Datasheet

pd
oh CCout
pd
R
V V
1.5kΩ R
= ´
+
ol CCout
pu
1.5kΩ
V V
1.5kΩ R
= ´
+
I
IN
V
T
/1k
-(VCC – V )/1k
T
0
V
T
V
IN
TXB0304
www.ti.com SCES831D –SEPTEMBER 2011–REVISED OCTOBER 2012
(1) V
CC
is power supply of TXB0304.
(2) V
T
is the input threshold voltage of TXB0304 (typically it is V
CC
/2).
Figure 2. Typical I
IN
vs V
IN
Curve
Power Up
There is no requirement for the power sequence. During operation, TXB0304 can work at both V
CCA
≤ V
CCB
and
V
CCA
≥ V
CCB
, During power-up sequencing, any power supply can be ramped up first. The TXB0304 has circuitry
that disables all output ports when either V
CC
is switched off (V
CCA/B
= 0 V).
Enable and Disable
The TXB0304 has an OE input that is used to disable the device by setting OE = low, which places all I/Os in the
high-impedance (Hi-Z) state. The disable time (t
dis
) indicates the delay between when OE goes low and when the
outputs actually get disabled (Hi-Z). The enable time (t
en
) indicates the amount of time the user must allow for the
one-shot circuitry to become operational after OE is taken high.
Pullup or Pulldown Resistor on I/O Lines
The TXB0304 is designed to drive capacitive loads of up to 100 pF. The output drivers of the TXB0304 have low
dc drive strength. If pullup or pulldown resistors are connected externally to the data I/Os, their values must be
kept higher than 20 kΩ to ensure that they do not contend with the output drivers of the TXB0304. but if the
receiver is integrated with the smaller pull down or pull up resistor, below formula can be used for estimation to
evaluate the Voh and Vol.
(1)
(2)
For the same reason, the TXB0304 should not be used in applications such as I
2
C or 1-Wire where an open-
drain driver is connected on the bidirectional data I/O. For these applications, use a device from the TI TXS01xx
series of level translators.
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