Datasheet

NCL30081
http://onsemi.com
19
Figure 45. Winding Short Circuit Protection, Max. Peak Current Limit Circuits
S
R
Q
CS
Rsense
LEB1
+
−
S
R
Q
VCC
aux
Vcc
management
Vdd
grand
reset
DRV
Ipkmax
PWMreset
VCCstop
+
−
LEB2
WOD_SCP
Vcontrol
+
−
STOP
from Fault Management Block
OVP
UVLO
S
R
Q
grand
reset
OVP
8_HICC
OFF
WOD_SCP
latch
latch
8_HICC
V
ILIMIT
V
CS(stop)
Q
Q
Q
Step Dimming
The step dimming function decreases the output current
from 100% to 5% of its nominal value in discrete steps.
There are 5 steps in total. Table 4 shows the different steps
value and the corresponding output current set−point. Each
time a brown−out is detected, the output current is decreased
by decreasing the reference voltage V
REF
setting the output
current value.
When the 5% dimming step is reached, if a brown−out
event occurs, the controller restarts at 100% of the output
current.
Table 4. DIMMING STEPS
Dimming Step I
out
Perceived Light
ON 100% 100%
1 70% 84%
2 40% 63%
3 25% 50%
4 10% 32%
5 5% 17%
Note:
The power supply designer must ensure that V
CC
stays
high enough when the light is turned−off to let the controller
memorize the dimming step state.
The power supply designer should use a split V
CC
circuit
for step dimming with a capacitor allowing providing
enough V
CC
for 1 s (47 mF to 100 mF capacitor).
The step dimming state is memorized by the controller
until V
CC
crosses V
CC(reset)
.
VCC
4.7 mF
Figure 46. Split VCC Supply
47 − 100 mF