SGS Thomson Microelectronics TEA2018A Datasheet

POWER SUPPLY CONTROLCIRCUIT

.

DIRECT DRIVE OF THE EXTERNAL
SWITCHING TRANSISTOR

.

POSITIVE AND NEGATIVE OUTPUT CUR­RENTSUP TO 0.5 A

.

CURRENT LIMITATION

.

TRANSFORMER DEMAGNETIZATION
SENSING

.

FULL OVERLOAD AND SHORT-CIRCUIT
PROTECTION

.

PROPORTIONALBASECURRENT DRIVING

.

LOW STANDBY CURRENT BEFORE START­ING (< 1.6 mA)

.

THERMAL PROTECTION

DESCRIPTION

The TEA2018Aisan 8-pin DIP low-cost integrated
circuit designed for the control of switch mode
power supplies.

Due to its current mode regulation,the TEA2018A
facilitates design of power supplies with following
features :

.

High stability regulationloop

.

Automatic input voltage feed-forward in dis­continuousmode fly-back

.

Automaticpulse-by-pulsecurrent limitation
Typical applications: VideoDisplayUnits, TVsets,
typewriters,microcomputersandindustrialapplica­tions

Where synchronization is required, use the
TEA2019. For more details, see application
note AN406/0591

TEA2018A

CURRENT MODE SWITCHING

DIP8

(Plastic Package)

ORDER CODE : TEA2018A

PINCONNECTIONS

OSCILLATOR

COLLECTOR CURRENT SENSING

NEGATIVE SUPPLY VOLTAGE

May 1993

GROUND

1
2
3
4

8

ERROR AMPLIFIER NON-INVERTING INPUT

7

DEMAGNETIZATION SENSING

6

POSITIVE SUPPLY VOLTAGE

5

OUTPUT

2018A-01.EPS

1/7

TEA2018A

BLOCK DIAGRAM

TEA2018A

7

I

S

DEMAGNETIZATION

SENSING

INTERNAL

BIAS

V

CC

”Good”

V

CC

6

V

CC

MONITORING

V

REF

2.4V

Undervoltage0.1V

2.4V

OSCILLATOR1

MAXIMUM

DUTYCYCLE

70%

COMPARATOR

G ≅ 50

-1V

VOLTAGE

LIMITATION

I

SENSE

&

FLIP-FLOP

&

1

THERMAL

SHUTDOWN

3

GROUND

Ic

RECOPY

DELAY

500ns

5

OUTPUT

1

42

V

CC

RC

tt

8

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

+ Positive Supply Voltage 15 V

CC

V

- Negative Supply Voltage -5 V

CC

I

(peak) Peak Output Current (duty cycle < 5%) ±1A

O

I

I

T

T

oper

T

stg

Input Current (Pin 3) ±5mA
Junction Temperature +150

j

Operating Ambient Temperature Range -20, +70
Storage Temperature Range -40, +150

o

C

o

C

o

C

2018A-02.EPS

2018A-01.TBL

THERMALDATA

Symbol Parameter Value Unit

R

th (j-a)

Junction-ambient Thermal Resistance 80

o

ELECTRICAL OPERATINGCHARACTERISTICS

=25oC, potentials referenced to ground (unless otherwise specified) (see testcircuit)

T

amb

Symbol Parameter Min. Typ. Max. Unit

V

+ Positive Supply Voltage 6.6 8 15 V

CC

V

- Negative Supply Voltage -1 -3 -5 V

CC

2/7

V

CC(start)

V

CC(stop)

Minimum Positive Supply Voltage required for starting (VCC+ rising) 6 6.6 V
Minimum Positive Voltage below wich device stopsoperating (VCC+ falling) 4.2 4.9 5.6 V

C/W

2018A-02.TBL

2018A-03.TBL

TEA2018A

ELECTRICAL OPERATINGCHARACTERISTICS

=25oC, potentials referenced to ground (unless otherwise specified) (see testcircuit)

T

amb

Symbol Parameter Min. Typ. Max. Unit

∆V

+ Hysteresis on VCC+ Threshold 0.7 1.1 1.6 V

CC

I

CC(sb)

V

th(IC)

R

V

τ

max

A
I

V

∆V

∆T

t

OSC

∆f

∆T

∆f

∆V

t

on(min)

