UL
®
LSI/CSI
LS7636 LS7637
LS7636FO LS7637FO
(631) 271-0400 FAX (631) 271-0405
June 2009
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
A3800
SENS
(Pin 5) - See Table 1
A Logic 0 applied to this input alters the Gate Drive output
APPLICATIONS:
Electronic dimmers for wall-switch control of ceiling mounted either by turning it on, turning it off or by changing its
lighting, foot-switch control of large floor lamps and hand- conduction angle. Specifically which action takes place is
dependent on the type of activation of the SENS input,
switch control of table lamps.
namely SHORT or LONG duration and the prior state of the
Gate Drive output.
BACKGROUND AND GENERAL DESCRIPTION:
Since the operating currents of some electronic transformers
are below the holding current of most triacs, a typical triac-
OVC - Overcurrent Sense Input
(Pin 6)
based (leading-edge) dimmer may not operate properly when The voltage at this input is sampled every half-cycle in a
driving an electronic transformer-coupled low-voltage halogen four-cycle period. If the voltage reaches the OVC threshold
lamp. The filtering components in the electronic transformer four times, then the Gate Output is turned Off shutting down
which prevent its operating frequency from generating line in- the current through the load. Six cycles after shutdown
terference
can
also
inhibit
triac
triggering.
The occurs, the output is turned On to the previous conduction
LS7636_LS7637
family of reverse-phase dimmer ICs drive angle, the OVC counter is reset and a new four-cycle period
FETs or IGBTs (see Figure 3 and Figure 4) and ‘slowly’ turns begins. The OVC voltage may be generated with a
on current beginning at the AC input zero-crossing. This ‘slow’ fractional-Ohm resistor as shown in Figure 4 and Figure 5.
current turn on is ideal for interfacing with the primary of
any
When OVC is not being used, Pin 6 must be tied to Pin 7.
electronic transformer and also eliminates the RFI generation
caused by the sudden turn on of current when using a triac-
Gate
(Pin 8)
The Gate Drive output is a positive-going pulse that initiates
based dimmer.
at every zero-crossing of the AC input. The width of the
Gate Drive signal determines the conduction angle as
INPUT/OUTPUT DESCRIPTION:
shown in Figure 2.
V
DD
(Pin 1) Supply voltage positive terminal.
Test
(Pin 3)
For factory use only.
V
SS
(Pin 7) Supply voltage negative terminal.
MODE
(Pin 2) - See Table 1
All variations of
LS7636
and
LS7637
can operate in 3 different
modes. The 3-state MODE input selects the operating modes:
V
SS
= Mode 0; Float = Mode 1; V
DD
= Mode 2
SYNC
(Pin 4) - See Figure 2
The AC line frequency is applied to this input.
All internal timings are synchronized to the AC.
7636-061009-1
FEATURES:
• Pushbutton or touch control of high-voltage lamps and
all electronic transformer-coupled
low-voltage
halogen lamps.
• Controls
Fluorescents
and
CFLs
via dimming ballasts.
• Reverse-phase technology
eliminates RFI
generation.
• “FO" versions power up
Full On
after application of AC.
• Soft turn-on and soft turn-off
• Three operating modes.
• Inputs for direct or remote activation.
• 50Hz/60Hz AC line frequency.
• +12V Power Supply (V
DD
- V
SS
).
•
LS7636, LS7637
(DIP);
LS7636-S, LS7637-S
(SOIC);
LS7636FO, LS7637FO
(DIP);
LS7636FO-S, LS7637FO-S
(SOIC)
- See Figure 1 -
REVERSE PHASE (TRAILING-EDGE) HALOGEN LAMP DIMMER
PIN ASSIGNMENT - TOP VIEW
V
DD
(+V )
MODE
TEST
SYNC
1
2
3
4
8
7
6
5
LSI
FIGURE 1
LS7636
LS7637
GATE
V
SS
(-V )
OVC
SENS
The information included herein is believed to be
accurate and reliable. However, LSI Computer Systems,
Inc. assumes no responsibilities for inaccuracies, nor for
any infringements of patent rights of others which may
result from its use.
LSI [ LSI COMPUTER SYSTEMS ]
