SLIN-03E1A_10 Datasheet, PDF (18/26 Pages) Bel Fuse Inc. – NON-ISOLATED DC/DC CONVERTERS

NON-ISOLATED DC/DC CONVERTERS
4.5 Vdc - 14 Vdc Input, 0.59 Vdc - 5.5 Vdc /3 A Outputs
December 3, 2010
Bel Power, Inc. , a subsidiary of Bel Fuse, Inc.
Output Voltage Sequencing (continued)
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 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
according to the following equation:
R1 = ^{24950 ohms}
V_IN − 0.05
The voltage at the sequencing pin will be 50mV when the sequencing signal is at zero.
MODULE
VIN+
499K
R1
SEQ
10K
+
OUT
-
GND
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 basis 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 sequencing 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 sequencing 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 sequencing feature must be disabled. For additional guidelines on using the sequencing
feature please contact the Bel Power technical representative for additional information.
Bel Fuse Inc. 206 Van Vorst Street, Jersey City, NJ 07302 • Tel [phone] • Fax [phone] • www.belfuse.com
18