SP6127_07 Datasheet, PDF (2/8 Pages) Sipex Corporation – Evaluation Board Manual

USING THE EVALUATION BOARD
1) Powering Up the SP6127EB Circuit
Connect the SP6127 Evaluation Board to an external +12V power supply. Connect with
short leads directly to the “VIN” and “GND” posts. Connect a Load between the “VOUT”
and “GND” posts, again using short leads to minimize inductance and voltage drop.
2) Measuring Output Load Characteristics
It’s best to GND reference scope and digital meters using the Star GND post near the
output of the board. VOUT ripple can best be seen touching probe tip to the pad for
COUT and scope GND collar touching Star GND post – avoid a GND lead on the scope
which will increase noise pickup.
3) Using the Evaluation Board with Different Output Voltages
While the SP6127 Evaluation Board has been tested and delivered with the output set
to 1.80V, by simply changing one resistor, R2, the SP6127 can be set to other output
voltages. The relationship in the following formula is based on a voltage divider from the
output to the feedback pin FB, which is set to an internal reference voltage of 0.60V.
Standard 1% metal film resistors of surface mount size 0603 are recommended.
R2
=
R1

Vout
Vref
− 1_{}
Where R1 = 200kΩ. For Vout = 0.60V setting, simply remove R2 from the board.
Note that since the SP6127 Evaluation Board design was optimized for 12V down
conversion to 1.80V, changes of output voltage and/or input voltage will alter
performance from the data given in the Power Supply Data section.
Using the SHDN (ON/OFF function)
Feedback pin serves a dual role of ON/OFF control. The MOSFET driver is disabled
when a voltage greater than 1V is applied at FB pin. Maximum voltage rating of this pin
is 5.5V. The controlling signal should be applied through a small signal diode as shown
on page 1. Note that under no-load condition an optional 10kOhm bleeding resistor
across the output helps keep the output capacitor discharged.
POWER SUPPLY DATA
The SP6127EB is designed with an accurate 2% reference over line, load and
temperature. Figure 1 data shows a typical SP6127 Evaluation Board efficiency plot,
with efficiencies to 75% and output currents to 2A. SP6127 Load Regulation in Figure 2
shows very little change in output voltage from no load to 2A load. Figures 3 and 4 show
the transient response of the SP6127 and overcurrent shutdown. Figures 5 and 6 show
a controlled start-up with no load and 2A load when power is applied where the input
current rises smoothly as the soft-start ramp increases. Figures 7 and 8 show the output
ripple under no load and 2A load.
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