TEXAS INSTRUMENTS UC1853, UC2853, UC3853 Technical data
High Power Factor Preregulator
UC1853
UC2853
UC3853
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
BLOCK DIAGRAM
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.
11/97
UDG-94120-1
UC1853
UC2853
UC3853
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
CONNECTION DIAGRAM
DIL-8, SOIC-8 (Top View)
JorN,DPackage
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.
ELECTRICAL CHARACTERISTICS
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
Undervoltage Lockout Section
VCC Turn-on Threshold V
Hysteresis 1.5 1.8 2.1 V
Supply Current Section
CC Startup VCC = 8V, IAC = 100µA; VVCOMP,VICOMP Open 250 500
IV
IVCC IAC=0µA, VICOMP =0V 10 15 mA
Voltage Loop Error Amplifier Section
Transconductance IOUT=±20µA 0-70C 300 450 575 µmho
Input Voltage 0-70C 2.925 3 3.075 V
AVOL V
Output Sink Current V
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 06mV
Voltage Gain V
Sink Current VIMO = 100mV, VICOMP =3V 1 mA
Source Current VIMO = –0.1V, VICOMP = 3V –150 –80
Output High I
Output Low IICOMP =50mA 0.3 0.8 V
PWM Modulator Gain VICOMP = 2V – 3V (Note 1) 20 %/V
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.
VCOMP,VICOMP Open 11.5 13 V
m
A
Temperature 135 640 µmho
Temperature 2.9 3.1 V
VCOMP =1V–4V 50 60 dB
FB = 3.2V, VVCOMP = 3.75V 20 50 µA
ICOMP =1V–4V 70 dB
m
A
ICOMP = –50mA 6 6.8 V
2
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