2

USING THE EVALUATION BOARD

1) Powering Up the SP6126EB Circuit

Connect the SP6126 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 SP6126 Evaluation Board has been tested and delivered with the output set

to 3.30V, by simply changing one resistor, R2, the SP6126 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.













−

=

1

1

2

Vref

Vout

R

R

Where R1 = 200kΩ. For Vout = 0.60V setting, simply remove R2 from the board.

Note that since the SP6126 Evaluation Board design was optimized for 12V down

conversion to 3.30V, 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. Under no-load condition an optional 10kOhm bleeding resistor across the

output helps keep the output capacitor discharged.

POWER SUPPLY DATA

The SP6126EB is designed with an accurate 2% reference over line, load and

temperature. Figure 1 data shows a typical SP6126 Evaluation Board efficiency plot,

with efficiencies to 92% and output currents to 2.5A. SP6126 Load Regulation in Figure

2 shows no change in output voltage from no load to 2A load. Figures 3 and 4 show the

transient response of the SP6126. 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.