NCP3170AGEVB ON Semiconductor, NCP3170AGEVB Datasheet - Page 22

• Manufacturer Part Number: NCP3170AGEVB
• Description: BOARD EVALUATION NCP3170ADR2G
• Manufacturer: ON Semiconductor
• Series: -r

Specifications of NCP3170AGEVB

• Design Resources: NCP3170 Schematic NCP3170AGEVB BOM
• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Power - Output: -
• Voltage - Output: Adj down to 0.8V
• Current - Output: 3A
• Voltage - Input: 4.5 ~ 18 V
• Regulator Topology: Buck
• Frequency - Switching: 500kHz
• Board Type: Fully Populated
• Utilized Ic / Part: NCP3170
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: NCP3170AGEVBOS

gm
y
C
C
F
R
C
F
R
frequency, a CF compensation capacitor may be needed for
stability as the output LC filter is considered high Q and thus
will not give the phase boost at the crossover frequency.
C
F
gm
Calculating Input Inrush Current
charging and output charging. The input charging of a buck
stage is usually controlled, but there are times when it is not
and is limited only by the input RC network, and the output
impedance of the upstream power stage. If the upstream
power stage is a perfect voltage source and switches on
instantaneously, then the input inrush current can be
depicted as shown in Figure 47 and calculated as:
P
ESR
cross
C
OUT
C
P
C
F
If the ESR frequency is greater than the switching
The input inrush current has two distinct stages: input
Figure 47. Input Charge Inrush Current
14.25 kW +
IPK
15.4 fF +
= Transconductance of amplifier
= Amplitude ratio
= Compensation resistor
= Compensation resistor
= Cross over frequency
= Compensation capacitance
= Output capacitance
= Current mode pole frequency
= Compensation pole capacitor
= Capacitor ESR zero frequency
= Compensation pole capacitor
= Transconductance of amplifier
C
127 pF +
R
P
I
C
ICinrush_PK
+
C
+
14.25 kW
F
R
2p
2p
+
C
1.2 kA +
2p @ 5 @ F
2p
2p
3.87 nF
C
1 +
1
1
C
200 ms
5
gm
2p
F
1
CIN
0.01
12
F
1
ESR
CROSS
V
P
50 kHz
IN
ESR
³
723 MHz
2.885 kHz
³
³
(eq. 43)
(eq. 44)
(eq. 45)
(eq. 46)
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22
C
CIN
t
V
starts to switch and a second inrush current can be
calculated:
C
C
D
I
I
t
V
is dependent on the type of load that is connected to the
output. Two types of load are considered in Figure 48: a
resistive load and a stepped current load.
increase with soft start linearly which can be quantified in
Equation 49.
I
I
R
V
DELAY_TOTAL
SS
CL
OCinrush_RMS
CLR_RMS
CR_PK
I
12.58 A +
IN
I
OUT
LOAD
I
191 mA +
OUT
IN
OUT
OUT
Once the t
From the above equation, it is clear that the inrush current
Current
If the load is resistive in nature, the output current will
ICinrush_RMS
OCinrush_RMS
CLR_RMS
Inrush
Figure 48. Load Connected to the Output Stage
ESR
+
12 V
0.01
1
DELAY_TOTAL
3
= RMS resistor current
= Peak resistor current
= Output resistance
= Output voltage
1 +
1
3
+
= Output capacitor
= Output capacitor ESR
= Total delay interval
= Input Voltage
= Total converter output capacitance
= Total load capacitance
= Duty ratio of the load
= Applied load at the output
= RMS inrush current during start−up
= Soft start interval
= Output voltage
3.3 V
XCP3170
10 W
CIN
C
0.316
R
V
V
OUT
OUT
OUT
IN
ESR
) C
has expired, the buck converter
0.316
LOAD
t
SS
5
I
300 mA +
CR_PK
0.01 W
1 ms
V
OUT
5
+
t
DELAY_TOTAL
V
R
22mF
D
3.3 V
10 W
CIN
3
OUT
OUT
) I
ESR
OR
Load
CL
(eq. 47)
(eq. 48)
(eq. 49)
D
C
IN