UC2855BNG4

application INFO available UC2855A/B UC3855A/B High Performance Power Factor Preregulator FEATURES DESCRIPTION • Controls Boost PWM to Near Unity Power Factor The 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 programming without the need for slope compensation. In addition, the UC3855 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. • 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 The UC3855A/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 License Patent from Pioneer Magnetics. Pin numbers refer to DIL-20 J or N packages. SLUS328B JUNE 1998 - REVISED October 2005 UDG-94001-2 UC2855A/B UC3855A/B CONNECTION DIAGRAMS 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 PLCC-20 & LCC-20 (Top View) Q or L Package 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. DIL–20 (Top View) J or N Package SOIC-20 (Top View) DW Package ELECTRICAL CHARACTERISTICS:Unless otherwise specified: VCC = 18V, RVS = 23k, CT = 470pF, CI = 150pF, VRMS = 1.5V, IAC = 100µA, ISENSE = 0V, CAO = 4V, VAOUT= 3.5V, VSENSE = 3V. –40°C to 85°C (UC2855A/B), 0°C to 70°C (UC3855A/B). PARAMETER TEST CONDITIONS MIN TYP MAX UNITS CAO, VAOUT = 0V, VCC = UVLO −0.3V 150 500 µA 17 25 mA VCC Turn-On Threshold UC3855A 15.5 17.5 VCCTurn-Off Threshold UC3855A,B Overall Supply Current, OFF Supply Current, OPERATING 9 VCC Turn-On Threshold UC3855B VCC Clamp I(VCC) = ICC(on) + 5mA 10 V V 10.5 10.8 V 20 22 V 3.1 V −500 25 500 nA 18 Voltage Amplifier Input Voltage 2.9 VSENSE Bias Current Open Loop Gain VOUT = 2 to 5V 65 80 VOUT High ILOAD = –300µA 5.75 6 6.25 VOUT Low ILOAD = 300µA 0.3 0.5 V Output Short Circuit Current VOUT = 0V 0.6 3 mA 2 dB V UC2855A/B UC3855A/B ELECTRICAL CHARACTERISTICS:Unless otherwise specified: VCC = 18V, RVS = 23k, CT = 470pF, CI = 150pF, VRMS = 1.5V, IAC = 100µA, ISENSE = 0V, CAO = 4V, VAOUT= 3.5V, VSENSE = 3V. –40°C to 85°C (UC2855A/B), 0°C to 70°C (UC3855A/B). PARAMETER TEST CONDITIONS MIN TYP MAX UNITS Current Amplifier −4 4 mV Input Offset Voltage VCM = − 2.5V −500 500 nA Input Bias Current (Sense) VCM = 2.5V 80 110 dB Open Loop Gain VCM = 2.5V, VOUT = 2 to 6V ILOAD = −500µA 6 V VOUT High ILOAD = 500µA 0.3 0.5 V VOUT Low 1 3 mA Output Short Circuit Current VOUT = 0V Common Mode Range −0.3 5 V 2.5 5 MHz Gain Bandwidth Product FIN = 100kHz, 10mV, P–P, TA = 25°C Reference 7.388 7.5 7.613 V Output Voltage IREF = 0mA, TA = 25°C 7.313 7.5 7.688 V IREF = 0mA −15 15 mV Load Regulation IREF = 1 to 10 mA Line Regulation VCC = 15 to 35V −10 10 mV Short Circuit Current REF = 0V 20 45 65 mA Oscillator 170 200 230 kHz Initial Accuracy TA = 25°C 1 % Voltage Stability VCC = 12 to 18V Total Variation Line, Temp. 160 240 kHz Ramp Amplitude (P–P) Outputs at 0% duty cycle 4.7 5.7 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 1.25 1.5 1.75 V PKLIMIT Threshold VPKLIMIT = 1.5V 100 µA PKLIMIT Input Current 100 ns PKLIMIT Prop. Delay Soft Start Soft Start Charge Current -10 -13 -20 mA Soft Start Discharge Current 2 10 20 mA 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 3 UC2855A/B UC3855A/B ELECTRICAL CHARACTERISTICS:Unless otherwise specified: VCC = 18V, RVS = 23k, CT = 470pF, CI = 150pF, VRMS = 1.5V, IAC = 100µA, ISENSE = 0V, CAO = 4V, VAOUT= 3.5V, VSENSE = 3V. –40°C to 85°C (UC2855A/B), 0°C to 70°C (UC3855A/B). PARAMETER TEST CONDITIONS MIN TYP MAX UNITS Gate Driver Output Output High Voltage Output Low Voltage Output Low Voltage Output Low (UVLO) Output RISE/FALL Time Output Peak Current lOUT = −200mA, VCC = 15V lOUT = 200mA lOUT = 10mA lOUT = 50mA, VCC = 0V CLOAD = 1nF CLOAD = 10nF ZVT ZVS Threshold Input Bias Current Propagation Delay Maximum Pulse Width Output High Voltage Output Low Voltage 0.5 2.3 V = 2.5V, VCT = 0 Measured at ZVTOUT lOUT = −100mA, VCC = 15V lOUT = 100mA lOUT = 10mA lOUT = 50mA, VCC = 0V CLOAD = 1nF CLOAD = 10nF Output Low (UVLO) Output RISE/FALL Time Output Peak Current Current Synthesizer ION to CS Offset Cl Discharge Current VION = 0V IAC = 50µA IAC = 500µA IAC Offset Voltage ION Buffer Slew Rate ION Input Bias Current RVS Output Voltage Note 1: Gain constant (K) = 12 12 0.25 105 0.3 VION = 2V 23k from RVS to GND IAC • (VAOUT – 1. 