NCP1422EVB ON Semiconductor, NCP1422EVB Datasheet - Page 11

• Manufacturer Part Number: NCP1422EVB
• Description: EVAL BOARD FOR NCP1422
• Manufacturer: ON Semiconductor

Specifications of NCP1422EVB

• Design Resources: NCP1422 EVB BOM NCP1422EVB Gerber Files NCP1422EVB Schematic
• Main Purpose: DC/DC, Step Up
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3.3 ~ 5 V
• Current - Output: 800mA
• Voltage - Input: 2.5V, 3.6V
• Regulator Topology: Boost
• Frequency - Switching: 1.2MHz
• Board Type: Fully Populated
• Utilized Ic / Part: NCP1422
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: NCP1422
• Other names: NCP1422EVBOS

complicated process. Selecting the right inductor and
capacitor values can allow the converter to provide
optimum performance. The following is a simple method
based on the basic first−order equations to estimate the
inductor and capacitor values for NCP1422 to operate in
Continuous Conduction Mode (CCM). The set component
values can be used as a starting point to fine tune the
application circuit performance. Detailed bench testing is
still necessary to get the best performance out of the circuit.
Design Parameters:
Calculate the feedback network:
Calculate the Low Battery Detect divider:
Low Battery
Switching mode converter design is considered a
Open Drain
Open Drain
Shutdown
Output
Input
V
V
I
V
V
Select R2 = 200 k
V
Select R4 = 330 k
R3 + R4
R3 + 300 k
R1 + R2
R1 + 200 k
OUT
IN
OUT
LB
OUT−RIPPLE
LB
V
= 1.8 V to 3.0 V, Typical 2.4 V
= 2.0 V
= 2.0 V
IN
= 500 mA
= 3.3 V
*Optional
R2 200 k
V REF
V OUT
V REF
V LB
1.20 V
= 40 mV
1.20 V
2.0 V
3.3 V
Figure 23. Typical Application Schematic for 2 Alkaline Cells Supply
* 1
* 1
* 1 + 220 k
* 1 + 350 k
p−p
C4
10 p*
at I
OUT
R3
220 k
R4
330 k
GENERAL DESIGN PROCEDURES
TYPICAL APPLICATION CIRCUIT
= 500 mA
R1
350 k
http://onsemi.com
C3
200 nF
NCP1422
FB
LBI/EN
LBO
REF
11
V
maximum I
and calculate the inductor value:
Assume I
power inductor can be calculated as follows:
A standard value of 6.5 mH is selected for initial trial.
calculate the output capacitor value:
V
where t
NCP1422
IN
OUT−RIPPLE
Determine the Steady State Duty Ratio, D, for typical
Determine the average inductor current, I
Determine the peak inductor ripple current, I
Determine the output voltage ripple, V
C OUT u
C OUT u
. The operation is optimized around this point:
C1
22 mF
L +
ON
I LAVG +
GND
RIPPLE−P
2 I RIPPLE*P
OUT
D + 1 *
BAT
= 0.75 mS and ESR
V IN
LX
OUT
V OUT*RIPPLE * I OUT
45 mV * 500 mA
= 40 mV
:
500 mA
t ON
is 20% of I
1 * D
I OUT
V OUT
V IN
V OUT
V IN
P−P
+
+ 500 mA
I OUT
+ 1 * 2.4 V
at I
2.4 V
+
1 * 0.273
0.75 mS
2 (137.6 mA)
LAVG
OUT
33 mF
COUT
1 * D
C2
L
6.5 mH
1
3.3 V
0.05 W
t ON
= 500 mA
. The inductance of the
0.75 mS
= 0.05 ,
+
+ 688 mA
+ 0.273
ESR COUT
+ 18.75 mF
OUT−RIPPLE,
+ 6.5 mH
V
800 mA
OUT
LAVG,
RIPPLE−P,
= 3.3 V
and
at