Feb21-07

SP7662 Evaluation Manual

©2007 Sipex Corporation

Page 2 of 11

Using the Evaluation Board

1) Powering Up the SP7662EB Circuit

Connect the SP7662 Evaluation Board with an external +12V power supply. Connect with short

leads and large diameter wire directly to the “VIN” and “GND” posts. Connect a Load between

the VOUT and GND posts, again using short leads with large diameter wire to minimize

inductance and voltage drops. Provide >=100lfm of airflow if powering the evaluation board

beyond 10 Amps for extended periods.

2) Measuring Output Load Characteristics

VOUT ripple can best be seen by touching the probe tip to the pad for C5 and the scope GND

collar touching the Output 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 SP7662 Evaluation Board has been tested and delivered with the output set to 3.30V,

by simply changing one resistor, R2, the SP7662 can be set to other output voltages. The

which is set to an internal reference voltage of 0.80V. Note, due 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

Equation 1

Where R1 = 10k

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 10K

Ω ≤ R1 ≤ 100KΩ for overall

system loop stability.

Note that since the SP7662 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 SP7662ER provides short circuit protection by

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 upward is done by adjusting resistor R9.

60mV)

-

DCR

(

max

R4)

R3

(

60mV

R9

⋅

+

⋅

=

I

Equation 2

Where

DCR is the Inductor winding resistance