Maxim Integrated MAX15303 PMBus Command Set - Manual (Page 20)

MAX15303 PMBus Command Set User’s Guide
Page 20 of 52
VOUT_OV_FAULT_RESPONSE
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]. (Default setting)
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 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. (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 MAX15303 to use the minimum possible timing value, typically about 30-40ms. (The
default timing for overvoltage faults is 000
bin
.)
VOUT_UV_FAULT_LIMIT
Reference: Standard Command Lockable: Yes
Command Code: 0x44 Format: Unsigned integer mantissa
Data Bytes: 2 Units: V
Transfer: Read/Write Word Factory Value: 0x019A (0.100V)
Description/Notes: See Section 15.6 of the PMBus Specification Part II.
VOUT_UV_FAULT_LIMIT mantissa data sent to and from the MAX15303 must be divided by 4096 to
determine the actual voltage value, according to the fixed value of
VOUT_MODE .
In the MAX15303, there are seven possible output voltage ranges based on seven corresponding
internal feedback divider taps. The MAX15303 hardware has 8-bit resolution for the undervoltage
fault limit within each of these seven ranges.
The desired value of VOUT_UV_FAULT_LIMIT is retained in memory, regardless of limitations
imposed by the feedback divider range and the 8-bit fault limit resolution, but the read-back value is
based on actual hardware register settings.
The factory value of 0x019A (0.100V) will be overridden during initialization to
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 MAX15303 does not support finite, non-zero restart-attempt counts. (Continuous
restart attempts are supported.)