Analog Devices Linear LTM 4700 User Manual page 86

LTM4700
PMBus COMMAND DETAILS
VOUT_MODE
The data byte for VOUT_MODE command, used for commanding and reading output voltage, consists of a 3-bit mode
(only linear format is supported) and a 5-bit parameter representing the exponent used in output voltage Read/Write
commands.
This read-only command has one data byte.
VOUT_MAX
The VOUT_MAX command sets an upper limit on any voltage, including VOUT_MARGIN_HIGH, the unit can com-
mand regardless of any other commands or combinations. The maximum allowed value of this command is 3.6V.
The maximum output voltage the LTM4700 can produce is 3.3V including VOUT_MARGIN_HIGH. However, the
VOUT_OV_FAULT_LIMIT can be commanded as high as 3.6V.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_OV_FAULT_LIMIT
The VOUT_OV_FAULT_LIMIT command sets the value of the output voltage measured by the OV supervisor compara-
tor at the sense pins, in volts, which causes an output overvoltage fault.
If the VOUT_OV_FAULT_LIMIT is modified and the part is in the RUN state, allow 10ms after the command is modi-
fied to assure the new value is being honored. The part indicates if it is busy making a calculation. Monitor bits 5 and
6 of MFR_COMMON. Either bit is low if the part is busy. If this wait time is not honored and the VOUT_COMMAND
is modified above the old overvoltage limit, an OV condition might temporarily be detected resulting in undesirable
behavior and possible damage to the switcher.
If VOUT_OV_FAULT_RESPONSE is set to OV_PULLDOWN or 0x00, the FAULT pin will not assert if VOUT_OV_FAULT is
propagated. The LTM4700 will pull the TG low and assert the BG bit as soon as the overvoltage condition is detected.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_OV_WARN_LIMIT
The VOUT_OV_WARN_LIMIT command sets the value of the output voltage measured by the ADC at the sense pins,
in volts, which causes an output voltage high warning. The MFR_VOUT_PEAK value can be used to determine if this
limit has been exceeded.
In response to the VOUT_OV_WARN_LIMIT being exceeded, the device:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Sets the VOUT bit in the STATUS_WORD
• Sets the VOUT Overvoltage Warning bit in the STATUS_VOUT command
• Notifies the host by asserting ALERT pin, unless masked
This condition is detected by the ADC so the response time may be up to t .
CONVERT
This command has two data bytes and is formatted in Linear_16u format.
Rev. B
86
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