7
dc2313af
DEMO MANUAL DC2313A
Quick start proceDure (without software)
software controL with LtpowerpLay
After the fault goes away the next automatic re-sequence
will succeed. The FAULTB pin will de-assert. The FAULT
LED will go off. Initiation of the next sequence-up operation
will clear the fault information in registers. The ALERTB
pin will remain asserted low until the ALERT condition is
cleared with an I
2
C bus operation.
Margining The Supplies
Margin testing stresses the system by moving voltages
beyond their normal OV and UV limits without generating
a fault. The MARGIN switch on the DC2313A board pulls
down the MARGB pin on the LTC2937, causing it to ignore
OV and UV faults while in the sequenced-up state. Note
that the LTC2937 does not control the voltages. Margining
the supplies involves pulling the regulators to out-of-spec
voltages, which is done outside of the LTC2937. The LDO
regulators on the DC2313A board do not change voltage,
but we can demonstrate MARGIN capability while disabling
one of the LDOs.
1) Begin with the system sequenced-down (all supplies
OFF)
While the supplies are down, the RST LED is illumi-
nated.
2) Switch SW3 to the MARGIN position (MARGIN active).
Observe the RST LED goes off, indicating that the
LTC2937 is ignoring the UV conditions.
3) Press the “SEQUENCE UP/DOWN” pushbutton to
sequence-up normally.
The PB_EN and GLOBAL_ON LEDs will illuminate.
The ENn LEDs will illuminate in sequence: 1-6.
The CHn LEDs will illuminate in sequence with the
ENn LEDs.
The RST LED will remain off because the MARGIN
function is active.
The FAULT LED will remain off.
The ALERT LED will remain off.
No voltage (UV and OV) limits are measured. The
default timing parameters should not detect faults.
4) While the MARGIN switch is active, short the EN4 turret
to GND by pressing the FAULT pushbutton.
The corresponding CH4 will go down and the LED
will go off.
No faults are detected due to the MARGIN function.
Note that the MARGIN function is only useful while the
supplies are sequenced-up, not while they are in the process
of sequencing. Holding the MARGB pin asserted low does
not mask SEQUENCE (timing) faults during sequencing-
up operations. If a supply fails to meet its programmed
sequence-up voltage/timing requirements then the normal
fault response prevails, regardless of MARGB state.
LTpowerPlay is a convenient PC software GUI that gives
complete access to the registers of the LTC2937, and many
other Linear Technology Power System Management parts.
Use it in off-line mode to build a system configuration file,
even with no hardware plugged-in, and use it with hard-
ware connected to configure and debug your application.
LTpowerPlay communicates using the I
2
C bus in the demo
system (covered in this manual), or in your real-world
product environment. It provides unprecedented control
over the Linear Technology chips on the I
2
C bus. Use it
during board bring-up to tune and optimize the power
system parameters. Use it during system debug to view
critical system information and troubleshoot board design
or manufacturing issues. LTpowerPlay includes extensive
help and documentation under the Help menu. On-line
help includes quick-start videos and tutorials, and detailed
technical documentation from the Linear Technology web
site. Getting started with LTpowerPlay is easy. Simply
download and install the PC software from here:
http://www.linear.com/ltpowerplay