Application information

DAP005

24/39

and check that at minimum mains voltage Vin1 the peak voltage on pin 3 is greater than

0.65V.

3.

Determine R1, the upper resistor of the output divider:

Equation 8

4.

Calculate the lower resistor R2 of the output divider and the adjustment resistor RT:

Equation 9

5.

Check that the maximum current sourced by the TBO pin (pin 6) does not exceed the

maximum specified (0.25mA):

Equation 10

In the following Mathcad® sheet, as an example, the calculation is shown for the circuit

illustrated in Figure 40.

Figure 41 shows the internal block diagram of the tracking boost function.

R1

Vo

∆

20

----------- 10

6

⋅

=

R2

2.5 R1

Vin

2

Vin

1

–

Vo

1

2.5

–

() Vin

2

Vo

2

2.5

–

() Vin

1

⋅

–

⋅

--------------------------------------------------------------------------------------------------

⋅

⋅

=

R

T

2kR1

Vin

2

Vin

1

–

Vo

2

Vo

1

–

------------------------------

⋅⋅

⋅

=

I

TBOmax

3

R

T

-------

0.25 10

3

–

⋅

≤

=