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

GE
Data Sheet
12V MicroTLynx TM 12A: Non-Isolated DC-DC Power Modules
4.5Vdc –14Vdc input; 0.69Vdc to 5.5Vdc output; 12A Output Current
May 2, 2013 ©2013 General Electric Company. All rights reserved. Page 17
Figure 46. Circuit Configuration for margining Output
voltage
For proper voltage sequencing, first, input voltage is applied to
the module. The On/Off pin of the module is left unconnected
(or tied to GND for negative logic modules or tied to V
IN
for
positive logic modules) so that the module is ON by default.
After applying input voltage to the module, a minimum 10msec
delay is required before applying voltage on the SEQ pin.
During this time, a voltage of 50mV (± 20 mV) is maintained on
the SEQ pin.
This can be done by applying the sequencing voltage through
a resistor R1connected in series with the SEQ pin. This delay
gives the module enough time to complete its internal power-
up soft-start cycle. During the delay time, the SEQ pin should be
held close to ground (nominally 50mV ± 20 mV). This is required
to keep the internal op-amp out of saturation thus preventing
output overshoot during the start of the sequencing ramp. By
selecting resistor R1 (see fig. 47) according to the following
equation
05 . 0
24950
1
−
=
IN
V
R ohms,
the voltage at the sequencing pin will be 50mV when the
sequencing signal is at zero.
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.
Figure 47. Circuit showing connection of the sequencing
signal to the SEQ pin.
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 MIcro TLynx TM 12A 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 Micro 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 Micro TLynx TM 12A 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
Vo
MODULE
GND
Trim
Q1
Rtrim
Rmargin-up
Q2
Rmargin-down
R1
GND
VIN+
SEQ
+
-
OUT
10K
499K
MODULE