SNVAA98 January   2024 LM25148 , LM74910-Q1 , TPS38700 , TPS389006 , TPS389006-Q1 , TPS628301 , TPS628302 , TPS628303 , TPS6287B10 , TPS6287B15 , TPS6287B20 , TPS6287B25 , TPS746

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Design Parameters
  6. 3 Schematics
  7. 4 Design Considerations
  8. 5 Front-End Protection
  9. 6 3.3V Always-ON Bias Supply
  10. 7 5V Pre-Regulator Buck Converter
  11. 8 Low-Voltage High-Current Core Rail Buck Converter
  12. 9 On-Board Core Rail Output Load Transient Stepper
  13. 10Multiple Peripheral Rail Buck Converters Sub-Circuits Schematic
  14. 11Voltage Supervisor and Sequencer
  15. 1212-Channel Sequencer Alternative
  16. 13Summary
  17. 14References

5 Front-End Protection

A LM74910 front-end protection (FEP) circuit is found at the main input of the circuit where the main power source connects. This FEP controller provides features such as:

  • Reverse-polarity protection
  • Programmable over-current protection (OCP) disconnect (through R1, R16, and R4 component values)
  • Programmable under-voltage disconnect/lockout protection (through R2 and R9 divider values)
  • Programmable over-voltage disconnect/lockout protection (through R10 and R12 divider values)
  • Programmable output-voltage ramp/slew time, which enables a controlled current into bulk capacitance, upon startup (through R8 and C10 component values)
  • Programmable protection/fault delay time (through a resistor or capacitor, R18 or C12, from the TMR pin to GND)
  • Current monitoring (through R1, R17, and R4 components values)

For details on the functionality mentioned and other features, please see corresponding sections of the LM74910 data sheet.

Other options are available for the front-end protection IC, aside from the LM74910. Please see the Texas Instrument website and search in the Ideal diode/ORing controllers section for alternatives.

If a front-end protection is not needed, omit the entire LM74910 sub-circuit (everything to the right of TP1 and to the left of TP2) and, in this circuit depiction, connect the main input supply +12Vin_Main to the 12Vs node by installing J1 and J2 jumpers.