Datasheet

MAX34446
PMBus Power-Supply Data Logger
13Maxim Integrated
receive the same command. However, no more than
one command can be sent to any one device in one
group command packet. The group command must not
be used with commands that require receiving devices
to respond with data, such as the STATUS_BYTE com-
mand. When the device receives a command through
this protocol, it immediately begins execution of the
received command after detecting the STOP condition.
The device supports the PAGE command and uses it to
select which individual channel to access. When a data
word is transmitted, the lower order byte is sent first and
the higher order byte is sent last. Within any byte, the
most significant bit (MSB) is sent first and the least sig-
nificant bit (LSB) is sent last.
PMBus Protocol Support
The device supports a subset of the commands defined
in the PMBus Power System Management Protocol
Specification Part II - Command Language, Revision
1.1. For detailed specifications and the complete list of
PMBus commands, refer to Part II of the PMBus speci-
fication available at www.PMBus.org. The supported
PMBus commands and the corresponding device behav-
ior are described in this document. All data values are
represented in DIRECT format, unless otherwise stated.
Whenever the PMBus specification refers to the PMBus
device, it is referring to the MAX34446. While the com-
mand can call for turning on or turning off the PMBus
device, the MAX34446 always remains on to continue
communicating with the PMBus master.
Data Format
Voltage data for commanding or reading the output
voltage or related parameters (such as the overvoltage
threshold) is presented in DIRECT format. DIRECT format
data is a 2-byte, two’s complement binary value. DIRECT
format data can be used with any command that sends
or reads a parametric value. The DIRECT format uses
an equation and defined coefficients to calculate the
desired values. Table 3 shows the coefficients used by
the device.
Table 3. PMBus Command Code Coefficients
PARAMETER COMMANDS UNITS RESOLUTION MAX m b R
Voltage
VOUT_OV_FAULT_LIMIT
VOUT_UV_FAULT_LIMIT
POWER_GOOD_ON
POWER_GOOD_OFF
READ_VOUT
MFR_VOUT_PEAK
MFR_VOUT_MIN
mV 1 32,767 1 0 0
Voltage Scaling VOUT_SCALE_MONITOR — 1/32,767 1 32,767 0 0
Current
IOUT_OC_FAULT_LIMIT
READ_IOUT
MFR_IOUT_PEAK
MFR_IOUT_AVG
mA 1 32,767 1 0 0
Current Scaling IOUT_CAL_GAIN
mI
0.1 3276.7 1 0 1
Temperature
OT_FAULT_LIMIT
READ_TEMPERATURE_1
MFR_TEMPERATURE_PEAK
MFR_TEMPERATURE_AVG
NC
0.01 327.67 1 0 2
Timing
MFR_FAULT_RETRY
MFR_PG_DELAY
ms 1 32,767 1 0 0
Power
READ_POUT
MFR_POUT_PEAK
MFR_POUT_AVG
W 1 32,767 1 0 0