AN 896: Multi-Rail Power Sequencer and Monitor Reference Design

ID 683778
Date 9/30/2019
Public
Document Table of Contents

2.3.3.1. Sequencer Voltage Monitor Parameter Settings

There are two groups of options: Parameters and Voltage Monitor Thresholds, with a calculated Derived Thresholds section for each voltage rail.
Table 3.   Sequencer Voltage Monitor Parameters - Parameters
Parameter Description
Output Voltage Rails

Specify the number of output voltage rails to sequence.

The number must match the value you specify in the other components of the system. Otherwise, the interface bus widths between components will not match.

Power Good Inputs

Specify the number of power good inputs to monitor.

The number must match the value you specify in the other components of the system. Otherwise, the interface bus widths between components will not match.

ADC Reference Voltage

Specify the reference voltage value.

The component uses this value to calculate the various power good, undervoltage, and overvoltage thresholds to compare to the ADC output.

Functionality Level

Select the functionality level of the Sequencer Voltage Monitor component:

  • No PMBus—the design uses the hardcoded levels specified in the parameter editor. Dynamic adjustment or monitoring via the PMBus* is not available.
  • Hard-Coded Thresholds—you can use the PMBus* Slave to Avalon®-MM Master Bridge to monitor fault and status but you cannot dynamically adjust the voltage level thresholds.
  • Full-featured—the design contains the full PMBus* command set for dynamic adjustment, status, and error monitoring. For more information, refer to the related information.

This option allows you to optimize the design and reduce its overall logic footprint. For the logic utilization estimates, refer to the related information.

ADC Samples to Check

Specify the number of contiguous ADC samples to check per input before declaring a warning or a fault such as overvoltage, undervoltage, and power good on or off.

Retry Attempts

Specify the number of attempts the Power Sequencer component should make to sequence power up—following a complete, controlled sequence down—after detecting an error condition.

Timeout Interval on Retry

Select the delay interval the Power Sequencer component waits before retrying the power up sequence:

  • No Delay—retries the power up sequence immediately after all rails have sequenced down
  • Use Delay Specified by the Sequencer—delays the retry attempts according to the Delay Time Between Restarts setting in the Power Sequencer component
Table 4.   Sequencer Voltage Monitor Parameters - Voltage Monitor Thresholds

Specify the VIN and VOUT thresholds in their respective tabs:

  • The Derived Thresholds section displays the calculated voltage thresholds.
  • Ensure that each calculated threshold does not exceed the ADC Reference Voltage setting in the Parameters section.
  • The default thresholds are based on the typical expected voltage for that rail, after any voltage dividers.
  • The component converts all voltage settings in this table to the PMBus* DIRECT format. For information about translating to and from the DIRECT format, refer to the related information.
Parameter Description Default Threshold
VIN/VOUTN Typical Voltage, Monitored

Specify the typical voltage level that you expect to observe at the ADC analog input.

In your expectation, include the effect of all voltage divider circuitries on the board.

VIN/VOUTN Overvoltage Fault

Specify the percentage of the VIN/VOUTN Typical Voltage, Monitored at which to declare an overvoltage fault.

107%
VIN/VOUTN Overvoltage Warning

Specify the percentage of the VIN/VOUTN Typical Voltage, Monitored at which to declare an overvoltage warning.

105%
VIN/VOUTN Undervoltage Warning

Specify the percentage of the VIN/VOUTN Typical Voltage, Monitored at which to declare an undervoltage warning.

97%

VIN ON Level

(VIN tab only)

Specify the percentage of the VIN Typical Voltage, Monitored at which to consider the monitored input rail as good and start the power up sequencing of the output rails.

97%

VOUT Power Good Assertion Level

(VOUTN tabs only)

Specify the percentage of the VOUTN Typical Voltage, Monitored at which to consider the output voltage of the rail as good and start the power up sequencing of the next output rail.

97%
VIN/VOUTN Undervoltage Fault

Specify the percentage of the VIN/VOUTN Typical Voltage, Monitored at which to declare an undervoltage fault.

93%

VIN OFF Level

(VIN tab only)

Specify the percentage of the VIN Typical Voltage, Monitored at which to consider the monitored input rail as bad and start the power down sequencing of all rails.

90%

VOUTN Power Good Deassertion Level

(VOUTN tabs only)

Specify the percentage of the VOUTN Typical Voltage, Monitored at which to consider the output voltage of the rail as bad and start the power down sequencing of all rails.

90%
Overvoltage Faults cause controlled sequence down

Turn this on to sequence power down for all rails, based on the fault response, if the component detects an overvoltage fault in the VIN or VOUTN rail.

Undervoltage Faults cause controlled sequence down

Turn this on to sequence power down for all rails, based on the fault response, if the component detects an undervoltage fault in the VIN or VOUTN rail.

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