Instruction Manual

MAX15303 PMBus Command Set User’s Guide
Page 22 of 52
IOUT_OC_FAULT_RESPONSE
•
MAX15303 does not support finite, non-zero restart-attempt counts. (Continuous restart
attempts are supported.)
• MAX15303 also does not support the “delay before shutdown”
(sometimes referred to as
“wait for abate”) option for overcurrent faults.
The IOUT_OC_FAULT_RESPONSE command data comprises three bit-fields:
Bits [7:6] determine the basic fault-response mode. The MAX15303 supports the following modes:
00 Ignore the fault condition.
01 Same as setting 10.
10 Stop regulating immediately, delay for the time specified in bits [2:0], then attempt to
restart according to bits [5:3]. (Default setting)
11 Same as setting 10.
Bits [5:3] determine the number of retry attempts. The MAX15303 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.
111 Attempt to restart continuously until commanded off, or until another fault
condition causes the unit to shut down. (Default setting)
Bits [2:0] determine the 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 MAX15303 to
use the minimum possible timing value, typically about 30-40ms. (The default timing for overcurrent
faults is 700ms.)
OT_FAULT_LIMIT
Reference:
Standard Command
Lockable:
Yes
Command Code:
0x4F
Format:
Linear
Data Bytes:
2
Units:
°C
Transfer:
Read/Write Word
Factory Value:
0xEB98 (115°C)
Description/Notes:
See Section 15.17 of the PMBus Specification Part II.
The MAX15303 has an internal temperature signal and can also measure temperature at an external
location, using a diode junction.
The OT_FAULT_LIMIT applies to the external temperature signal, if a valid sensor is detected during
initialization. If no external sensor is detected, the OT_FAULT_LIMIT applies to the internal
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
MAX15303.
Overtemperature fault hysteresis is achieved in the MAX15303 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.