Information

TFP401
TFP401A
SLDS120E –MARCH 2000–REVISED JULY 2013 www.ti.com
Drive Strength (ST = high for high drive strength, ST = low for low drive strength). The TFP401/401A allows for
selectable output drive strength on the data, control, and ODCK outputs. See the DC Electrical Characteristics
table for the values of I
OH
and I
OL
current drives for a given ST state. The high output drive strength offers
approximately two times the drive as the low-output drive strength.
Time-Staggered Pixel Output. This option works only in conjunction with the 2-pixel/clock mode (PIXS = high).
Setting STAG = low time-staggers the even- and odd-pixel outputs 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 t
cip
. (t
cip
is the period of ODCK. The ODCK period is
2 t
pix
when in 2-pixel/clock mode.)
Depending on system constraints of output load, pixel rate, panel input architecture, and board cost, the
TFP401/401A drive-strength and staggered-pixel options allow flexibility to reduce system power-supply noise,
ground bounce, and EMI.
Power Management. The TFP401/401A 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 TFP401/401A 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 TFP401/401A does 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 default the TFP401/401A to normal
operating modes.
Sync Detect. The TFP401/401A offers an output, SCDT, to indicate link activity. The TFP401/401A 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 TFP401/401A considers the link inactive, and SCDT is driven low. While SCDT is low, if two DE
transitions are detected within 1600 pixel clock periods, the link is 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 TFP401/401A PDO input to power down the
output drivers when the link is inactive. It is not recommended to use SCDT to drive the PD input, because once
in complete power-down, the analog inputs are ignored and the SCDT state does not change. An external
system power-management circuit to drive PD is preferred.
TI PowerPAD 100-TQFP PACKAGE
The TFP401/401A is packaged in TI's thermally enhanced PowerPAD 100-TQFP packaging. The PowerPAD
package is a 14-mm × 14-mm × 1-mm TQFP outline with 0.5-mm lead pitch. The PowerPAD package has a
specially designed die mount pad that offers improved thermal capability over typical TQFP packages of the
same outline. The TI 100-TQFP PowerPAD package offers a back-side solder plane that connects directly to the
die mount pad for enhanced thermal conduction. Soldering the back side of the TFP401/401A to the application
board is not required thermally, because the device power dissipation is well within the package capability when
not soldered.
Soldering the back side of the device to the PCB ground plane is recommended for electrical considerations.
Because the die pad is electrically connected to the chip substrate and hence to chip ground, connection of the
PowerPAD back side to a PCB ground plane helps to improve EMI, ground bounce, and power-supply noise
performance.
Table 1 outlines the thermal properties of the TI 100-TQFP PowerPAD package. The 100-TQFP non-PowerPAD
package is included only for reference.
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