TRIGGER Input (TRIG, Pin 18)

A transition at the TRIG input causes OUT to switch with or

without delay, depending on the selected mode. The TRIG in-

put to OUT transition relation is always opposite in polarity,

with the exception of One-Shot mode. (See Mode definitions

above.) TRIG input has an internal pull-down resistor of

about 500kΩ and is buffered by a Schmitt trigger to provide

input hysteresis.

LS7211N TIME BASE Input (RC/CLOCK, Pin 4)

For

LS7211N, the basic timing signal is applied at the RC/

CLOCK input. The clock can be provided from either an ex-

ternal source or generated by an internal oscillator by con-

necting an R-C network to this input.

The frequency of oscillation is given by

ƒ 1/RC. Chip-to-

chip oscillation tolerance is ± 5% for a fixed value of RC.

The external clock mode is selected by applying a logic low

to the RCS/CLKS input (Pin 5); the internal oscillator mode is

selected by applying a high level to the RCS/CLKS input.

LS7212N TIME BASE Input (XTLI/CLOCK, Pin 4)

For

LS7212N, the basic timing clock is applied to the XLTI/

CLOCK input from either an external clock source or gener-

ated by an internal crystal oscillator by connecting a crystal

between XTLI/CLOCK input and the XTLO output (Pin 5).

LS7211N TIME BASE SELECT Input (RCS/CLKS, Pin 5)

For

LS7211N, the external clock operation at Pin 4 is se-

lected by applying a logic low to the RCS/CLKS input. The in-

ternal oscillator option with RC timer at Pin 4 is selected by

applying a logic high at the RCS/CLKS input. RCS/CLKS in-

put has an internal pull-down resistor of about 500kΩ.

LS7212N TIME BASE Output (XTLO, Pin 5)

For

LS7212N, when a crystal is used for generating the time

base oscillation, the crystal is connected between XTLI/

CLOCK and XTLO pins.

PRESCALER SELECT Input (PSCLS, Pin 6)

The PSCLS input is a 3-state input, which selects one of

three prescale factors according to Table 2.

TABLE 2. PRESCALE FACTOR SELECTION

PSCLS Input

S (Prescale Factor )

Logic Level

LS7211N

LS7212N

Float

1

1

3,000

32,768

3,600

32,768x60

Using prescale factors of 3000 and 3600, delays in units of

minutes can be produced from 50Hz and 60Hz line sources.

Prescale factors of 32,768 and 32,768 x 60 can be used to

generate accurate delays in units of seconds and minutes,

respectively, from a 32kHz watch crystal.

7211N-062209-2

TIMER RESET Input (RESET, Pin 7)

When RESET input switches high, any timeout in progress

is aborted and OUT switches high without delay. With RE-

SET high, OUT remains high. When RESET switches low

with TRIG low in any mode, OUT remains high. When RE-

SET switches low with TRIG high in Delayed Operate and

Dual Delay modes, the delay timer is started and OUT

switches low at the end of the delay timeout. When RE-

SET switches low with TRIG high in Delayed Release

mode, OUT switches low without delay. When RESET

switches low with TRIG high in One-Shot mode, OUT re-

mains high. RESET input has an internal pull-down resistor

of about 500kΩ, and is buffered by a Schmitt Trigger to

provide input hysteresis.

Supply voltage negative terminal or GND.

DELAY Output (OUT, Pin 9)

Except in One-Shot mode, OUT switches with or without

delay (depending on mode) in inverse relation to the logic

level of the TRIG input. In One-Shot mode, a timed low

level is produced at OUT, in response to a positive transi-

tion of the TRIG input.

WEIGHTING BIT Inputs (WB7 to WB0, Pins 10 - 17)

Inputs WB0 through WB7 are binary weighted delay bits

used to program the delay according to the following

relations:

One-Shot Mode: Pulse width = SW

ƒ

All other Modes: Delay = SW + 0.5

ƒ

Where:

S = Prescale factor (See Table 2)

ƒ = Time base frequency at Pin 4

W = WB0 + WB1 + ....... WB7

The weighting factor W is calculated by substituting in the

equation above for W, the weighted values for all the WB

inputs that are at logic high. The weighted values for the

WB inputs are shown in Table 3. Each WB input has an in-

ternal pull-down resistor of about 500kΩ.

TABLE 3. BIT WEIGHTS

BITS

VALUE

WB0

1

WB1

2

WB2

4

WB3

8

WB4

16

WB5

32

WB6

64

WB7

128

Supply voltage positive terminal.