Manual
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 OT_WARN_LIMIT as 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.
d
(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 OT_FAULT_LIMIT) is not considered to have abated until
the temperature has fallen below the OT_WARN_LIMIT value.