NCP5212A ON Semiconductor, NCP5212A Datasheet - Page 14

• Manufacturer Part Number: NCP5212A
• Description: Single Synchronous Step-Down Controller
• Manufacturer: ON Semiconductor

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The load line impendence R
Where DCR is inductor DC resistance. Gain_CS is a gain
from [(CS+)−(CS−)] to IDRP Gain (At electrical table, the
symbol is IDRP_GAIN), the typical value is 0.525 mA/mV.
Rocp resistor into ground.
resistor Rt can affect the amount of R
recommended to define the amount of R
defining the compensation component value. And if the user
wants to fine tune the compensation network for optimizing
the transient performance, it is NOT recommend to adjust
the value of Rt. Otherwise, both transient performance and
AVP amount will be affected. The following diagram shows
the typical waveform of AVP. Note that the Rt typical value
should be above 1 kW.
Over Current Protection (OCP)
event occurs. The current is continuously monitored by the
differential current sensing circuit. The current limit
threshold voltage VOCSET can be programmed by resistor
ROCSET connecting at the IDRP/OCP pin. However, fixed
default VOCSET can be achieved if ROCSET is less than
2 kW.
continuously, the top gate driver will be turned off cycle by
cycle. If it happens over consecutive 16 clock cycles time
(16 x 1/f
bottom gate drivers are off. EN resets or power recycle the
device can exit the fault. The following diagram shows the
typical behavior of OCP.
The AVP function can be easily disable by shorting the
From the equation we can see that the value of “top”
The NCP5212A protects power system if over current
If the inductor current exceeds the current threshold
R
SW
Figure 22. Typical waveform of AVP
Top to Bottom: SWN, Vo, Transient Signal
LL
), the device is latched off such that top and
+ DCR * Gain_CS * Rt *
LL
is given by:
Rs1 ) Rs2
LL
Rs2
FRIST before
LL
, so it is
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(eq. 3)
14
acquiring current information. In addition, the threshold
OCP voltage can be programmed to some desired value by
setting the programming resistor Rocp.
Rocp resistor. If Adaptor Voltage Position (AVP) is used, the
Rocp should be connected to FB pin. If AVP is not used, the
Rocp should be connected to ground. At the IDRP/OCP pin,
there is a constant current(24 mA typ.) flowing out during
the programming stage at system start up. This is used to
The NCP5217A uses lossless inductor current sensing for
It should be noted that there are two configurations for
DCR
DCR
Vo
L
Figure 23. Overcurrent Protection
Top to Bottom : SWN, Vo, PGOOD, Io
Vo
L
Figure 24. OCP Configuration
Rs1
Cs
Rb
Rt
Cs
Rs1
Rb
IDRP/OCP
Rt
IDRP/OCP
Rocp
Rs2
Rocp
CS+
CS−
CS+
Rs2
CS−
FB
FB
+
−
+
−
Without AVP
Vref
Vref
With AVP
+
+
+
+
G i
G i
I DRP
I DRP
COMP
COMP