Datasheet LND494 Datasheet (Linear Dimensions)

DATA SHEET

LND494

Pulse-Width-Modulation Control Circuits

GENERAL DESCRIPTION

The LND494 incorporate on a single monolithic
chip all the functions required in the construction
of a pulse-width-modulation control circuit.
Designed primarily for power supply control,
these devices offer the systems engineer the
flexibility to tailor the power supply control
circuitry to his application. The LND494
contains an error amplifier, an on-chip
adjustable oscillator, a dead time control
comparator, pulse –steering control flip-flop, a 5­volt, 5% precision regulator, and output-control
circuits. The error amplifier exhibits a common­mode voltage range from –0.3 volts to Vcc-2
volts. The dead-time control compactor has a
fixed offset that provides approximately 5% dead
time when externally altered. The on-chip
oscillator may be by passed by terminating R
(pin 6) to the reference output and providing a
sawtooth input to C

(pin 5), or it may be used to

T

drive the common circuits in synchronous
multiple-rail power supplies. The uncommitted
output transistors provide either common-emitter
or emitter-follower output capability. Each
device provides for push-pull or single-ended
output operation, which may be selected through

`

the output-control function. The architecture of
these devices prohibits the possibility of either
output being pulsed twice during push-pull
operation.

T

FEATURES

• Complete PWM Circuitry Power Control

• Uncommitted Outputs for 200mA Sink

or source current

• Output Control Selects Single-Ended or

Push-Pull operation

• Internal Circuitry Prohibits Double

Pulse at Either Output

• Variable Dead-Time Provides a stable

5-V Reference Supply, 5%

• Circuit Architecture Allows Easy

Synchronization

LND494

(Top View)

NON INV INPUT 1 16 NON INV INPUT

INV INPUT 2 15 INV INPUT

FEEDBACK 3 14 REF OUT

DEAD-TIME CONTROL 4 13 OUTPUT CONTROL

Error
Amp1

Error
Amp2

C

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5 12 Vcc

T

R

GND 7 10 E2

C1 8 9 E1

6 11 C2

T

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ABSOLUTE MAXIMUM RATINGS

Rating Value Unit

Supply voltage, V

cc

41
Amplifier input voltage Vcc+0.3
Collector output voltage 41
Collector output current 250 mA
Operating free-air temperature

range

0 to 70

Storage temperature range -65 to 150
Lead temperature 1,6 mm from

case for 10 seconds

260

RECOMMENDED OPERATING CONDITIONS

Value

Parameter

MIN MAX

Supply voltage, V
Amplifier input voltage, V
Collector output voltage,V

cc

i

o

Collector output current(each
transistor)

740

-0.3 Vcc-2
40

200

Current into feedback terminal 0.3
Timing capacitor,C
Timing resistor, R

T

T

0.47 10000 nF

1.8 500
Oscillator Frequency 1 300 kHz
Operating free-air temperature,

T

A

070 ºC

Unit

mA

LND494

V

ºC

V

kΩ

FUNCTIONAL BLOCK DIAGRAM

R

T

C

T

DEAD
TIME
CONTROL

NON ­INVERTING
INPUT

INVERTING
INPUT

NON ­INVERTING
INPUT

INVERTING
INPUT

+

-

+

-

0.1V

ERROR
AMPLIF IER

1

ERROR
AMPLIF IER

2

OSCILLATOR

DEAD TIME CONTROL

COMPAR ATOR

PWM

COMPAR ATOR

FEEDBAC K

PULSE STEER ING

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OUTPUT CONTROL

C1

FLIP - FLOP

REFERENCE

C1

Q1

E1

C2

Q2

E2

V

CC

V

REF

GND

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PARAMETER MEASUREMENT INFORMATION

Vcc= 15V

V

CC

TEST
INPUTS

.01uF

{

50k

DEAD TIME

FEEDBACK

12k

R

C

+ 1

- 1

+ 2

- 2

OUTP UT
CONTROL

T

T

ERROR

}

TEST CIRCUIT

GND

REF
OUT

C1
E1

C2
E2

1502W150

2W

OUTP UT 1

OUTP UT 2

LND494

Voltage At
C1

Voltage At
C2

Voltage At
C

T

Dead-Time
Control
Input

Feedback

Duty Circle

0V

0.7V

0%

MAX

Vcc

Vcc

0%

0

0

AMPLIFIER
UNDER TEST

+

V

I

-

OTHER
AMPLIFIER

+

V

REF

-

FEEDBACK
TER MIN AL

Figure 1: Operational Test Circuit and Waveforms

Figure 2: Amplifier Characteristics

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LND494

15V

68
2W

TEST CIRCUIT

C

t

OUTP UT

= 15pF

L

f

OUTPUT VOLTAGE WAVEFORM

t

r

90%90%

10%10%

TEST CIRCUIT

CL= 15pF

15V

OUTP UT

68
2W

t

r

OUTPUT VOLTAGE WAVEFORM

90%90%

10%10%

t

f

Figure 3: Common-Emitter Configuration Figure 4: Emitter-Follower Configuration

ELECTRICAL CHARACTERISTICS

Electrical characteristics over recommended operating free-air temperature range Vcc=15V, f=10kHz(unless otherwise
noted)

