Texas Instruments UC2871QTR, UC2871Q, UC2871N, UC2871J, UC2871DWTR Datasheet

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10/94

BLOCK DIAGRAM

• 1µA ICC when Disabled

• PWM Control for LCD Supply

• Zero Voltage Switched (ZVS) on

Push-Pull Drivers

• Open Lamp Detect Circuitry

• 4.5V to 20V Operation

• Non-saturating Transformer

Topology

• Smooth 100% Duty Cycle on

Buck PWM and 0% to 95% on

Flyback PWM

The UC1871 Famil y of IC’s is optimized for highly efficient fl uorescent lamp

control. An additional PWM controller is integrated on the IC for applications re-

quiring an additional suppl y, as in LCD displays . When disabled the IC draws

only 1µA, providing a true disconnect feature, which is optimum for battery

powered systems. The switching frequency of all outputs are synchronized to

the resonant frequency of the e xternal passive network, which provides Zero

V oltage Switching on the Push-Pull drivers.

Soft-Start and open lamp detect circuitry have been incorporated to minimize

component stress. An open lamp i s detected on the compl etion of a soft-start

cycle.

The Buck control ler is optimized for smooth duty cycle control to 100%, while

the flyback control ensures a maximum duty cycle of 95%.

Other features include a precision 1% reference, under voltage lockout, flyback

current limit, and accurate minimum and maximum frequency control.

Resonant Fluorescent Lamp Driver

FEATURES

DESCRIPTION

UDG-92061-1

UC1871

UC2871

UC3871

Note: Pin number s refer to DIL- 18 an d SOIC- 18 pa ckag es only.

PARAMETER TEST CONDITION S MIN TYP MAX UNITS

Reference Sect ion

Output Voltage T

J=25°C 2.963 3.000 3.037 V

Overtemp 2.940 3.000 3.060 V

Line Regulation V

CC = 4.75V to 18V 10 mV

Load Regulat io n Io=0 to -5mA 10 mV

Oscillator Section

Free Running Freq T

J=25°C 576878kHz

Max Sync Frequency T

J=25°C 160 200 240 kHz

Charge Curr ent V

CT = 1.5V 180 200 220 µA

Voltage Sta bi lity 2%

Temperature Stability 48%

Zero Detect Threshold 0.46 0.5 0.56 V

Error Amp 1 Sectio n

Input Voltage V

O = 2V 1.445 1.475 1.505 V

Input Bias Current -0.4 -2 µA

Open Loo p Ga in V

O = 0.5 to 3V 65 90 dB

Output High V

EA(-) = 1.3V 3.1 3.5 3.9 V

Output Low V

EA(-) = 1.7V 0.1 0.2 V

Output Source Current V

EA(-) = 1.3V, Vo = 2V -350 -500 µA

Output Sink Current V

EA(-) = 1.7V, Vo = 2V 10 20 mA

Common Mode Range 0V

IN-1V V

Unity Gain Bandwidth T

J = 25°C (Note 4) 1 MHz

Maximum Source Im peda nce Note 5 100k Ω

UC1871

UC2871

UC3871

ELECTRICAL CHARACTERIST ICS

Unless otherwise stated , thes e par am eters apply f or TA = -55°C to +125°C for the

UC1871; -25°C to +85°C for the UC2 871; 0°C t o +70°C f or the UC3871; V

CC = 5V,

C = 15V, VENABLE = 5V, CT = 1nF , Z ero Det = 1V.

ABSOLUTE MAXIMUM RATINGS

Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . −0.3 to +10V

CC, VC Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +20V

Zero Detect I nput Current

High Impedanc e Source . . . . . . . . . . . . . . . . . . +10mA

Zero Detect

Low Impedance Source. . . . . . . . . . . . . . . . . . . . . +20V

Power Dissipation at T

A = 25°C . . . . . . . . . . . . . . . . . . . 1W

Storage T e mperature. . . . . . . . . . . . . . . . -65 °C to +150°C

Lead Temp erature . . . . . . . . . . . . . . . . . . . . . . . . . . 300°C

Note 1: Current s are pos itive int o, nega tive out of the sp ecif ied te r-

minal.

Note 2: Consult Packaging Sec tion of Databook f or therma l

limitations and considerations of package.

DIL-18, SOIC-18 ( TOP VIEW)

J or N, DW Package

PACKAGE PIN FUNCTION

FUNCTION PIN

Gnd 1

B Out 2

A Out 3

VC 4

E/A 1 Comp 5

SS 6

E/A 1(-) 7

N/C 8

T 9

Zero Detect 10

N/C 11

VREF 12

E/A 2(+) 13

E/A 2(-) 14

E/A 2 Comp 15

CC 16

Enable 17

Flyback I

SENSE 18

D Out 19

C Out 20

PLCC-20 (Top View)

Q Package

CONNECTION DIAG RAMS

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