Datasheet

–(V – V )/4 k
D T
Ω
V /4 k
T
Ω
V
IN
I
IN
Auto-Direction Sensing Voltage Translator Architecture www.ti.com
The O.S. reduces the output impedance during the transition allowing the TXB device to drive a load while
maintaining fast propagation delays and edge rates. Once the transition is completed, the O.S. circuit
times out, and the buffer and the 4-kΩ pullup resistor hold the B-port signal high or low.
We call the TXB-type translator "weak-buffered", because it is strong enough to hold the output port high
or low during a dc state, but weak in that the 4-kΩ impedance buffer can be easily over-driven by a
system driver connected to the A or B port when a bus direction change is desired.
Figure 4 shows a typical I
IN
vs V
IN
curve.
Figure 4. Typical I
IN
vs V
IN
Curve
Where,
V
T
is the input threshold voltage of the TXB010x; V
T
is typically V
CCI
/2.
V
D
is the supply voltage of the external system driver.
An external system driver must supply more than ±2 mA of current to reliably overdrive the hold provided
by the weak buffer.
4
A Guide to Voltage Translation With TXB-Type Translators SCEA043–March 2010
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