SPV1020

Detailed description

Doc ID 17588 Rev 3

9/19

5.2

Oscillator

The switching frequency Fswitch is internally fixed at 100 kHz and each phase operates at

the frequency fixed by the oscillator. To set the default value of 100 kHz, connect OSC_IN to

VREG. The switching frequency can be adjusted from 50 kHz to 200 kHz by connecting an

external resistor R6 between OSC and SGND. The relationship between R6 and Fswitch is:

5.3

Input voltage sensing

The device monitors the input voltage generated by the PV cells through VIN_SNS. This

value is used to calculate the power generated by the PV cell string and then to adjust the

PWM duty cycle to provide the maximum power point.

The input voltage must be scaled to a reference voltage level of 1.25 V at the input of the

ADC integrated in the SPV1020.

Referring to the schematic shown in the application circuit of

Figure 1, R1 and R2 are the

resistors used for partitioning the input voltage.

If Vin_max is the maximum input voltage of the supply source (e.g. the PV panel or the PV

string), R1 and R2 must be selected according to the following formula:

Also, in order to optimize the efficiency of the whole system, when selecting R1 and R2,

their power dissipation must be taken into account.

Assuming negligible the current flowing through pin VIN_SNS, maximum power dissipation

in the series R1+R2 is:

As an empirical rule, R1 and R2 should be selected according to:

Note:

In order to guarantee the proper functionality of pin VIN_SNS, current flowing in the series

R1+R2 should be in the range between 20 µA and 200 µA.

R1

R2

--------

V

inmax

1.25

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

1

–

=

2

R

1

R

)

V

(

P

2

max

_

in

sns

_

vin

+

=

)

I

V

(

x

01

.

P

max

_

in

max

_

in

sns

_

vin

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