5V ) (VR MS 2 • IMO ) 2.87 12.8 1 300 0.9 35 1.5 2.6 6 100 400 12.8 1 300 0.9 35 0.75 30 118 5 0.65 10 2 3 2.2 500 1.5 2.9 20 2.2 900 1.5 50 140 1.1 15 3.13 V V mV V ns A V µA ns ns V V mV V ns A mV µA µA V V/µs µA V at VRMS = 1.5V, VAOUT = 5.5V. PIN DESCRIPTIONS CI: The level shifted current sense signal is impressed upon a capacitor connected between this pin and GND. The buffered current sense transformer signal charges the capacitor when the boost switch is on. When the switch is off, the current synthesizer discharges the capacitor at a rate proportional to the dI/dt of the boost inductor current. In this way, the discharge current is approximately equal to CA This is the inverting input to the current amplifier. Connect the required compensation components between this pin and CAOUT. The common mode operating range for this input is between −0.3V and 5V. CAO: This is the output of the wide bandwidth current amplifier and one of the inputs to the PWM duty cycle comparator. The output signal generated by this amplifier commands the PWM to force the correct input current. The output can swing from 0.1V to 7.5V. 3V IAC . – R R VS 4 Discharging the CI capacitor in this fashion, a “reconstructed” version of the inductor current is generated using only one current sense transformer. 4 UC2855A/B UC3855A/B PIN DESCRIPTIONS (cont.) CS: The reconstructed inductor current waveform generated on the CI pin is level shifted down a diode drop to this pin. Connect the current amplifier input resistor between CS and the inverting input of the current amplifier. The waveform on this pin is compared to the multiplier output waveform through the average current sensing current amplifier. The input to the peak current limiting comparator is also connected to this pin. A voltage level greater than 1.5 volts on this pin will trip the comparator and disable the gate driver output. ION: This pin is the current sensing input. It should be connected to the secondary side output of a current sensing transformer whose primary winding is in series with the boost switch. The resultant signal applied to this input is buffered and level shifted up a diode to the CI capacitor on the CI pin. The ION buffer has a source only output. Discharge of the CI cap is enabled through the current synthesizer circuitry. The current sense transformer termination resistor should be designed to obtain a 1V input signal amplitude at peak switch current. CT: A capacitor from CT to GND sets the PWM oscillator frequency according to the following equation: OVP: This pin senses the boost output voltage through a voltage divider. The enable comparator input is TTL compatible and can be used as a remote shutdown port. A voltage level below 1.8V, disables VREF, oscillator, and the PWM circuitry via the enable comparator. Between 1.8V and VREF (7.5V) the UC is enabled. Voltage levels above 7.5V will set the PWM latch via the hysteretic OVP comparator and disable both ZVTOUT and GTOUT until the OVP level has decayed by the nominal hysteresis of 400mV. If the voltage divider is designed to initiate an OVP fault at 5% of OV, the internal hysteresis enables normal operation again when the output voltage has reached its nominal regulation level. Both the OVP and enable comparators have direct logical connections to the PWM output and exhibit typical propagation delays of 200ns. f≈ 1 . 