KA3842AES - Fairchild Semiconductor

March 2006

KA3842AC/KA3842AE Rev. 1.0.1

KA3842AC/KA3842AE SMPS Controller

KA3842AC/KA3842AE

SMPS Controller

Features

Low start current 0.2mA (Typ.)

Operating range up to 500kHz

Cycle by cycle current limiting

Under Voltage Lock Out (UVLO) with hysteresis

Short shutdown delay time: Typ.100ns

High current totem-pole output

Output swing limiting: 22V

Description

The KA3842AC/KA3842AE are fixed PWM controllers

for Off Line and DC to DC converter applications. The

internal circuits include UVLO, low start up current, tem-

perature compensated reference, high gain error ampli-

fier, current sensing comparator, and high current totem

pole output for driving a POWER MOSFET. Also

KA3842AC/KA3842AE provides low start up current

below 0.3mA and short shutdown delay time, typically

100ns. The KA3842AC/KA3842AE has a UVLO thresh-

old of 16V(on) and 10V(off). The KA3842AC/KA3842AE

can operate within a 100% duty cycle.

Ordering Information

Part Number

Operating

Temp. Range Pb-Free Package Packing Method

KA3842AC -0 to +70°C Yes 8-DIP Tube

KA3842AE

8-DIP

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KA3842AC/KA3842AE Rev. 1.0.1

KA3842AC/KA3842AE SMPS Controller

Internal Block Diagram

Internal

Bias

VREF

SET/

RESET

Good LOGIC

OSCILLATOR

UVLO

29V

22V

1/3

Error Amp

1/2 VREF

C.S

Comp. PWM

LATCH

VREF

VFB

COMP

C.S

RT/CT

OUTPUT

VCC

GND

PWR

GND

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KA3842AC/KA3842AE Rev. 1.0.1

KA3842AC/KA3842AE SMPS Controller

Absolute Maximum Ratings

The “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed.

The device should not be operated at these limits. The parametric values defined in the Electrical Characteristics

tables are not guaranteed at the absolute maximum ratings. The “Recommended Operating Conditions” table will

define the conditions for actual device operation.

Symbol Parameter Value Unit

VCC Supply Voltage 30 V

IO Output Current ±1 A

VI(ANA) Analog Inputs (Pins 2, 3) -0.3 to 6.3 V

ISINK(EA) Error Amp. Output Sink Current 10 mA

PD Power Dissipation 1 W

Rθja Thermal Resistance, Junction-to-Air(4) 95 °C/W

Electrical Characteristics

(VCC = 15V, RT = 10k¾, CT = 3.3nF, TA = 0°C to +70°C, unless otherwise specified)

Symbol Parameter Conditions Min. Typ. Max. Unit

REFERENCE SECTION

VREF Output Voltage TJ = 25°C, IO = 1mA 4.9 5.0 5.1 V

ΔVREF Line Regulation VCC = 12V to 25V – 6 20 mV

Load Regulation IO = 1mA to 20mA – 6 25 mV

ISC Output Short Circuit TA = 25°C – -100 -180 mA

OSILLATOR SECTION

FOSC Initial Accuracy TJ = 25°C 47 52 57 kHz

STV Voltage Stability VCC = 12V to 25V – 0.2 1 %

VOSC Amplitude VPIN4, Peak to Peak – 1.7 – V

IDISCHG Discharge Current TJ = 25°C, Pin 4 = 2V 7.8 8.3 8.8 mA

CURRENT SENSE SECTION

GV Gain(2)(3) 2.85 3 3.15 V/V

VI(MAX) Maximum Input Signal(2) V

PIN1 = 5V 0.9 1.0 1.1 V

PSRR PSRR(1)(2) VCC = 12V to 25V – 70 – dB

IBIAS Input Bias Current – -2 -10 µA

TD Delay to Output(1) V

PIN3 = 0 V to 2V – 100 200 ns

ERROR AMPLIFIER SECTION

VI Input Voltage TPIN1 = 2.5V 2.42 2.50 2.58 V

IBIAS Input Bias Current – -0.3 -2 µA

GVO Open Loop Gain(1) V

O = 2V to 4V 65 90 – dB

GBW Unity Gain Bandwidth(1) T

J = 25°C 0.7 1 – MHz

PSRR PSRR(1) V

CC = 12V to 25V 60 70 – dB

ISINK Output Sink Current VPIN2 = 2.7V

VPIN1 = 1.1V

2 6 – mA

ISOURCE Output Source Current VPIN2 = 2.3V

VPIN1 = 5.0V

-0.5 -0.8 – mA

VOH Output High Voltage VPIN2 = 2.3V, R1 = 15k¾ to GND 5 6 – V

VOL Output Low Voltage VPIN2 = 2.7V

R1 = 15k¾ to Pin 8

– 0.8 1.1 V

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KA3842AC/KA3842AE Rev. 1.0.1

