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http://www.union-ic.com Rev.15 Aug.2015

9/15

UM3304/UM3304Q/UM3304QT

Applications Information

UM3304/UM3304Q/UM3304QT ESD protected level translator provides level shifting necessary

Block Diagram

The UM3304/UM3304Q/UM3304QT (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 UM3304/UM3304Q/UM3304QT 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.

P

One Shot

N

One Shot

4K

I/O A

I/O B

VCCA

VCCB

P

One Shot

N

One Shot

4K

T3

T4

T2

T1

Figure 1 Block Diagram of UM3304/UM3304Q/UM3304QT I/O Cell