GE Industrial Solutions 20A Digital MicroDLynx - Manual (Page 18)

GE
Data Sheet
20A Digital MicroDLynx TM : Non-Isolated DC-DC Power Modules
3Vdc –14.4Vdc input; 0.45Vdc to 5.5Vdc output; 20A Output Current
April 24, 2013 ©2012 General Electric Company. All rights reserved. Page 18
Tunable Loop TM
The module has 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 VS+
and TRIM pins of the module, as shown in Fig. 46. This R-C
allows the user to externally adjust the voltage loop
feedback compensation of the module.
Figure. 46. 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 3
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 3 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 10A to 20A step change (50% of full
load), with an input voltage of 12V.
Please contact your Lineage Power 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.
Table 2. General recommended values of of R
TUNE
and
C
TUNE
for Vin=12V and various external ceramic capacitor
combinations.
Co 2x47  F 4x47  F 6x47  F 10x47  F 20x47  F
R
TUNE 330 330 270 220 180
C
TUNE 47pF 560pF 1200pF 2200pF 4700pF
Table 3. Recommended values of R
TUNE
and C
TUNE
to obtain
transient deviation of 2% of Vout for a 10A step load with
Vin=12V.
Vo 5V 3.3V 2.5V 1.8V 1.2V 0.6V
Co 8x47  F
5x47  F +
1x330  F
Polymer
2x47  F
+
2x330  F
Polymer
2x47  F
+
3x330  F
Polymer
1x47  F
+
5x330  F
Polymer
1x47  F
+
11x330  F
Polymer
R
TUNE 220 220 220 220 180 180
C
TUNE 1500pF 2200pF 3300pF 5600pF 10nF 47nF
 V 100mV 64mV 49mV 36mV 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.
VS+
MODULE
SIG_GND
TR IM
VOUT
RTune
CTune
RTrim
CO
GN D