SLUSC82A March   2015  – March 2015 UCC24630

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Start Up and UVLO
      2. 7.3.2 Volt-Sec SR Driver On-Time Control
      3. 7.3.3 CCM Dead Time
      4. 7.3.4 Standby Operation
      5. 7.3.5 Pin Fault Protection
        1. 7.3.5.1 VPC Pin Overvoltage
        2. 7.3.5.2 VPC Pin Open
        3. 7.3.5.3 VSC Pin Open
        4. 7.3.5.4 TBLK Pin Open
        5. 7.3.5.5 VPC and VSC Short to Ground
        6. 7.3.5.6 TBLK Pin Short to Ground
    4. 7.4 Device Functional Modes
      1. 7.4.1 Start-Up
      2. 7.4.2 Normal Operation
      3. 7.4.3 Standby Operation
      4. 7.4.4 Conditions to Stop Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 AC-to-DC Adapter, 19.5 V, 65 W
      2. 8.2.2 Design Requirements
      3. 8.2.3 Calculation of Component Values
        1. 8.2.3.1 VPC Input
        2. 8.2.3.2 VSC Input
        3. 8.2.3.3 TBLK Input
      4. 8.2.4 Application Curves
    3. 8.3 Do's and Don'ts
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 VDD Pin
      2. 10.1.2 VPC Pin
      3. 10.1.3 VSC Pin
      4. 10.1.4 GND Pin
      5. 10.1.5 TBLK Pin
      6. 10.1.6 DRV Pin
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
        1. 11.1.1.1 Definition of Terms
      2. 12.3   Electrostatic Discharge Caution
      3. 12.4   Glossary
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The UCC24630 is a high performance controller driver for N-channel MOSFET power devices used for secondary-side synchronous rectification. The UCC24630 is designed to operate as a companion device to a primary-side controller to help achieve efficient synchronous rectification in switching power supplies. The controller features a high-speed driver and provides appropriately timed logic circuitry that seamlessly generates an efficient synchronous rectification system. With its current emulator architecture, the UCC24630 has enough versatility to be applied in DCM, TM and CCM modes. The UCC24630 SR on-time adjustability allows optimizing for PSR and SSR applications. Additional features such as pin fault protection, dynamic VPC threshold sensing, and voltage sense blanking time and make the UCC24630 a robust synchronous controller. CCM dead-time protection shuts off the DRV signal in the event of an unstable switching frequency.

8.2 Typical Application

8.2.1 AC-to-DC Adapter, 19.5 V, 65 W

This design example describes the design of a 65-W off-line flyback converter providing 19.5 V at 3.33-A maximum load and operating from a universal AC input. The design uses the LM5023 AC-to-DC quasi-resonant primary-side controller in a DCM type flyback converter and achieves over 92% full-load efficiency with the use of the secondary side UCC24630 synchronous rectifier controller.

UCC24630 fig1_luub81.gifFigure 23. AC-to-DC Adapter 19 V, 65 W 

8.2.2 Design Requirements

For this design example, use the parameters listed in Table 1.

Table 1. Performance Specifications AC-to-DC Adapter 19 V, 65 W

PARAMETER TEST CONDITIONS MIN NOM MAX UNIT
Input Characteristics
VACIN Input voltage 90 115/230 265 V
fLINE Frequency 47 50/60 64 Hz
VAC(uvlo) Brownout voltage IOUT = IOUT(nom) 80 VRMS
VAC(run) Brownout recovery voltage 90 VRMS
IIN Input current VACIN = VACIN(min), IOUT = IOUT(nom) 1.65 A
Output Characteristics
VOUT Output voltage VACIN = VACIN(min) to VACIN(max),
IOUT = 0 to IOUT(nom)		 18.5 19.5 20.5 V
IOUT(nom) Nominal output current VACIN = VACIN(min) to VACIN(max) 3.33 A
IOUT(min) Minimum output current VACIN = VACIN(min) to VACIN(max) 0 A
ΔVOUT Output voltage ripple VACIN = VACIN(min) to VACIN(max),
IOUT = 0 to IOUT(nom)		 500 mV
POUT Output power VACIN = VACIN(min) to VACIN(max) 65
System Characteristics
ηavg Average efficiency VACIN = VACIN(nom), IOUT = 25%, 50%, 75%, 100% of IOUT(nom) 89% 90%
ƞ10% 10% Load efficiency VACIN = VACIN(nom), IOUT = 10% of IOUT(nom) 79% 82%
PNL No load power VACIN = VACIN(nom), IOUT = 0 60 120 mW

