HCC4541B Datasheet, PDF (2/10 Pages) STMicroelectronics – PROGRAMMABLE TIMER

HCF4541B
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 2^N 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
INPUT EQUIVALENT CIRCUIT
RC OSCILLATOR CIRCUIT
"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 R_TC C_TC
where f is between 1KHz and 100KHz and RS >
10 KΩ and ≈2 R_TC
PIN DESCRIPTION
PIN No
12, 13
4, 11
1, 2
3
5
6
10
9
8
7
14
SYMBOL
A, B
NC
R_TC, C_TC
R_S
AR
MR
MODE
Q/Q
SELECT
Q
V_SS
V_DD
NAME AND FUNCTION
Time Select Input
Not Connected
External Resistor, Capaci-
tor Connection
External Resistor Con-
nection or External Clock
Input
Auto Reset Input
Master Reset Input
Mode Select Input
Output Selector
Output
Negative Supply Voltage
Positive Supply Voltage
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