TSB17BA1

IEEE STD 1394b SINGLEPORT CABLE TRANSCEIVER

SLLS568C − JANUARY 2004 − REVISED MARCH 2004

13

POST OFFICE BOX 655303

1

2

3

6

7

8

4

5

9

10

11

14

15

16

12

13

E_OUT

E_INN

E_INP

VSS33

BETA_OUTP

BETA_OUTN

VDD33

BETA_INP

BETA_INN

PD_SE

TEST0

TEST1

VREG_PD

VONTROL

R1

R0

UTP5_INP

UTP5_INN

VDD18

UTP5_OUTP

UTP5_OUTN

VSS18

TEST3

TEST2

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

R55

49.9

R56

49.9

C25

0.001

µF

C28

0.1

µF

C29

0.1

µF

1.3 V

T1/T1

HB726

R64

1.2 k

U3

TSB17BA1

UTP_TPA2+

UTP_TPA2−

UTP_TPB2+

UTP_TPB2−

Figure 5. Workaround Circuit

This circuit, when used with parts received from Texas Instruments after 2003, should allow the device to reject

in-band noise and crosstalk of at least 20 mVp-p. Alternate connection of the transformer center tap (pin 7) may

provide noise immunity advantages.

The dc offset provided by the workaround circuit reduces the sensitivity of the device to both desired and

undesired signals. This offset method proved successful with a sampling of TSB17BA1 devices (under nominal

conditions) connected by 100m of CAT 5e cable in three segments with jack-to-jack adapter boards.

In some cases it may be possible to cycle system power to all nodes simultaneously after all UTP cables are

connected (that is, terminated) and have ports connect normally. In this configuration the noise levels from

issues 2 and 3 may be reduced by the cable termination. This noise reduction combined with the presence of

a real signal may have enough signal-to-noise difference to allow the system to connect and operate. This

solution may not work for issues 1 and 3 with large amplitude noise environments.

UTP output level issue

problem description

The TSB17BA1 UTP5_OUT output drive level is designed and tested to the same limits that the IEEE Std

1394b-2002 specification table 12−2 provides for the transmit system. Losses in the transformer, PCB,

connector, etc., of a product using the TSB17BA1 may result in degraded UTP transmit levels. These reduced

output levels may not meet the 1394b specification but may still operate satisfactorily.

workaround

None