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LM3524D Datasheet

Download or read online National Semiconductor LM3524D Regulating Pulse Width Modulator pdf datasheet.



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LM2524D LM3524D
Regulating Pulse Width Modulator
General Description
The LM3524D family is an improved version of the industry
standard LM3524 It has improved specifications and addi-
tional features yet is pin for pin compatible with existing
3524 families New features reduce the need for additional
external circuitry often required in the original version
The LM3524D has a
1% precision 5V reference The cur-
g
rent carrying capability of the output drive transistors has
been raised to 200 mA while reducing V
CEsat
V
breakdown to 60V The common mode voltage range
CE
of the error-amp has been raised to 5 5V to eliminate the
need for a resistive divider from the 5V reference
In the LM3524D the circuit bias line has been isolated from
the shut-down pin This prevents the oscillator pulse ampli-
tude and frequency from being disturbed by shut-down Also
at high frequencies ( j 300 kHz) the max duty cycle per
output has been improved to 44% compared to 35% max
duty cycle in other 3524s
In addition the LM3524D can now be synchronized exter-
nally through pin 3 Also a latch has been added to insure
Block Diagram
C 1995 National Semiconductor Corporation
TL H 8650
one pulse per period even in noisy environments The
LM3524D includes double pulse suppression logic that in-
sures when a shut-down condition is removed the state of
the T-flip-flop will change only after the first clock pulse has
arrived This feature prevents the same output from being
pulsed twice in a row thus reducing the possibility of core
saturation in push-pull designs
and increasing
Features
Fully interchangeable with standard LM3524 family
Y
1% precision 5V reference with thermal shut-down
Y
g
Output current to 200 mA DC
Y
60V output capability
Y
Wide common mode input range for error-amp
Y
One pulse per period (noise suppression)
Y
Improved max duty cycle at high frequencies
Y
Double pulse suppression
Y
Synchronize through pin 3
Y
January 1995
TL H 8650 – 1
RRD-B30M115 Printed in U S A

Summary of Contents

Page 1

... In the LM3524D the circuit bias line has been isolated from the shut-down pin This prevents the oscillator pulse ampli- tude and frequency from being disturbed by shut-down Also ...

Page 2

... 125 125 C a 150 150 260 C LM3524D Tested Design Units Typ Limit Limit (Note 3) (Note Min Max Max ...

Page 3

... 001 LM3524D Tested Design Units Typ Limit Limit (Note 3) (Note Max Min Max Max Max 65 A Min ...

Page 4

... IN IN Note 1 Unless otherwise stated these specifications apply for and LM3524D 20V and OSC Note 2 For operation at elevated temperatures devices in the N package must be derated based on a thermal resistance junction to ambient Devices ...

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Typical Performance Characteristics Switching Transistor Peak Output Current vs Temperature Output Transistor Saturation Voltage Standby Current vs Voltage Maximum Maximum Average Power Duty Cycle Threshold Dissipation (N M Packages) Voltage Output Transistor Emitter Reference Transistor Voltage Peak Output Current Standby ...

Page 6

... Test Circuit Functional Description INTERNAL VOLTAGE REGULATOR The LM3524D has an on-chip short circuit pro- tected voltage regulator This voltage regulator provides a supply for all internal circuitry of the device and can be used as an external reference For input voltages of less than 8V the 5V output should be ...

Page 7

... OUTPUT STAGES The outputs of the LM3524D are NPN transistors capable TL H 8650 – maximum current of 200 mA These transistors are driv- en 180 out of phase and have non-committed open collec- tors and emitters as shown in Figure 6 FIGURE 8650– ...

Page 8

Typical Applications FIGURE 7 Positive Regulator Step-Up Basic Configuration (I FIGURE 8 Positive Regulator Step-Up Boosted Current Configuration Design Equations OSC o(MAX 8650 – mA) ...

Page 9

Typical Applications (Continued) FIGURE 9 Positive Regulator Step-Down Basic Configuration (I FIGURE 10 Positive Regulator Step-Down Boosted Current Configuration Design Equations OSC o(MAX) 80 mA) e IN(MAX ...

Page 10

... AND APPLICATIONS The basic circuit of a step-down switching regulator circuit is shown in Figure 12 along with a practical circuit design us- ing the LM3524D in Figure 15 FIGURE 12 Basic Step-Down Switching Regulator The circuit works as follows Q1 is used as a switch which has ON and OFF times controlled by the pulse width modu- ...

Page 11

Typical Applications (Continued From the relation Neglecting ...

Page 12

... A complete step-down switching regulator schematic using the LM3524D is illustrated in Figure 15 Transistors Q1 and Q2 have been added to boost the output to 1A The 5V regulator of the LM3524D has been divided in half to bias the error amplifiers non-inverting input to within its com- mon-mode range Since each output transistor is on for half ...

Page 13

Typical Applications (Continued) Parameter Output Voltage Switching Frequency Short Circuit Current Limit Load Regulation Line Regulation Efficiency Output Ripple FIGURE Amp Switching Regulator Foil Side FIGURE 17 Stuffing Diagram Component Side TABLE I Typical Conditions Characteristics V ...

Page 14

Typical Applications (Continued) THE STEP-UP SWITCHING REGULATOR Figure 18 shows the basic circuit for a step-up switching regulator In this circuit Q1 is used as a switch to alternately apply V across inductor L1 During the time t IN and ...

Page 15

Typical Applications (Continued From OFF and Since ...

Page 16

... By adding a reference voltage at the non- inverting input to the error amplifier see Figure 21 the input voltage variations are rejected R1 The LM3524D can also be used in inductorless switching regulators Figure 22 shows a polarity inverter which if con- nected to Figure 20 provides a FIGURE 8650 – 15V unregulated output 8650– ...

Page 17

... Connection Diagram Top View Physical Dimensions inches (millimeters) Order Number LM2524DN or LM3524DN See NS Package Number N16E Order Number LM3524DM See NS Package Number M16A TL H 8650 2 Surface-Mount Package (M) Order Number LM3524DM NS Package Number M16A 17 ...

Page 18

... Physical Dimensions inches (millimeters) (Continued) Order Number LM2524DN or LM3524DN LIFE SUPPORT POLICY NATIONALS PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or ...

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