LND494 - Linear Dimensions Semiconductor

LND494

Pulse-Width-Modulation Control Circuits

DATA

SHEET

GENERAL DESCRIPTION

• 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

FEATURES

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 5-

volt, 5% precision regulator, and output-control

circuits. The error amplifier exhibits a common-

mode 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 RT

(pin 6) to the reference output and providing a

sawtooth input to CT (pin 5), or it may be used to

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.

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

CT 5 12 Vcc

RT 6 11 C2

GND 7 10 E2

C1 8 9 E1

Error

Amp1

Error

Amp2

LND494

(Top View)

• Linear Dmensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •

Rating Value Unit

Supply voltage, Vcc 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

ºC

Value

Parameter

MIN MAX

Unit

Supply voltage, Vcc 740

Amplifier input voltage, Vi-0.3 Vcc-2

Collector output voltage,Vo40

Collector output current(each

transistor) 200

Current into feedback terminal 0.3

Timing capacitor,CT0.47 10000 nF

Timing resistor, RT1.8 500 kΩ

Oscillator Frequency 1 300 kHz

Operating free-air temperature,

070 ºC

ABSOLUTE MAXIMUM RATINGS

LND494

RECOMMENDED OPERATING CONDITIONS

• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •

FUNCTIONAL BLOCK DIAGRAM

OSCILLATOR

ERROR

AMPLIFIER

ERROR

AMPLIFIER

DEAD

TIME

CONTROL

REFERENCE

GND

REF

DEAD TIME CONTROL

COMPARATOR

PWM PULSE STEERING

FLIP - FLOP

OUTPUT CONTROL

NON -

INVERTING

INPUT

NON -

INVERTING

INPUT

INVERTING

INPUT

INVERTING

INPUT

0.1V

FEEDBACK

Vcc

0.7V MAX 0%

LND494

Voltage At

Dead-Time

Control

Input

Feedback

Duty Circle

Threshold Voltage

VOLTAGE WAVEFORMS

Figure 1: Operational Test Circuit and Waveforms

• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •

PARAMETER MEASUREMENT INFORMATION

DEAD TIME

FEEDBACK

+ 1

- 1

+ 2

- 2

OUTP UT

CONTROL

GND

REF

OUT

VCC

cc= 15V

{

TEST

INPUTS

TEST CIRCUIT

150

50k

12k

.01uF

}

ERROR

OUTP UT 1

OUTP UT 2

REF

FEEDBACK

TER MI N AL

AMPLIFIER

UNDER TEST

OTHER

AMPLIFIER

Figure 2: Amplifier 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(Vref)I

o=1mA 4.75 5 5.25 V

Input regulation Vcc=7V to 40V 2 25

Output regulation Io=1mA to 10mA 1 15 mV

Output voltage change

with temperature ∆TA = MIN to MAX 0.2 1 %

Short-circuit output

current*** Vref=0 35 mA

Oscillator Section (See Figure 1)

Value

Parameter Test conditions*

MIN TYP MAX

Unit

Frequency CT=0.01µF,RT =12kΩ10 kHz

Standard deviation of

frequency ****

All values of VCC, CT, RT

and TA constant 10

Frequency change with

voltage Vcc=7V to 40V, TA=25ºC 0.1

Frequency change with

temperature*****

CT =0.01µF, RT

=12kΩ,∆TA=MIN TO

MAX

ELECTRICAL CHARACTERISTICS

LND494

• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •

15V

OUTP UT

L= 15pF

TEST CIRCUIT

90%90%

10%10%

OUTPUT VOLTAGE WAVEFORM

15V

OUTP UT

CL= 15pF

TEST CIRCUIT

90%90%

10%10%

OUTPUT VOLTAGE WAVEFORM

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

Amplifier Section (See Figure 2)

Value

Parameter Test conditions MIN TYP MAX Unit

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 Vcc=7V to 40V

-0.3

Vcc-2

Open Loop Voltage

Amplification

Vo=3V,RL=2kΩ

Vo=0.5 to 3.5V 70 95 DB

Unity Gain Bandwidth Vo=0.5 to 3.5V, RL=2kΩ800 kHZ

Common- Mode

Rejection Ratio Vo=40V,TA = 25º C 65 80 dB

Output Sink Current VID= -15Mv TO –5v

V(PIN3) =0.7v 0.3 0.7 mA

Output Source Current VID= -15mV TO –5V

V(PIN3) =3.5v -2 mA

*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 TA =25º C

***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.

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

Output Section

Value

Parameter Test conditions MIN TYP* MAX Unit

Collector off-state

current Vce=40V Vcc =40 V 2 100 µA

Emitter off-state current Vce=Vcc=40V Ve=0 -100 %

Collector-emitter

saturation Voltage

Common-Emitter

Emitter-Follower

Ve=0,Ic=200mA

Vc=15V, Ie=-200mA

1.1

1.5

1.3

2.5

Output control input

current VI=Vref 3.5

LND494

1/2

σ = [ ∑ N-1 ]

n=1

( xn - x )2

• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •

Dead-Time Control Section (See figure 1)

Value

Parameter Test conditions MIN TYP* MAX Unit

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

Maximum Duty

Cycle,Each output

VI(pin 4)=0,CT =0.1µF,

RT =12KΩ45 %

Input Threshold Voltage

(pin4)

Zero duty cycle

Maximum Duty Cycle 0

33.3 V

PWM comparator section (see figure 1)

Value Unit

Parameter Test Conditions MIN TYP* MAX

Input threshold voltage

(pin 3)

Zero duty cycle 4 4.5 V

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

Total Device

Value

Parameter Test Conditions MIN TYP MAX Unit

Vcc=15V 6 10Standby supply

current

Pin 6 at Vref, all other

inputs and outputs open Vcc=40V 9 15

Average supply

current

VI ( pin 4) =2V, See figure 1 7.5

Switching characteristics, Ta=25ºC

VALUE

PARAMETER TEST CONDITIONS MIN TYP* MAX UNIT

Output voltage rise time 100 200

Output voltage fall time

Common-emitter configuration

See figure 3 25 100

Output voltage rise time 100 200

Output voltage fall time

Emitter-follower configuration

See Figure 4 40 100

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

LND494

• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •