ZHCSES5A March   2016  – March 2016 UCC24636

PRODUCTION DATA.  

  1. 特性
  2. 应用
  3. 说明
  4. 修订历史记录
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Start Up and UVLO
      2. 8.3.2 Volt-Sec SR Driver On-Time Control
      3. 8.3.3 Standby Operation
      4. 8.3.4 Pin Fault Protection
        1. 8.3.4.1 VPC Pin Overvoltage
        2. 8.3.4.2 VPC Pin Open
        3. 8.3.4.3 VSC Pin Open
        4. 8.3.4.4 TBLK Pin Open
        5. 8.3.4.5 VPC and VSC Short to Ground
        6. 8.3.4.6 TBLK Pin Short to Ground
    4. 8.4 Device Functional Modes
      1. 8.4.1 Start-Up
      2. 8.4.2 Normal Operation
      3. 8.4.3 Standby Operation
      4. 8.4.4 Conditions to Stop Operation
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 AC-to-DC Adapter, 5 V, 15 W
      2. 9.2.2 Design Requirements
      3. 9.2.3 Calculation of Component Values
        1. 9.2.3.1 VPC Input
        2. 9.2.3.2 VSC Input
        3. 9.2.3.3 TBLK Input
      4. 9.2.4 Application Waveforms And Curves
    3. 9.3 Do's and Don'ts
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 VDD Pin
      2. 11.1.2 VPC Pin
      3. 11.1.3 VSC Pin
      4. 11.1.4 GND Pin
      5. 11.1.5 TBLK Pin
      6. 11.1.6 DRV Pin
    2. 11.2 Layout Example
  12. 12器件和文档支持
    1. 12.1 器件支持
      1. 12.1.1 器件命名规则
        1. 12.1.1.1 术语定义(用于设计示例)
    2. 12.2 文档支持
      1. 12.2.1 相关文档 
    3. 12.3 商标
    4. 12.4 静电放电警告
    5. 12.5 Glossary
  13. 13机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

9 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.

9.1 Application Information

The UCC24636 is a high performance controller driver for N-channel MOSFET power devices used for secondary-side synchronous rectification. The UCC24636 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 UCC24636 has enough versatility to be applied in DCM and TM operation. The UCC24636 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 UCC24636 a robust synchronous controller.

9.2 Typical Application

9.2.1 AC-to-DC Adapter, 5 V, 15 W

This design example describes the design of a 15-W off-line flyback converter providing 5 V at 3-A maximum load and operating from a universal AC input. The design uses the UCC28740 AC-to-DC valley-switching primary-side controller in a DCM type flyback converter and achieves over 86% full-load efficiency with the use of the secondary side UCC24636 synchronous rectifier controller.

UCC24636 app_schematic_ac_dc_chrgr_sluscg2.gif Figure 18. AC-to-DC Charger: 5 V, 15 W 

9.2.2 Design Requirements

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

Table 1. Performance Specifications AC-to-DC Charger 5 V, 15 W

PARAMETER TEST CONDITIONS MIN NOM MAX UNIT
INPUT CHARACTERISTICS
VACIN Input voltage 90 115/230 265 VRMS
fLINE Frequency 47 50/60 64 Hz
VAC(uvlo) Brownout voltage IOUT = IOUT(nom) 72 VRMS
VAC(run) Brownout recovery voltage 85 VRMS
IIN Input current VACIN = VACIN(min), IOUT = IOUT(nom) 335 mA
OUTPUT CHARACTERISTICS
VOUT Output voltage VACIN = VACIN(min) to VACIN(max),
IOUT = 0 to IOUT(nom)
4.9 5.0 5.1 V
IOUT(nom) Nominal output current VACIN = VACIN(min) to VACIN(max) 3.0 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)
80 mV
POUT Output power VACIN = VACIN(min), IOUT = IOUT(nom) 15 W
SYSTEM CHARACTERISTICS
ηavg Average efficiency VACIN = VACIN(nom), IOUT = 25%, 50%, 75%, 100% of IOUT(nom) 85% 87%
ƞ10% 10% Load efficiency VACIN = VACIN(nom), IOUT = 10% of IOUT(nom) 73.5% 82.5%
PNL No load power VACIN = VACIN(nom), IOUT = 0 14 22 mW

9.2.3 Calculation of Component Values

UCC24636 fig24new_lusc82.gif Figure 19. UCC24636 Circuit Design

For ease of understanding, Figure 19 is a modified version of Figure 15 where the component reference designators are the same as the schematic drawing of Figure 18.

