AN2846 datasheet(25/35 Pages) STMICROELECTRONICS

25 / 35 page

AN2846

Isolation management

Doc ID 15130 Rev 1

25/35

Isolation management

There are two solutions proposed for galvanic isolation between the SCLT3-8 and the

microcontroller.

●

Opto-coupler isolation

●

Magnetic digital isolation

4.1

Opto-coupler isolation

The first solution is given by opto-couplers which must run at a bit rate compatible with the

SCK frequency and meet SCLT3-8 requirements in terms of consumption.

HCPL4506 or HCPL0466 can be a solution to drive a single SCLT3-8 for a 1 MHz

application.

Figure 33.

Single SCLT3-8 and HCPL4506 or 0466

If several SCLT3-8s are used, more current is available through VDD pins to supply the opto-

couplers. The different outputs VDD can be tied together but, low serial resistors (22 Ω) must

be inserted to balance the different regulated output voltages. The load current is shared

between the two SCLT3s and allows the voltage drop reduction across each RC resistor.

SCK

/CS

/MISO

MOSI

MISO

VCC

MISO

/CS

SCK

3 k

1 k

750

HCPL4506

or 0466

VDD

VDD2

AN2846 Datasheet(PDF) 25 Page - STMicroelectronics