GE Data Sheet
4A Digital PicoDLynxIITM: Non-Isolated DC-DC Power Modules
4.5Vdc –14.4Vdc input; 0.51Vdc to 5.5Vdc output; 4A Output Current
April 8, 2019 ©2017 General Electric Company. All rights reserved. Page 22
VREF(MH) = -(33)/1000 = - 0.033 Volts (- sign since we are
margining down)
V
REF(ML) = (Step_Vref_margin_low + Vref_trim) x 2 -9
Assume Vref_Trim = - 3 here (from V Ref_Trim example
earlier)
Step_Vref_margin_low = VREF(ML) x 512 - Vref_trim
Step_Vref_margin_low = -0.033 x 512 – (-3) = -16.9+3 = -13.9 =
-14 (rounded to nearest integer
The module will support the margined high or low voltages
using the OPERATION command. Bits [5:2] are used to
enable margining as follows:
00XX : Margin Off
0101 : Margin Low (Act on Fault)
0110 : Margin Low (Act on Fault)
1001 : Margin High (Act on Fault)
1010 : Margin High (Act on Fault)
PMBus Adjustable Overcurrent Warning
The module can provide an overcurrent warning via the
PMBus. The threshold for the overcurrent warning can be
set using the parameter IOUT_OC_WARN_LIMIT. This
command uses the “Linear” data format with a two byte
data word where the upper five bits [7:3] of the high byte
represent the exponent and the remaining three bits of the
high byte [2:0] and the eight bits in the low byte represent
the mantissa. The exponent is fixed at –1 (decimal). The
upper five bits of the mantissa are fixed at 0 while the lower
six bits are programmable with a default value of 19A
(decimal). The resolution of this warning limit is 500mA. The
value of the IOUT_OC_WARN_LIMIT can be stored to non-
volatile memory using the STORE_DEFAULT_ALL command
Temperature Status via PMBus
The module will provide information related to temperature
of the module through the READ_TEMPERATURE_2
command. The command returns external temperature in
degrees Celsius. This command will use the “Linear” data
format with a two byte data word where the upper five bits
[7:3] of the high byte will represent the exponent and the
remaining three bits of the high byte [2:0] and the eight bits
in the low byte will 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) is 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) that is
implemented with an open-drain output to indicate that the
output voltage is within the regulation limits of the power
module. The PGOOD signal is 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 are user selectable via the PMBus (the default
values are as shown in the Feature Specifications Section).
Each threshold is set up symmetrically above and below the
nominal value. The PGL (POWERGOODLOW) command will
set the output voltage level above which PGOOD is asserted
(lower threshold). The PGH(POWERGOODHIGH) command
will set the level above which the PGOOD command is de-
asserted. This command will also set two thresholds
symmetrically placed around the nominal output voltage.
Normally, the PGL threshold is set higher than the PGH
threshold.
The PGOOD terminal can be connected through a pullup
resistor (suggested value 100K) 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 will 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 is 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 will represent
the exponent (fixed at -2) and the remaining 11 bits will
represent the mantissa. For the mantissa, the four most
significant bits are fixed at 0.
Measurement of Output Current and Voltage
The module is capable of measuring key module
parameters such as output current and voltage 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 –4 (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. DONOT CHANGE THE
FACTORY PROGRAMMED VALUE
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