Reference Section

Value

Parameter Test conditions*

MIN TYP** MAX

Unit

Output voltage(V

)I

ref

=1mA 4.75 5 5.25 V

o

Input regulation Vcc=7V to 40V 2 25
Output regulation Io=1mA to 10mA 1 15
Output voltage change

with temperature
Short-circuit output

current***

∆T

MIN to MAX

A =

=0 35 mA

V

ref

0.2 1 %

Oscillator Section (See Figure 1)

Value

Parameter Test conditions*

MIN TYP MAX

Frequency
Standard deviation of

frequency ****
Frequency change with

voltage

Frequency change with
temperature*****

C

=0.01µF,RT =12kΩ

T

All values of VCC, CT, R

T

and TA constant

V

=7V to 40V, TA=25ºC 0.1

cc

=0.01µF, R

C

T

T

=12kΩ,∆TA=MIN TO
MAX

10 kHz

10

mV

Unit

%

1

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LND494

Amplifier Section (See Figure 2)

Value

Parameter Test conditions

MIN TYP MAX

Input Offset Voltage Vo=(pin 3)=2.5V 2 10 mV
Input Offset Current Vo=(pin 3)= 2.5V 25 250 nA
Input Bias Current Vo=(pin 3)=2.5V 0.2 1 µA

Common Mode Input
Voltage Range

Open Loop Voltage
Amplification

Unity Gain Bandwidth
Common- Mode

Rejection Ratio

Output Sink Current

Output Source Current

=7V to 40V

V

cc

V

=3V,RL=2kΩ

o

=0.5 to 3.5V

V

o

=0.5 to 3.5V, RL=2kΩ

V

o

V

=40V,T

o

V

-15Mv TO –5v

ID=

V

(PIN3)

V

-15mV TO –5V

ID=

V

(PIN3)

25º C 65 80 dB

A =

=0.7v

=3.5v

-0.3
to

Vcc-2

70 95 DB

800 kHZ

0.3 0.7 mA

-2 mA

Unit

V

*For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating
conditions.
** All typical values except for parameter changes with temperature are at T

=25º C

A

***Duration of the short-circuit should not exceed one second.
****Standard deviation is a measure of the statistical distribution about the mean as derived from the formula.

1/2

σ =

N

∑

[

n=1

( xn - x )

N-1

2

]

******Temperature coefficient of timing capacitor and timing resistor not taken into account

Output Section

Parameter Test conditions

Collector off-state
current

V

=40V Vcc =40 V 2 100 µA

ce

MIN TYP* MAX

Value

Unit

Emitter off-state current Vce=Vcc=40V Ve=0 -100 %
Collector-emitter
saturation Voltage

Common-Emitter
Emitter-Follower
Output control input
current

V

=0,Ic=200mA

e

V

=15V, Ie=-200mA

c

V

I=Vref

1.1

1.5

1.3

2.5

3.5

V

mA

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Dead-Time Control Section (See figure 1)

LND494

Parameter Test conditions

MIN TYP* MAX

Value

Unit

Input Bias current (pin4) VI=0 to 5.25V -2 -10 µA
Maximum Duty

Cycle,Each output

Input Threshold Voltage
(pin4)

(pin 4)=0,C

I

R

12KΩ

T =

Zero duty cycle
Maximum Duty Cycle 0

T =

0.1µF,
45 %

33.3
V

V

PWM comparator section (see figure 1)

Parameter Test Conditions

Input threshold voltage

Zero duty cycle 4 4.5 V

MIN TYP* MAX

Value Unit

(pin 3)
Input sink current (pin 3) V(pin3)= 0.7V 0.3 0.7 mA

Total Device

Parameter Test Conditions

current
Average supply

Pin 6 at V
inputs and outputs open

V

I ( pin 4

, all other

ref

) =2V, See figure 1 7.5

MIN TYP MAX

Vcc=15V 6 10Standby supply
V

=40V 9 15

cc

Value

current

Unit

mA

Switching characteristics, Ta=25ºC

PARAMETER TEST CONDITIONS

Output voltage rise time 100 200
Output voltage fall time
Output voltage rise time 100 200
Output voltage fall time

Common-emitter configuration
See figure 3

Emitter-follower configuration
See Figure 4

MIN TYP* MAX

VALUE

25 100

40 100

*All typical values except for temperature coefficient at TA= 25ºC

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UNIT

nS

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