NCP1215 Ver la hoja de datos (PDF) - ON Semiconductor
Número de pieza
componentes Descripción
Lista de partido
NCP1215 Datasheet PDF : 16 Pages
| |||
NCP1215
To Current Sense Comparator
17 k
FB
Current
Mirror
4:3
37.5 mA
CS
12.5 mA
Figure 15. Feedback Loop − Current Sense Control
The resulting current sense regulation characteristic can
be seen from Figure 16.
CT
CT
From Feedback Loop Block
Voffset
−
+
Voffset to VDD
− To Latch’s Set Input
+
10 mA
To Latch’s Output
50 mA
GND
12.5 mA
0 mA
50 mA
100 mA
FB Pin Sink Current
140 mA
Figure 16. Current Sense Regulation Characteristic
When the load goes light, the compression circuitry
decreases the peak current. This has the effect of slightly
increasing the switching frequency but the compression
ratio is selected to not hamper the standby power.
OFF Time Control
The loop signal together with the internal current source,
via an external capacitor, controls the switch−off time. This
is portrayed in Figure 17.
Figure 17. OFF Time Control
During the switch−ON time, the CT capacitor is kept
discharged by a MOSFET switch. As soon as the latch
output changes to a low state, the voltage across CT created
by the internal current source, starts to ramp−up until its
value reaches the threshold given by the feedback loop
demand.
V
VDD
CT Pin
Voltage
Voffset
POUT Goes Down
POUT Goes Up
P3
P2
P1
toff−min
t
Figure 18. CT Pin Voltage (Pout1 u Pout2 u Pout3)
The voltage that can be observed on CT pin is shown in
Figure 18. The bold waveform shows the maximum output
power when the OFF time is at its minimum. The IC allows
an OFF time of several seconds.
http://onsemi.com
8
Share Link: 