M491B datasheet(4/16 Pages) STMICROELECTRONICS

4 / 16 page

DC ELECTRICAL CHARACTERISTICS (continued)

Symbol

Parameter

Test Conditions

Min.

Typ. Max.

Unit

18–19–20

VIL

1.5

VIH

3.5

IIL

VDD = 5.25 V, VIL = 0.8 V

–0.4

Pull-up Resistor

Ω

21–22–23–24

VOL

VDD = 4.75 V, IOL = 1 mA

0.4

IO (off)

VO (off) = 5.5 V

µA

25–Mains On En-

able

VIL

0.8

VIH

2.4

IIL

VDD = 5.25 V

–0.4

Pull-up Resistor

VIL = 0.8 V

Ω

26–Mains On/Off

VOL

VDD = 4.75 V, IOL = 100

µA

0.4

VDD = 4.75 V, VO = 0.7 V

–1.6

31–Z2

32–Z1

MPX for

Display Out

VOL

VDD = 4.75 V, IOL = 1 mA

0.4

IO (off)

VDD = 5.25 V, VO (off) = 13.2 V

µA

37–UHF

38–CATV

39–VHFIII

40–VHFI

VOL

VDD = 4.75 V, IOL = 1 mA

VOH

VDD = 4.75 V, IOH = – 150

µA

2.4

VIL

0.3

VIH

IO (off)

VDD = 5.25 V, VO (off) = 13.2 V

µA

27-28-29-30-33-

34-35 Display Out

VOL

VDD = 4.75 V, IOL = 20 mA

1.5

36-Display Out

VOL

VDD = 4.75 V, IOL = 30 mA

1.5

31-Memory 8/16

VIH

2.0

VIL

0.8

Keyboard

}

Keyboard

Out

}

DESCRIPTION (All timings at fclock = 500kHz)

PIN 1 : VSS

The substrate of the IC is connected to this pin. This

is the reference pin for all parameters of the IC.

PIN 2 : MEMORY SUPPLY VOLTAGE

A supply voltage of 25

± 1 V has to be applied to

this pin during the modify and read cycles.

MODIFY CYCLE

A modify cycle consists of three steps :

1. All ”1”s are written in the bits of the selected word.

2. All bits of the selected word are erased (all ”0”s)

3. The new content is written.

Thus a constant aging of all the bits of the word is

obtained.

During both write and erase cycles the memory

status is checked continuously ; therefore after

each write or erase pulsea read operationis carried

out. The write or the erase operations are stopped

as soon as the result of the read operation is valid.

WRITE CYCLE. The peak of the current flowing

through pin 2 during a write operation is shown in

fig. 1, while fig. 2 shows the envelope of the same

current.

The typical write time is 3-4 ms for the first cycles

and increases to about 30 ms after 1000 cycles.

M491B

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