Device operation

M27W512

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2.3

Two line output control

Because EPROMs are usually used in larger memory arrays, the product features a 2 line

control function which accommodates the use of multiple memory connection. The two line

control function allows:

●

The lowest possible memory power dissipation

●

Complete assurance that output bus contention will not occur.

For the most efficient use of these two control lines, E should be decoded and used as the

primary device selecting function, while G should be made a common connection to all

devices in the array and connected to the READ line from the system control bus. This

ensures that all deselected memory devices are in their low power standby mode and that

the output pins are only active when data is required from a particular memory device.

2.4

System considerations

The power switching characteristics of Advanced CMOS EPROMs require careful

the system designer: the standby current level, the active current level, and transient current

peaks that are produced by the falling and rising edges of E. The magnitude of the transient

current peaks is dependent on the capacitive and inductive loading of the device at the

output.

The associated transient voltage peaks can be suppressed by complying with the two line

output control and by properly selected decoupling capacitors. It is recommended that a

high frequency capacitor of low inherent inductance and should be placed as close to the

device as possible. In addition, a 4.7µF bulk electrolytic capacitor should be used between

supply connection point.The purpose of the bulk capacitor is to overcome the voltage drop

caused by the inductive effects of PCB traces.