The functional differences of the modes of the LS7232ND are explained
in Table 1 and the TRIG output conduction angle diagrams in Figure 4.
TABLE 1
TOUCH TYPE
SHORT (T
S1
Duration)
PRE-TOUCH
脴
Off
Max
Intermediate
POST-TOUCH
脴
Max
Off
Off
PRE-TOUCH
脴
Off
Max
Intermediate
LONG (T
S2
Duration)
POST-TOUCH
脴
Starts varying at Min
Starts varying at Max
Starts varying at
Pre-Touch brightness
Starts varying at
Memory (Note 2)
Starts varying at Max
Starts varying at
Pre-Touch brightness
Starts varying at Min
Starts varying at Max
Starts varying at
Pre-Touch brightness
DIMMING
DIRECTION
REVERSAL
(Note 3)
MODE
0
(LS7231)
N/A
N/A
NO
1
(LS7232)
Off
Max
Intermediate
Memory
(Note 1)
Off
Off
Off
Max
Intermediate
YES
N/A
YES
2
(LS7233)
Off
Max
Intermediate
Max
Off
Off
Off
Max
Intermediate
N/A
N/A
YES
NOTE 1:
"Memory" refers to the conduction angle, 脴, which existed prior to the current off-state.
First time after power-up, the Memory value defaults to maximum conduction angle.
NOTE 2:
First time after power-up, LONG touch causes intensity to vary starting at minimum conduction angle.
NOTE 3:
NO = Dimming direction does not reverse from prior dimming direction.
YES = Dimming direction does reverse from prior dimming direction.
N/A = Does not apply
V
DD
(Pin 7)
Supply voltage negative terminal.
TRIG (Pin
8)
The TRIG output is a low level pulse occurring once every half-
cycle of the SYNC input. The conduction angle, 脴, of the output
in relation to the SYNC signal controls the lamp brightness.
In continuous dimming operation (i.e. when the SENS input is
continuously held low) the TRIG conduction angle, 脴, sweeps up
and down between 41藲 and 158藲 continuously. The time vs 脴
curve is not linear (See Figure 4). Between two maxima on this
curve, there are 4 discontinuous points labeled A1, B1, B2, A2.
The discontinuities are as follows:
1. From maximum to A1. In this region, 脴 is changed by
equal increments (鈭喢? for every 2 SYNC clocks.
2. From A1 to B1. In this region, the increments (鈭喢? take
place for every 4 SYNC clocks.
3. From B1 to B2. In this region 脴 is held at a constant
level (鈭喢?= 0).
4. From B2 to A2. Same as 2.
5. From A2 to Max. Same as 1.
The slower rate of change in 酶 over A1B1B2A2 region is to
accommodate for eye adjustment at lower light intensity.
SYNC
CAP
MODE
4
3
2
BUF
PHASE
LOCK
LOOP
脴
MEMORY
DIGITAL
COMPARATOR
OUTPUT
DRIVER
8
TRIG
EXT
6
BUF
CONTROL
LOGIC
脴
POINTER
SENS
5
BUF
V
SS
V
DD
1
7
(+V)
(-V)
FIGURE 2
LS7232ND BLOCK DIAGRAM
7232ND-012703-2
1
2
3
4
5
