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EVM Assembly Drawing and Layout

Figure 19. Bottom Signal Trace Layer

Figure 20. Bottom Side Component Assembly

Using the UCC2891 Active Clamp Current Mode PWM Controller

16

SLUU178A – November 2003 – Revised December 2006

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Summary of Contents for UCC2891

Page 1: ...48 V to 3 3 V Forward Converter with Active Clamp Reset Using the UCC2891 Active Clamp Current Mode PWM Controller User s Guide December 2006 Power Supply MAN SLUU178A ...

Page 2: ...48 V to 3 3 V Forward Converter with Active Clamp Reset Using the UCC2891 Active Clamp Current Mode PWM Controller User s Guide Literature Number SLUU178A November 2003 Revised December 2006 ...

Page 3: ... ability to drive either a P channel or N channel MOSFET in either a high side or low side active clamp configuration The UCC2891 also allows the ability to start up directly from the 48 V telecom bus voltage eliminating the need for external start up circuitry It includes programmable soft start internal slope compensation for peak current mode control internal low line voltage sensing internal s...

Page 4: ...2 28 0 5 inches Complementary auxilliary drive for active clamp with programmable dead time for ZVS Current mode control with synchronization function Internal PWM slope compensation Start up directly from telecom input voltage Synchronous rectifier output stage allows high efficiency operation Programmable soft start Up to 30 A dc output current Regulation to zero load current Non latching output...

Page 5: ...91EVM is shown in Figure 1 Terminal block J1 is the 48 V input voltage source connector and J8 is the output and return for the 3 3 V output voltage On the primary side U1 is the UCC2891 shown with the necessary discrete circuitry for configuring the controller to operate at 300 kHz with the maximum duty clamp set for 0 65 The EVM is programmed to start at VIN 36 V as determined by R11 and R12 To ...

Page 6: ...www ti com Schematic Figure 1 UCC2891EVM Schematic 6 Using the UCC2891 Active Clamp Current Mode PWM Controller SLUU178A November 2003 Revised December 2006 Submit Documentation Feedback ...

Page 7: ...y a higher average current than seen by Q3 and Q4 The output inductor L1 has a coupled secondary referenced to the primary side used to provide bootstrapping voltage to U1 A stable bias for the optocoupler U2 is provided by the series pass regulator made up of D6 Q6 and some associated filtering Scope jacks J2 and J3 allow the user to measure the gate to source and drain to source signals for Q2 t...

Page 8: ...rted between VIN and J1 as shown in Figure 2 A network analyzer can be connected directly to J6 and J7 The UCC2891EVM provides a 51 1 Ω resistor R25 between the output and the voltage feedback to allow easy non invasive measurement of the control to output loop response The connection between the source voltage VIN and J1 of the EVM can carry as much as 3 25ADC The minimum recommended wire size is...

Page 9: ...tially set to 0 V and connected to J1 as shown in Figure 2 3 Connect the ammeter A1 0A to10A range between VIN and J1 as shown in Figure 2 4 Connect voltmeter can optionally use voltmeter from VIN source if available V1 across VIN as shown in Figure 2 5 Connect LOAD1 to J8 as shown in Figure 2 Set LOAD1 to constant current mode to sink 0 ADC before VIN is applied 6 Connect voltmeter V2 across J9 a...

Page 10: ... 60 120 60 180 VIN 36 V IOUT 10 A gM 8 dB FM 50 Gain Phase f Frequency Hz Gain dB Phase GAIN AND PHASE vs FREQUENCY 4 2 10 6 12 8 6 18 26 30 22 10 14 2 IOUT Output Current A VIN 36 V VIN 72 V VIN 48 V P LOSS Power Loss W VOUT 3 3 V fS 300 kHz POWER LOSS vs OUTPUT CURRENT Power Up Down Test Procedures Figure 3 Figure 5 Figure 4 Using the UCC2891 Active Clamp Current Mode PWM Controller 10 SLUU178A ...

Page 11: ...NCY t Time 2 5 µs div VIN 72 V IOUT 30 A 50 mV div 36 mV peak to peak Output Ripple Voltage 10 40 60 100 1 k 10 k 100 k 0 20 40 20 60 120 180 0 60 120 60 180 VIN 72 V IOUT 10 A gM 9 dB F M 50 Gain Phase f Frequency Hz Gain dB Phase GAIN AND PHASE vs FREQUENCY Power Up Down Test Procedures Figure 8 Figure 6 Figure 9 Figure 7 SLUU178A November 2003 Revised December 2006 Using the UCC2891 Active Clam...

