ncp3101c ON Semiconductor, ncp3101c Datasheet - Page 19

• Manufacturer Part Number: ncp3101c
• Description: Ncp3101c Wide Input Voltage Synchronous Buck Converter
• Manufacturer: ON Semiconductor

In practical design, the feed through resistor should be at 2X
the value of R
through noise. Using the 2X assumption, R
20 kW and the feed through capacitor can be calculated as
shown below:
C
f
R
R
R
The crossover of the overall feedback occurs at F
C
f
F
F
R
R
R
VCC
V
cross
cross
LC
PO
C
F
1
2
F
F
18.9 kHz +
F
1
2
F
ramp
PO
F
+
+
2p * R
2p
2
1
2
* C
2p
= Feed through capacitor
= Crossover frequency
= Top resistor divider
= Bottom resistor divider
= Feed through resistor
* R
to minimize error from high frequency feed
F
2
F
= Feed through capacitor
= Crossover frequency
= Frequency of the output inductor and capacitor
= Pole frequency
= Top of resistor divider
= Bottom of resistor divider
= Feed through resistor
= Input voltage
= Peak−to−peak voltage of the ramp
* 214 pF
2
) R
R
R
1
2
1
) R
* R
) R
F
2
F
R
) R
2
31.6 kW ) 20 kW * 10 kW ) 31.6 kW * 20 kW 20 kW ) 31.6 kW
1
* R
) R
2
2
* R
) R
F
1
* f
1
* R
cross
F
31.6 kW ) 20 kW
F
will be set to
* R
³
214 pF +
PO
F
) R
:
http://onsemi.com
1
*
2 * p * 31.6 kW * 20 kW ) 10 kW * 20 kW ) 10 kW * 31.6 kW * 27 kHz
F
LC
V
19
ramp
* V
IN
31.6 kW ) 10 kW
(eq. 45)
*
2.35 kHz * 12 V
1.1 V
(eq. 44)