UNITRODE UC1853, UC2853, UC3853 Technical data

UC1853

UC1853

UC2853

UC3853

High Power Factor Preregulator

FEATURES

∙Complete 8-pin Power Factor Solution

∙Reduced External Components

∙RMS Line Voltage Compensation

∙Precision Multiplier/Squarer/Divider

∙Internal 75kHz Synchronizable Oscillator

∙Average Current Mode PWM Control

∙Overvoltage Protection Comparator

∙High Current, Clamped Gate Driver

DESCRIPTION

The UC3853 provides simple, yet high performance active power factor correction. Using the same control technique as the UC1854, this 8-pin device exploits a simplified architecture and an internal oscillator to minimize external component count. The UC3853 incorporates a precision multiplier/squarer/divider circuit, voltage and current loop error amplifiers, and a precision voltage reference to implement average current mode control with RMS line voltage compensation. This control technique maintains constant loop gain with changes in input voltage, which minimizes input line current distortion over the worldwide input voltage range.

The internal 75kHz oscillator includes an external clock input, allowing synchronization to downstream converters. Additionally, the device features an overvoltage protection comparator, a clamped MOSFET gate driver which self-biases low during undervoltage lockout, and low startup and supply current.

These devices are available in 8-pin plastic and ceramic dual in-line (DIP) packages, and 8-lead small outline (SOIC) packages. The UC1853 is specified for operation from –55°C to +125°C, the UC2853 is specified for operation from –25°C to +85°C, and the UC3853 is specified for operation from 0°C to +70°C.

BLOCK DIAGRAM

UDG-94120-1

11/97

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V Output Drive Current,

Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.125A Peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5A Output Minimum Voltage . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V IAC Maximum Input Current . . . . . . . . . . . . . . . . . . . . . . . . 1mA IMO Maximum Output Current . . . . . . . . . . . . . . . . . . . . . –2mA IMO Minimum Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V FB Maximum Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 5V VCOMP Maximum Voltage. . . . . . . . . . . . . . . . . . . . . . . . . 6.2V ICOMP Sourcing Current . . . . . . . . . . . . . . . . . . . . Self-Limiting ICOMP Sinking Current . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA ICOMP Maximum Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 7.2V Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C Junction Temperature. . . . . . . . . . . . . . . . . . . –55°C to +150°C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C

All voltages with respect to GND. Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages.

UC1853

UC2853

UC3853

CONNECTION DIAGRAM

DIL-8, SOIC-8 (Top View)

J or N, D Package

ELECTRICAL CHARACTERISTICS	Unless otherwise stated, these parameters apply for TA = –55°C to +125°C for the
	UC1853; –25°C to +85°C for the 2853; and 0°C to +70°C for the UC3853; VCC =
	16V, VFB = 3V, IAC = 100mA, VVCOMP = 3.75V, VICOMP = 3V, TA = TJ.
PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNITS
Undervoltage Lockout Section
VCC Turn-on Threshold	VVCOMP, VICOMP Open		11.5	13	V
Hysteresis		1.5	1.8	2.1	V
Supply Current Section
IVCC Startup	VCC = 8V, IAC = 100μA; VVCOMP, VICOMP Open		250	500	mA
IVCC	IAC = 0μA, VICOMP = 0V		10	15	mA
Voltage Loop Error Amplifier Section
Transconductance	IOUT = ± 20μA 0-70C	300	450	575	μmho
	Temperature	135		640	μmho
Input Voltage	0-70C	2.925	3	3.075	V
	Temperature	2.9		3.1	V
AVOL	VVCOMP = 1V – 4V	50	60		dB
Output Sink Current	VFB = 3.2V, VVCOMP = 3.75V	20	50		μA
Output Source Current	VFB = 2.8V, VVCOMP = 3.75V		–50	–20	μA
Output Voltage High		5.5	6		V
Output Voltage Low			0.6	0.9	V
Current Loop Error Amplifier Section
Offset Voltage		0		6	mV
Voltage Gain	VICOMP = 1V – 4V		70		dB
Sink Current	VIMO = 100mV, VICOMP = 3V	1			mA
Source Current	VIMO = –0.1V, VICOMP = 3V		–150	–80	mA
Output High	IICOMP = –50mA	6	6.8		V
Output Low	IICOMP = 50mA		0.3	0.8	V
PWM Modulator Gain	VICOMP = 2V – 3V (Note 1)		20		%/V

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