TFP101, TFP101A

TI PanelBus DIGITAL RECEIVER

SLDS119C - MARCH 2000 − REVISED OCTOBER 2003

14

POST OFFICE BOX 655303

TFP101/101A output driver configurations (continued)

Time Staggered Pixel Output. This option works only in conjunction with the 2-pixel/clock mode (PIXS = high).

Setting STAG = low will time stagger the even and odd pixel output so as to reduce the amount of instantaneous

current surge from the power supply. Depending on the PCB layout and design this can help reduce the amount

of system ground bounce and power supply noise. The time stagger is such that in 2-pixel/clock mode the even

pixel is delayed from the latching edge of ODCK by 0.25 Tcip. (Tcip is the period of ODCK. The ODCK period

is 2Tpix when in 2-pixel/clock mode.)

Depending on system constraints of output load, pixel rate, panel input architecture and board cost the

TFP101/101A drive strength and staggered pixel options allow flexibility to reduce system power-supply noise,

ground bounce and EMI.

Power Management. The TFP101/101A offers several system power management features.

The output driver power down (PDO = low) is an intermediate mode which offers several uses. During this mode,

all output drivers except SCDT and CTL1 are driven to a high impedance state while the rest of the device

circuitry remains active

The TFP101/101A power down (PD = low) is a complete power down in that it powers down the digital core,

the analog circuitry, and output drivers. All output drivers are placed into a Hi-z state. All inputs are disabled

except for the PD input. The TFP101/101A will not respond to any digital or analog inputs until PD is pulled high.

Both PDO and PD have internal pullups so if left unconnected they will default the TFP101/101A to normal

operating modes.

Sync Detect. The TFP101/101A offers an output, SCDT to indicate link activity. The TFP101/101A monitors

activity on DE to determine if the link is active. When 1 million (1e6) pixel clock periods pass without a transition

on DE, the TFP101/101A considers the link inactive and SCDT is driven low. While SCDT is low, if two DE

transitions are detected within 1024 pixel clock periods, the link will be considered active and SCDT is pulled

high.

SCDT can be used to signal a system power management circuit to initiate a system power down when the link

is considered inactive. The SCDT can also be tied directly to the TFP101/101A PDO input to power down the

output drivers when the link is inactive. It is not recommended to use the SCDT to drive the PD input since, once

in complete power-down, the analog inputs are ignored and the SCDT state will not change. An external system

power management circuit to drive PD is preferred.