SENS (Pin 6)

A positive signal applied at the SENS input controls the turn-on,

turn-off and dimming function of the LS7232NT. The SENS in-

put is designed to operate with very low levels of signal, so that

it can be directly interfaced with the photoamplifier output. Sig-

nal at the SENS input is amplified with a gain of 30. If a photo-

sensor is not to be used, the SENS input can easily be adapted

to a touch plate.

Signals at the SENS input are classified as SHORT touch and

LONG touch. Signals between 50ms and 350ms constitute a

SHORT touch, whereas signals longer than 350ms constitute a

LONG touch. The functions of these two types of touches are

explained in the mode description section.

SENS input has an internal pull-down resistor of 10k

Ω.

REMOTE (Pin 7)

For performing dimming operation from remote sites or through

wire extensions, the REMOTE input is used. This input is sam-

pled twice during both negative and positive half cycles of the

AC, rendering it more immune to noise and hence more suited

for carrying signals over extension wires.

Vss (Pin 8)

Supply voltage, negative terminal

.

Trigger ouput for driving the gate of a triac. A negative pulse of

nominally 130.2µs duration is generated at this output which

can be varied between 19.7° and 119.5° from the zero-

crossover of the AC during every half cycle. The control of con-

duction angle of the TRIG/ output is effected by Short and Long

touches at the SENSE and REMOTE inputs.

LEDO (Pin 10)

A positive pulse of 32µs is generated at this output during every

negative half-cycle of the AC. If the TRIG/ output is Off, the

LEDO is generated nominally 911µs after the AC zero-

crossover in the negative half-cycles. If the TRIG/ output is on,

the LEDO tracks the TRIG/ output signal and is generated

170µs ahead of the TRIG/ output, during every negative half-

cycle of the AC.

The LEDO is used to drive an infra-red LED. When a reflecting

object, such as a human hand, is brought close to the infrared

LED, the light is reflected back to the Photo-diode, which is

mounted in physical proximity to the infra-red LED. The change

of intensity of the received light by the photo-diode results in a

change of the photo-diode current which in turn is amplified by

the transconductance amplifier as described in the ANODE

input section.

RC (Pin 11)

A resistor-capacitor pair connected externally to the RC input

constitutes the timing element for the delay generation in Modes

4, 5, 6, and 7. The delay is given by the expression,

∆ = 63RC.

M1 and M2 (Pin 12 and Pin 13)

Each of these inputs are 3-state inputs, namely Low (L), High

(H) and Float (F). The logic levels of these two inputs together,

configures the operating modes of the LS7232NT according to

Table 1.

MODE DESCRIPTIONS:

See Figures 2, 3, and 4 for further explanations.

MODE 1 - Touch causes the TRIG/ output to toggle between

Off and Max. The Off to Max transition slews in 350ms(tr). Long

and Short Touch operate in identical manner. Leading edge

touch sense (change occurs upon initiation of touch)

7232NT-082101-2

TABLE 1. OPERATING MODES

M1

M2

MODE

DESCRIPTION

L

L

1

ON - OFF

L

F

2

ON - OFF - DIMMER

L

H

3

ON - OFF - MEMORY - DIMMER

F

F

4

ON - DELAYED_OFF - DIMMER

F

H

5

ON - DELAYED_OFF - MEMORY-DIMMER

F

L

6

ON - DELAYED_OFF

H

L

7

ON - AUTO_OFF_TIMER

H

F

X

NOT ALLOWED

H

H

X

NOT ALLOWED

MODE 2 - Same effect for Short Touch as in Mode 1. Long Touch

causes the output to sweep between conduction angles of 38° (Min)

and 155° (Max) in increments of 1.4°. The sweep direction auto-

matically reverses at Min and Max. Sweep direction also reverses for

every Long Touch. Trailing edge sensing for Short Touch. (Change

occurs upon removal of touch.)

MODE 3 - Same as Mode 2 except for Short Touch the output

toggles between Off and Memory. Memory is updated with the long

touch.

MODE 4 - Same as Mode 2 except the On to Off operation with

Short Touch is delayed. At the termination of the Short Touch the out-

put level instantaneously drops by an amount of

Ư to indicate the

capacitor pair at the RC (Pin 11) input, according to the

following

expression:

The magnitude of

Ư is dependent on the pre-touch intensity from

where the turn-off delay is initiated and can have one of the values in

Table 2 (See Fig. 2 and 3).

MODE 5 - Same as Mode 4, except a Short Touch in the Off state

switches the output to memory.

MODE 6 - Same as Mode 4, except that there is no dimming func-

tion in Mode 6. Both Short and Long touches operate as Short Touch

(leading edge touch sense).

MODE 7 - Output switches from Off to Max with either Short or Long

description of Mode 4) the output drops by an angle

Ư according to

Table 2. After another fixed delay of 10sec (tf) the output slews off in

effect. A touch during tf and td7 timeouts aborts the timeout and

restores output to Max.

TABLE 2. BRIGHTNESS DROP AT DELAY START,

Ư

PRE-TOUCH CONDUCTION ANGLE

Ø

155° to 130°

-35°

129° to 115°

-25°

114° to 95°

-20°

94° to 45°

-10°

44° to 38°

Instantaneous Off