8.2.3 Calculation of Component Values

UCC24630 fig24new_lusc82.gifFigure 24. UCC24630 Circuit Design

For ease of understanding, Figure 24 is a modified version of Figure 17 where the component reference designators are the same as the schematic drawing of Figure 23.

8.2.3.1 VPC Input

For minimal power dissipation:

Equation 8. UCC24630 qu7_lusc82.gif

With R15 = 576 kΩ

Equation 9. UCC24630 qu8_lusc82.gif
Equation 10. UCC24630 qu9_lusc82.gif

Therefore, VVPC is within the recommended range of 0.45 V to 2 V.

8.2.3.2 VSC Input

The value of R18 is recommended to be with the range of 25 kΩ to 50 kΩ.

Equation 11. UCC24630 Eq10_R17_slusc82.gif

With R17 = 590 kΩ the operating range of the VSC pin is:

Equation 12. UCC24630 qu11_lusc82.gif
Equation 13. UCC24630 qu12_lusc82.gif

Therefore, VVSC is within the recommended range of 0.3 V to 2 V.

8.2.3.3 TBLK Input

The blanking time is set with resistor R19.

Select the blanking time to meet the following criteria based on minimum primary on-time at high line.

tVPC-BLK = (tPRI × 0.85) – 120 ns

spacer

Equation 14. UCC24630 Eq12_R19_slusc82.gif

A value of R19 = 18 kΩ results in a blanking time of approximately 420 ns.

8.2.4 Application Curves

UCC24630 fig18_luub81.gif
C2(RED): DRV signal to synchronous rectifier Q1
C1(YELLOW): Drain of synchronous rectifier Q1
Figure 25. DRV Timing at 230 VAC, 65 W
UCC24630 fig21_luub81.gif
C2(RED): DRV signal to synchronous rectifier Q1
C1(YELLOW): Drain of primary-side MOSFET Q3
Figure 27. DRV Timing at 230 VAC, 12 W
UCC24630 D121_SLUUB81.gif
Figure 29. Efficiency vs Output Power
UCC24630 fig18_luub81.gif
C2(RED): DRV signal to synchronous rectifier Q1
C1(YELLOW): Drain of synchronous rectifier Q1
Figure 26. DRV Timing at 115 VAC, 65 W
UCC24630 fig20_luub81.gif
C2(RED): DRV signal to synchronous rectifier Q1
C1(YELLOW): Drain of primary-side MOSFET Q3
Figure 28. Light-Load Behavior (230 VAC, 8 W)

8.3 Do's and Don'ts

  • Do operate the device within the recommended operating maximum parameters. Consider output overvoltage conditions when determining stress.
  • Do consider the guideline for setting the blanking time resistor value illustrated in Figure 18.
  • Do not use the UCC24630 with converters that operate in constant skip cycle mode at high-power levels. The skip cycle behavior results in numerous CCM faults and missing DRV pulses.
  • Do not use the UCC24630 in CCM designs that are operating in CCM while the flyback controller is operating in variable frequency, FM, modulation. The CCM dead-time function is compatible with CCM operation during fixed-frequency, PWM operation.
  • Do not use the UCC24630 in hysteretic control CCM flyback converters. Constant skip-cycle operation at high-power levels results in numerous CCM cycle faults resulting in efficiency loss.
  • Do not use the UCC24630 in LLC converters.