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PDF LS7540 Data sheet ( Hoja de datos )
| Número de pieza | LS7540 | |
| Descripción | TOUCH CONTROL CONTINUOUS DIMMER | |
| Fabricantes | LSI | |
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LSI/CSIwww.DataSheet4U.com
LS7540
U® L LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405
A3800
TOUCH CONTROL CONTINUOUS DIMMER with
AUTOMATIC GAIN CONTROL (AGC)
FEATURES:
June 2006
• Touch or pushbutton control of incandescent lamps.
• Touch Sensitivity guaranteed to 600pF Touch Plate Capacitance.
• Touch Operation independent of line plug polarity.
• Minimal external components.
• AGC Loop stabilizes immediately after Power-Up.
• Brightness state is Off after AC power applied.
• No change of Brightness state if AC power interrupted < 0.5 sec
• Advanced CMOS design for reliable operating characteristics
and low power.
• 50/60 Hz Line Frequency.
• 5V Operation (VDD - VSS).
• LS7540 (DIP); LS7540-S (SOIC) - See Figure 1 -
PIN ASSIGNMENT
TOP VIEW
CLOCK 1
SYNC 2
V DD (+V ) 3
TOUCH 4
8 TRIG/
7 V SS (-V )
6 RAMP
5 CONTROL
APPLICATIONS:
• Screw-in and built-in adapter modules for converting table
and floor lamps to touch control for continuous dimming.
DESCRIPTION:
The LS7540 is a CMOS integrated circuit for controlling the
brightness of incandescent lamps with momentary touch. When
its TOUCH input is connected to a lamp body, the entire lamp
turns into a touch plate. A built-in AGC circuit allows for a wide
range of lamp sizes to be used, ranging from very small table
lamps to very large floor lamps. The brightness is controlled by
controlling the conduction angle of a triac in series with the lamp
and triggered by the TRIG/ output. Between off and maximum,
there are 124 steps of brightness levels, level zero being off and
level 124 being maximum. The phase reference of the Trig/ sig-
nal with respect to the AC line is maintained through the SYNC
input.
Touch Operation
The on/off and brightness control of the lamp is made with brief
touches of the lamp body as described below:
• In the off state a single touch will turn the lamp to full_on.
• At full-on a single touch will start a dim-cycle causing the
brightness to diminish gradually until the lamp turns off.
• During a dim-cycle a single touch will stop the dim-cycle and
lock in the brightness present at that time. Another touch will re-
start the dim-cycle from the present brightness causing the
brightness to ramp down towards off again. The start and stop of
dim-cycle can be repeated over and over again until the lamp
turns off.
INPUT/OUTPUT DESCRIPTION:
CLOCK Input (Pin 1)
An external resistor connected between this input and VDD, along
with an internal capacitor and oscillator stage, generates a clock
which is used for all timing functions. The recommended value of
this resistor for 50Hz and 60Hz operation is specified in the
ELECTRICAL CHARACTERISTICS.
FIGURE 1
SYNC Input (Pin 2)
50Hz or 60Hz AC input for zero crossing detection.
VDD (Pin 3) Supply voltage positive terminal.
TOUCH Input (Pin 4)
Input for sensing that a touch has been made on a lamp surface or
other touch plate. This action alters the state of the TRIG output as
described in the Touch Operation section of the General De-
scription.
CONTROL I/O (Pin 5)
An external R-C network connected between this pin and VDD es-
tablishes the controlling feedback for the AGC Loop.
RAMP Input/Output (Pin 6)
The ramp down rate of the brightness in the dimming cycle is regu-
lated by a resistor-capacitor (RC) pair connected to the RAMP in-
put. The ramp rate is equal to 4TRC per step, where TRC = 0.48RC.
Total ramp down time (TT) from maximum brightness to off is
equal to 496TRC.
Example:
R = 200kΩ, C = 0.22uF;
TRC = 0.48 x (200x103) x (0.22x10-6) = 0.02 sec.
Ramp rate = 4 x TRC = 0.08 sec/step;
Total ramp time, TT = 496 x TRC = 9.92 sec.
VSS (Pin 7) Supply voltage negative terminal.
TRIG/ output (Pin 8)
The TRIG/ output produces a negative pulse every half cycle of
the AC line period to turn on a triac in series with the lamp or any
other load device. The brightness of the lamp is regulated by regu-
lating the conduction angle, Ø (See Fig. 2) of the TRIG/ signal.
The conduction angles at maximum brightness (level 124) and
mimimum brightness (level 1) are 162° and 50° with 0.91° in-
cremental steps.
7540-060906-1
1 page  
AC
MAINS
FIGURE 6. TOUCH LAMP APPLICATION SCHEMATIC #2
R1 D1
Z1
-V
-
C1
+
+V
R2
LOAD
MT2
MT1
T1
G
R6
C7
+
R7
R5
C6
-
87
6
5
C2 TRIG/ V SS RAMP CONT
LS7540
CLOCK SYNC V DD TOUCH
1
23
4
R4 D2 D3
TOUCH
PLATE
(LAMP BODY)
C3 C4
R3
C8*
(SEE NOTE 2)
The Figure 6 Application Schematic functions identically to that shown in Figure 5 with one less component.
Referencing Triac T1 to the +V power supply of the IC eliminates the need to AC couple the TRIAC/ pulse
to the Triac Gate thereby eliminating component C5.
7540-060906-5
5 Page | ||
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| PDF Descargar | [ Datasheet LS7540.PDF ] | |
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