Hardware Reference
In-Depth Information
The maximum current level is further de-rated or adjusted for the number of circuits in a
given connector housing due to the heat of any adjacent terminals. For example, a power
connector might be able to carry 8 amps per circuit in a 4-position connector, but the
same connector and terminal design might be able to handle only 6 amps per circuit in a
20-position connector.
All the modern form factor power supplies since ATX have standardized on the use of
Molex Mini-Fit Jr. connectors for the main and +12V connectors. A number of connector
housings are used with anywhere from 4 to 24 positions or terminals. Molex makes three
types of terminals for these connectors: a standard version, an HCS version, and a Plus
HCS version. The current ratings for these terminals are shown in
Table 18.6
.
Table 18.6 Current Ratings for Mini-Fit Jr. Connectors
The ATX main power connector is either a 20-pin or 24-pin connector, which, if standard
terminals are used, is rated for up to 6 amps of current per terminal. If the connector were
upgraded to HCS terminals, the rating would increase to 9 amps per terminal, and if up-
graded to Plus HCS terminals, the rating would increase further to 11 amps per termin-
al. Prior to March 2005, all the power supply form factor specifications called for using
standard terminals, but all the ratings from March 2005 to the present have changed to
require HCS terminals instead. If your power supply connector has been overheating, you
can easily install HCS or Plus HCS terminals to increase the power-handling capability of
your connector by 50% or more.
By counting the number of terminals for each voltage level, you can calculate the power-
handling capability of the connector, as shown in
Table 18.7
.
Table 18.7 ATX 20-pin Main Power Connector Maximum Power Handling Capabilities
