HCC4541B datasheet(2/10 Pages) STMICROELECTRONICS

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HCF4541B

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select inputs A or B (see frequency selection

table). The output is available in one of the two

modes that can be selected via the MODE input

pin 10 (see truth table). The output turns out as a

continuos square wave, with a frequency equal to

the oscillator frequency divided by 2N when this

MODE input is a logic "1". When it is a logic "0"

and

after a MASTER RESET is started, and Q

output has been selected, the output goes up to a

high state after 2 N-1 counts. It remains in that

state till another MASTER RESET pulse is apply

or the mode input is a logic "1". The process starts

by setting the AUTO RESET input (pin 5) to logic

"0" and switching power on. If pin 5 is set to logic

"1", the AUTO RESET circuit is not enabled and

counting cannot start till a positive MASTER

RESET pulse is applied, returning to a low level.

The AUTO RESET consumes a remarkable

amount of power and should not be used if low

power operation is wanted. The frequency of the

oscillator depends on the RC network. It can be

calculated using the following formula :

f = 1 / 2.3 RTC CTC

where f is between 1KHz and 100KHz and RS >

10 K

Ω and ≈2 R

INPUT EQUIVALENT CIRCUIT

PIN DESCRIPTION

RC OSCILLATOR CIRCUIT

PIN No

SYMBOL

NAME AND FUNCTION

12, 13

A, B

Time Select Input

4, 11

Not Connected

1, 2

RTC, CTC

External Resistor, Capaci-

tor Connection

External Resistor Con-

nection or External Clock

Input

Auto Reset Input

Master Reset Input

MODE

Mode Select Input

Q/Q

SELECT

Output Selector

Output

VSS

Negative Supply Voltage

VDD

Positive Supply Voltage

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