LS7538 Datasheet, PDF (1/4 Pages) LSI Computer Systems – TOUCH CONTROL STEP DIMMER LIGHT SWITCH WITH AUTOMATIC GAIN CONTROL (AGC)

LSI/CSI
LS7538-LS7539
U
®
L
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 [phone] FAX [phone]
A3800
TOUCH CONTROL STEP DIMMER LIGHT SWITCH
WITH AUTOMATIC GAIN CONTROL (AGC)
December 2002
FEATURES:
• Touch Sensitivity guaranteed to 600pF Touch Plate Capacitance.
• Touch Operation independent of line plug polarity.
• Pin selection of three available Brightness Step Sequences.
• Minimal external components.
• AGC Loop stabilizes immediately after Power-Up.
• Brightness state is Off after AC power applied.
• Brightness state is unchanged if AC power interrupted for < 0.5 sec.
• Advanced CMOS design for reliable operating characteristics and low power.
• 50/60 Hz Line Frequency.
• +6V to +9.5V Operation (VDD-VSS).
• LS7538, LS7539 (DIP); LS7538-S, LS7539-S (SOIC) - See Figure 1
APPLICATIONS:
• Screw-in and built-in adapter modules for converting table and floor lamps
to touch control for step dimming.
• On-Off touch control of under-cabinet fluorescent lamps (LS7539 only).
PIN ASSIGNMENT
TOP VIEW
CLOCK ¹
SYNC ²
) V DD(+V
3
TOUCH ⁴
8 _TRIG
7 _{V SS(-V)}
6 _MODE
5 _CONTROL
FIGURE 1
DESCRIPTION:
The LS7538 and LS7539 are CMOS integrated circuits which provide trigger pulses for triac phase control of incandescent lamps.
The circuits are designed to operate with a wide variety of lamp sizes ranging from small table lamps to large floor lamps.
The AGC Loop automatically adjusts Touch Sensitivity to be independent of lamp size.
There are 3 different Brightness Step Sequences for each version of the IC which can be selected by the Three-State
MODE pin as shown in Table 1.
TABLE 1. BRIGHTNESS STEP MODES
MODE PIN
BRIGHTNESS STEP SEQUENCE
FLOAT
OFF-NIGHT LIGHT-MEDIUM-MAXIMUM-OFF
VDD
OFF-NIGHT LIGHT- LOW MEDIUM-HIGH MEDIUM-MAXIMUM-OFF
Vss (LS7538)
(LS7539)
OFF-MAXIMUM-MEDIUM-NIGHT LIGHT-OFF
OFF-MAXIMUM-OFF
The lamp brightness is made to vary by changing the delay of the TRIG pulse to the triac from the zero-crossing of the
SYNC input. The delays are shown in Table 2 for 50Hz and 60Hz operation along with Delivered Power as a percentage
of Full Power. Figure 2 illustrates the delay.
TABLE 2. BRIGHTNESS POWER LEVELS
Brightness
Night Light
Low Medium
Medium
High Medium
Maximum
60Hz Delay (1)
6.0 ms
4.8 ms
4.0 ms
3.2 ms
0.85 ms
50Hz Delay (2)
7.2 ms
5.7 ms
4.8 ms
3.8 ms
1.0 ms
% PWR (3)
12
35
53
72
99
(1) With 300kΩ connected between Pin 1 and VDD.
(2) With 360kΩ connected between Pin 1 and VDD.
(3) Percentage of Full Power delivered to a resistive load by the Triac Switch.
7538/39-120202-1