Cirrus Logic EDB9315A User Manual

Page 14

EDB9315A
Technical Reference Manual

DS638DB3

Page 14

Power and reset circuits are shown on this page. Most of the changes made to this revision of the
EDB9315A board were made in this section. The most important change made is that the board is now
powered from a +12V power supply instead of the former +5V supply.

The board has two connectors for input power. J10 is the standard power connector and is where the
power supply provided in the kit attaches. However, a 3x1 header, J11 is also available to supply power
to the board.

The 3.3V power rail is generated from a 3A, adjustable, switching regulator, U27. The 5V power rail is
generated from an identical 3A switching regulator, U28. The 5V supply requires a diode, D7. The 3.3V
supply does not require this diode.

The 1.8V power rail is generated from an 800mA linear regulator. Both the 3.3V and 1.8V power rails are
are monitored by U22 and it will issue a reset if either supply falls below the threshold voltage.

The reset pushbutton can connect directly to the voltage monitor reset input or to a supplementary reset-
detect circuit. Refer to AN258 for more information. This circuit is implemented by U24 and some passive
devices. In general, this circuit is not required with EP9315 Rev E2 devices and may be removed if
desired. It is installed by default. If removed, R109 needs to be installed if the use of the reset pushbutton
is desired.