參數(shù)資料
型號(hào): FAN5233MTCX
廠商: FAIRCHILD SEMICONDUCTOR CORP
元件分類: 穩(wěn)壓器
英文描述: Analog IC
中文描述: SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO24
封裝: TSSOP-24
文件頁數(shù): 14/15頁
文件大?。?/td> 388K
代理商: FAN5233MTCX
FAN5233
PRODUCT SPECIFICATION
14
REV. 1.0.6 1/22/02
100
90
80
70
60
50
40
30
20
10
0
E
Load Current mA
PWM
Hyst
1
10
100
1,000
10,000
MOSFET Selection
The notebook application circuit shown in Figure 1 is designed
to run with an input voltage operating range of 5.4-24V.
This wide input range helps determine the selection of the
MOSFETs for the 3.3V and 5V converters, since the high-side
MOSFET is on (V
out
/ V
in
) of the time, and the low-side
MOSFET 1 – (V
out
/ V
in
) of the time. The maxima and minima
are tabulated in Table 2:
Table 2. MOSFET Duty Cycles
High-side FET
Low-side FET
All four MOSFETs have maximum duty cycles greater than
50%. Thus, it is necessary to size all four approximately the
same.
3.3V and 5V Schottky Selection
The maximum current at which the converters operate in PFM
mode determines selection of a Schottky. In the application
shown in Figure 8, since the transition can occur at a current as
high as 28mV * (17.5K
/ 10K
) / 35m
= 1.4A, the diode
(with 24V input) will be conducting 86% of the period (from
Table 2). It thus has an average current of 1.4A * 0.86 = 1.2A,
which requires a Schottky current rating >1A.
3.3V and 5V Inductor Selection
See Table 1.
3.3V and 5V Output Cap Selection
See Table 1.
12V Component Selection
Calculation of the inductor, diode and output capacitor for the
+12V output fly-back is complex, depending on output power
and efficiency. See Applications Bulletin AB-19 for an Excel
spreadsheet calculation tool. See Table 1 also.
Input Capacitor Selection
Input capacitor selection is determined by ripple current rating.
With two converters operating in parallel at differing duty
cycles, calculation of input ripple current is complex; see
Applications Bulletin AB-19 for an Excel spreadsheet
calculation tool.
V
out
3.3V
5V
V
in
5.4V
.61
.43
24V
.14
.21
V
out
3.3V
5V
V
in
5.4V
.34
.07
24V
.86
.79
Ef
fi
ciency
相關(guān)PDF資料
PDF描述
FAN5234MTC Mobile-Friendly PWM/PFM Controller
FAN5234MTCX Mobile-Friendly PWM/PFM Controller
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FAN5234 Terminal Block; Pitch Spacing:0.197"; Mounting Type:PC Board RoHS Compliant: Yes
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