Feb21-07

SP7661 Evaluation Manual

©2007 Sipex Corporation

Page 3 of 11

Adjusting the current downwards is controlled by adjusting R8.













⋅

⋅

+

⋅

=

DCR)

(Imax

-

60mV

DCR)

(Imax

60mV)

-

(Vout

R4

R8

Equation 3

Where

DCR is the Inductor winding resistance and

Further details on the current limit can be found in the SP7661 data sheet. For the Wurth

Inductor on this demo board, DCR= 14m

Ω nominal.

POWER SUPPLY DATA

The SP7661ER is designed with an accurate 2.0% reference over line, load and

temperature. Figure 1 data shows a typical SP7661 evaluation board efficiency plot, with

efficiencies up to 90% and output currents up to 3A. The output voltage ripple of less than 10mV

at full load and the LX node are shown in figure 2. Figures 3 and 4 illustrate a 0A to 3A and 1A

to 3A Load Step. Short circuit and current limit are shown in Figures 5 and 6. Typical startup

characteristics into a full load and no load are shown in figure 7 and 8. All data was taken at

While data on individual power supply boards may vary, the capability of the SP7661ER

of achieving high accuracy over a range of load conditions shown here is quite impressive and

desirable for accurate power supply design.

7661 Efficiency

12Vin, 3.3Vout, 3Amps

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

90.0

95.0

0.51

1.52

2.53

Iout (Amps)

Figure 1. Efficiency vs. Load