ICLS6022J Datasheet, PDF (15/33 Pages) Infineon Technologies AG – LED System Driver ICs

3.3
Startup Phase
LED System Driver ICs
ICLS6x Series
Functional Description
3. 25kΩ
5V
RSoftS
SoftS
CSoftS
Freq Jitter
Charging
current I FJ
Freq Jitter
Discharging
current I FJ
T2
T3
0.8V
Freq Jitter
Control
Soft Start
C7
Soft -Start
Comparator
&
G7
Gate Driver
C2
3. 2V
0. 6V
PWM OP
x3.2
CS
Figure 6 Soft start
At the beginning of the startup phase, the IC provides a soft start period during which it controls the maximum
primary current by means of duty cycle limitation. A capacitor C_Softs in combination with the internal pull-up resistor
R_SoftS determines the duty cycle until V_SoftS exceeds 3.2 V.
When the soft start begins, C_SoftS is immediately charged up to approx. 0.8 V by T2. The soft start phase takes
place between 0.8 V and 3.2 V. Above V_SoftsS = 3.2 V there is no longer any duty cycle limitation DC_max that is
controlled by the comparator C7 since the comparator C2 blocks the gate G7 (see Figure 7). This maximum
charge current in the very first stage when V_SoftS is below 0.8 V is limited to 0.9 mA.
V_SoftS
4.0V
3.2V
max . Startup Phase
0.8V
max. Soft Start Phase
DC_max
t
DC1
DC2
Figure 7 Startup phase
Data Sheet
t1
t2 t
15
Version 1.0, 2011-05-19