5.3

Switching frequency programming and dithering

The L7983 has one programming pin, FSW (pin 4), which is used to set the regulator free running switching

frequency.

The switching frequency programming feature is performed by selecting the proper 1% accuracy resistor, to be

mounted between pin 4 and ground or VCC, as summarized in the following table. The pinstrapping is active only

before the soft-start phase to minimize the IC consumption.

Refer also to Figure 1 for reference schematic.

Dithering enabled

Dithering disabled

#

RVCC [kΩ]

RGND [kΩ]

Fsw [kHz] (1)

#

RVCC [kΩ]

RGND [kΩ]

Fsw [kHz] (1)

1

0

--

1000

1

--

0

1000

2

1,8

--

200

2

--

1,8

200

3

3,3

--

400

3

--

3,3

400

4

5,6

--

500

4

--

5,6

500

5

10

--

700

5

--

10

700

6

18

--

1500

6

--

18

1500

7

33

--

2000

7

--

33

2000

8

56

--

2200

8

--

56

2200

1. Typical value. Refer to Table 6 for details.

L7983

Switching frequency programming and dithering

DS13354 - Rev 1

page 15/43