FIGURE 4. TOUCH LAMP APPLICATION SCHEMATIC
+V
R1
D1
MT2
LOAD
+
C1
AC
MAINS
T1
MT1
Z1
-
R5
G
R6
+
-
C6
-V
C2
C5
8
TRIG
SEE
NOTE 1
7
V
SS
6
MODE
5
CONT
C7*
(SEE NOTE 2)
LS7541
CLOCK SYNC V
DD
TOUCH
R2
1
2
3
D2
4
D3
R4
TOUCH PLATE
(LAMP BODY)
R3
C3
C4
115VAC APPLICATION
R1 = 20kΩ, 1W
R2 = 470kΩ, 1/4W
R3 = 1kΩ, 1/4W
(1)
R4 = 400kΩ, 1/4W, 1%
R5 = 10MΩ, 1/4W
R6 = 100Ω, 1/4W
C1 = 47µF, 10V
C2 = 1000pF, 10V
C3 = 1000pF, 1kV
C4 = 1000pF, 1kV
C5 = 0.03µF, 10V
C6 = 1µF, 10V
Z1 = 5.1V, 1/4W Zener
D1 = 1N4004
D2 = 1N4148
D3 = 1N4148
T1 = Q2004L4 (Typical Triac)
or Q2004F41 (Typical Triac)
220VAC APPLICATION
R1 = 39kΩ, 2W
R2 = 910kΩ, 1/4W
(1
)
R4 = 470kΩ, 1/4W, 1%
D1 = 1N4005
T1 = Q4004L4 (Typical Triac)
or Q4004F41 (Typical Triac)
All other values remain the same.
(1)
Resistor should be placed adjacent to Pin 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 1kΩ to 5.1kΩ and add C7, a 0.1µF capacitor, between V
DD
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)
7541-011706-4
LSI [ LSI COMPUTER SYSTEMS ]
