Mar12-07 RevD

SP7663 Evaluation Board Manual

©2007 Sipex Corp.

Page 2 of 16

USING THE EVALUATION BOARD

1) Powering Up the SP7663EB Circuit

Connect the SP7663 Evaluation Board with an external +12V power supply. Connect

with short leads and large diameter wire directly to the “VIN” and “GND2” posts. Connect

a Load between the VOUT and GND1 posts, again using short leads with large diameter

wire to minimize inductance and voltage drops.

2) Measuring Output Load Characteristics

It’s best to GND reference all scope and digital meters using the Star GND post in the

center of the board. VOUT ripple can best be seen by touching the probe tip to the pad

for C3 and the scope to the 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 SP7663 Evaluation Board has been tested and delivered with the output set to

3.30V, by simply changing one resistor, R2, the SP7663 can be set to other output

voltages. The relationship in Equation 1 is based on a voltage divider from the output to

the common mode voltage range of the current sense amplifier, output voltages greater

than 3.3V are only possible if the current sense is disabled. To disable current limit,

remove R3 and R4. Standard 1% metal film resistors of surface mount size 0603 are

recommended.

1)

.80V

VOUT

(

R1

R2

−

=

Equation1

Furthermore, one could select the value of the R1 and R2 combination to meet the exact

output voltage setting by restricting R1 resistance range such that 50KΩ ≤ R1 ≤ 100KΩ

for overall system loop stability.

Note that since the SP7663 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. In addition, the

the converter is set to about 9A which is accomplished by sensing the current through

the inductor. To adjust the current limit, follow Equations 2 and 3 to set the current limit

accordingly. The current limit should be set to about 50% higher than the maximum

output current that is desired. This will prevent the part from accidentally triggering the

current limit during large transient load steps.

Adjusting the current upwards is done by adjusting resistor R9.

60mV)

-

DCR

(

max

R4)

R3

(

60mV

R9

•

+

•

=

I

Equation 2

Where:

DCR is the Inductor winding resistance

is the desired output current