Stand-by Supply Current before starting (VCC+<V

) 1 1.6 mA

CC(start)

Current Limitation Threshold Voltage (Pin 3) -1100 -1000 -880 mV
Collector Current Sensing Input Resistance 1000 Ω

(IC)

Demagnetization Sensing Threshold 75 100 125 mV

7(th)

I

Demagnetization Sensing Input Current (Pin7 = 0V) 1 µA

S

Maximum Duty Cycle 60 70 %
ErrorAmplifier Gain 50

V

+ Error Amplifier Input Current (non-inverting input) 2 µA

I

Internal Reference Voltage 2.3 2.4 2.5 V

REF

REF

ReferenceVoltage Temperature Drift 10

-4

Oscillator Free-running Period ( R = 59kΩ, C = 1.2nF) 44 48 52 µs

OSC

Oscillator Frequency Drift with Temperature (V

OSC

Oscillator Frequency Drift with VCC+ (+8V < VCC+ < +14V) 0.5 %/V

CC

+ = +8V) 0.05 %/oC

CC

Minimum Conducting Time (Ct= 1nF) 2 µs

V/oC

2018A-04.TBL

RECOMMENDEDOPERATINGCONDITIONS

Symbol Parameter Min. Typ. Max. Unit

V

+ Positive Supply Voltage 8 V

CC

V

- Negative Supply Voltage -3 V

CC

I

Output Current 0.5 A

O

f

oper

Operating Frequency 30 kHz

TEST CIRCUIT

V8 V7 V6

10

Ω

4321

470nF

22nF

59k

1%

1.2nF
1%

470

22nF

22nF

8765

Ω

TEA2018A

4.7nF

Ω

2018A-05.TBL

100Ω

V1 V3 V4

2018A-03.EPS

3/7

TEA2018A

GENERALDESCRIPTION

(see applicationnote AN-086)
OperatingPrinciples (Figure 1)

On every period, the beginning of the conduction
time of the transistor is triggered by the fall of the
oscillatorsawtoothwhich acts as clock signal. The
period T
(T

osc

is givenby : T

osc

in seconds,Ctin Farad, Rtin Ω)

≅ 0.66 Ct(Rt+ 200)

osc

The end of the conduction time is determinedby a
signal issued from comparing the following sig­nals :

a) the sawtooth waveform representing the

collector current of the switching transistor,
sampledacross the emitter shunt resistor,

b) the outputof the erroramplifier.

Base Drive

- Fast turn-on : On each period, a current pulse
ensuresfast transistor switch-on.
This pulse performs also the t

on(min)

function at

the beginning of theconduction.

- Proportionalbase drive : Inorder to save power,
the positive base current afterthe starting pulse
becomesan image of the collectorcurrent.

I

C

The ratio

isprogrammedas follows Figure2) :

I

B

TEST CIRCUIT

I

R

C

B

=

I

R

B

e

- Efficient and fast switch-off : When the positive
base driveis removed, 1ms(typically) will elapse
before the application of negative current there­fore allowing a safe and rapid collector current
fall.

Safety Functions

- Overload & short-circuit protection : When the
voltage applied to pin 3 exceeds the current
limitation threshold voltage [V

)], the output

th(Ic

flip-flopis reset andthe transistoris turned off.
The shuntresistorR

mustbecalculatedso asto

e

obtain the current limitation thresholdon pin 3at
the maximumallowable collectorcurrent.

- Demagnetizationsensing:This functiondisables
any newconductioncycleof thetransistoraslong
as thecore is not completelydemagnetized.
When not used, pin 7 must be grounded.

-t

on(max)

: Outside the regulation area and in the
absence of current limitation, the maximum con­duction time is set atabout 70 % of theperiod.

-t

: Aminimum conducting time is ensured

on(min)

during each period(see Figure 2)

- Supply voltage monitoring : The TEA2018Awill
stop operating if V
thresholdlevel V

CC

CC(stop)

+

on pin 6 falls below the

V

REF

ERROR
AMPLIFIER

ERROR
SIGNAL

OSCILLATOR
SAW-TOOTH

I (sample)

C

FLIP-FLOP
OUTPUT

OSCILLATOR

COMPARATO R

I SENSE

C

FLIP-FLOP

S

R

Re

V

i

OUTPUT

FILTER

I

C

Q

t

Errorsignal

t

t

LOAD

2018A-04.EPS - 2018A-05.EPS

4/7

Figure2

R

TEA2018A

5

B

I

B

3

R

e

SCHEMATICS OF INPUTS AND OUTPUTS

TEA2018A

I

C

COLLECTOR
CURRENT

0

I

I

C

B

t

on(min)

BIAS
CURRENT

I

B

0

I

C

t

R

B

I

C

R

e

t

2018A-06.EPS

DISCH.

