6

ACS103 Issue 2.03 May 1996.

2

1 DR3

2 DR1

3IC

4 DM1

5 RxD1

6IC

7 XO3

8IC

9NC

10 RTS / XI1

11 TxD3

12 TxD1

13 VD+

14 XTI

15 XTO

16 CKC

17 TxCL

18 RxCL

19 XI3

20 DM2

21 SEL

22 DM3

23 GND

24 DTR / XI2

25 TxD2

26 ERD

27 NC

28 IC

29 RxD2

30 PORB

31 RxD3

32 CTS / XO1

33 DSR / XO2

34 DCDB

60

59

58

57

56

55

54

53

52

51

50

49

48

47

46

45

44

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

Figure 1. Top view of 68 PLCC package

NC = Not Connected IC = Internally Connected

The power coupled to the cable is a function of the

efficiency of the LED, the current applied to the LED

and the diameter of the fiber optic cable. The larger

the cable diameter the greater the power coupled.

The conversion current produced by the receive

diode is a function of the LED efficiency and the

cable diameter.

The conversion efficiency is

measured in terms of its ability to convert the

available power to current, known as the

responsivity, given by (A/W). Some examples of link

budgets are given in the Table 1., though note that

significantly better "A" spec. LEDs available, e.g.

from Acapella. “A” spec. LEDs can offer > 12 dB link

budget on 50 µm fiber.

Maximum Link Length

The internal timing chain within the ACS103 limits

the link length to 2.5 km ('Standard' mode) and 5 km

('Double' mode) with a crystal frequency of

9.216 MHz. However, the maximum link length as

determined by the ACS103 timing chain is inversely

proportional to the crystal frequency. Please contact

Acapella if you wish to discuss longer links.

TxD inputs

There is a choice of pins for TxD1, pins 12 and 41.

Only one input should be used. The other input will

pull-up to VDD via an internal resistor. Pin 12 is the

recommended choice since it is further away from

the sensitive analogue pins.

However, pin 41 is

available for designers if required.

Digital Mode

The ACS103 may be used as a controller and data

buffer which allows the device to be used with an

external amplifier and receiver, e.g. for non-fiber

applications. Check with Acapella for details.

Data delay and skew

The data delay in synchronous mode is typically 48

data-bit periods and worst case 100 data-bit periods.

When configured in asynchronous mode the worst

case data delay is 300 µs at 9.216 MHz and 550 µs at

5 MHz. The additional data transmission channels

(XI1/2/3) are delayed by up to 1.2 ms in 'Standard'

mode and up to 2.4 ms in 'Double' mode when used

with a crystal frequency of 9.216 MHz.

For other

crystal values the delay changes inversely

proportional to the frequency of operation.

The worst case data skews between the main data

channels TxD1/RxD1, TxD2/RxD2 and TxD3/RxD3

across the link are as follows.

Synchronous : zero data bits.

Asynchronous : 216 * (crystal clock period).

ACAPELLA

ACS103

1-Fiber Modem

VD+

68

VD+

67

GND 66

GND 65

DR2

64

TRC

63

DR4

62

NC

61

NC

60

NC

59

NC

58

NC

57

VG

56

VA+

55

CON2 54

LDP

53

NC

52

NC

51

LDN

50

CON1 49

CNT

48

GND 47

NC

46

NC

45

NC

44

NC

43

IC

42

TXD1 41

LIN

40

RSS

39

VD+

38

VD+

37

GND 36

GND 35