9.2.3.1 VPC Input

For designs operating in constant current (CC) with low VOUT, there are two cases to examine. At maximum power, VIN(MIN) will be lower but VOUT is nominal. In constant current operation, VOUT is the minimum but VIN(MIN) will be higher. Determine R9 for both conditions, and choose the lowest value.

For minimal power dissipation, select:

Equation 8. UCC24636 qu7_lusc82.gif
Equation 9. UCC24636 qu7-2_lusc82.gif

With R9 = 147 kΩ :

Equation 10. UCC24636 qu8_lusc82.gif

Therefore, VVPC is within the recommended range of 0.45 V to 2.2 V.

9.2.3.2 VSC Input

The value of R23 is recommended to be with the range of 25 kΩ to 50 kΩ.

There is a 10% margin included for the initial value calculation of R11 to provide timing margin during initial operation verification.

Equation 11. UCC24636 Eq10_R17_slusc82.gif

With R11 = 115 kΩ, the operating range of the VSC pin is:

Equation 12. UCC24636 qu11_lusc82.gif
Equation 13. UCC24636 qu12_lusc82.gif

Therefore, VVSC is within the recommended range of 0.3 V to 2.2 V.

The UCC24636 SR timing can be optimized (SR on time increased) by increasing the R115 value after initial operation confirmation. The RatioVPC_VSC parameter has a positive tolerance of 5.3%. Using 1% divider resistors for VPC and VSC should allow reducing the 10% initial SR timing margin.

9.2.3.3 TBLK Input

The blanking time is set with resistor R22.

Select the blanking time to meet the following criteria based on 660-ns minimum primary on-time at high line.

tVPC-BLK = (tPRI × 0.85) – 120 ns

spacer

Equation 14. UCC24636 Eq12_R19_slusc82.gif

A value of R22 = 20 kΩ results in a blanking time of approximately 460 ns.

9.2.4 Application Waveforms And Curves

UCC24636 DRVTiming_115VAC_5V_3A.png
CH2 (Blue): Drain of synchronous rectifier Q1, 10V/Div
CH3 (Mag): VOUT, 2V/Div
CH4 (Green): DRV signal to Q1, 10V/Div
Figure 20. DRV Timing at 115 VAC, 5 V, 3 A
UCC24636 DRVTiming_115VAC_5V_300mA.png
CH2 (Blue): Drain of synchronous rectifier Q1, 10V/Div
CH3 (Mag): VOUT, 2V/Div
CH4 (Green): DRV signal to Q1, 10V/Div
Figure 22. DRV Timing at 115 VAC, 5 V, 300 mA
UCC24636 D002_SLUSCG2.gif Figure 24. Efficiency vs Output Current
UCC24636 DRVTiming_230VAC_5V_3A.png
CH2 (Blue): Drain of synchronous rectifier Q1, 10V/Div
CH3 (Mag): VOUT, 2V/Div
CH4 (Green): DRV signal to Q1, 10V/Div
Figure 21. DRV Timing at 230 VAC, 5 V, 3 A
UCC24636 DRVTiming_115VAC_18V_33A.png
CH2 (Blue): Drain of synchronous rectifier Q1, 10V/Div
CH3 (Mag): VOUT, 2V/Div
CH4 (Green): DRV signal to Q1, 10V/Div
Figure 23. DRV Timing at 115 VAC, 1.8 V, 3.3 A
UCC24636 D001_SLUSCG2.gif Figure 25. Output Voltage vs Output Current

9.3 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 16.
  • Do not use the UCC24636 in CCM flyback converter designs. For CCM designs, use the UCC24630 with the CCM dead time control function.
  • Do not use the UCC24636 in LLC converters as they can operate in CCM.
  • Do not add capacitance to the TBLK pin.
  • Do not add significant external capacitance to the VPC pin as there will be increased delay of the signal. If filtering is necessary a recommended maximum capacitance is 15 pF with a lower resistor divider network value of 10 kΩ.