POWER MANAGER DESIGN EXAMPLES Lattice Applications Group DESIGN POWR1220AT8-1 Features File: POWR1220AT8-1-SSt_Seq_RG_Sup_Trm.PAC Implemented Functions • De-bounce and Soft-start Backplane 5V and 3.3V Power Feed • Sequence On board Power Supplies – First 3.3V, Next 2.5V & Next 1.8V • 6 Supply Reset Generator With Pulse Stretching After Sequencing • Activate Brown_Out Signal is Any Supply Fails • Sequence Supplies In the Reverse Order • Trim Onboard DC-DC Converters (2.5V & 1.8V) to Within 1% of Their Rated Voltage Programmable Features • Each of the Voltage Monitoring Thresholds are Programmable From 0.67V to 5.8V • Reset Pulse Stretch Duration is Programmable From 32 µs to 2 Seconds • Brown Out Processing Duration Programmable From 32 µs to 2 Seconds • Initial Contact De-bounce Period Programmable From 32 µs to 2 Seconds • Each of the Voltage Monitoring Thresholds are Programmable From 0.67V to 5.8V Possible Additions • Watchdog Timer • Monitor and Sequence 5 More Supplies • Manual Reset Input • Margining of Onboard DC-DC Converter Power Manager II Design Examples Page: 2 © Lattice Semiconductor 2011 SOFT START, SEQUENCE, RESET, SUPERVISOR, TRIM File: POWR1220AT8-1-SSt_Seq_RG_Sup_Trm.PAC Power Manager II Design Examples Page: 3 © Lattice Semiconductor 2011 DESIGN POWR1220AT8-1 Algorithm File: POWR1220AT8-1-SSt_Seq_RG_Sup_Trm.PAC Main Sequence 1. Wait for 3.3V and 5V From Backplane to Stabilize for 100 ms 2. Enable Soft Start Operation of 3.3V and 5V Using MOSFET Enable 3. Wait for Board 3.3V to Reach Acceptable Voltage Level 4. Enable 2.5V Supply 5. Wait for 2.5V Supply to Reach Acceptable Voltage Level 6. Enable 1.8V Supply 7. Wait for 1.8V Supply to Reach Acceptable Voltage Level 8. Release CPU_Reset After 100 ms, Enable Closed Loop Trimming of 2.5V and 1.8V DC-DC Converters, and Release the Brown_Out Interrupt 9. Monitor for Any Supply Failure 10. Activate Brown_Out Signal and Disable Closed Loop Trimming & Wait for Interrupt Process to Complete 11. Activate CPU_Reset Signal and Disable 1.8V Supply 12. Wait for a Couple of Milliseconds and Disable 2.5V Supply 13. Wait for a Couple of Milliseconds and Turn off 3.3V and 5V MOSFET Power Manager II Design Examples Page: 4 © Lattice Semiconductor 2011