tape Width. ±. d Cover Tape Thickness. max Max. Component Rotation or Tilt R Min. Bending Radius Reflow Profile Temperature ( C) 4 C, s C peak Time above C, < sec Ramp up = C/sec Time (Minute) Peak reflow temperature: C (package surface temperature) Time of temperature higher than C for seconds or less One time soldering reflow is recommended FODA Rev... 4

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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2711 DESCRIPTION FEATURES APPLICATIONS PIN DEFINITIONS 9/6/02

OPTICALLY ISOLATED ERROR AMPLIFIER FOD2711 DESCRIPTION FEATURES APPLICATIONS PIN DEFINITIONS 9/6/02 DESCRIPTION The Optically Isolated Amplifier consists of the popular RC4A precision programmable shunt reference and an optocoupler. The optocoupler is a gallium arsenide (GaAs) light emitting diode optically