ncp1231d65r2g ON Semiconductor, ncp1231d65r2g Datasheet - Page 17

• Manufacturer Part Number: ncp1231d65r2g
• Description: Lowstandby Power High Performance Pwm Controller
• Manufacturer: ON Semiconductor

implemented in the NCP1231. The NCP1231 Pin 7 can
perform three different functions; 1) softïstart 2) EMI
jittering and 3) shortïcircuit timeout (Fault Timer). The
1V Error
Flag
Fault
signal
Css
Drv
Figure 39 shows the details of the internal circuitry
Figure 40. Internal SoftïStart, 100 msec Timer and
4V
2V
0V
7
SS
5ms
60mA
Vd
Icharge1
Icharge
Idischarge
Frequency Jittering
Figure 39. SoftïStart is Activated during a Startup Sequence an OCP Condition
Fault not
confirmed
+
ï
+
ï
Vref1
100ms
+
+
Vref2
2.2 V
4 V
f
Softï
jittering
max
f
min
ï
+
Jittering 10ms
Fault management
http://onsemi.com
Fault
NCP1231
17
charge and discharge current sources are 60 ma (typical), so
if a 82 nF capacitor is connected to Pin 7, one can achieve
a typical softïstart of 5 ms, a frequency modulation of 5 ms
and a fault timeout of 100 ms.
Frequency Jittering
signature by spreading out the average switching energy
around the controller operating switching frequency. The
NCP1231 offers a nominal r4% deviation of the nominal
switching frequency. The sweep sawtooth is internally
generated and modulates the clock up and down with a 4 ms
period. Figure 41 illustrates the NCP1231 behavior:
Frequency jittering is a method used to soften the EMI
100ms
Time scale
has been
purposely
reduced
SS
5ms
Time scale
has been
purposely
reduced
Reset at UVLO
Fault
confirmed