Linear Technology DC2028A Manual page 14

ADvAnceD Demo BoArD operAtions
There are two types of actions to fault conditions: How a channel responds to another channel's fault and whether a
particular channel propagates its fault to other channels. FAULT pins are bidirectional, meaning the device may drive
its fault pin low (output) or may respond to the fault pin when another device drives it low (input). Because all fault
pins are wire OR'd on the DC2028A, this hardware configuration allows one to program each device's fault settings on
a channel-by-channel basis. By default, the LTC2977 is configured to shut down its channels if the FAULT pin is low
and to propagate its own fault via the FAULT pin. You can think of the Response switches as shut this channel down
when another channel faults, and the Propagate switches as drive a fault pin to broadcast to other channels that this
channel faulted.
FAULT CONFIGURATION EXAMPLE
Let's explore two different examples. Suppose we do not want
channel U0:0 (CH0 1.2V rail) to propagate its fault to the other
channels when it faults. And suppose we do not want channel
U0:1 (CH1 1.5V rail) to shut down in response to another chan-
nel's fault. We can configure the switches as shown in
Figure 11. Simply click the switches to open/close. Click
OK to close the dialog box. Click the PC->RAM icon to
write the changes to the DC2028A.
We can now create a fault on U0:0 (CH0) by shorting the output
to ground. You may use a coin or a jumper to temporarily connect
CH0 to the GND turret. You will notice that the channel shuts off
but the other channels remain powered up because its fault is not
propagated to the other channels. After the retry period, channel
U0:0 (CH0) will power back up. We can now observe the effect of
changing the response setting on U0:1 (CH1). If you short U0:3
(CH3 2.0V rail) to ground, notice that all rails shut down except
U0:1 (CH1). This is an example of a keep alive channel that remains
powered up independent of faults to other channels.
DEMO MANUAL DC2028A
Figure 11. Updated Fault Sharing Configuration
dc2028af
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