Linear Technology DC2028A Manual page 8

common Demo BoArD operAtions
MARGIN ALL RAILS
The LTC2977 Power System Manager on the DC2028A not only monitors
each of the eight outputs but can margin the outputs either high or low.
Margining is the operation that moves a rail either up or down for testing
purposes. It allows a system to be fully characterized over supply limits
without the use of external hardware or resources. The GUI provides an
easy way to margin all rails high or all low by clicking one of four buttons.
To invoke the margining dialog, click the GroupOp icon in the toolbar.
The buttons labeled ignore faults will margin without creating a fault
even if the fault limits are exceeded.
A look at the telemetry window shows the effect of the margin high or
margin low operation. The screen shot shows all rails going from nominal
setpoints to margin high, margin low, and back to nominal voltages.
The LTC2977 has a multiplexed ADC that is used to provide voltage, cur-
rent, and temperature readback values. The telemetry plot in the GUI is
similar to a multi-channel oscilloscope which is capable of displaying any
parameter that is displayed in the telemetry window. Due to the nature
of a multiplexed ADC converter, it has an associated ADC loop time. The
total ADC loop time (~100-160ms) for a given channel is dependent on
the device's configuration.
CREATING A FAULT
There is a pushbutton on the DC2028A board that is used to force a fault
and demonstrate the demo board's ability to detect it and respond accord-
ing to the configuration. When depressed, the pushbutton creates a fault
(short to ground) on channel 7, the 3.3V output (GUI channel U0:7). The
user should see all outputs power off, the fault LED momentarily illuminate,
the alert LED illuminate continuously, and all rails sequence
back on after a retry period. The user may also short any
power supply output indefinitely. This is a good way to
induce UV faults and shows that a shorted channel will not
be damaged. Use a jumper wire or a coin to short any
output.
DEMO MANUAL DC2028A
dc2028af
7