參數(shù)資料
型號(hào): NCP1421DMR2
廠商: ON SEMICONDUCTOR
元件分類: 穩(wěn)壓器
英文描述: 600 mA Sync-Rect PFM Step-Up DC-DC Converter Step-Up DC-DC Converter with True-Cutoff and Ring-Killer
中文描述: 1.5 A SWITCHING REGULATOR, 1200 kHz SWITCHING FREQ-MAX, PDSO8
封裝: MICRO PACK-8
文件頁(yè)數(shù): 11/14頁(yè)
文件大小: 116K
代理商: NCP1421DMR2
NCP1421
http://onsemi.com
11
TYPICAL APPLICATION CIRCUIT
LBI/EN
FB
LBO
REF
BAT
GND
LX
OUT
1
2
3
4
8
7
6
5
NCP1421
R4
330 k
R2 200 k
Shutdown
Open Drain
Input
Low Battery
Open Drain
Output
C3
200 nF
R1
350 k
C2
22 F
+
V
OUT
=3.3 V
500 mA
C1
22 F
V
IN
L
6.5 H
Figure 26. Typical Application Schematic for 2 Alkaline Cells Supply
R3
220 k
C4
10 p*
*Optional
GENERAL DESIGN PROCEDURES
Switching mode converter design is considered a
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 firstorder equations to estimate the
inductor and capacitor values for NCP1421 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:
V
IN
= 1.8 V to 3.0 V, Typical 2.4 V
V
OUT
= 3.3 V
I
OUT
= 500 mA (600 mA max)
V
LB
= 2.0 V
V
OUTRIPPLE
= 45 mV
pp
at I
OUT
= 500 mA
Calculate the feedback network:
Select R2 = 200 k
VOUT
VREF
R1
R2
1
R1
200 k
3.3 V
1.20 V
1
350 k
Calculate the Low Battery Detect divider:
V
LB
= 2.0 V
Select R4 = 330 k
R3
R4
VLB
VREF
1
R3
300 k
2.0 V
1.20 V
1
220 k
Determine the Steady State Duty Ratio, D, for typical
V
IN
. The operation is optimized around this point:
VOUT
VIN
1
1
D
D
1
VIN
VOUT
1
2.4 V
3.3 V
0.273
Determine the average inductor current, I
LAVG,
at
maximum I
OUT
:
IOUT
1
D
1
Determine the peak inductor ripple current, I
RIPPLEP,
and calculate the inductor value:
Assume I
RIPPLEP
is 20% of I
LAVG
. The inductance of the
power inductor can be calculated as follows:
VIN
tON
2 IRIPPLE
P
2 (137.6 mA)
A standard value of 6.5 H is selected for initial trial.
Determine the output voltage ripple, V
OUTRIPPLE,
and
calculate the output capacitor value:
V
OUTRIPPLE
= 40 mV
PP
at I
OUT
= 500 mA
IOUT
VOUT
RIPPLE
where t
ON
= 0.75 uS and ESR
COUT
= 0.05 ,
500 mA
0.75 S
45 mV
500 mA
ILAVG
500 mA
0.273
688 mA
L
2.4 V
0.75 S
6.5 H
COUT
tON
IOUT
ESRCOUT
COUT
0.05
18.75 F
相關(guān)PDF資料
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