GE Industrial Solutions 12V TLynx 20A - Manual (Page 17)

GE
Data Sheet
12V TLynx TM 20A: Non-Isolated DC-DC Power Modules
4.5Vdc –14Vdc input; 0.69Vdc to 5.5Vdc output; 20A Output Current
May 2, 2013 ©2013 General Electric Company. All rights reserved. Page 17
After the 10msec delay, an analog voltage is applied to the SEQ
pin and the output voltage of the module will track this voltage
on a one-to-one volt bases until the output reaches the set-
point voltage. To initiate simultaneous shutdown of the
modules, the SEQ pin voltage is lowered in a controlled manner.
The output voltage of the modules tracks the voltages below
their set-point voltages on a one-to-one basis. A valid input
voltage must be maintained until the tracking and output
voltages reach ground potential.
When using the EZ-SEQUENCE
TM feature to control start-up of
the module, pre-bias immunity during start-up is disabled. The
pre-bias immunity feature of the module relies on the module
being in the diode-mode during start-up. When using the EZ-
SEQUENCE
TM feature, modules goes through an internal set-up
time of 10msec, and will be in synchronous rectification mode
when the voltage at the SEQ pin is applied. This will result in the
module sinking current if a pre-bias voltage is present at the
output of the module. When pre-bias immunity during start-up
is required, the EZ-SEQUENCE
TM feature must be disabled. For
additional guidelines on using the EZ-SEQUENCE TM feature
please refer to Application Note AN04-008 “Application
Guidelines for Non-Isolated Converters: Guidelines for
Sequencing of Multiple Modules”, or contact the GE Technical
representative for additional information.
Power Good
The 12V TLynx TM modules provide a Power Good (PGOOD) signal
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 will be 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
±11% outside the setpoint value. The PGOOD terminal should be
connected through a pullup resistor (suggested value 100K
Ω) to
a source of 6VDC or less.
Synchronization
The 12V TLynx TM series of modules can be synchronized using
an external signal. Details of the SYNC signal are provided in the
Electrical Specifications table. If the synchronization function is
not being used, leave the SYNC pin floating.
Tunable Loop TM
The 12V TLynx TM 20A modules have a new 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 41) 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. 47.
This R-C allows the user to externally adjust the voltage
loop feedback compensation of the module.
MODULE
VOUT
SENSE
TRIM
GND
RTUNE
CTUNE
RTrim
C O
Figure. 48. 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 940 F 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 10A to 20A 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 10x47μF 20x47μF
R
TUNE
240 240 240 150 150
C
TUNE
1500pF 2700pF 5600pF 12nF 15nF