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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2741A
DESCRIPTION
The FOD2741 Optically Isolated Amplifier consists of the popular KA431 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 3 grades of reference voltage tolerance = 2%, 1%, and 0.5%. The Current Transfer Ratio (CTR) ranges from 100% to 200%. It also has an outstanding temperature coefficient of 50 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 FOD2741, 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 8-pin dip white package.
8 1 8 1 8 1
FOD2741B
FOD2741C
FEATURES
Optocoupler, precision reference and error amplifier in single package 2.5V reference CTR 100% to 200% 5,000V RMS isolation UL approved E90700, Volume 2 CSA approval 1296837 VDE approval 40002463 BSI approval 8702, 8703 • Low temperature coefficient 50 ppm/°C max • FOD2741A: tolerance 0.5% FOD2741B: tolerance 1% FOD2741C: tolerance 2% • • • • •
FUNCTIONAL BLOCK DIAGRAM
NC
1
8 LED
C
2
7 FB
E
3
6 COMP
NC
4
5 GND
APPLICATIONS
• Power supplies regulation • DC to DC converters
PIN DEFINITIONS
Pin Number 1 2 3 4 5 6 7 8 Pin Name NC C E NC GND COMP FB LED Pin function description Not connected Phototransistor Collector Phototransistor Emitter Not connected Ground Error Amplifier Compensation. This pin is the output of the error amplifier. * Voltage Feedback. This pin is the inverting input to the error amplifier Anode LED. This pin is the input to the light emitting diode.
* The compensation network must be attached between pins 6 and 7.
© 2003 Fairchild Semiconductor Corporation
Page 1 of 15
4/14/03
OPTICALLY ISOLATED ERROR AMPLIFIER FOD2741A
TYPICAL APPLICATION
FOD2741B
FOD2741C
V1
FAN4803 PWM Control
VO
FOD2741 2 8
6
R1
3
7 R2
5
ABSOLUTE MAXIMUM RATINGS (TA = 25°C Unless otherwise specified.)
Parameter Storage Temperature Operating Temperature Lead Solder Temperature Input Voltage Input DC Current Collector-Emitter Voltage Emitter-Collector Voltage Collector Current Input Power Dissipation (note 1) Transistor Power Dissipation (note 2) Total Power Dissipation (note 3) Symbol TSTG TOPR TSOL VLED ILED VCEO VECO IC PD1 PD2 PD3 Value -55 to +125 -25 to +85 260 for 10 sec. 37 20 30 7 50 145 85 145 Units °C °C °C V mA V V mA mW mW mW
Notes 1. Derate linearly from 25°C at a rate of 2.42 mW/ °C 2. Derate linearly from 25°C at a rate of 1.42 mW/ °C. 3. Derate linearly from 25°C at a rate of 2.42 mW/ °C. 4. Functional operation under these conditions is not implied. Permanent damage may occur if the device is subjected to conditions outside these ratings.
© 2003 Fairchild Semiconductor Corporation
Page 2 of 15
4/14/03
OPTICALLY ISOLATED ERROR AMPLIFIER FOD2741A FOD2741B FOD2741C
ELECTRICAL CHARACTERISTICS (TA = 25°C Unless otherwise specified.) INPUT CHARACTERISTICS
Parameter LED Forward Voltage Test Conditions (ILED = 10 mA, VCOMP = VFB) (fig.1) ILED = 10 mA, VCOMP = VFB Symbol VF VREF Device ALL A Reference Voltage Deviation of VREF over temperature Ratio of VREF variation to the output of the error amplifier Feedback Input Current Deviation of IREF over temperature Minimum Drive Current Off-state error amplifier current Error amplifier output impedance (see note 2) ILED = 10 mA B C TA = -25°C to +85°C VREF (DEV) ∆VCOMP = 10V to VREF ∆VCOMP = 36V to 10V ∆VREF/ ∆VCOMP IREF IREF (DEV) ILED (MIN) I(OFF) |ZOUT| ALL ALL ALL ALL ALL ALL ALL 2.482 2.470 2.450 2.495 2.495 2.500 4.5 -1.0 -0.5 1.5 0.4 0.45 0.05 0.15 Min. Typ. Max. 1.5 2.508 2.520 2.550 17 -2.7 -2.0 4 1.2 1.0 1.0 0.5 Unit V V V V mV mV/ V µA µA mA µA Ω
ILED = 10mA, R1 = 10kΩ (fig 3) TA = -25°C to +85°C VCOMP = VFB (fig.1) VLED = 37V, VFB = 0 (fig 4.) VCOMP = VREF, ILED = 1mA to 20mA, f ≥ 1.0 kHz
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: { V REF ( DEV ) /V REF ( T A = 25°C ) } × 10 ∆ V REF ( ppm/°C ) = ---------------------------------------------------------------------------------------------------∆ TA where ∆TA is the rated operating free-air temperature range of the device. 2. The dynamic impedance is defined as |ZOUT| = ∆VCOMP/∆ILED. When the device is operating with two external resistors (see Figure 2), the total dynamic impedance of the circuit is given by: ∆V R1 Z OUT, TOT = ------- ≈ Z OUT × 1 + ------∆I R2
6
© 2003 Fairchild Semiconductor Corporation
Page 3 of 15
4/14/03
OPTICALLY ISOLATED ERROR AMPLIFIER FOD2741A FOD2741B FOD2741C
OUTPUT CHARACTERISTICS (TA = 25°C Unless otherwis.