FP3-4R7-R datasheet(3/14 Pages) VICOR

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Page 3

2. Default Pin Strap Configuration

a. Ensure the pin straps are in the following default locations before proceeding:

ENABLE = Not Used (enabled)

TRIM_UP = Not Used

TRIM_DN = Not Used

OPT1 = Not Used

OPT2 = Not Used

3. Pin Strap Functions

a. ENABLE – adding a strap on this pin will cause the converter to shut down.

b. TRIM_UP – Adding a strap in this location will adjust the output voltage

up by 10%.

c. TRIM_DN – Adding a strap in this location will adjust the output voltage down

by 10%. Only one strap can be connected at a time. If both trim straps are out,

the output voltage should be set to the model’s nominal output.

4. Trimming And Soft Start

a. For those customers who wish to trim to another voltage by changing the preset

trim resistors to another value, the trim equation shown in Figure 2 can be used:

low =

(–V ) •

INT

(–Vout

nom

) + V

desired

high = (–RSS) •

(–Voutnom) • VERO + V •Vref

ref

[(–Vout

nom) + V

]

desired

Where: R1 = Rlow R3 = Rhigh VERO = 4.9 and Vref can be found in the appropriate

model datasheet.

Figure 3 shows an equation for soft start configuration where C7 = CREF

REF =

ssdesired – 230 • 10

−6

23000

ENABLE

TRIM/SS

SGND

RSS

Rhigh

Rlow

VERO

Vref

PI31xx

10k

•

Figure 4.

PI31xx Trimming Equivalent

Circuit

Figure 2.

PI31xx Trim Equation

Figure 3.

PI31xx Soft Start Equation

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