+

E

50µA

7.5kΩ

V

CC

7.5kΩ15kΩ

V

Is

ref

V H = 0.66 V

th

V L = 0.33 V

Vd + 0.1V

CC

CCth

2kΩ

+

V

CC

V

CC

1kΩ

1kΩ

Vo

15kΩ

1kΩ

OSC.

GND Ic

-

V

CC

2018A-07.EPS

5/7

TEA2018A

StartingProcess (Figure 3)

Prior to starting, a low current is drawn from the
high voltage source through a high valueresistor.

This current charges the power supply voltage
capacitorof the device.

No output pulses are available before the voltage
on pin6 hasreached the thresholdlevel [V

CC(start)

Figure3 : NormalStart-up Sequence

+

V

CC

6V

4.9V

V

+

CC

V (start)

CC

V (stop)

CC

t

V

rising].

CC

During this time the TEA2018A draws only 1mA
(typically). When the voltage on pin6 reaches this
threshold,base drivepulses appear.

The energy drawn by these pulses tends to dis­charge the power supply storage capacitor. How­ever a hysteresisof about 1.1V (typically) (∆ V

,

is implemented to avoidthe device from stopping.

Figure4 : t

t (µs)

on (min.)

ON (min.)

versusC

t

12

10

8

6

4

2

12345678910

2018A-08.EPS

C (nF)

t

CC

)

2018A-09.EPS

TYPICALAPPLICATION

4 x 1N4007

0.1µF

RF Filter

2 x 12mH

0.1µF

0.5A

220 V

AC

Maximum Power ≅ 30W
Operating Frequency≅30kHz

47µF
385V

4.7µF4.7kΩ

22kΩ

Ω

1k

8765

47kΩ

TEA2018A

1.2nF

100

Ω

1N4148 68Ω

220µF
16V

10µF150Ω

4321

3.9V

1N414815Ω

4.7kΩ

47µF

R

8.2Ω

BUV
46A

BYW98-50

1000µF

BYW98-50

BA

159

B

BA

159

R
1

2.2kΩ
3W

1kΩ 3W

1nF
1kV

e

Ω

Primary Ground
SecondaryGround

+12V

+5V

4700µF

2018A-10.EPS

6/7

PACKAGE MECHANICAL DATA

8 PINS - PLASTICDIP

b

Z

TEA2018A

e4

I

A

L

a1

B

B1

e

e3

D

Z

E

b1

Dimensions

8

14

Millimeters Inches

Min. Typ. Max. Min. Typ. Max.

5

F

A 3.32 0.131

a1 0.51 0.020

B 1.15 1.65 0.045 0.065

b 0.356 0.55 0.014 0.022

b1 0.204 0.304 0.008 0.012

D 10.92 0.430
E 7.95 9.75 0.313 0.384

e 2.54 0.100
e3 7.62 0.300
e4 7.62 0.300

F 6.6 0260

i 5.08 0.200

L 3.18 3.81 0.125 0.150

Z 1.52 0.060

Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility
for the consequences of use of suchinformation nor for any infringement of patents or other rights of third parties which may result
from its use. No licence is granted by implication or otherwiseunder anypatent or patent rights of SGS-THOMSON Microelectronics.
Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all
information previously supplied.SGS-THOMSON Microelectronics products are not authorized for use as critical components in life
support devices or systems without express written approval of SGS-THOMSON Microelectronics.

PM-DIP8.EPS

DIP8.TBL

 1994 SGS-THOMSON Microelectronics - All Rights Reserved

Purchase of I

2

I

C Patent. Rights to usethese components in a I2C system,is granted provided that the system conforms to

2

C Components of SGS-THOMSON Microelectronics, conveys a license under the Philips

2

the I

C Standard Specifications as defined by Philips.

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