UM3308 Datasheet, PDF (9/12 Pages) Union Semiconductor, Inc. – 8-Bit Bidirectional Voltage-Level Translator with Auto Direction sensing and ±15kV ESD Protection

UM3308
Input Driver Requirements
Typical I_IN vs V_IN characteristics of the UM3308 are shown in Figure 2. For proper operation, the
device driving the data I/Os of the UM3308 must have drive strength of at least ±2 mA.
I_IN
V_T/4kΩ
V_IN
-(V_D-V_T)/4kΩ
A: V_T is the input threshold voltage of the UM3308 (typical V_CCI/2)
B: V_D is the supply voltage of the external driver.
Power Up
Figure 2 Typical I_IN vs V_IN Curve
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 UM3308 has
circuitry that disables all output ports when either V_CC is switched off (V_CCA/B = 0 V).
Enable and Disable
The UM3308 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 (tdis) indicates the delay between
when OE goes low and when the outputs actually get disabled (Hi-Z). The enable time (ten)
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 UM3308 is designed to drive capacitive loads of up to 50pF. The output drivers of the
UM3308 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 theUM3308.
For the same reason, the UM3308 should not be used in applications such as I²C or 1-Wire
where an open-drain driver is connected on the bidirectional data I/O.
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http://www.union-ic.com Rev.08 Apr.2014
9/12