LS7631_05 Datasheet, PDF (1/4 Pages) LSI Computer Systems – TOUCH CONTROL HALOGEN LAMP DIMMER

LSI/CSI
LS7631
LS7632
U_{® L LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 [phone] FAX [phone]}
A3800
TOUCH CONTROL HALOGEN LAMP DIMMER ^{December 2005}
FEATURES:
• Touch or pushbutton control of incandescent lamps
and *transformer-coupled halogen lamps.
*Magnetic transformers and most Electronic transformers
• Direct replacement for P/N SLB0587
(See “DISCUSSION” on Page 3)
• Automatic safety shutdown
• PLL synchronization allows use as a Wall Switch
• Three operating modes
• Extension input for remote activation
• 50Hz/60Hz AC line frequency
• +5V operating voltage (VDD - VSS)
• LS7631, LS7632 (DIP); LS7631-S, LS7632-S (SOIC)
- See Figure 1 -
APPLICATIONS:
Electronic dimmers for wall switch control of ceiling mounted
lighting, foot switch control of large floor lamps and hand switch
control of table lamps.
BACKGROUND AND GENERAL DESCRIPTION:
A typical electronic dimmer may not operate properly with the in-
ductive load encountered when driving a magnetic transformer-
coupled low-voltage halogen lamp. The inductive load can cause
a phenomenon called half-waving, wherein the triac fires in al-
ternate half-cycles only, which may lead to the thermal de-
struction of the load transformer. The problems encountered in
driving an inductive load are addressed by the LS7631/LS7632
CMOS ICs as follows:
1. Compensation for delayed triac cut-off.
When a trigger pulse is due to occur at a conduction
angle which coincides with the on-state of the triac,
the trigger pulse is delayed until the triac has turned off.
This eliminates the underlying cause of half-waving.
.
2. Compensation for delayed triac turn-on.
At the set conduction angle, a triac trigger pulse of 130.2µs
(60Hz) is issued by the IC. If the triac fails to fire, a second
trigger pulse of 260.4µs width is issued 1ms later as a
second attempt to fire the triac during the same half-cycle.
3. Safety-shutdown.
If the frequency of occurrences of the delayed turn-on exceeds
a preset threshold, a shutdown is initiated by turning off the
triac trigger pulses. The safety-shutdown threshold value is
accumulated in a 4-bit Up/Down counter. The count
increments for every occurrence of delayed turn-on and
decrements once every 8 SYNC pulses (AC line cycles).
The counter will not decrement below zero. If the count
reaches 15, the safety-shut-down is effected.
PIN ASSIGNMENT - TOP VIEW
V DD (+V) ₁
MODE ₂
CAP ³
SYNC 4
8 TRIG
7 V SS (-V)
6 _EXT
5 SENS
FIGURE 1
INPUT/OUTPUT DESCRIPTION:
VDD (Pin 1) Supply voltage positive terminal.
Vss (Pin 7) Supply voltage negative terminal.
MODE (Pin 2) - See Table 1
Both LS7631 and LS7632 can operate in 3 different modes.
The 3-state MODE input selects the operating modes:
Vss = Mode 0; Float = Mode 1; VDD = Mode 2
CAP (Pin 3) - PLL filter capacitor input. See Figure 5.
SYNC (Pin 4) - See Figure 5
The AC line frequency is applied to this input. All internal timings
are synchronized to the AC phase through a PLL circuit.
The Load On/Off status information is also derived from this input.
SENS (Pin 5) - See Table 1
A Logic 0 applied to this input alters the TRIG output either by
turning it on, turning it off or by changing its conduction angle.
Specifically which action takes place is dependent on the type of
activation of the SENS input, namely SHORT or LONG touch
and the prior state of TRIG output.
EXT (Pin 6)
Same functionality as the SENS input, except that a Logic 1 is the
active level at this input. EXT input is intended to be operated
from a remote site with long cable connection, when noise can be
expected. The sampling method used at this input makes it less
sensitive to noise.
TRIG (Pin 8)
The TRIG output is a low level pulse occurring once every half-
cycle of the AC and is intended to drive the gate of a triac in se-
ries with the load. The conduction angle, ø, of the TRIG pulse can
be varied by means of LONG and SHORT touches at either the
SENS or the EXT input.
7631-120505-1