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

UM3308
Applications Information
UM3308 ESD protected level translator provides level shifting necessary to allow data transfer in
a multi-voltage system. Externally applied voltages, V_CCA and V_CCB set the logic levels on either
side of device. A low voltage signal present on V_CCA side of the device appears as a high voltage
logic signal on the V_CCB side of the device, and vice-versa.
Block Diagram
The UM3308 (block diagram see Figure 1) does not require a direction-control signal to control
the direction of data flow from A to B or from B to A. In a dc state, the output drivers of the
UM3308 can maintain a high or low, but are designed to be weak, so that they can be overdriven
by an external driver when data on the bus starts flowing to the opposite direction.
The output one shot detects rising or falling edges on the A or B ports. During a rising edge, the
one shot turns on the PMOS transistors (T1, T3) for a short duration, which speeds up the
low-to-high transition. Similarly, during a falling edge, the one shot turns on the NMOS
transistors (T2, T4) for a short duration, which speeds up the high-to-low transition.
VCCA
VCCB
I/O A
T3
4K
T4
T1
4K
T2
I/O B
Figure 1 Block Diagram of UM3308 I/O Cell
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http://www.union-ic.com Rev.08 Apr.2014
8/12