UC2855ADW ,High Performance Power Factor PreregulatorMAXIMUM RATINGSSupply Voltage VCC........ Internally LimitedPLCC-20 & LCC-20 (Top View)VCC Supply C ..
UC2855AN , High Performance Power Factor Preregulator
UC2855BDW ,High Performance Power Factor PreregulatorMAXIMUM RATINGSSupply Voltage VCC........ Internally LimitedPLCC-20 & LCC-20 (Top View)VCC Supply C ..
UC2855BDWTR ,High Performance Power Factor PreregulatorELECTRICAL CHARACTERISTICS:Unless otherwise specified: VCC = 18V, RVS = 23k, CT = 470pF, CI = 150pF ..
UC2855BDWTRG4 ,High Performance Power Factor Preregulator 20-SOIC -40 to 85applicationUC2855A/BINFOUC3855A/BavailableHigh Performance Power Factor Preregulator
UC2855BN ,High Performance Power Factor Preregulatorfeatures. Avail-• Precision 1% 7.5V Referenceable packages include: 20 pin N, DW, Q, J, and L.
UM8237AE-5 , CMOS CLOCK GENERATOR & DRIVER
UM8237AE-5 , CMOS CLOCK GENERATOR & DRIVER
UM8237AE-5 , CMOS CLOCK GENERATOR & DRIVER
UM82450L , Asynchronous Communication Element(ACE)
UM91214B , Tone / Pulse Dialer
UM91214B , Tone / Pulse Dialer
UC2855ADW
High Performance Power Factor Preregulator
UC2855A/B
UC3855A/B
DESCRIPTIONThe UC3855A/B provides all the control features necessary for high
power, high frequency PFC boost converters. The average current mode
control method allows for stable, low distortion AC line current program-
ming without the need for slope compensation.In addition, the UC3855
utilizes an active snubbingor ZVT (Zero Voltage Transition technique)to
dramatically reduce diode recovery and MOSFET turn-on losses, result-
ingin lower EMI emissions and higher efficiency. Boost converter switch-
ing frequencies upto 500kHz are now realizable, requiring only an
additional small MOSFET, diode, and inductorto resonantly soft switch
the boost diode and switch. Average current sensing canbe employed us-
inga simple resistive shuntora current sense transformer. Using the cur-
rent sense transformer method, the internal current synthesizer circuit
buffers the inductor current during the switch on-time, and reconstructs the
inductor current during the switch off-time. Improved signalto noise ratio
and negligible current sensing losses make this an attractive solution for
higher power applications.
The UC3855A/B also featuresa single quadrant multiplier, squarer, and
divider circuit which provides the programming signalfor the current loop.
The internal multiplier current limit reduces output power during low line
conditions. An overvoltage protection circuit disables both controller out-
putsin the eventofa boost output OV condition.
Low startup supply current, UVLO with hysteresis,a 1% 7.5V reference,
voltage amplifier with softstart, input supply voltage clamp, enable com-
parator, and overcurrent comparator complete the listof features. Avail-
able packages include:20 pinN, DW,Q,J, andL.
BLOCK DIAGRAMHigh Performance Power Factor Preregulator
FEATURES Controls Boost PWMto Near Unity
Power Factor Fixed Frequency Average Current
Mode Control Minimizes Line Current
Distortion Built-in Active Snubber (ZVT) allows
Operationto 500kHz, improved EMI
and Efficiency Inductor Current Synthesizer allows
Single Current Transformer Current
Sense for Improved Efficiency and
Noise Margin Accurate Analog Multiplier with Line
Compensator allows for Universal
Input Voltage Operation High Bandwidth (5MHz), Low Offset
Current Amplifier Overvoltage and Overcurrent
protection Two UVLO Threshold Options 150µA Startup Supply Current Typical Precision 1% 7.5V Reference