Page 12: ...age t Time 1 µs div VIN 72 V 12 3 V QF Gate J5 5 V div 5 4 V QR Gate J6 5 V div SR Gate Drive t Time 2 5 µs div VIN 48 V IOUT 10 A VPRI 40 V div IPRI 0 5 A div Transformer Primary Power Up Down Test Procedures Figure 12 Figure 10 Figure 13 Figure 11 12 Using the UCC2891 Active Clamp Current Mode PWM Controller SLUU178A November 2003 Revised December 2006 Submit Documentation Feedback ...

Page 13: ...th an internal ground plane The PCB dimensions are 3 6 x 2 7 with a design goal of fitting all components within the industry standard half brick format as outlined by the box dimensions 2 28 x 2 20 shown in Figure 15 All components are standard OTS surface mount components placed on the both sides of the PCB The copper etch for each layer is also shown Figure 14 Top Side Component Assembly SLUU17...

Page 14: ...ly Drawing and Layout Figure 15 Top Side Silk Screen Figure 16 Top Signal Trace Layer 14 Using the UCC2891 Active Clamp Current Mode PWM Controller SLUU178A November 2003 Revised December 2006 Submit Documentation Feedback ...

Page 15: ...wing and Layout Figure 17 Internal Split Ground Plane Figure 18 Internal Signal Trace Layer SLUU178A November 2003 Revised December 2006 Using the UCC2891 Active Clamp Current Mode PWM Controller 15 Submit Documentation Feedback ...

Page 16: ...wing and Layout Figure 19 Bottom Signal Trace Layer Figure 20 Bottom Side Component Assembly Using the UCC2891 Active Clamp Current Mode PWM Controller 16 SLUU178A November 2003 Revised December 2006 Submit Documentation Feedback ...

Page 17: ...pacitor ceramic 220 pF 50 V NPO 10 805 Vishay VJ0805A221KXAA C19 C20 2 Capacitor POSCAP 330 µF 6 3 V 20 7343 D Sanyo 6TPD330M D1 D2 D3 D4 D5 5 Diode schottky 200 mA 30 V SOT23 Vishay BAT54 D8 1 Diode switching 200 mA 200 V SOT23 Philips NXP BAS21 D6 1 Diode zener 5 1 V 350 mW SOT23 Vishay BZX84C5V1 D7 1 Adjustable precision shunt regulator 0 5 SOT23 TI TLV431BCDBZ J1 1 Terminal block 2 pin 15 A 5 ...

Page 18: ...0R0 F R17 R18 2 Resistor chip 499 Ω 1 10 W 1 805 Vishay CRCW0805 4990 F R19 1 Resistor chip 665 Ω 1 10 W 1 805 Vishay CRCW0805 6650 F R21 R22 2 Resistor chip 10 kΩ 1 10 W 1 805 Vishay CRCW0805 1002 F R25 1 Resistor chip 51 1 Ω 1 10 W 1 805 Vishay CRCW0805 51R1 F R26 1 Resistor chip 28 7 kΩ 1 10 W 1 805 Vishay CRCW0805 2872 F R27 1 Resistor chip 12 1 kΩ 1 10 W 1 805 Vishay CRCW0805 1212 F R28 1 Res...

Page 19: ...ling or use of the goods Please be aware that the products received may not be regulatory compliant or agency certified FCC UL CE etc Due to the open construction of the product it is the user s responsibility to take any and all appropriate precautions with regard to electrostatic discharge EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY IN...

Page 20: ...ainty as to the load specification please contact a TI field representative During normal operation some circuit components may have case temperatures greater than 50 C The EVM is designed to operate properly with certain components above 50 C as long as the input and output ranges are maintained These components include but are not limited to linear regulators switching transistors pass transisto...

Page 21: ...ice and is an unfair and deceptive business practice TI is not responsible or liable for any such statements TI products are not authorized for use in safety critical applications such as life support where a failure of the TI product would reasonably be expected to cause severe personal injury or death unless officers of the parties have executed an agreement specifically governing such use Buyer...

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