11200 • CT Use a high quality ceramic capacitor with low ESL and ESR for best results. A minimum CT value of 200pF insures good accuracy and less susceptibility to circuit layout parasitics. The oscillator and PWM are designed to provide practical operation to 500kHz. GND: All voltages are measured with respect to this pin. All bypass and timing capacitors connected to GND should have leads as short and direct as possible. GTOUT: The output of the PWM is a 1.5A peak totem pole MOSFET gate driver on GTOUT. A series resistor between GTOUT and the MOSFET gate of at least 10 ohms should be used to limit the overshoot on GTOUT. In addition, a low VF Schottky diode should be connected between GTOUT and GND to limit undershoot and possible erratic operation. REF: REF is the output of the precision reference. The output is capable of supplying 25mA to peripheral circuitry and is internally short circuit current limited. REF is disabled and low whenever VCC is below the UVLO threshold, and when OVP is below 1.8V. A REF “GOOD” comparator senses REF and disables the stage until REF has attained approximately 90% of its nominal value. Bypass REF to GND with a 0.1µF or larger ceramic capacitor for best stability. IAC: This is a current input to the multiplier. The current into this pin should correspond to the instantaneous value of the rectified AC input line voltage. This is accomplished by connecting a resistor directly between IAC and the rectified input line voltage. The nominal 650mV level present on IAC negates the need for any additional compensating resistors to accommodate for the zero crossings of the line. A current equal to one fourth of the IAC current forms one of the inductor current synthesizer inputs. RVS: The nominal 3V signal present on the VSENSE pin is buffered and brought out to the RVS pin. A current proportional to the output voltage is generated by connecting a resistor between this pin and GND. This current forms the second input to the current synthesizer. SS: Soft-start VSS is discharged for VVCC low conditions. When enabled, SS charges an external capacitor with a current source. This voltage is used as the voltage error signal during start-up, enabling the PWM duty cycle to increase slowly. In the event of a VVCC dropout, the OVP/EN is forced below 1.8V (typ), SS quickly discharges to disable the PWM. IMO: This is the output of the multiplier, and the noninverting input of the current amplifier. Since this output is a current, connect a resistor between this pin and ground equal in value to the input resistor of the current amplifier. The common mode operating range for this pin is −0.3V to 5V. 5 UC2855A/B UC3855A/B PIN DESCRIPTIONS (cont.) VAO: This is the output of the voltage amplifier. At a given input RMS voltage, the voltage on this pin will vary directly with the output load. The output swing is limited from approximately 100mV to 6V. Voltage levels below 1.5V on this pin will inhibit the multiplier output. VSENSE: This pin is the inverting input of the voltage amplifier and serves as the output voltage feedback point for the PFC boost converter. It senses the output voltage through a voltage divider which produces a nominal 3V. The voltage loop compensation is normally connected between this pin and VAO. The VSENSE pin must be above 1.5V at 25°C, (1.9V at –55°C) for the current synthesizer to work properly. VCC: Positive supply rail for the IC. Bypass this pin to GND with a 1µF low ESL, ESR ceramic capacitor. This pin is internally clamped to 20V. Current into this clamp should be limited to less than 10mA. The UC3855A has a 15.5V (nominal) turn on threshold with 6 volts of hysteresis while the UC3855B turns on at 10.5V with 500mV of hysteresis. ZVS: This pin senses when the drain voltage of the main MOSFET switch has reached approximately zero volts, and resets the ZVT latch via the ZVT comparator. A