Maxim Integrated MAX15301 PMBus Command Set - Manual (Page 22)

MAX15301 PMBus Command Set User’s Guide
Rev 1 Page 22 of 53
VOUT_UV_FAULT_LIMIT
VOUT_COMMAND x 0.85, unless a specific value has been written to the User Store.
VOUT_UV_FAULT_RESPONSE
Reference: Standard Command Lockable: Yes
Command Code: 0x45 Format: Bit field
Data Bytes: 1 Units: N/A
Transfer: Read/Write Byte Factory Value: 0x00 (Ignore undervoltage faults)
Description/Notes: See Sections 10.5.1 and 15.7 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 VOUT_UV_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. (Default setting)
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.
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 undervoltage faults is 000
bin
.)
IOUT_OC_FAULT_LIMIT
Reference: Standard Command Lockable: Yes
Command Code: 0x46 Format: Linear
Data Bytes: 2 Units: A
Transfer: Read/Write Word Factory Value: 0xDB20 (25A)
Description/Notes: See Section 15.8 of the PMBus Specification Part II.
The MAX15301 hardware has 8-bit resolution for the overcurrent fault limit within a 30A full-scale
load current range.
The desired value of IOUT_OC_FAULT_LIMIT is retained in memory, regardless limitations imposed by
the 8-bit fault limit resolution, but the read-back value is based on actual hardware register settings.