Texas Instruments UC3852N, UC3852DTR, UC3852D, UC2852N, UC2852DTR Datasheet

TYPICAL APPLICATION

10/94

FEATURES

•

Low-Cost Power Factor
Correction

• Power Factor Greater Than 0.99

• Few External Parts Required

• Controlled On-Time Boost PWM

• Zero-Current Switching

• Limited Peak Current

• Min and Max Frequency Limits

• Starting Current Less Than 1mA

• High-Current FET Drive Output

• Under-Voltage Lockout

DESCRIPTION

The UC1852 provides a low-cost so lution to active power-f actor correction ( PF C)
for systems that would otherwise draw high peak current pulses from AC power
lines. This circuit implements zero-current switched boost conversion, producing
sinusoidal input currents with a minimum of external components, while keeping
peak current substantially below that of fully-discontinuous convert ers.

The UC1852 provides controlled switch on-time to regulate the output bulk DC
voltage, an off-time defined by the boost inductor, and a zero-current sensing
circuit to reactivate the switch cycle. Even though switching frequency var ies with
both load and instantaneous line voltage, it can be maintained within a reasonable
range to minimize noise generation.

While allowing higher peak switch currents than continuous PFCs such as the
UC1854, this device offers less externa l circuitry and smaller inductors, yet better
performance and easier line-noise filtering than discontinuous current PFCs with
no sacrifice in complexity or c ost. The ability to obtain a power fact or in excess of

0.99 makes the UC1852 an optimum choice for low-cost applications in the 50 to
500 watt power range. Protect ion features of these devices include under-vo ltage
lockout, output clamping, peak-current limiting, and maximum-frequency
clamping.

The UC1852 family is available in 8-pin plastic and ceramic dual in-line packages,
and in the 8-pin small outline IC package (SOIC). The UC1852 is specified for
operation from -55°C to +125°C, the UC2852 is specified for operation from -40°C
to +85°C, and the UC3852 is specified for operation from 0°C to +70° C.

UC1852
UC2852
UC3852

High Power-Factor Preregulato r

UDG-92001

SOIC–8 (TOP VIEW)

D Package

Unless otherwise stated, VCC=24V, ISET=50kΩ to GND, RAMP=1nF to GND, ISNS=
–0.1V, VFB c onne cted to COM P, no load on OUT , –5 5 °C<Ta<+125°C for the UC1852,
–40°C<Ta<+85°C f or the UC2852, and 0 °C<Ta<+70°C for the UC3852, and Ta=Tj.

UC1852
UC2852
UC3852

ELECTRICAL CHARACTERIST ICS

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (Lo w-im peda nce Sou rce )..........................30.0V

Supply Current (High-impedance Source)......................30.0mA

OUT Current, Peak..................... . .... .... .... .... .... ... .... .... .... ....±1.0A

OUT Energy, Capacitive Load................ .... .... .... ..... .... .... ...5.0 µJ

Input Voltage, ISNS............................................................±5.0V

Input Voltage, VFB.............................................–0.3V to +10.0V

COMP Current...............................................................±10.0mA

ISET Current............ .... .... ... .... . .... .... ... .... . .... .... ... .... . .... ..–10.0mA

Power Dissipation at Ta≤25°C (Note 3) ..............................1.0W

Storage Temperature .......................................–65°C to +150 °C

Lead Temperat ur e (Soldering, 10 Sec onds )...................+300°C

Note 1: All voltages with respe ct to GND (Pin 1).
Note 2: All current s are posit ive in to the specified t erminal.
Note 3: Refers to DIL-8 Packa ge. Consu lt Packaging Sec tion of
Unitrode Inte gra ted C ircuit s datab ook f or thermal lim ita tion s and
consideratio ns of package.

DIL–8 (TOP VIEW)

J or N Package

CONNECTION DIAG RAM

PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNITS

Timer Sectio n

ISET Voltage 4.5 5.0 5.5 V
RAMP Charge Current RAMP=2.5V 88 98 108

µA
RAMP Discharge Current ISNS= –1.0V, RAMP= 1 .0V 12 28 50 mA
RAMP Saturation Volt age

ISNS= –1.0V, I

RAMP=100µA

0.006 0.200 V
RAMP Threshold - Maximum Fre quen cy VFB=10V, COMP open 0.92 1.02 1.12 V
RAMP Threshold - PWM Comparator 3.9 4.3 4.8 V

Current Sense Co mparator

ISNS Restart Threshold –18 –10 –4 m V
ISNS Fault Thres hold –550 –45 0 –350 mV
ISNS Input Current –100 –30 100

µA

Error Amplifier Se cti o n

VFB Input Voltage 4.6 5.0 5.3 V
VFB Input Bias Current –5.00 –0.03 5.00

µA
COMP Sink Current COMP=7.5V 10 mA
COMP Source Current COMP=2.5V –300 –175 –100

µA
COMP Clamp Voltage VFB=0.0V, COMP open 9.2 10.0 10.6 V

OUT Output

OUT Saturation Voltag e High VCC=13V, I

OUT= –200mA, RAMP=2V 0.5 1.7 2.5 V

OUT Saturation Voltag e Low I

OUT=200mA, ISNS= –1.0V 0.5 1.6 2.2 V

OUT Saturation Voltag e Low @ 10m A I

OUT=10mA, ISNS= –1.0V 0.05 0.40 V

OUT Clamp Voltage I

OUT= –200mA, RAMP=2V 10.0 12.0 14.5 V

OUT Voltage during UVLO I

OUT=100mA, VCC=0V 0.5 1.0 2.2 V

Overall Secti on

Inactive Supply Current VCC=10V 0.2 0.4 1.0 mA
Active Supply Current 3.0 6.0 10.0 mA
VCC Clamp Voltage ICC=25mA 30 33 36 V
VCC Turn-On Threshold 14.5 16.3 17.5 V
VCC Turn-Off Threshold 10.5 11.5 13.0 V
VCC Threshold Hysteresis 3 5 7 V

UDG-92002

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