GE Industrial Solutions 3A Analog PicoDLynx - Manual (Page 15)

GE
Preliminary Data Sheet
3A Analog PicoDLynx TM : Non-Isolated DC-DC Power Modules
3Vdc –14.4Vdc input; 0.6Vdc to 5.5Vdc output; 3A Output Current
December 7, 2012 ©2012 General Electric Company. All rights reserved. Page 15
Tunable Loop TM
The 3A PicoDLynx TM modules have a feature that optimizes
transient response of the module called Tunable Loop TM .
External capacitors are usually added to the output of the
module for two reasons: to reduce output ripple and noise (see
Figure 38) and to reduce output voltage deviations from the
steady-state value in the presence of dynamic load current
changes. Adding external capacitance however affects the
voltage control loop of the module, typically causing the loop to
slow down with sluggish response. Larger values of external
capacitance could also cause the module to become unstable.
The Tunable Loop TM allows the user to externally adjust the
voltage control loop to match the filter network connected to
the output of the module. The Tunable Loop
TM is implemented
by connecting a series R-C between the SENSE and TRIM pins of
the module, as shown in Fig. 45. This R-C allows the user to
externally adjust the voltage loop feedback compensation of
the module.
Figure. 45. Circuit diagram showing connection of R
TUME
and
C
TUNE
to tune the control loop of the module.
Recommended values of R
TUNE
and C
TUNE
for different output
capacitor combinations are given in Tables 2 and 3. Table 2
shows the recommended values of R
TUNE
and C
TUNE
for different
values of ceramic output capacitors up to 1000uF that might
be needed for an application to meet output ripple and noise
requirements. Selecting R
TUNE
and C
TUNE
according to Table 2
will ensure stable operation of the module.
In applications with tight output voltage limits in the presence
of dynamic current loading, additional output capacitance will
be required. Table 3 lists recommended values of R
TUNE
and
C
TUNE
in order to meet 2% output voltage deviation limits for
some common output voltages in the presence of a 1.5A to 3A
step change (50% of full load), with an input voltage of 12V.
Please contact your GE technical representative to obtain more
details of this feature as well as for guidelines on how to select
the right value of external R-C to tune the module for best
transient performance and stable operation for other output
capacitance values or input voltages other than 12V.
Table 2. General recommended values of of R
TUNE
and
C
TUNE
for Vin=12V and various external ceramic
capacitor combinations.
Co 1x47 μF 2x47μF 4x47μF 6x47μF 10x47μF
R
TUNE
270 220 180 180 180
C
TUNE
1500pF 1800pF 3300pF 4700pF 4700pF
Table 3. Recommended values of R
TUNE
and C
TUNE
to
obtain transient deviation of 2% of Vout for a 1.5A step
load with Vin=12V.
Vo 5V 3.3V 2.5V 1.8V 1.2V 0.6V
Co 1x47μF 1x47μF 2x47 μF
1x330 μF
Polymer
1x330 μF
Polymer
2x330 μF
Polymer
R
TUNE 270 220 180 180 180 180
C
TUNE 1500pF 1800pF 3300pF 8200pF 8200pF 33nF
ΔV 68mV 60mV 37mV 18mV 18mV 10mV
Note: The capacitors used in the Tunable Loop tables
are 47 μF/3 mΩ ESR ceramic and 330 μF/12 mΩ ESR
polymer capacitors.
MODULE
VOUT
SENSE
TRIM
GND
RTUNE
CTUNE
RTrim
C O