LS7636 Datasheet, PDF (1/7 Pages) LSI Computer Systems – REVERSE PHASE (TRAILING-EDGE) HALOGEN LAMP DIMMER

LSI/CSI
LS7636 LS7637
LS7636FO LS7637FO
U_{® L}
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 [phone] FAX [phone]
A3800
REVERSE PHASE (TRAILING-EDGE) HALOGEN LAMP DIMMER ^{June 2009}
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 (VDD - VSS).
• LS7636, LS7637 (DIP); LS7636-S, LS7637-S (SOIC);
LS7636FO, LS7637FO (DIP);
LS7636FO-S, LS7637FO-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:
Since the operating currents of some electronic transformers
are below the holding current of most triacs, a typical triac-
based (leading-edge) dimmer may not operate properly when
driving an electronic transformer-coupled low-voltage halogen
lamp. The filtering components in the electronic transformer
which prevent its operating frequency from generating line in-
terference can also inhibit triac triggering. The
LS7636_LS7637 family of reverse-phase dimmer ICs drive
FETs or IGBTs (see Figure 3 and Figure 4) and ‘slowly’ turns
on current beginning at the AC input zero-crossing. This ‘slow’
current turn on is ideal for interfacing with the primary of any
electronic transformer and also eliminates the RFI generation
caused by the sudden turn on of current when using a triac-
based dimmer.
INPUT/OUTPUT DESCRIPTION:
VDD (Pin 1) Supply voltage positive terminal.
VSS (Pin 7) Supply voltage negative terminal.
PIN ASSIGNMENT - TOP VIEW
V DD (+V ) 1
MODE ₂
TEST 3
SYNC 4
8 _GATE
7 VSS (-V )
6 OVC
5 SENS
FIGURE 1
SENS (Pin 5) - See Table 1
A Logic 0 applied to this input alters the Gate Drive 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 duration and the prior state of the
Gate Drive output.
OVC - Overcurrent Sense Input (Pin 6)
The voltage at this input is sampled every half-cycle in a
four-cycle period. If the voltage reaches the OVC threshold
four times, then the Gate Output is turned Off shutting down
the current through the load. Six cycles after shutdown
occurs, the output is turned On to the previous conduction
angle, the OVC counter is reset and a new four-cycle period
begins. The OVC voltage may be generated with a
fractional-Ohm resistor as shown in Figure 4 and Figure 5.
When OVC is not being used, Pin 6 must be tied to Pin 7.
Gate (Pin 8)
The Gate Drive output is a positive-going pulse that initiates
at every zero-crossing of the AC input. The width of the
Gate Drive signal determines the conduction angle as
shown in Figure 2.
Test (Pin 3)
For factory use only.
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:
VSS = Mode 0; Float = Mode 1; VDD = 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
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.