GE Industrial Solutions 12A Analog PicoDLynx - Manual (Page 15)

GE
Data Sheet
12A Analog PicoDLynx TM : Non-Isolated DC-DC Power Modules
3Vdc –14.4Vdc input; 0.6Vdc to 5.5Vdc output; 12A Output Current
August 13, 2013 ©2013 General Electric Corporation. All rights reserved. Page 15
Tunable Loop TM
The 12A 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 6A to 12A 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 1x47µF 2x47µF 4x47µF 6x47µF 10x47µF 20x47µF
R
TUNE 330 330 330 330 270 180
C
TUNE
100pF 560pF 1500pF 2200pF 3900pF 6800pF
Table 3. Recommended values of R
TUNE
and C
TUNE
to obtain
transient deviation of 2% of Vout for a 6A step load with
Vin=12V.
Vo 5V 3.3V 2.5V 1.8V 1.2V 0.6V
Co 5x47µF
1x47µF
+
330µF
Polymer
3x47µF
+
330µF
Polymer
1x47µF +
2x330µF
Polymer
1x47µF +
3x330µF
Polymer
3x47µF +
6x330µF
Polymer
R
TUNE 330 330 270 270 220 180
C
TUNE 1500pF 2700pF 3300pF 5600pF 10nF 47nF
∆V 99mV 58mV 47mV 34mV 24mV 12mV
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