minimum and maximum ZVTOUT pulse width are programmable from this pin. To directly sense the ≈400V drain voltage of the main switch, a blocking diode is connected between ZVS and the high voltage drain. When the drain reaches 0V, the level on ZVS is ≈0.7V which is below the 2.6V ZVT comparator threshold. The maximum ZVTOUT pulse width is approximately equal to the oscillator blanking period time. VRMS: This pin is the feedforward line voltage compensation input to the multiplier. A voltage on VRMS proportional to the AC input RMS voltage commands the multiplier to alter the current command signal by 2 1/VRMS to maintain a constant power balance. The input to VRMS is generally derived from a two pole low pass filter/voltage divider connected to the rectified AC input voltage. This feature allows universal input supply voltage operation and faster response to input line fluctuations for the PFC boost preregulator. For most designs, a voltage level of 1.5V on this pin should correspond to low line, and 4.7V for high line. The input range for this pin extends from 0 to 5.5V. ZVTOUT: The output of the ZVT block is a 750mA peak totem pole MOSFET gate driver on ZVTOUT. Since the ZVT MOSFET switch is typically 3X smaller than the main switch, less peak current is required from this output. Like GTOUT, a series gate resistor and Schottky diode to GND are recommended. This pin may also be used as a high current synchronization output driver. For more information see Unitrode Applications Note U-153. 5.992 496 516 MHz 120 Gain -90 100 120 Phase Margin degrees Phase -45 Phase Gain (dB) 80 Degrees 0 60 100 80 60 40 Open-Loop 40 20 Gain dB 0 20 0 -20 0.1 -20 1 10 100 1000 10000 Frequency kHz -40 -60 10kHz 100kHz 1MHz 10MHz log f Figure 1. Current Amplifier Frequency Response Figure 2. Voltage Amplifier Gain Phase vs Frequency 6 UC2855A/B UC3855A/B 24 3.10 3.08 22 3.06 20 3.04 3.02 18 2.98 mA VOLTS 3.00 2.96 16 14 2.94 12 2.92 2.90 -60 -40 -20 0 20 40 60 10 80 100 120 140 -60 -40 -20 TEMP ERATURE °C 20 40 60 80 100 120 140 TEMP ERATURE °C Figure 3. Voltage Amplifier Input Threshold Figure 4. Supply Current ON 230 -0.75 225 -0.77 220 -0.79 215 -0.81 210 -0.83 205 -0.85 200 kHz GAIN CONSTANT (K) 0 -0.87 195 190 -0.89 185 -0.91 180 -0.93 175 -0.95 170 -60 -40 -20 0 20 40 60 80 100 120 140 -60 -40 -20 TEMP ERATURE °C 0 20 40 60 TEMP ERATURE °C Figure 5. Multiplier Current Gain Constant Figure 6. Oscillator Initial Accuracy 7 80 100 120 140 UC2855A/B UC3855A/B TYPICAL APPLICATION UDG-95165-1 Figure 7. Typical Application 8 PACKAGE OPTION ADDENDUM www.ti.com 14-Oct-2022 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) Samples (4/5) (6) UC2855ADW ACTIVE SOIC DW 20 25 RoHS & Green NIPDAU Level-2-260C-1 YEAR -40 to 85 UC2855ADW Samples UC2855BDW ACTIVE SOIC DW 20 25 RoHS & Green NIPDAU Level-2-260C-1 YEAR -40 to 85 UC2855BDW Samples UC2855BDWTR ACTIVE SOIC DW 20 2000 RoHS & Green NIPDAU Level-2-260C-1 YEAR -40 to 85 UC2855BDW Samples UC2855BN ACTIVE PDIP N 20 20 RoHS & Green NIPDAU N / A for Pkg Type -40 to 85 UC2855BN Samples UC3855ADW ACTIVE SOIC DW 20 25 RoHS & Green NIPDAU Level-2-260C-1 YEAR 0 to 70 UC3855ADW Samples UC3855ADWTR ACTIVE SOIC DW 20 2000 RoHS & Green NIPDAU Level-2-260C-1 YEAR 0 to 70 UC3855ADW Samples UC3855BDW ACTIVE SOIC DW 20 25 RoHS & Green NIPDAU Level-2-260C-1 YEAR 0 to 70 UC3855BDW Samples UC3855BDWG4 ACTIVE SOIC DW 20 25 RoHS & Green NIPDAU Level-2-260C-1 YEAR 0 to 70 UC3855BDW Samples UC3855BDWTR ACTIVE SOIC DW 20 2000 RoHS & Green NIPDAU Level-2-260C-1 YEAR 0 to 70 UC3855BDW Samples UC3855BN ACTIVE PDIP N 20 20 RoHS & Green NIPDAU N / A for Pkg Type 0 to 70 UC3855BN Samples UC3855BNG4 ACTIVE PDIP N 20 20 RoHS & Green NIPDAU N / A for Pkg Type 0 to 70 UC3855BN Samples (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of