ADM1065
SEQUENCE DETECTOR
The sequence detector block is used to detect when a step in a
sequence has been completed. It looks for one of the inputs to
the SE to change state, and is most often used as the gate on
successful progress through a power-up or power-down
sequence. A timer block is included in this detector, which can
insert delays into a power-up or power-down sequence, if
required. Timer delays can be set from 10 μs to 400 ms.
Figure 22 is a block diagram of the sequence detector.
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0
SUPPLY FAULT
DETECTION
LOGIC INPUT CHANGE
OR FAULT DETECTION
WARNINGS
FORCE FLOW
(UNCONDITIONAL JUMP)
VP1
VX5
INVERT
SEQUENCE
DETECTOR
SELECT
TIMER
Figure 22. Sequence Detector Block Diagram
The sequence detector can also help to identify monitoring
faults. In the sample application shown in Figure 21, the FSEL1
and FSEL2 states first identify which of the VP1,VP2, or VP3
pins has faulted, and then they take the appropriate action.
MONITORING FAULT DETECTOR
The monitoring fault detector block is used to detect a failure
on an input. The logical function implementing this is a wide
OR gate, which can detect when an input deviates from its
expected condition. The clearest demonstration of the use of
this block is in the PWRGD state, where the monitor block
indicates that a failure on one or more of the VP1,VP2, or VP3
inputs has occurred.
No programmable delay is available in this block, because the
triggering of a fault condition is likely to be caused when a
supply falls out of tolerance. In this situation, the user would
want to react as quickly as possible. Some latency occurs when
moving out of this state, however, because it takes a finite
amount of time (~20 μs) for the state configuration to
download from EEPROM into the SE. Figure 23 is a block
diagram of the monitoring fault detector.
0
SUPPLY FAULT
DETECTION
LOGIC INPUT CHANGE
OR FAULT DETECTION
VP1
VX5
MONITORING FAULT
DETECTOR
MASK
SENSE
1-BIT FAULT
DETECTOR
FAULT
WARNINGS
MASK
1-BIT FAULT
DETECTOR
FAULT
MASK
SENSE
1-BIT FAULT
DETECTOR
FAULT
Figure 23. Monitoring Fault Detector Block Diagram
TIMEOUT DETECTOR
The timeout detector allows the user to trap a failure to make
proper progress through a power-up or power-down sequence.
In the sample application shown in Figure 21, the timeout next-
state transition is from the EN3V3 and EN2V5 states. For the
EN3V3 state, the signal 3V3ON is asserted upon entry to this
state (on the PDO1 output pin) to turn on a 3.3 V supply. This
supply rail is connected to the VP2 pin, and the sequence detec-
tor looks for the VP2 pin to go above its UV threshold, which is
set in the supply fault detector (SFD) attached to that pin.
The power-up sequence progresses when this change is
detected. If, however, the supply fails (perhaps due to a short
circuit overloading this supply), then the timeout block traps
the problem. In this example, if the 3.3 V supply fails within
10 ms, then the SE moves to the DIS3V3 state and turns off this
supply by bringing PDO1 low. It also indicates that a fault has
occurred by taking PDO3 high. Timeout delays of from 100 μs
to 400 ms can be programmed.
FAULT REPORTING
The ADM1065 has a fault latch for recording faults. Two
registers are set aside for this purpose. A single bit is assigned to
each input of the device, and a fault on that input sets the
relevant bit. The contents of the fault register can be read out
over the SMBus to determine which input(s) faulted. The fault
register can be enabled/disabled in each state. This ensures that
only real faults are captured and not, for example, undervoltage
trips when the SE is executing a power-down sequence.