KA3842AC/KA3842AE SMPS Controller

* Adjust VCC above the start threshold before setting at 15V

Notes:

1. These parameters, although guaranteed, are not 100% tested in production.

2. Parameter measured at trip point of latch with V2 = 0V.

3. Gain defined as: GV = ΔVPIN1ΔVPIN3(VPIN3 = 0 to 0.8V)

4. Junction-to-air thermal resistance test environments

PCB information:

Board thickness; 1.6mm, Board dimension: 76.2 X 114.3mm2, Ref.: EIA/JSED51-3 and EIA/JSED51-7

Board structure; Using the single layer PCB.

OUTPUT SECTION

VOL Output Low Level ISINK = 20mA – 0.1 0.4 V

ISINK = 200mA – 1.5 2.2 V

VOH Output High Level ISOURCE = 20mA 13 13.5 – V

ISOURCE = 200mA 12 13.5 – V

tR Rise Time(1) T

J = 25°C, C1 = 1nF – 40 100 ns

tF Fall Time(1) T

J = 25°C, C1 = 1nF – 40 100 ns

VOLIM Output Voltage Swing Limit VCC = 27V, C1 = 1nF – 22 – V

UNDER VOLTAGE LOCKOUT SECTION

VTH Start Threshold 15 16 17 V

VTL Min. Operating Voltage

(After turn on)

9 10 11 V

PWM SECTION

DMAX Maximum Duty Cycle 94 96 100 %

DMIN Minimum Duty Cycle – – 0 %

TOTAL STANDBY CURRENT

IST Start-Up Current – 0.2 0.4 mA

ICC Operating Supply Current VPIN2 = VPIN3 = 0V – 11 17 mA

VZ VCC Zener Voltage ICC = 25mA – 29 – V

Electrical Characteristics (Continued)

(VCC = 15V, RT = 10k¾, CT = 3.3nF, TA = 0°C to +70°C, unless otherwise specified)

Symbol Parameter Conditions Min. Typ. Max. Unit

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KA3842AC/KA3842AE Rev. 1.0.1

KA3842AC/KA3842AE SMPS Controller

Package Dimensions

8-Pin DIP

Dimensions in millimeters

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KA3842AC/KA3842AE Rev. 1.0.1

KA3842AC/KA3842AE SMPS Controller

DISCLAIMER

FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHTTO MAKE CHANGES WITHOUT FURTHER NOTICE TOANY

PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOTASSUMEANY LIABILITY

ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT

CONVEYANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.

TRADEMARKS

The following are registered and unregistered trademarks Fairchild Semiconductor owns or is authorized to use and is

not intended to be an exhaustive list of all such trademarks.

LIFE SUPPORT POLICY

FAIRCHILDíS PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION.

As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant into

the body, or (b) support or sustain life, or (c) whose

failure to perform when properly used in accordance

with instructions for use provided in the labeling, can be

reasonably expected to result in significant injury to the

user.

2. A critical component is any component of a life

support device or system whose failure to perform can

be reasonably expected to cause the failure of the life

support device or system, or to affect its safety or

effectiveness.

PRODUCT STATUS DEFINITIONS

Definition of Terms

Datasheet Identification Product Status Definition

Advance Information

Preliminary

No Identification Needed

Obsolete

This datasheet contains the design specifications for

product development. Specifications may change in

any manner without notice.

This datasheet contains preliminary data, and

supplementary data will be published at a later date.

Fairchild Semiconductor reserves the right to make

changes at any time without notice in order to improve

design.

This datasheet contains final specifications. Fairchild

Semiconductor reserves the right to make changes at

any time without notice in order to improve design.

This datasheet contains specifications on a product

that has been discontinued by Fairchild semiconductor.

The datasheet is printed for reference information only.

Formative or

In Design

First Production

Full Production

Not In Production

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