Datasheet

TXS0206
www.ti.com SCES697C –AUGUST 2009–REVISED JANUARY 2010
APPLICATION INFORMATION
The TXS0206 has integrated pullup resistors on the data and command ports and their values dynamically
change. When the port is in a low signal state, there is a nominal pullup resistor value of 40 kΩ, and power
consumption is minimized. When the port is in a high signal state, the nominal pullup resistor value changes to 4
kΩ, and simultaneous switching performance is improved as a result. The threshold at which the resistance
changes is approximately V
CCx
/2.
When using the TXS0206 device with MMCs, SD, and Memory Stick™ to ensure that a valid receiver input
voltage high (V
IH
) is achieved, the value of any pulldown resistors (external or internal to a memory card) must
not be smaller than a 10-kΩ value. The impact of adding too heavy (i.e., <10-kΩ value) a pulldown resistor to the
data and command lines of the TXS0206 device and the resulting 4-kΩ pullup / 10-kΩ pulldown voltage divider
network has a direct impact on the V
IH
of the signal being sent into the memory card and its associated logic.
The resulting V
IH
voltage for the 10-kΩ pulldown resistor value would be:
V
CC
× 10 kΩ / (10 kΩ+ 4 kΩ) = 0.714 × V
CC
This is marginally above a valid input high voltage for a 1.8-V signal (i.e., 0.65 × V
CC
).
The resulting V
IH
voltage for 20-kΩ pulldown resistor value would be:
V
CC
× 20 kΩ / (20 kΩ + 4 kΩ) = 0.833 × V
CC
Which is above the valid input high voltage for a 1.8-V signal of 0.65 × V
CC
.
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