DP83907 datasheet(19/70 Pages) NSC

19 / 70 page

40 Functional Description (Continued)

TLF12082 – 52

FIGURE 16b Circuitry to Connect DP83907 to Twisted Pair Cable with Internal Filter

On-Chip Filters

The on-chip filters are enabled via an external pull-up resis-

tors on MSDk12l at configuration Only an isolation trans-

former and impedance matching resistors are needed for

the transmit and receive twisted pair interface

UTPSTP Function

The TPI transceiver supports both shielded and unshielded

twisted pair cable UTP is default but STP can be enabled

during configuration by a pull-up on MSAk7l or by setting

bit D6 of configuration register C In UTP mode TXOa and

TXODa are driven and TXOb and TXODb are TRI-STAT-

ED In STP mode TXOb and TXODb are driven and

TXOa and TXODa are TRI-STATED

Auto-Switch Function

When an auto-switch function is enabled at configuration by

a pull-up on MSAk5l or by setting bit D4 of the configura-

tion register C it allows the transceiver to switch between

TP and AUI outputs If there is an absence of link pulses

the transceiver will switch to AUI mode Similarly when the

transceiver starts detecting link pulses it will switch to TP

mode The switching from one mode to the next is only

done after the current package has been transmitted or re-

ceived If the twisted pair output is jabbering and gets into

link fail state then the switch to AUI mode is only done after

the jabbering is done including the time it takes to unjab

(unjab time) When auto-switching is enabled the THIN out-

put is automatically generated if AUI is selected

TLF12082 – 12

FIGURE 17 Typical DP83907 LED Connection

Status Information

Status information is provided by the DP83907 on the

ACT

led

COL

led and GDLNK

led outputs as de-

scribed in the pin description table These outputs are suit-

able for driving status LED’s as shown in

Figure 17 All out-

puts are open drain

Recommended Transformers for Internal Filter mode

1) Valor PT4160

2) Pulse PE-68029

3) PCA EPE6087A

4) Delta THX16B02

5) Belfus A553-3899-06

6) Kappa TP3036

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