Soft-Start Window - Analog Devices ADP1055-EVALZ User Manual

UG-710

SOFT-START WINDOW

This window programs PMBUS functions TON_DELAY,
TON_RISE (the soft-start time), and TON_MAX. In the
Additional Settings tab, several faults can be blanked during
soft start and additional features, such as soft start from
precharge can be selected.
Figure 30. Soft-Start Window
The settings can be changed in a simple drag-and-drop fashion
and or by checking/unchecking the checkbox. Changes take
place immediately and are stored in the RAM of the IC, but
need to be saved to EEPROM for permanent storage.
Figure 31. PSU Soft Start at 20 A Load
Green Trace: Output Voltage
Red Trace: PWM
To facilitate a proper soft start from the precharge/prebias
condition where the output bus has not yet discharged to zero,
the ADP1055 uses the SR phase in and SR transition function to
ensure that the output voltage reaches the setpoint value in a
monotonic fashion. The SR phase in and SR transition function
changes the width of SR1 and SR2 from light load mode setting
to the normal mode setting, the setting for continuous
conduction mode (CCM), in steps of 5 ns per x switching
periods where x ranges from 1 to 1024. This prevents a
momentary dip in output voltage when the power supply is
turned on.
Things to Try
1. Change the soft-start timing in the Soft-Start window.
2. Adjust/change the blanking of faults during soft start.
Rev. B | Page 12 of 43
ADP1055-EVALZ User Guide
Figure 32. PSU Soft Start from Precharge
Green Trace: Output Voltage
Blue Trace: Hardware PSON
Yellow Trace: Primary Current