SLLSFM0A March   2022  – June 2022 SN6507

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 Switching Characteristics
    7. 6.7 Typical Characteristics, SN6507
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Push-Pull Converter
      2. 8.3.2 Core Magnetization
      3. 8.3.3 Duty Cycle Control
      4.      Programmable Switching Frequency
      5. 8.3.4 Spread Spectrum Clocking
      6. 8.3.5 Slew Rate Control
      7. 8.3.6 Protection Features
        1. 8.3.6.1 Over Voltage Protection (OVP)
        2. 8.3.6.2 Over Current and Short Circuit Protection (OCP)
        3. 8.3.6.3 Under Voltage Lock-Out (UVLO)
        4. 8.3.6.4 Thermal Shut Down (TSD)
    4. 8.4 Device Functional Modes
      1. 8.4.1 Start-Up Mode
        1. 8.4.1.1 Soft-Start
      2. 8.4.2 Operation Mode
      3. 8.4.3 Shutdown Mode
      4. 8.4.4 SYNC Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Pin Configuration
        2. 9.2.2.2 LDO Selection
        3. 9.2.2.3 Diode Selection
        4. 9.2.2.4 Capacitor and Inductor Selection
        5. 9.2.2.5 Transformer Selection
          1. 9.2.2.5.1 V-t Product Calculation
          2. 9.2.2.5.2 Turns Ratio Estimate
        6. 9.2.2.6 Low-Emissions Designs
      3. 9.2.3 Application Curves
      4. 9.2.4 System Examples
        1. 9.2.4.1 Higher Output Voltage Designs
        2. 9.2.4.2 Commercially-Available Transformers
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Community Resources
    4. 10.4 Trademarks
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.6.2 Over Current and Short Circuit Protection (OCP)

The SN6507 is protected from overcurrent conditions with cycle-by-cycle current limiting on both NMOS switches. OCP is disabled during soft-start. After soft-start finishes, the OCP is enabled, and the threshold is set at the programmed value. The switch current is sensed and compared to the current threshold that is programmed by the external resistor on SS/ILIM pin, RILIM. Common current limit thresholds (ILIM) and their corresponding resistor values for RILIM are listed in Table 8-3 below. Leaving the ILIM/SS pin floating is not recommended for this device.

Table 8-3 Recommended 1% RILIM values
RILIMILIM (Typical)
18 kΩ1.3 A
20 kΩ1.2 A
22 kΩ1.1 A
24 kΩ1.0 A
27 kΩ900 mA
30 kΩ 800 mA
35 kΩ 700 mA
40 kΩ 600 mA
50 kΩ 500 mA
62 kΩ 400 mA
85 kΩ 300 mA
127 kΩ 200 mA
261 kΩ 100 mA
In case of an extreme over-load condition on the isolated output due to a short circuit, the device behaves as follows:

  • In the event of a transient overload or short circuit, if the resulting voltage dip is lower than 2.5 V (typical) on the SS/ILIM pin, the device considers it as a “soft-short” condition. In soft-shorts, the converter goes into hiccup mode: on hitting the programmed OCP threshold, the driver will be shut-off for 100 ns (typical), and then retry driving. If the OCP trips again, the cycle continues. This retry keeps occurring for entire TON time of SW1 and SW2 until OCP does not trip or a "hard-short" is triggered. During the OCP retry events, both FETs are turned OFF, and the transient peak current may go higher than OCP limit.

  • If the voltage dip is more than 2.5 V (typical), the devices considers it as a “hard-short” condition. The hard-short OCP threshold is fixed at 5 A (typical). If a hard-short condition lasts more than 200 μs, it indicates that the system is in a serious short-circuit fault condition, the device will fully discharge the soft-start cap and enters soft start once the short circuit is cleared. Note there is a 65 ns (typ.) response time to trigger hard-short OCP.