GE Industrial Solutions 12V PicoTLynx 3A - Manual (Page 16)

GE
Data Sheet
12V PicoTLynx TM 3A: Non-Isolated DC-DC Power Modules
4.5Vdc –14Vdc input; 0.59Vdc to 5.5Vdc output; 3A Output Current
May 2, 2013 ©2013 General Electric Company. All rights reserved. Page 16
R1
GND
VIN+
SEQ
+
-
OUT
10K
499K
MODULE
Figure 47. Circuit showing connection of the sequencing
signal to the SEQ pin.
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 Pico TLynx TM 3A 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 ±10% outside
the setpoint value. The PGOOD terminal should be
connected through a pullup resistor (suggested value
100K
Ω) to a source of 5VDC or less.
Tunable Loop TM
The 12V Pico TLynx TM 3A 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. 48. 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 470uF
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.