NCP1060, NCV1060, NCP1063, NCV1063
www.onsemi.com
20
Drain current
V
CC
V
CCON
Max Ip
4 ms
0V (fresh PON)
Figure 35. The 4 ms Soft−start Sequence
Jittering
Frequency jittering is a method used to soften the EMI
signature by spreading the energy in the vicinity of the main
switching component. The NCP106X offers a
±
6%
deviation of the nominal switching frequency. The sweep
sawtooth is internally generated and modulates the clock up
and down with a fixed frequency of 300 Hz. Figure 36 shows
the relationship between the jitter ramp and the frequency
deviation. It is not possible to externally disable the jitter.
60 kHz
63.6 kHz
56.4 kHz
Jitter ramp
Internal
sawtooth
adjustable
Figure 36. Modulation Effects on the Clock Signal by the Jittering Sawtooth
Line Detection (for A version only)
An internal comparator monitors the drain voltage as
recovering from one of the following situations:
•
Short Circuit Protection,
•
V
CC
OVP is confirmed,
•
UVLO
•
TSD
If the drain voltage is lower than the internal threshold
V
HV(EN)
(87 Vdc typically), the internal power switch is
inhibited. This avoids operating at too low ac input.
