SLIN-30E1AX Datasheet, PDF (16/26 Pages) Bel Fuse Inc. – 6.0 Vdc - 14 Vdc Input, 0.8 Vdc - 2.75 Vdc /30 A Outputs

NON-ISOLATED DC/DC CONVERTERS
6.0 Vdc - 14 Vdc Input, 0.8 Vdc - 2.75 Vdc /30 A Outputs
Jan. 11, 2010
Output Voltage Sequencing
Bel Power Inc., a subsidiary of Bel Fuse Inc.
The SLIN-30E1Ax modules include a sequencing feature that enables users to implement various types of output
voltage sequencing in their applications. This is accomplished via an additional sequencing pin. When not using
the sequencing feature, either tie the SEQ pin to VIN or leave it unconnected.
When an analog voltage is applied to the SEQ pin, the output voltage tracks this voltage until the output reaches
the set-point voltage. The final value of the SEQ voltage must be set higher than the set-point voltage of the
module. The output voltage follows the voltage on the SEQ pin on a one-to-one basis. By connecting multiple
modules together, multiple modules can track their output voltages to the voltage applied on the SEQ pin.
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 VIN 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. 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 representatives for additional information.
Bel Fuse Inc. 206 Van Vorst Street, Jersey City, NJ 07302 • Tel [phone] • Fax [phone] • www.belfuse.com
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