AN2014 datasheet(8/65 Pages) STMICROELECTRONICS

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EEPROM cell and memory array architecture

AN2014

8/65

DocID10701 Rev 10

Figure 3. Floating gate reservoir full of electrons (Erased state)

1. Control Gate threshold value (Vth.erase) is positive.

2. Id = f(Vg) characteristic shows Id=0 for Vg<Vth.erase.

The effect, as viewed from the channel region of the transistor, is that the Control Gate

voltage, Vg, is offset by an extra negative or positive amount. Viewed from the outside,

black-box electrical behavior of the device, the charge on the floating gate has the effect of

moving the threshold MOSFET voltage, Vth, at which the linear conduction region begins. In

other words, a FLOTOX transistor is a MOS transistor with a variable Control Gate threshold

value, Vth.

The floating gate acts as the storage element, and, being completely surrounded by

insulating oxide, as shown in Figure 1, keeps its charge even when there is no power

supply.

Figure 4. Floating gate reservoir empty of electrons (Written state)

1. Control Gate threshold value (Vth.write) is negative

2. Id=f(Vg) characteristic shows Id=0 for Vg<Vth.write.

AI10228

Tunnel Oxide

Control Gate

- - - - - - - - - - - - - - - -

Source

Drain

Gate Oxide

Oxide

- - - - - -

Vth.erase

Channel Region

AI10229

Tunnel Oxide

Control Gate

+ + + + + + + + + + + + +

Source

Drain

Gate Oxide

Oxide

+ + + + +

Vth.write

Channel Region

AN2014 Datasheet(PDF) 8 Page - STMicroelectronics