SLAN-03D2A0 Datasheet, PDF (17/25 Pages) Bel Fuse Inc. – NON-ISOLATED DC/DC CONVERTERS

NON-ISOLATED DC/DC CONVERTERS
3 Vdc – 14.4 Vdc Input, 0.6 Vdc - 5.5 Vdc /3 A Outputs
Mar. 16, 2012
Tunable Loop^TM
Bel Power Inc., a subsidiary of Bel Fuse Inc.
The SLAN-03D2Ax 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
VOUT
SENSE
RTUNE
MODULE
TRIM
CO
CTUNE
GND
RTri m
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 Bel 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 or input voltages other than 12V.
Table 2
Co 1x47F 2x47F 4x47F 6x47F 10x47F
RTUNE
270
220
180
180
180
CTUNE 1500pF 1800pF 3300pF 4700pF 4700pF
General recommended values of of R_TUNE and C_TUNE for Vin=12V and various external ceramic capacitor
combinations.
Bel Fuse Inc. 206 Van Vorst Street, Jersey City, NJ 07302  Tel [phone]  Fax [phone]  www.belfuse.com
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