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參數(shù)資料
| 型號： | FAN5070M |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Voltage-Mode SMPS Controller |
| 中文描述： | SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | SOIC-20 |
| 文件頁數(shù)： | 12/14頁 |
| 文件大小： | 147K |
| 代理商： | FAN5070M |
FAN5070
12
REV. 1.0.1 8/7/01
Appendix
Worst-Case Formulae for the Calculation of
C
in
, C
out
, R5, R7 and R
offset
(Circuits similar
to Figure 1 only)
The following formulae design the FAN5070 for worst-case
operation, including initial tolerance and temperature depen-
dence of all of the IC parameters (initial setpoint, reference
tolerance and tempco, internal droop impedance, current
sensor gain), the initial tolerance and temperature depen-
dence of the MOSFET, and the ESR of the capacitors. The
following information must be provided:
V
S+
, the value of the positive static voltage limit;
|V
S-
|, the absolute value of the negative static voltage limit;
V
T+
, the value of the positive transient voltage limit;
|V
T-
|, the absolute value of the negative transient voltage
limit;
I
O
, the maximum output current;
V
nom
, the nominal output voltage;
V
in
, the input voltage (typically 5V);
I
rms
, the ripple current rating of the input capacitors, per cap
(2A for the Sanyo parts shown in this data sheet);
R
D
, the resistance of the current sensor (usually the MOSFET);
RD
, the tolerance of the current sensor (usually about 67%
for MOSFET sensing, including temperature); and
ESR, the ESR of the output capacitors, per cap (44m
for
the Sanyo parts shown in this data sheet).
Number of capacitors needed for C
OUT
= the greater of:
Example: Suppose that the static limits are +89mV/-79mV,
transient limits are ±134mV, current I is 14.2A, and the nom-
inal voltage is 2.000V, using MOSFET current sensing. We
have V
S+
= 0.089, |V
S-
| = 0.079, V
T+
= |V
T-
| = 0.134, I
O
=
14.2, V
nom
= 2.000, and
R
D
= 1.67. We calculate:
Since Y > X, we choose Y, and round up to find we need 7
capacitors for C
OUT
.
A detailed explanation of this calculation may be found in
Applications Bulletin AB-24.
2
I
rms
.029 * V
nom
V
in
V
nom
V
in
V
nom
*
IO
C
in
–
=
45 * 10
-6
I
O
* R
D
* (1 +
R
D
)
R7
* 1K
=
V
S+
–
.014 * V
nom
–
.029
R
offset
=
18 * (V
S+
+ V
S-
–
.024 * V
nom
)
14400 * I
O
* R
D
* (1 +
R
D
) *1.1
R5 =
V
T-
+ V
S+
–
.024 * V
nom
ESR * I
O
ESR * I
O
X =
18 * R5 * 1.1
14400 * I
O
* R
D
Y
or
V
T+
–
V
S+
+
=
2
5
2.000
5
2.000
*
14.2
C
in
2
3.47
4 caps
=
–
=
=
=
3.48K
18 * (0.089 + 0.079
–
.024 * 2.000)
14400 * 14.2 * 0.020 * (1 + 0.67) * 1.1
R5
=
=
10.5K
45 * 10
-6
14.2 * 0.020 * (1 + 0.67)
R7
=
*1000 = 15.8
0.29 + 2.000
0.089
–
.014 * 2.000
–
.029
R
offset
3.57
0.134 + 0.089
–
.024 * 2.00
0.044 * 14.2
X
=
=
6.14
18 * 3640 * 1.1
14400 * 14.2 * 0.020
0.134
–
0.089
0.044 * 14.2
Y
=
+
=
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| FAN5071 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:High Performance Programmable Synchronous DC-DC Controller for Multi-Voltage Platforms |
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| FAN5071MX | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| FAN5077MPX | 制造商:Fairchild Semiconductor Corporation 功能描述: |
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