NCP1217P100 ON Semiconductor, NCP1217P100 Datasheet - Page 14

• Manufacturer Part Number: NCP1217P100
• Description: IC CTRLR PWM CM OVP HV 8DIP
• Manufacturer: ON Semiconductor
• Type: PWM Current-Mode Controller For High-Power Universal Off-Line Suppliesr

Specifications of NCP1217P100

• Output Isolation: Isolated
• Frequency Range: 90 ~ 110kHz
• Voltage - Input: 10 ~ 16 V
• Operating Temperature: 0°C ~ 150°C
• Package / Case: 8-DIP (0.300", 7.62mm), 7 Leads
• Input Voltage Range: 16 V
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: NCP1217P100OS

Protecting the Controller Against Negative Spikes
is the designer’s duty to avoid the presence of negative
spikes on sensitive pins. Negative signals have the bad habit
to forward bias the controller substrate and induce erratic
behaviors. Sometimes, the injection can be so strong that
As with any controller built upon a CMOS technology, it
Figure 26. Another Way of Shutting Down the IC
Without a Definitive Latchoff State
ON/OFF
Q1
1
2
3
4
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8
7
6
5
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internal parasitic SCRs are triggered, engendering
irremediable damages to the IC if a low impedance path is
offered between V
often the seat of such spurious signals, the high- -voltage pin
can also be the source of problems in certain circumstances.
During the turn- -off sequence, e.g. when the user unplugs the
power supply, the controller is still fed by its V
and keeps activating the MOSFET ON and OFF with a peak
current limited by Rsense. Unfortunately, if the quality
coefficient Q of the resonating network formed by Lp and
Cbulk is low (e.g. the MOSFET Rdson + Rsense are small),
conditions are met to make the circuit resonate and thus
negatively bias the controller. Since we are talking about ms
pulses, the amount of injected charge (Q = I * t) immediately
latches the controller that brutally discharges its V
capacitor. If this V
stored energy damages the controller. Figure 27 depicts a
typical negative shot occurring on the HV pin where the
brutal V
CC
discharge testifies for latchup.
CC
CC
and GND. If the current sense pin is
capacitor is of sufficient value, its
CC
capacitor
CC