ADuM2250/ADuM2251

Data Sheet

Rev. A | Page 10 of 16

APPLICATIONS INFORMATION

FUNCTIONAL DESCRIPTION

unidirectional channels communicating in opposite directions

via dedicated iCoupler isolation channels. One channel of each

pair (the Side 1 input of each I/O pin in Figure 6) implements

a special input buffer and output driver that can differentiate

between externally generated inputs and its own output signals.

It only transfers externally generated input signals to the

corresponding Side 2 data or clock pin.

on either side causes the corresponding I/O pin across the

coupler to be pulled low enough to comply with the logic low

contention and latch-up is avoided by guaranteeing that the

the output low signal at the same pin. This prevents an output

logic low at Side 1 being transmitted back to Side 2 and pulling

Because the Side 2 logic levels/thresholds and drive capabilities

ADuM2251 devices connected to a bus by their Side 2 pins

can communicate with each other and with other devices

or drive capability of a component do not necessarily meet the

compliance refers to situations in which the logic levels and

drive capability of a component fully meet the requirements

Because the Side 1 pin has a modified output level/input thresh-

old, Side 1 of the ADuM2250/ADuM2251 can only communicate

buffers that implement a similar scheme of dual I/O threshold

detection. This latch-up prevention scheme is implemented in

currently available from Analog Devices and other manufac-

turers. Care should be taken to review the data sheet of

buffer on a bus segment implements a dual threshold scheme.

other portions of the bus by galvanic isolation, bus extenders, or

level shifting buffers. Table 11 shows how multiple ADuM2250/

ADuM2251 components can coexist on a bus as long as two

Side 1 buffers are not connected to the same bus segment.

Table 11. ADuM225x Buffer Compatibility

Side 1

Side 2

Side 1

No

Yes

Side 2

Yes

Yes

ments. The Side 1 and Side 2 I/O pins have open-collector

outputs whose high levels are set via pull-up resistors to their

respective supply voltages.

DECODE

ENCODE

ENCODE

DECODE

DECODE

ENCODE

ENCODE

DECODE

NC

NC

NC

NC

NC

NC

8

7

5

6

4

3

2

1

12

11

13

14

15

16

10

ADuM2250

SYMBOL INDICATES A DUAL THRESHOLD INPUT BUFFER.

NC = NO CONNECT

9

Figure 6. ADuM2250 Block Diagram

Figure 7 shows a typical application circuit including the pull-up

resistors required for both Side 1 and Side 2 busses. Bypass capacitors

is required for latch-up immunity if the ambient temperature

can be between 105°C and 125°C.

OPTIONAL

200Ω

8

7

5

6

4

3

2

1

9

12

11

13

14

15

16

10

ADuM2250

µCPU

OR

SECONDARY

BUS

SEGMENT