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LM494CJ 데이터시트 PDF




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기능 Pulse Width Modulated Control Circuit
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LM494CJ 데이터시트, 핀배열, 회로
June 1989
LM494
Pulse Width Modulated Control Circuit
General Description
The LM494 is a monolithic integrated circuit which includes
all the necessary building blocks for the design of pulse
width modulated (PWM) switching power supplies including
push-pull bridge and series configurations The device can
operate at switching frequencies between 1 0 kHz and
300 kHz and output voltages up to 40V The operating tem-
perature range specified for the LM494C is 0 C to 70 C and
for the LM494V is b40 C to a85 C
Features
Y Uncommitted output transistors capable of 200 mA
source or sink
Y On-chip error amplifiers
Y On-chip 5 0V reference
Y Internal protection from double pulsing of outputs with
narrow pulse widths or with supply voltages below
specified limits
Y Dead time control comparator
Y Output control selects single ended or push-pull opera-
tion
Y Easily synchronized (slaved) to other circuits
Block Diagram
Connection Diagram
16-Lead DIP
Ordering Information
Device
Code
LM494IN
LM494CJ
LM494CN
Package
Code
N16A
J16A
N16A
TL H 10056 – 2
Package
Description
Molded DIP
Ceramic DIP
Molded DIP
Top View
C1995 National Semiconductor Corporation TL H 10056
TL H 10056 – 1
RRD-B30M115 Printed in U S A




LM494CJ pdf, 반도체, 판매, 대치품
Functional Description
The basic oscillator (switching) frequency is controlled by an
external resistor (RT) and capacitor (CT) The relationship
between the values of RT CT and frequency is shown in
Figure 10
The level of the sawtooth wave form is compared with an
error voltage by the pulse width modulated comparator The
output of the PWM Comparator directs the pulse steering
flip-flop and the output control logic
The error voltage is generated by the error amplifier The
error amplifier boosts the voltage difference between the
output and the 5 0V internal reference See Figure 7 for
error amp sensing techniques The second error amp is typi-
cally used to implement current-limiting
The output control logic selects either push-pull or single-
ended operation of the output transistors (see Figure 6 )
The dead time control prevents on-state overlap of the out-
put transistors as can be seen in Figure 5 The dead time is
approximately 3 0% or 5 0% of the total period if the dead
time control is grounded This dead time can be increased
by connecting the dead time control to a voltage up to 5 0V
The frequency response of the error amps (Figure 11) can
be modified by using external resistors and capacitors
These components are typically connected between the
compensation terminal and the inverting input of the error
amps
The switching frequency of two or more LM494 circuits can
be synchronized The timing capacitor CT is connected as
shown in Figure 8 Charging current is provided by the mas-
ter circuit Discharging is through all the circuits slaved to
the master RT is required only for the master circuit
Test Circuits
TL H 10056–3
FIGURE 1 Error Amplifier Test Circuit
TL H 10056 – 5
TL H 10056 – 6
FIGURE 3 Common Emitter Configuration
Test Circuit and Waveform
TL H 10056 – 7
TL H 10056 – 8
FIGURE 4 Emitter Follower Configuration
Test Circuit and Waveform
TL H 10056–4
FIGURE 2 Current Limit Sense
Amplifier Test Circuit
4
TL H 10056 – 9
FIGURE 5 Dead Time and Feedback
Control Test Circuit

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LM494CJ 전자부품, 판매, 대치품
Voltage Waveforms
Physical Dimensions inches (millimeters)
TL H 10056 – 18
16-Lead Ceramic Dual-In-Line Package (J)
Order Number LM494CJ
NS Package Number J16A
7

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관련 데이터시트

부품번호상세설명 및 기능제조사
LM494CJ

Pulse Width Modulated Control Circuit

National Semiconductor
National Semiconductor
LM494CN

Pulse Width Modulated Control Circuit

National Semiconductor
National Semiconductor

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