GE Industrial Solutions 2 × 12A Digital Dual Output MicroDLynx - Manual (Page 21)

GE
Datasheet
2 × 12A Digital Dual MicroDlynx TM : Non-Isolated DC-DC Power Modules
4.5Vdc –14.4Vdc input; 0.51Vdc to 5.5Vdc output; 2 × 12A Output Current
February 14, 2014 ©2014 General Electric Corporation. All rights reserved. Page 21
format with a two byte data word where the upper five bits
[7:3] of the high byte shall represent the exponent and the
remaining three bits of the high byte [2:0] and the eight bits
in the low byte shall represent the mantissa. The exponent
is fixed at 0 (decimal). The lower 11 bits are the result of the
ADC conversion of the external temperature
PMBus Adjustable Output Over, Under Voltage
Protection and Power Good
The module has a common command to set the PGOOD,
VOUT_UNDER_VOLTAGE(UV) and VOUT_OVER_VOLTAGE (OV)
limits as a percentage of nominal. Refer to Table 6 of the
next section for the available settings. The PMBus command
VOUT_OVER_VOLTAGE (OV) shall be used to set the output
over voltage threshold from two possible values: +12.5% or
+16.67% of the commanded output voltage for each output.
The module provides a Power Good (PGOOD) for each output
signal that shall be implemented with an open-drain output
to indicate that the output voltage is within the regulation
limits of the power module. The PGOOD signal shall be de-
asserted to a low state if any condition such as
overtemperature, overcurrent or loss of regulation occurs
that would result in the output voltage going outside the
specified thresholds. The PGOOD thresholds shall be user
selectable via the PMBus (the default values are as shown in
the Feature Specifications Section). Each threshold shall be
set up symmetrically above and below the nominal value.
The PGL (POWERGOODLOW) command shall set the output
voltage level above which PGOOD is asserted (lower
threshold). The PGH(POWERGOODHIGH) command shall set
the level above which the PGOOD command is de-asserted.
This command shall also set two thresholds symmetrically
placed around the nominal output voltage. Normally, the
PGL threshold shall be set higher than the PGH threshold.
The PGOOD terminal can be connected through a pullup
resistor (suggested value 100K
Ω) to a source of 5VDC or
lower. The current through the PGood terminal should be
limited to a max value of 5mA
PMBus Adjustable Input Undervoltage Lockout
The module allows for adjustment of the input under voltage
lockout and hysteresis. The command VIN_ON allows setting
the input voltage turn on threshold for each output, while
the VIN_OFF command shall set the input voltage turn off
threshold. For the VIN_ON command, possible values are
4.25V to 16V in variable steps. For the VIN_OFF command,
possible values are 4V to 15.75V in 0.5V steps. If other values
are entered for either command, they shall be mapped to
the closest of the allowed values.
Both the VIN_ON and VIN_OFF commands use the “Linear”
format with two data bytes. The upper five bits shall
represent the exponent (fixed at -2) and the remaining 11
bits shall represent the mantissa. For the mantissa, the four
most significant bits are fixed at 0.
Measurement of Output Current, Output Voltage
and Input Voltage
The module is capable of measuring key module
parameters such as output current and voltage for each
outputs and input voltage for each input and providing this
information through the PMBus interface.
Measuring Output Current Using the PMBus
The module measures current by using the inductor winding
resistance as a current sense element. The inductor winding
resistance is then the current gain factor used to scale the
measured voltage into a current reading. This gain factor is
the argument of the IOUT_CAL_GAIN command, and
consists of two bytes in the linear data format. The exponent
uses the upper five bits [7:3] of the high data byte in two-s
complement format and is fixed at –15 (decimal). The
remaining 11 bits in two’s complement binary format
represent the mantissa. During manufacture, each module
is calibrated by measuring and storing the current gain
factor into non-volatile storage.
The current measurement accuracy is also improved by
each module being calibrated during manufacture with the
offset in the current reading. The IOUT_CAL_OFFSET
command is used to store and read the current offset. The
argument for this command consists of two bytes
composed of a 5-bit exponent (fixed at -4d) and a 11-bit
mantissa. This command has a resolution of 62.5mA and a
range of -4000mA to +3937.5mA.
The READ_IOUT command provides module average output
current information. This command only supports positive or
current sourced from the module. If the converter is sinking
current a reading of 0 is provided. The READ_IOUT
command returns two bytes of data in the linear data
format. The exponent uses the upper five bits [7:3] of the
high data byte in two-s complement format and is fixed at –
4 (decimal). The remaining 11 bits in two’s complement
binary format represent the mantissa with the 11
th bit fixed
at 0 since only positive numbers are considered valid.
Measuring Output Voltage Using the PMBus
The module provides output voltage information using the
READ_VOUT command for each output. In this module the
output voltage is sensed at the remote sense amplifier
output pin so voltage drop to the load is not accounted for.
The command shall return two bytes of data all representing
the mantissa while the exponent is fixed at -9 (decimal).
Reading the Status of the Module using the PMBus
The module supports a number of status information
commands implemented in PMBus. However, not all
features are supported in these commands. A 1 in the bit
position indicates the fault that is flagged.
STATUS_BYTE : Returns one byte of information with a
summary of the most critical device faults.
Bit
Position
Flag
Default
Value
7 X 0
6 OFF 0
5 VOUT
Overvoltage 0
4 IOUT Overcurrent 0