參數(shù)資料
型號: NCP1410
廠商: ON SEMICONDUCTOR
元件分類: DC/DC變換器
英文描述: 250 mA Sync-Rect PFM Step-Up DC-DC Converter with Low-Battery Detector
中文描述: 250毫安同步整流PFM升壓型DC - DC轉(zhuǎn)換器與低電池檢測器
文件頁數(shù): 12/16頁
文件大?。?/td> 126K
代理商: NCP1410
NCP1410
http://onsemi.com
12
GENERAL DESIGN PROCEDURES
Switching mode converter design is considered as black
magic to most engineers, some complicate empirical
formulae are available for reference usage. Those formulae
are derived form the assumption that the key components,
i.e. power inductor and capacitors are available with no
tolerance. Practically, its not true, the result is not a matter
of how accurate the equations you are using to calculate the
component values, the outcome is still somehow away from
the optimum point. In below a simple method base on the
most basic first order equations to estimate the inductor and
capacitor values for NCP1410 operate in Continuous
Conduction Mode is introduced. The component value set
can be used as a starting point to fine tune the circuit
operation. By all means, detail bench testing is needed 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
= 200 mA (250 mA max)
V
LB
= 2.0 V
V
OUT–RIPPLE
= 40 mV
P–P
at I
OUT
= 250 mA
Calculate the feedback network:
Select R
FB2
= 200 K
RFB1
RFB2
VOUT
VREF
1
RFB1
200 K
3.3 V
1.19 V
1
355 K
Calculate the Low Battery Detect divider:
V
LB
= 2.0 V
Select R
LB2
= 330 K
RLB1
RLB2
VLB
VREF
1
RLB1
330 K
2.0 V
1.19 V
1
225 K
Determine the Steady State Duty Ratio, D for typical V
IN
,
operation will be 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
ILAVG
250mA
0.273
344 mA
Determine the peak inductor ripple current, I
RIPPLE–P
and
calculate the inductor value:
Assume I
RIPPLE–P
is 20% of I
LAVG
, the inductance of the
power inductor can be calculated as in below:
I
RIPPLE–P
= 0.20 x 344 mA = 68.8 mA
VIN
tON
2 IRIPPLE
Standard value of 22
μ
H is selected for initial trial.
L
P
2.4 V
2(68.8 mA)
0.4 S
24.4 H
Determine the output voltage ripple, V
OUT–RIPPLE
and
calculate the output capacitor value:
V
OUT–RIPPLE
= 40 mV
P–P
at I
OUT
= 250 mA
IOUT
VOUT–RIPPLE
where t
ON
= 1.4
μ
S and ESR
COUT
= 0.1
,
250 mA
0.4 S
40 mV
250 mA
COUT
tON
IOUT
ESRCOUT
COUT
0.1
23.33 F
From above calculation, you need at least 23.33 F in
order to achieve the specified ripple level at conditions
stated. Practically, a one level larger capacitor will be used
to accommodate factors not take into account in the
calculation, therefore a capacitor value of 33 F is selected.
相關(guān)PDF資料
PDF描述
NCP1411DMR2 Sync-Rect PFM Step-Up DC-DC Converter with Low-Battery Detector and Ring-Killer
NCP1411D Sync-Rect PFM Step-Up DC-DC Converter with Low-Battery Detector and Ring-Killer
NCP1411DMR2G Sync-Rect PFM Step-Up DC-DC Converter with Low-Battery Detector and Ring-Killer
NCP1411 Sync-Rect PFM Step-Up DC-DC Converter(帶有同步整流器的PFM升壓DC-DC轉(zhuǎn)換器)
NCP1417DMR2(中文) 200 mA DC-DC Step-up Converter with Dual Low Battery Protection(帶雙路低電池保護(hù)的200mA步升DC-DC轉(zhuǎn)換器)
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