Texas Instruments UC3855BN, UC3855BDWTR, UC3855BDW, UC3855AN, UC3855ADWTR Datasheet

UC1855A/B
UC2855A/B
UC3855A/B

DESCRIPTION

The UC1855A/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 program­ming without the need for slope compensation. In addition, the UC1855
utilizes an active snubbing or ZVT (Zero Voltage Transition technique) to
dramatically reduce diode recovery and MOSFET turn-on losses, result­ing in lower EMI emissions and higher efficiency. Boost converter switch­ing frequencies up to 500kHz are now realizable, requiring only an
additional small MOSFET, diode, and inductor to resonantly soft switch
the boost diode and switch. Average current sensing can be employed us­ing a simple resistive shunt or a current sense transformer. Using the cur­rent 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 signal to noise ratio
and negligible current sensing losses make this an attractive solution for
higher power applications.

The UC1855A/B also features a single quadrant multiplier, squarer, and
divider circuit which provides the programming signal for the current loop.
The internal multiplier current limit reduces output power during low line
conditions. An overvoltage protection circuit disables both controller out­puts in the event of a 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 com­parator, and overcurrent comparator complete the list of features. Avail­able packages include: 20 pin N, DW, Q, J, and L.

BLOCK DIAGRAM

High Performance Power Factor Preregulator

FEATURES

• Controls Boost PWM to Near Unity
Power Factor

• Fixed Frequency Average Current
Mode Control Minimizes Line Current
Distortion

• Built-in Active Snubber (ZVT) allows
Operation to 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

6/98

License Patent from PioneerMagnetics.Pin numbers refer to DIL-20 J or N packages.

UDG-94001-2

2

UC1855A/B
UC2855A/B
UC3855A/B

ABSOLUTE MAXIMUM RATINGS

Supply Voltage VCC..........................Internally Limited

VCC Supply Clamp Current .......................20mA

PFC Gate Driver Current (continuous) ..............±0.5A

PFC Gate Driver Current (peak) ...................±1.5A

ZVT Drive Current (continuous) ...................±0.25A

ZVT Drive Current (peak) .......................±0.75A

Input Current (IAC, RT, RVA) .......................5mA

Analog Inputs (except Peak Limit)..............−0.3 to 10V

Peak Limit Input ...........................−0.3 to 6.5V

Softstart Sinking Current .........................1.5mA

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

Junction Temperature...................−55°C to +150°C

Lead Temperature (Soldering, 10 sec.).............+300°C

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

CONNECTION DIAGRAMS

PLCC-20 & LCC-20 (Top View)
QorL Package

DIL–20 (Top View)
JorNPackage

SOIC-20 (Top View)
DW Package

ELECTRICAL CHARACTERISTICS: Unless otherwise specified: VCC = 18V, R

T

= 15k, RVS = 23k, CT = 470pF, CI =

150pF, VRMS = 1.5V, IAC = 100µA, I

SENSE

= 0V, CA

OUT

= 4V, VAOUT= 3.5V, VSENSE = 3V. TA =TJ. TA = –55°C to 125°C

(UC1855A/B), –40°C to 85°C (UC2855A/B), 0°Cto70°C (UC3855A/B).

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Overall

Supply Current, OFF CAO, VAOUT = 0V, VCC = UVLO −0.3V 150 500 µA
Supply Current, OPERATING 17 25 mA
VCC Turn-On Threshold UC1855A 15.5 17.5 V
VCCTurn-Off Threshold UC1855A,B 9 10 V
VCC Turn-On Threshold UC1855B 10.5 10.8 V
VCC Clamp I(VCC) = I

CC(on)

+ 5mA 18 20 22 V

Voltage Amplifier

Input Voltage 2.9 3.1 V
VSENSE Bias Current −500 25 500 nA
Open Loop Gain V

OUT

=2to5V 65 80 dB

V

OUT

High I

LOAD

= –300µA 5.75 6 6.25 V

V

OUT

Low I

LOAD

= 300µA 0.3 0.5 V

Output Short Circuit Current VOUT = 0V 0.6 3 mA

3

UC1855A/B
UC2855A/B
UC3855A/B

ELECTRICAL CHARACTERISTICS:

Unless otherwise specified: VCC = 18V, RT= 15k, RVS = 23k, CT = 470pF, CI =

150pF, VRMS = 1.5V, IAC = 100µA, I

SENSE

= 0V, CA

OUT

= 4V, VAOUT= 3.5V, VSENSE = 3V. TA =TJ. TA = –55°C to 125°C

(UC1855A/B), –40°C to 85°C (UC2855A/B), 0°Cto70°C (UC3855A/B).

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Current Amplifier

Input Offset Voltage VCM= − 2.5V −44mV
Input Bias Current (Sense) VCM= 2.5V −500 500 nA
Open Loop Gain VCM= 2.5V, VOUT =2to6V 80 110 dB
VOUT High I

LOAD

= −500µA6V

VOUT Low I

LOAD

= 500µA 0.3 0.5 V

Output Short Circuit Current V

OUT

=0V 1 3 mA
Common Mode Range −0.3 5 V
Gain Bandwidth Product FIN= 100kHz, 10mV, P–P, TA= 25°C 2.5 5 MHz

Reference

Output Voltage I

REF

= 0mA, TA = 25°C 7.388 7.5 7.613 V

I

REF

= 0mA 7.313 7.5 7.688 V

Load Regulation I

REF

=1to10mA −15 15 mV
Line Regulation VCC = 15 to 35V −10 10 mV
Short Circuit Current REF = 0V 20 45 65 mA

Oscillator

Initial Accuracy TA=25°C 170 200 230 kHz
Voltage Stability V

CC

=12to18V 1 %
Total Variation Line, Temp. 160 240 kHz
Ramp Amplitude (P–P) 4.9 5.9 V
Ramp Valley Voltage 1.1 1.6 V

Enable/OVP/Current Limit

Enable Threshold 1.8 2.2 V
OVP Threshold 7.5 7.66 V
OVP Hysteresis 200 400 600 mV
OVP Propagation Delay 200 ns
OVP Input Bias Current V= 7.5V 1 10 µA
PKLIMIT Threshold 1.25 1.5 1.75 V
PKLIMIT Input Current V

PKLIMIT

= 1.5V 100 µA

PKLIMIT Prop. Delay 100 ns

Multiplier

Output Current - IAC Limited IAC = 100µA, VRMS = 1V −235 −205 −175 µA
Output Current - Zero IAC = 0µA −2 −0.2 2 µA
Output Current - Power Limited VRMS = 1.5V, VAOUT = 5.5V −250 −209 −160 µA
Output Current VRMS = 1.5V, VAOUT = 2V −26 µA

VRMS = 1.5V VAOUT = 5V −190 µA
VRMS = 5V, VAOUT = 2V −3 µA
VRMS = 5V, VAOUT = 5V −17 µA

Gain Constant Refer to Note 1 −0.95 −0.85 −0.75 1/V

Gate Driver Output

Output High Voltage l

OUT

= −200mA, VCC = 15V 12 12.8 V
Output Low Voltage l

OUT

= 200mA 1 2.2 V
Output Low Voltage l

OUT

= 10mA 300 500 mV
Output Low (UVLO) lOUT = 50mA, VCC = 0V 0.9 1.5 V
Output RISE/FALL Time C

LOAD = 1nF 35 ns

Output Peak Current CLOAD = 10nF 1.5 A