Supplementary notes ST2329A
The ST2329A may be driven by an open drain or totem pole driver and the nature of the device output is “open drain”. It must not be used to drive a pull-down resistor as the impedance of the output at HIGH state depends on the pull-up resistor placed at the I/Os.
As the device has pull-up resistors on both the I/O
VCC
and I/O
VL
ports, the user needs to ensure that the driver is able to sink the required amount of current. For example, if the settings are V
CC
= 5.5 V, V
L
= 4.3 V, and the pull-up resistor is 10 k Ω , then the driver must be able to sink at least (5.5 V / 10 k Ω ) + (4.3 V / 10 k Ω )
=
1 mA and still meet the V
IL requirements of the ST2329A.
To support the open drain system, the one-shot transistor is turned on only during high transition at the output side. When it drives a high state, after the one-shot transistor is turned off, only the pull-up resistor is able to maintain the state. In this case, the resistive load is not recommended.
In some applications where it might be required to turn off one of the power supplies powering up the level translator, the user may turn off the V
CC
only when the OE pin is low
(device is disabled). There is no current consumption in V
L
due to floating gates or other causes, and the I/Os are in a high impedance state in this mode.
Table 3.
Truth table
Enable Bidirectional input/output
OE I/O
VCC
I/O
VL
H
(1)
H
(2)
H
(1)
H
(1)
L Z
L L
Z
(3)
1.
High level V
L
power supply referred.
2.
High level V
CC
power supply referred.
3.
Z = high impedance.
8/24 Doc ID 14907 Rev 3
