ST2129QTR datasheet(5/20 Pages) STMICROELECTRONICS

5 / 20 page

ST2129

Supplementary notes

Doc ID 15967 Rev 1

5/20

Supplementary notes

3.1

Driver requirement

For proper operation, the driver from each side of the device must have the capability to

source and sink a minimum of 1mA current. The device architecture requires the driver to

source/sink a maximum current of (VCC/4) mA to/from the weak 4 kΩ output buffer.

3.2

Load driving capability

To support the architecture that allows level translation without direction pin, the one-shot

transistor is turned on only during state transition at the output side. After the one-shot

transistor is turned off, only the 4 k

Ωresistor maintains the state. So, resistive load or pull-up

resistor less than 50 k

Ω is not recommended for a proper operation.

3.3

Power off feature

In some applications, where it might be required to turn off one of the power supplies

powering up the level translator, the device is automatically disabled when VCC supply is

turned off, even if the OE pin is set to HIGH (enabled). In this mode, all I/Os are in high

impedance state.

3.4

Truth table

(1) High level VL power supply referred.

(2) High level VCC power supply referred.

(3) Z = High impedance.

Table 3.

Truth table

Enable

Bidirectional Input/Output

I/OVCC

I/OVL

H(1)

H(2)

H(1)

LZ(3)

Z(3)

ST2129QTR Datasheet(PDF) 5 Page - STMicroelectronics