TXB0104 Datasheet, PDF (10/12 Pages) Texas Instruments – 4-BIT BIDIRECTIONAL VOLTAGE-LEVEL TRANSLATOR WITH AUTO DIRECTION SENSING AND ±15-kV ESD PROTECTION

TXB0104
4-BIT BIDIRECTIONAL VOLTAGE-LEVEL TRANSLATOR
WITH AUTO DIRECTION SENSING AND ±15-kV ESD PROTECTION
SCES650 – APRIL 2006
PRINCIPLES OF OPERATION (continued)
I_IN
V_T/4 kW
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V_IN
–(V_D – V_T)/4 kW
A. V_T is the input threshold voltage of the TXB0104 (typically V_CCI/2).
B. V_D is the supply voltage of the external driver.
Figure 2. Typical I_IN vs V_IN Curve
Power Up
During operation, ensure that V_CCA ≤ V_CCB at all times. During power-up sequencing, V_CCA ≥ V_CCB does not
damage the device, so any power supply can be ramped up first. The TXB0104 has circuitry that disables all
output ports when either V_CC is switched off (V_CCA/B = 0 V).
Enable and Disable
The TXB0104 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 acutally 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 Resistors on I/O Lines
The TXB0104 is designed to drive capacitive loads of up to 70 pF. The output drivers of the TXB0104 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 50 kΩ to ensure that they do not contend with the output drivers of the TXB0104.
For the same reason, the TXB0104 should not be used in applications such as I²C, 1-Wire, or an MMC card
interface 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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