EVAL-ADM1275EBZ Datasheet, PDF (31/48 Pages) Analog Devices – Hot-Swap Controller and Digital Power

Data Sheet
ADM1275
All warnings in the ADM1275 are generated by the power
monitor sampling voltage and current and then comparing
these measurements to the threshold values set by the various
limit commands. A warning has no effect on the hot-swap
controller, but it may generate an SMBAlert on one or both of
the GPOx/ALERTx output pins.
When a status bit is set, it always means that the status condition—
fault or warning—is active or was active at some point in the past.
When a fault or warning bit is set, it is latched until it is explicitly
cleared using either the OPERATION or the CLEAR_FAULTS
command. Some other status bits are live, that is, they always
reflect a status condition and are never latched.
STATUS_BYTE and STATUS_WORD Commands
The STATUS_BYTE and STATUS_WORD commands can
be used to obtain a snapshot of the overall part status. These
commands indicate whether it is necessary to read more
detailed information using the other status commands.
The low byte of the word returned by the STATUS_WORD
command is the same byte returned by the STATUS_BYTE
command. The high byte of the word returned by the
STATUS_WORD command provides a number of bits that can
be used to determine which of the other status commands
needs to be issued to obtain all active status bits.
STATUS_INPUT Command
The STATUS_INPUT command returns a number of bits
relating to voltage faults and warnings on the input supply.
STATUS_VOUT Command
The STATUS_VOUT command returns a number of bits
relating to voltage faults and warnings on the output supply.
This command is not available on the ADM1275-2.
STATUS_IOUT Command
The STATUS_IOUT command returns a number of bits
relating to current faults and warnings on the output supply.
STATUS_MFR_SPECIFIC Command
The STATUS_MFR_SPECIFIC command is a standard PMBus
command, but the contents of the byte returned is specific to
the ADM1275.
CLEAR_FAULTS Command
The CLEAR_FAULTS command is used to clear fault and
warnings bits when they are set. Fault and warnings bits are
latched when they are set. In this way, a host can read the bits
any time after the fault or warning condition occurs and
determine which problem actually occurred.
If the CLEAR_FAULTS command is issued and the fault or
warning condition is no longer active, the status bit is cleared.
If the condition is still active—for example, if an input voltage
is below the undervoltage threshold of the UV pin—the
CLEAR_FAULTS command attempts to clear the status bit, but
that status bit is immediately set again.
GPO AND ALERT PIN SETUP COMMANDS
Two multipurpose pins are provided on the ADM1275-1: GPO1/
ALERT1/CONV and GPO2/ALERT2. One multi-purpose pin is
provided on the ADM1275-2 (GPO1/ALERT1/CONV), and on
the ADM1275-3 (GPO2/ALERT2).
The GPO1/ALERT1/CONV and GPO2/ALERT2 pins have two
output modes of operation. These pins can be configured indepen-
dently over the PMBus as general-purpose digital outputs. They
can both be configured to generate an SMBAlert when one or more
fault/warning status bits become active in the PMBus status registers.
For an example of how to configure these pins to generate an
SMBAlert and how to respond and clear the condition, see the
Example Use of SMBUS Alert Response Address section.
The GPO1/ALERT1/CONV pin can also be configured as an
input (CONV) to drive the power monitor in single-shot run
mode and to control when a power monitor ADC sampling
cycle begins. This function can be used to synchronize sampling
across multiple ADM1275 devices, if required.
ALERT1_CONFIG and ALERT2_CONFIG Commands
Using combinations of bit masks, the ALERT1_CONFIG and
ALERT2_CONFIG commands can be used to select the status
bits that, when set, generate an SMBAlert signal to a processor.
They can also be used to set a GPO mode on the pin, so that it
is under software control. If this mode is set, the SMBAlert
masking bits are ignored.
On the ADM1275-1, one of the inputs can also be configured
as a hardware-based convert control signal. If this mode is set,
the GPO and SMBAlert masking bits are ignored.
POWER MONITOR COMMANDS
The ADM1275 provides a high accuracy, 12-bit current and
voltage power monitor. The power monitor can be configured
in a number of different modes of operation and can run in
either continuous mode or single-shot mode with a number
of different sample averaging options.
PMON_CONFIG Command
The power monitor can run in a number of different modes with
different input voltage range settings. The PMON_CONFIG
command is used to set up the power monitor.
The settings that can be configured are as follows:
• Single-shot or continuous sampling
• VIN or VOUT sampling (no VOUT sampling for the
ADM1275-2)
• Voltage input range
• Current and voltage sample averaging
Modifying the power monitor settings while the power monitor
is sampling is not supported. The power monitor must be
stopped before any of these settings are changed to ensure
correct operation and avoid any potential spurious data and
status alerts being generated.
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