Ot_fault_limit, Ot_fault_response – Maxim Integrated MAX15301 PMBus Command Set User Manual
Page 24
MAX15301 PMBus Command Set User’s Guide
Rev 1
Page 24 of 53
OT_FAULT_LIMIT
temperature signal instead.
In addition to the PMBus-programmable OT_FAULT_LIMIT value, there is also a hard-coded limit of
130°C that applies solely to the internal temperature signal to protect the flash memory of the
MAX15301.
Overtemperature fault hysteresis is achieved in the MAX15301 by using the
“fault cleared” threshold for OT_FAULT_LIMIT. For this reason, it is important to always set
OT_WARN_LIMIT below OT_FAULT_LIMIT.
OT_FAULT_RESPONSE
Reference:
Standard Command
Lockable:
Yes
Command Code:
0x50
Format:
Bit field
Data Bytes:
1
Units:
N/A
Transfer:
Read/Write Byte
Factory Value:
0xC0 (Shut down, restart when fault
abates)
Description/Notes: See Sections 10.5.1 and 15.18 of the PMBus Specification Part II.
Note that the MAX15301 does not support finite, non-zero restart-attempt counts. (Continuous
restart attempts are supported.)
The OT_FAULT_RESPONSE command data comprises three bit-fields:
Bits [7:6] determine the basic fault-response mode. The MAX15301 supports the following modes:
00
Ignore the fault condition.
01
Continue operating and wait for the fault to abate for time specified in bits [2:0]. If the
fault does not abate, shutdown and attempt to restart according to bits [5:3].
10
Stop regulating immediately, delay for the time specified in bits [2:0], then attempt to
restart according to bits [5:3].
11
Stop regulating immediately, and then restart as soon as possible after the fault
condition abates.
(Default setting)
Bits [5:3] determine the number of retry attempts. The MAX15301 supports only a subset of the full
PMBus functionality for this portion of the command:
000-110
No attempt is made to restart after a fault shutdown. (Default setting)
111
Attempt to restart continuously until commanded off, or until another fault
condition causes the unit to shut down.
Bits [2:0] determine the fault-tolerance or retry-delay timing. Each binary value in bits [2:0]
corresponds to a multiple of 100ms, up to a possible maximum of 111
bin
= 700ms. A value of 000
bin
will cause the MAX15301 to use the minimum possible timing value, typically about 30-40ms. (The
default timing for overtemperature faults is 000
bin
.)
d
An overtemperature fault (i.e. relevant temperature signal above
) is not considered to have abated until
the temperature has fallen below the