12.1.1.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the UCC28710 device with the WEBENCH® Power Designer.

1. Start by entering the input voltage (V_IN), output voltage (V_OUT), and output current (I_OUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.

The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability.

In most cases, these actions are available:

• Run electrical simulations to see important waveforms and circuit performance
• Run thermal simulations to understand board thermal performance
• Export customized schematic and layout into popular CAD formats
• Print PDF reports for the design, and share the design with colleagues

Get more information about WEBENCH tools at www.ti.com/WEBENCH.

12.1.2.1 Capacitance Terms in Farads

• C_BULK: total input capacitance of C_B1 and C_B2.
• C_DD: minimum required capacitance on the VDD pin.
• C_OUT: minimum output capacitance required.

12.1.2.2 Duty Cycle Terms

• D_MAGCC: secondary diode conduction duty cycle in CC, 0.425.
• D_MAX: MOSFET on-time duty cycle.

12.1.2.3 Frequency Terms in Hertz

• f_LINE: minimum line frequency.
• f_MAX: target full-load maximum switching frequency of the converter.
• f_MIN: minimum switching frequency of the converter, add 15% margin over the f_SW(min) limit of the device.
• f_SW(min): minimum switching frequency (see Electrical Characteristics).

12.1.2.4 Current Terms in Amperes

• I_OCC: converter output constant-current target.
• I_PP(max): maximum transformer primary current.
• I_START: start-up bias supply current (see Electrical Characteristics).
• I_TRAN: required positive load-step current.
• I_VSL(run): VS pin run current (see Electrical Characteristics).

12.1.2.5 Current and Voltage Scaling Terms

• K_AM: maximum-to-minimum peak primary current ratio (see Electrical Characteristics).
• K_LC: current-scaling constant (see Electrical Characteristics).

12.1.2.6 Transformer Terms

• L_P: transformer primary inductance.
• N_AS: transformer auxiliary-to-secondary turns ratio.
• N_PA: transformer primary-to-auxiliary turns ratio.
• N_PS: transformer primary-to-secondary turns ratio.

12.1.2.7 Power Terms in Watts

• P_IN: converter maximum input power.
• P_OUT: full-load output power of the converter.
• P_RSTR: VDD start-up resistor power dissipation.
• P_SB: total stand-by power.
• P_{SB_CONV}: P_SB minus start-up resistor and snubber losses.

12.1.2.8 Resistance Terms in Ω

• R_CS: primary current programming resistance.
• R_ESR: total ESR of the output capacitor(s).
• R_PL: preload resistance on the output of the converter.
• R_S1: high-side VS pin resistance.
• R_S2: low-side VS pin resistance.

12.1.2.9 Timing Terms in Seconds

• t_D: current-sense delay including MOSFET turn-off delay; add 50 ns to MOSFET delay.
• t_DMAG(min): minimum secondary rectifier conduction time.
• t_ON(min): minimum MOSFET on time.
• t_R: resonant frequency during the DCM (discontinuous conduction mode) time.

12.1.2.10 Voltage Terms in Volts

• V_BLK: highest bulk capacitor voltage for stand-by power measurement.
• V_BULK(min): minimum voltage on C_B1 and C_B2 at full power.
• V_OCBC: target cable compensation voltage at the output terminals.
• V_CBC(max): maximum voltage at the CBC pin at the maximum converter output current (see Electrical Characteristics).
• V_CCR: constant-current regulating voltage (see Electrical Characteristics).
• V_CST(max): CS pin maximum current-sense threshold (see Electrical Characteristics).
• V_CST(min): CS pin minimum current-sense threshold (see Electrical Characteristics).
• V_DD(off): UVLO turn-off voltage (see Electrical Characteristics).
• V_DD(on): UVLO turn-on voltage (see Electrical Characteristics).
• V_OΔ: output voltage drop allowed during the load-step transient.
• V_DSPK: peak MOSFET drain-to-source voltage at high line.
• V_F: secondary rectifier forward voltage drop at near-zero current.
• V_FA: auxiliary rectifier forward voltage drop.
• V_LK: estimated leakage inductance energy reset voltage.
• V_OCV: regulated output voltage of the converter.
• V_OCC: target lowest converter output voltage in constant-current regulation.
• V_REV: peak reverse voltage on the secondary rectifier.
• V_RIPPLE: output peak-to-peak ripple voltage at full-load.
• V_VSR: CV regulating level at the VS input (see Electrical Characteristics).

12.1.2.11 AC Voltage Terms in V_RMS

• V_IN(max): maximum input voltage to the converter.
• V_IN(min): minimum input voltage to the converter.
• V_IN(run): converter input start-up (run) voltage.

12.1.2.12 Efficiency Terms

• η_SB: estimated efficiency of the converter at no-load condition, not including start-up resistance or bias losses. For a 5-V USB charger application, 60% to 65% is a good initial estimate.
• η: converter overall efficiency.
• η_XFMR: transformer primary-to-secondary power transfer efficiency.

Table 2. Related Links