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PanelBus
SLDS149 − AUGUST 2004
21
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
I
2
C interface (continued)
Data
A
S
Slave Address
Sub Address
A
W
Sr
A
P
From Transmitter
From Receiver
Sr Restart Condition
A Acknowledge
S Start Condition
P Stop Condition
A
R
A
Slave Address
Data
A Not Acknowledge (SDA High)
W Write
R Read
Figure 19. I
2
C Read Cycle
Data
S
Slave Address
R
P
From Transmitter
From Receiver
R Read
A Acknowledge
S Start Condition
P Stop Condition
A
A Not Acknowledge (SDA High)
A
Data
A
Figure 20. HDCP Port Link Integrity Message Read
The DDC_SDA and DDC_SCL I
2
C interface is 3.3-V tolerant and both DDC_SDA and DDC_SCL require a level
shifter for connection to the external system 5-V DDC lines. The I
2
C SDA driver must provide the 0.4-V
maximum low level at 3 mA specified by the I
2
C specification under typical conditions. Stressed conditions can
make the output level marginal. The level shifter design must minimize loading and losses to provide the best
possible low level signal on the SDA line.
PowerPAD 100-terminal TQFP package
The TFP503 is packaged in TI’s thermally enhanced PowerPAD 100-terminal 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-terminal TQFP PowerPAD package offers a backside solder plane that connects
directly to the die-mount pad for enhanced thermal conduction. If traces or vias are located under the back side
pad, they must be protected by a suitable solder mask or other assembly technique to prevent inadvertent
shorting to the exposed backside pad.
Soldering the backside of the device to a thermal land connected to the PCB ground plane is recommended
for thermal, electrical, and EMI considerations. The thermal land may be soldered to the exposed PowerPAD
using standard reflow soldering techniques.
The recommended pad size for the grounded thermal land is 5.8 mm minimum, centered in the device land
pattern. When vias are required to ground the land, multiple vias are recommended for a low-impedance
connection to the ground plane. Multiple vias are also recommended when thermal flow from the land to another
plane is needed. Vias in the exposed pad must be small enough or filled to prevent wicking the solder away from
the interface between the package body and the thermal land on the surface of the board during solder reflow.