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NetFPGA-SUME™ Reference Manual
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Note: the DDRVTT and QDRVTT rails are not directly monitored by the LTC2974s.
Supply Rail Undercurrent Fault Limit Rated Current Overcurrent Warning Limit Overcurrent Fault Limit
VCC1V0
-1A
40A
40A
44A
VCC1V8
-2A
15A
15A
15.5A
VCC2V0
-1A
2A
2A
3A
MGTAVCC
-1A
8A
8A
8.5A
MGTAVTT
-1A
3A
3A
3.1992A
VCC3V3
-1A
15A
15A
15.5A
VCC1V5
-1A
15A
15A
15.5A
MGTVAUX
-1A
1A
1A
1.0996A
DDRVTT
N/A
3A
N/A
N/A
QDRVTT
N/A
3A
N/A
N/A
Table 3. Current fault and warning limits
Note: the DDRVTT and QDRVTT rails are not directly monitored by the LTC2974s.
2.4 Fault and Warning Interrupt Sources
When the LTC2974 detects a fault or a warning condition it may signal an interrupt by driving the ALERTB,
AUXFAULTB, or FAULTB1 pins.
The ALERTB pin of the LTC2974 is an open drain output that is driven low whenever a fault or warning occurs. The
ALERTB pins of the two LTC2974s (IC43 and IC44) are connected in a wire-and fashion via the PCON_ALERT_B net
to pin J41 of the FPGA (IC12), as shown in Fig. 9. Enabling the internal pull-up on pin J41 will allow the FPGA
application to use this pin as an interrupt when any of the following situations occur:
Output overvoltage or under voltage fault/warning
Output over current or under current fault/warning
Over temperature fault/warning
Channel output voltage has not reached or exceeded the under voltage fault limit set for that channel
within TON_MAX_FAULT_LIMIT milliseconds (set to 15ms) of the output being enabled
When any of the above faults occur, the PCON_ALERT_B net will be driven low until the fault condition has been
removed and the CLEAR_FAULTS command has been sent to both of the LTC2974s (IC43 and IC44).
Figure 9. ALERTB interrupt source.