Features

• Low Symmetrical Output Resistance, Typically 100Ω

at VDD = 15V

• Built-In Low-Power RC Oscillator

• Oscillator Frequency Range . . . . . . . . . . DC to 100kHz

• External Clock (Applied to Pin 3) can be Used Instead

of Oscillator

• Operates as 2N Frequency Divider or as a Single-

Transition Timer

• Q/Q Select Provides Output Logic Level Flexibility

• AUTO or MASTER RESET Disables Oscillator During

Reset to Reduce Power Dissipation

• Operates With Very Slow Clock Rise and Fall Times

• Capable of Driving Six Low Power TTL Loads, Three

Low-Power Schottky Loads, or Six HTL Loads Over

the Rated Temperature Range

• Symmetrical Output Characteristics

• 100% Tested for Quiescent Current at 20V

• 5V, 10V, and 15V Parametric Ratings

• Meets All Requirements of JEDEC Standard No. 13B,

“Standard Specifications for Description of ‘B’ Series

CMOS Devices”

Description

CD4541B programmable timer consists of a 16-stage binary

counter, an oscillator that is controlled by external R-C components

(2 resistors and a capacitor), an automatic power-on

reset circuit, and output control logic. The counter increments

on positive-edge clock transitions and can also be reset via the

MASTER RESET input.

The output from this timer is the Q or Q output from the 8th,

10th, 13th, or 16th counter stage. The desired stage is chosen

using time-select inputs A and B (see Frequency Select Table).

The output is available in either of two modes selectable via the

MODE input, pin 10 (see Truth Table).When this MODE input is

a logic “1”, the output will be a continuous square wave having

a frequency equal to the oscillator frequency divided by 2N.

With the MODE input set to logic “0” and after a MASTER

RESET is initiated, the output (assuming Q output has been

selected) changes from a low to a high state after 2N-1 counts

and remains in that state until another MASTER RESET pulse

is applied or the MODE input is set to a logic “1”.

Timing is initialized by setting the AUTO RESET input (pin 5) to

logic “0” and turning power on. If pin 5 is set to logic “1”, the

AUTO RESET circuit is disabled and counting will not start until

after a positive MASTER RESET pulse is applied and returns

to a low level. The AUTO RESET consumes an appreciable

amount of power and should not be used if low-power operation

is desired. For reliable automatic power-on reset, VDD should

be greater than 5V.

The RC oscillator, shown in Figure 2, oscillates with a

frequency determined by the RC network and is calculated

using: