4800 Great America Parkway Ste 202

Tel: 408-235-8680

Santa Clara, CA. 95054

Fax: 408-235-8685

Preliminary

5

EN27LV020 / EN27LV020B

READ MODE

The EN27LV020 / EN27LV020B has two control functions, both of which must be logically

satisfied in order to obtain data at the outputs. Chip Enable ( CE ) is the power control and

should be used for device selection. Output Enable ( OE ) is the output control and should be

used to gate data to the output pins, independent of device selection. Assuming that

STANDBY MODE

current to 10

in a high-impedance state, independent of the OE input.

TWO-LINE OUTPUT CONTROL FUNCTION

To accommodate multiple memory connections, a two-line control function is provided to

allow for:

1.

Low memory power dissipation,

2.

Assurance that output bus contention will not occur.

It is recommended that CE be decoded and used as the primary device-selection function,

while OE be made a common connection to all devices in the array and connected to the

READ line from the system control bus. This assures that all deselected memory devices are in

their low-power standby mode and that the output pins are only active when data is desired

from a particular memory device.

SYSTEM CONSIDERATIONS

During the switch between active and standby conditions, transient current peaks are produced

on the rising and falling edges of Chip Enable. The magnitude of these transient current peaks

is dependent on the output capacitance loading of the device. At a minimum, a 0.1

µF ceramic

capacitor (high frequency, low inherent inductance) should be used on each device between

VCC and VSS to minimize transient effects. In addition, to overcome the voltage drop caused

by the inductive effects of the printed circuit board traces on EPROM arrays, a 4.7

µF bulk

of the capacitor should be close to where the power supply is connected to the array.