The following table lists signals which are important when designing a battery powered
system that is in compliance with the congatec Battery Management Interface
Specification.
Signal
(COM Express™)
Description
BATLOW#
This signal is used by the battery system to generate interrupts upon special events such as AC
power changes, attaching/detaching of batteries, battery low conditions, etc. A low pulse of at
least one microsecond is necessary to be recognized by the system host.
PS_ON#
A low level on PS_ON# or high level on SUS_S3# indicates that the Battery Management
System should turn on system power. Otherwise the Battery Management System must turn off
system power.
PWRBTN#
This signal is used to send a power-on request to the CPU module. The low pulse should be
about 250 milliseconds long.
I2CLK
I²C-bus clock line used for communication between Battery Management System controller and
system host
I2DAT
I²C-bus data line used for communication between Battery Management System controller and
system host
SLP_S5#
This signal is active low when the system switches to the S5 (soft off) state.
4.4 Placement and Layout Considerations
The conga-SBM²C is designed to minimize component count and layout complexity of
the carrier baseboard but there is still the necessity to follow high power and noise
separation layout rules.
•
Utilize enough trace width for power rails such as 5V, battery rails, DC-in rails.
•
Keep the trace length of the power rails short.
•
Keep power rails away from noise sensitive COM Express™ signals (LVDS, IDE,
VGA, Ethernet, USB).
•
Keep power rails away from noisy COM Express™ signals (PCICLK, etc.).
•
Keep battery bus and COM Express™ I²C Bus away from noisy signals.
•
Route all I²C Buses and SMBuses CLK and DATA signals close together.
•
Add ESD protective devices to signals where necessary
For more detailed information about high power layout rules consult literature found on
the web.
Copyright © 2008 congatec AG
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