FOD2711S Datasheet FOD2711, FOD2711S, FOD2711V | P1-P3

9/6/02

OPTICALLY ISOLATED

ERROR AMPLIFIER

Page 1 of 14

FOD2711

DESCRIPTION

The FOD2711 Optically Isolated Ampliﬁer consists of the popular RC431A 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 1%. The current transfer ratio (CTR) ranges from 100% to 200%.

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 FOD2711, 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.

FEATURES

• Optocoupler, precision reference and error ampliﬁer in single package

• 1.240V ± 1% reference

• CTR 100% to 200%

• 5,000V RMS isolation

• UL approval E90700, Volume 2

CSA approval 1296837

VDE approval 40002463

BSI approval 8702, 8703

APPLICATIONS

• Power supplies regulation

• DC to DC converters

* The compensation network must be attached between pins 6 and 7.

PIN DEFINITIONS

Pin Number Pin Name Pin function description

1 NC Not connected

2 C Phototransistor Collector

3 E Phototransistor Emitter

4 NC Not connected

5 GND Ground

6 COMP Error Ampliﬁer Compensation. This pin is the output of the error ampliﬁer. *

7 FB Voltage Feedback. This pin is the inverting input to the error ampliﬁer

8 LED Anode LED. This pin is the input to the light emitting diode.

8

1

8

1

FUNCTIONAL BLOCK DIAGRAM

1

2

3

4 5

6

7

8

LED

FB

COMP

GND

NC

C

E

NC

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Page 2 of 14

OPTICALLY ISOLATED

ERROR AMPLIFIER

FOD2711

TYPICAL APPLICATION

V

O

V

1

R1

R2

2

3

8

6

7

5

PWM

Control

FAN4803

FOD2711

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.

ABSOLUTE MAXIMUM RATINGS

(T

A

= 25°C Unless otherwise speciﬁed.)

Parameter Symbol Value Units

Storage Temperature T

STG

-55 to +125 °C

Operating Temperature T

OPR

-40 to +85 °C

Lead Solder Temperature T

SOL

260 for 10 sec. °C

Input Voltage V

LED

13.2 V

Input DC Current I

LED

20 mA

Collector-Emitter Voltage V

CEO

30 V

Emitter-Collector Voltage V

ECO

7V

Collector Current I

C

50 mA

Input Power Dissipation (note 1) PD1 145 mW

Transistor Power Dissipation (note 2) PD2 85 mW

Total Power Dissipation (note 3) PD3 145 mW

9/6/02

Page 3 of 14

OPTICALLY ISOLATED

ERROR AMPLIFIER

FOD2711

1. 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:

where

∆

T

A

is the rated operating free-air temperature range of the device.

2. The dynamic impedance is deﬁned as |Z

OUT

| =

∆

V

COMP

/

∆

I

LED

. When the device is operating with two external resistors (see

Figure 2), the total dynamic impedance of the circuit is given by:

ELECTRICAL CHARACTERISTICS

(T

A

= 25°C Unless otherwise speciﬁed.)

INPUT CHARACTERISTICS

Parameter Test Conditions Symbol Min Typ** Max Unit

LED forward voltage (I

LED

= 10 mA, V

COMP

= V

FB

)(Fig.1) V

F

1.5 V

Reference voltage

(-40 to +85°C) (V

COMP

= V

FB

, I

LED

= 10 mA (Fig.1)

V

REF

1.221 1.259

V

(25°C) 1.228 1.240 1.252

Deviation of V

REF

over temperature - See Note 1

(T

A

= -40 to +85°C) V

REF (DEV)

4 12 mV

Ratio of Vref variation

to the output of the error ampliﬁer

(I

LED

= 10 mA,

V

COMP

= V

REF

to 12 V) (Fig.2)

∆

V

REF

/

∆

V

COMP

-1.5 -2.7 mV/V

Feedback input current (I

LED

= 10 mA, R1 = 10 k

Ω

) (Fig.3) I

REF

0.15 0.5 µA

Deviation of I

REF

over temperature - See Note 1

(T

A

= -40 to +85°C) I

REF (DEV)

0.15 0.3 µA

Minimum drive current (V

COMP

= V

FB

) (Fig.1) I

LED (MIN)

55 80 µA

Off-state error ampliﬁer current (V

LED

= 13.2 V, V

FB

= 0) (Fig.4) I

(OFF)

0.001 0.1 µA

Error ampliﬁer

output impedance - See Note 2

(V

COMP

= V

FB

, I

LED

= 0.1 mA to 15 mA,

f<1 kHZ)

|Z

OUT

| 0.25 Ohm

∆V

REF

ppm/°C()

V

REF DEV()

/V

REF

T

A

25°C=(){}10

6

×

∆T

A

-----------------------------------------------------------------------------------------------------=

Z

OUT, TOT

=

∆V

∆I

--------Z

OUT

1

R1

R2

--------+×≈

FOD2711S

FOD2711S

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