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Appendix 2.7 to ETSO-C153a - Integrated Modular Avionics (IMA) Platform and Module Minimum Performance Standard (MPS)

Available versions for ERULES-1963177438-18130

ED Decision 2020/011/R found in: CS-ETSO Amdt 17 - European Technical Standard Orders (Oct 2026)

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**Appendix
2.7 to ETSO-C153a – Integrated Modular Avionics (IMA) Platform and
Module Minimum Performance Standard (MPS)**

*ED
Decision
2020/011/R*

**CLASS PS: Power Supply (PS)**

**1. Purpose
and scope**

1.1. Introduction

This Appendix contains the Minimum Performance Standard (MPS) for the
CLASS PS Intended Function: Power Supply (PS).

These standards specify module characteristics that should be useful
to designers, manufacturers, installers and users of the module.

1.2. Definitions

For ETSO-C153a CLASS PS, the IMA module is a module, mounted into a
rack or the rack itself, able to supply power received from the
aircraft electrical network to one or more hardware modules mounted
in the same rack.

The following definitions are used:

—
Power supply unit: a set of physical
components (hardware and or software) in charge of managing a power
supply (or a part of the power supply) resource.

—
Power supply resource: obtained
electrical energy from the aircraft electrical network to be
distributed to electrical loads which are modules mounted into the
rack.

—
Power rail: a part of supplied
electrical energy for which a level of isolation is guaranteed by the
IMA module.

—
Mounted: it refers to another
hardware module installed and fixed inside the IMA Rack Module after
a manual operation.

—
Slot: a physical space inside the
Rack Module allocated to one hardware module.

—
Hold-up Capacity: The capacity of
the power supply to continue supplying output current after the input
voltage drops below the minimum level. This is usually expressed as
the time from the input voltage drop to the reset generated by the
power supply to the processor.

—
Output Current Capacity: the
continuously operating maximum current supplied for each output
voltage.

—
Power Monitors & Status
Outputs: a separate circuitry which checks the output voltage levels
and current loading of the power supply. This circuitry will generate
one or more binary signals that may be connected to the processor to
alert it to the ‘out of spec’ condition. These binary signals may
also force the power supply to shutdown to prevent damage to power
supply components.

—
Power Resets: a binary signal
output from the power supply that is asserted when the output
voltages are outside acceptable tolerances.

—
Regulation: the percentage of
variation of the output voltages when subjected to changes in load,
changes in temperature, and changes in all input voltage transients
and deviations.

—
Transient Immunity: the ability of
the power supply to continue operating normally during variations in
the input voltage. This is usually expressed as the time duration and
the voltage level of the transient.

—
Voltage Outputs and Tolerances: the
voltage levels and tolerances of the outputs produced by the power
supply.

In the context of PS class, the ‘concurrent item’ defined in
Appendix 2.1, paragraph 1 means ‘Power Rail’.

1.3. Intended Function

For ETSO-C153a CLASS PS, the intended function is to provide the
capability to share the Power Supply resource supplied by one or more
Power Supply unit(s).

The following figure provides an overview of the above-mentioned
intended function and definitions:

![](/static/files/file_jytjXw2lpRK/image136.png)

***Figure 22:
IMA module overview of ETSO-C153a CLASS PS***

**2. Requirements**

2.1. Functional requirements for ETSO-C153a CLASS PS

PS.a) The IMA module shall provide to hardware modules mounted in the
same rack Power Supply Resource which has the capacity to deliver a
quantity of electrical energy from power supply unit(s) to the
hardware modules while performing the regulation operations.

PS.b) The IMA module shall provide to hardware modules mounted into
the same rack the capacity to share the power supply resource thanks
to power rails accessible through physical interface(s).

![](/static/files/file_jytjXw2lpRK/image137.png)

***Figure 23:
CLASS PS (PS) — the relationship between the elements***

2.2. Characterisation requirements

PS.c) All aspects of the performance of the Power Supply of the
shared Power Supply Unit of the IMA module shall be characterised,
including but not limited to the following:

1. The needed input power budget characteristics (e.g. as a function
of temperature and load)

2. The performance of Output Currents and Tolerances;

3. The performance of Hold-up Capacity;

4. The performance of Power Monitors and Status Outputs;

5. The performance of Power Resets;

6. The performance of Power Regulation;

7. The performance of Transient Immunity;

8. The performance of Voltage Outputs and Tolerances;

9. The performance of User Interface Mechanism(s), Protocol(s) and
Service(s);

10. The performance of a supported Power Rail Type;

11. The Input and Output impedance; and

12. The capacitive load.

Note: These performance requirements are additional to those
applicable to and dictated by the design of the IMA module itself
(according to the ‘COMMON’ requirement of Appendix 2.1).

PS.d) In addition to the Common Requirement 0,
the characterisation shall address the safety aspects of events such
as a too low voltage or current, and a too high voltage or current.
The transient, as well as permanent effects, shall also be
characterised, if relevant.

PS.e) The characterisation shall provide any data needed to evaluate
the power profile characteristics (e.g. Maximum Value, InRush
Current) of managed power rails, and the IMA module power on/power
off behaviour characteristics.

**3. Verification
procedures**

The following table gives the verification method for each MPS;
nevertheless, an alternative method may be proposed to the
certification authority:

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<col/>
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
Requirement
				identifier
</td>
<td bgcolor="#808080">
Verification
				method
</td>
<td bgcolor="#808080">
Test
				under normal conditions
</td>
<td bgcolor="#808080">
Test
				under 

environmental
				conditions
</td>
<td bgcolor="#808080">
Comment
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
PS.a)
</td>
<td bgcolor="#d9d9d9">
T
</td>
<td bgcolor="#d9d9d9">
Y
</td>
<td bgcolor="#d9d9d9">
Y
</td>
<td bgcolor="#d9d9d9">
 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
PS.b)
</td>
<td bgcolor="#d9d9d9">
T
</td>
<td bgcolor="#d9d9d9">
Y
</td>
<td bgcolor="#d9d9d9">
Y
</td>
<td bgcolor="#d9d9d9">
 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
PS.c)
</td>
<td bgcolor="#d9d9d9">
T(A*)
</td>
<td bgcolor="#d9d9d9">
Y
</td>
<td bgcolor="#d9d9d9">
Y(1)
</td>
<td bgcolor="#d9d9d9">
 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
PS.d)
</td>
<td bgcolor="#d9d9d9">
T(A*)
</td>
<td bgcolor="#d9d9d9">
Y
</td>
<td bgcolor="#d9d9d9">
 

</td>
<td bgcolor="#d9d9d9">
 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
PS.e)
</td>
<td bgcolor="#d9d9d9">
A
</td>
<td bgcolor="#d9d9d9">
 

</td>
<td bgcolor="#d9d9d9">
 

</td>
<td bgcolor="#d9d9d9">
 

</td>
</tr>
</table>

***Table 7:
Verification Acceptance Criteria***

(A\*) means that verification by the Analysis method is possible for
the item that cannot be tested.

Note (1): applicable for a functional subset 
cf. CO.gg.

[Amdt ETSO/10]

[Amdt ETSO/16]