Rev. 5/23/01

SP6122 Evaluation Board Manual

© Copyright 2001 Sipex Corporation

3

SP612 Evaluation Board Divider Resistors: The values of R1 and R2 are selected

to program 1.9V output, with 1.5V trim voltage Vb, and R1 = 500ohm:

i3 = (Vout-Vb)/R1=(1.9-1.5)/500 = 800uA.

The external voltage divider will add only 800uA to the load. Divider Resistor R2 is:

R2 = Vb/(i3-i1)=1.5/(800uA-20uA) = 1.9K

The user of the SP6122 Evaluation Board can use the above equations for i3 and R2 to

modify R2 and change the output voltage to be any voltage from Vb (1.5V) to as high as

the input voltage. And if you want the output voltage to be the preset voltage Vb (1.5V),

just short a wire across R1.

Figure 1. Schematic: Output Voltage Divider Resistors

POWER SUPPLY DATA

The SP6122 is engineered for size and minimum pin count, yet has a very accurate

1.5% reference over line, load and temperature. Figure 2 data shows a typical SP6122

Evaluation Board Efficiency plot, with efficiencies to 88% and output currents to 4A.

Load Regulation plot in Figure 3 shows an essentially flat response of only 3mV change

for up to 4A load. Figure 4 Line Regulation illustrates a 1.90V output that varies only

4mV or 0.2% for an input voltage change from 3.3V to 5.5V. While data on individual

power supply boards may vary, the capability of the SP6122 of achieving high accuracy

over load and line shown here is quite impressive and desirable for accurate power

supply design.

Vout

Rin1

Rin2

62.5K

R1

500

R2

+

-

Error

Amplifier

+

-

1.25

SP6122

i1

i3

i2

Va

1.9K