UM0584

Demonstration board description

Doc ID 14974 Rev 1

5/9

The 5 V output is obtained from the 24 V output by means of an integrated power IC, the

L5970AD.

The L5970AD is a step-down monolithic power switching regulator with a switch current limit

of 1.5 A, capable of delivering more than 1 A of DC current to the load depending on

application conditions. The output voltage can be adjusted down to 1.235 V by a voltage

200 m

Ω as a switching element to avoid the need for a bootstrap capacitor and to guarantee

high efficiency. An internal oscillator sets the switching frequency at 500 kHz to minimize the

size of external components. The power IC features several protection functions, such as

pulse-by-pulse current limiting, with the internal frequency modulation aimed at effective

constant current short-circuit protection, feedback disconnection and thermal shutdown.

Finally, the device can be synchronized using a dedicated pin, and also inhibited for reduced

standby power consumption and time sequence operations.

The schematic of the board is shown in Figure 3. The complete power supply is built on a

double-sided 35 µm PCB in FR-4, sized 130 x 66 mm.

The bill of materials is given in table below.

1.1

Bill of materials

Table 2.

STEVAL-ISA031V1 bill of materials

Reference

Value

Description

C1

22 µF - 450 V

Elect. capacitor – 85 °C

C2

22 µF - 450 V

Elect. capacitor – 85 °C

C3

22 nF - 660 Vac

Polip. capacitor X2

C4

22 nF - 660 Vac

Polip. capacitor X2

C5

4.7 nF - 2 kV

Polip. capacitor FKP1 - WIMA

C6

1 nF

Elect. capacitor

C7

2.2 nF

Ceramic capacitor

C8

100 nF

Ceramic capacitor

C9

2.2 nF

Ceramic capacitor

C10

47 µF

Ceramic capacitor

C11

470 pF

Ceramic capacitor

C12

n.m.

Ceramic capacitor

C13

6.8 nF (n.m.)

Ceramic capacitor

C14

2.2 nF

Polip. capacitor X1 Y1

C15

220 µF – 35 V

Elect. capacitor

C16

22 µF – 35 V

Elect. capacitor

C17

220 µF – 10 V

Elect. capacitor

C18

22 nF

Ceramic capacitor

C19

220 pF

Ceramic capacitor