tAVPL

VALID

AI00725

A0-A18

Q0-Q7

VPP

VCC

G

DATA IN

DATA OUT

E

tQVEL

tVPHEL

tVCHEL

tEHQX

tELEH

tGLQV

tQXGL

tGHQZ

tGHAX

PROGRAM

VERIFY

Figure 6. Programming and Verify Modes AC Waveforms

System Considerations

The power switching characteristics of Advanced

CMOS OTP EPROMs require careful decoupling of

segments that are of interest to the system de-

signer : the standby current level, the active current

level, and transient current peaks that are pro-

duced by the falling and rising edges of E. The

magnitude of the transient current peaks is de-

pendent 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 ca-

pacitors. It is recommended that a 0.1

µF ceramic

of low inherent inductance and should be placed

as close to the device as possible. In addition, a

4.7

µF bulk electrolytic capacitor should be used

bulk capacitor should be located near the power

supply connection point.The purpose of the bulk

capacitor is to overcome the voltage drop caused

by the inductive effects of PCB traces.

Programming

When delivered, all bits of the M27C405 are in the

’1’ state. Data is introducedby selectively program-

ming ’0’s into the desired bit locations. Although

only ’0’s will be programmed, both ’1’s and ’0’s can

be present in the data word. The M27C405 is in

to be programmed is applied to 8 bits in parallel to

the data output pins. The levels required for the

to be 6.25V

± 0.25V.

8/15

M27C405