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LS7538 Datasheet(PDF) 4 Page - LSI Computer Systems

Part No. LS7538
Description  TOUCH CONTROL STEP DIMMER LIGHT SWITCH WITH AUTOMATIC GAIN CONTROL (AGC)
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Maker  LSI [LSI Computer Systems]
Homepage  http://www.lsicsi.com
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LS7538 Datasheet(HTML) 4 Page - LSI Computer Systems

   
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AC
MAINS
LOAD
C4
R1
R3
R4
C1
D1
FIGURE 4. TOUCH LAMP APPLICATION SCHEMATIC
C3
D2
8
7
6
5
4
3
2
1
TRIG
V SS
MODE CONT
CLOCK SYNC V DD TOUCH
D3
R2
TOUCH
PLATE
(LAMP BODY)
C2
(SEE NOTE 1)
T1
G
MT2
MT1
Z1
C5
C6
R5
+
-
+V
-V
LS7538
+
-
C7* (SEE NOTE 2)
R1 =
20k
Ω, 1W
R2 =
470k
Ω, 1/4W
R3 =
1k
Ω, 1/4W
R4 =
300k
Ω, 1/4W, 1%
R5 =
10M
Ω, 1/4W
C1 =
47µF, 16V
C2 =
1000pF, 16V
C3 =
1000pF, 1kV
R1 =
39k
Ω, 2W
R2 =
910k
Ω, 1/4W
R4 =
360k
Ω, 1/4W, 1%
D1 =
1N4005
T1 =
Q4004L4 (Typical Triac)
or
Q4004F41 (Typical Triac)
All other values remain the same.
C4 =
1000pF, 1kV
C5 =
.03µF, 16V
C6 =
1µF, 16V
Z1 =
8.2V, 1/4W Zener
D1 =
1N4004
D2 =
1N4148
D3 =
1N4148
T1 =
Q2004L4 (Typical Triac)
or Q2004F41 (Typical Triac)
220VAC APPLICATION
115VAC APPLICATION
(1) Resistor should be placed adjacent to Pin 1.
(1)
(1
)
NOTE 1: Connect MODE (Pin 6) for desired Brightness Step Sequence (See Table 1).
NOTE 2: A good PCB layout using through-hole components will provide protection for ESD introduced at the Touch Plate in the range
of 25kV. Using surface mount components and/or a poor PCB layout can reduce the ESD protection. The OEM can increase the ESD
protection provided by the product with any combination of the following steps:
Step 1: The most effective and least costly way to increase ESD protection is to create a spark gap around the Touch Plate input on
the PCB. This will increase ESD protection on a good PCB layout to abut 35kV. The gap should be made with a split metal ring with
each side of the metal ring connected back to opposite sides of the AC line. This ensures that a path for the spark back to house ground
through AC Neutral exists independent of line plug polarity. The split ring and the center conduction plate should be constructed so that
the spacing between them conforms to UL requirements. The spark gap will absorb most of the ESD leaving a remnant of about 10kV
for the rest of the circuit to absorb.
Step 2: Increase R3 from 1k
Ω to 5.1kΩ and add C7, a 0.1µF capacitor, between VDD and Vss.
(A minimal loss in touch sensitivity may be experienced.)
Step 3: Replace diodes D2 and D3 (1N4148) with Schottky diodes (1N5819 or similar)
7538/39-091100-4


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