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參數(shù)資料
| 型號： | RC2951M-3.3 |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 固定／可調(diào)正電壓單路輸出LDO穩(wěn)壓器 |
| 英文描述： | FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, 0.7 V DROPOUT, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁數(shù)： | 8/11頁 |
| 文件大?。?/td> | 213K |
| 代理商： | RC2951M-3.3 |
RC2951
PRODUCT SPECIFICATION
6
REV. 1.0.0 2/8/01
.
** Drive with TTL-high to shut down. Ground or leave open if shutdown feature is not to be used.
Figure 2. Adjustable Regulator
The complete equation for the output voltage is
Adding the error term,
where VREF is the nominal 1.235 reference voltage and IFB
is the feedback pin bias current, nominally -20 nA. The
minimum recommended load current of 1
A forces an
upper limit of 1.2 M
on the value of R
2, if the regulator
must work with no load (a condition often found in CMOS in
standby). IFB will produce a 2% typical error in VOUT which
may be eliminated at room temperature by trimming R1.
For better accuracy, choosing R2 = 100k reduces this error
to 0.17% while increasing the resistor program current to
12
A. Since the RC2951 typically draws 60 A at no load
with Pin 2 open-circuited, this is a small price to pay.
Reducing Output Noise
In reference applications it may be advantageous to reduce
the AC noise present at the output. One method is to reduce
the regulator bandwidth by increasing the size of the output
capacitor.
Noise can be reduced fourfold by a bypass capacitor across
R1, since it reduces the high frequency gain from 4 to unity.
Pick
or about 0.01
F. When doing this, the output capacitor must
be increased to 3.3
F to maintain stability. These changes
reduce the output noise from 430
V to 100 V rms for a
100 kHz bandwidth at 5V output. With the bypass capacitor
added, noise no longer scales with output voltage so that
improvements are more dramatic at higher output voltages.
RC2951
3.3
F
100K
Error
Output
ERROR
**Shutdown
Input
1.23V
1.2
30V
7
4
1
8
5
3
.01
F
++
R2
R1
VREF
+VIN
VOUT
SD
GND
FB
2950-11
V
OUT
V
REF 1
R
1
R
2
------
+
=
V
OUT
V
REF
1
R
1
R
2
------
+
I
FBR1
+
=
V
REF
R
2
--------------
V
OUT
R
1
R
2
+
-------------------
=
V
OUT
V
REF
R
1
R
2
+
R
2
-------------------
=
V
OUT
V
REF 1
R
1
R
2
------
+
=
V
OUT
V
REF 1
R
1
R
2
------
+
I
FBR2
+
=
C
BYPASS
1
2
πR
1
200Hz
------------------------------------
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| RC2951M33_32 | 功能描述:上下轉(zhuǎn)換器 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Down Converters 射頻:52 MHz to 78 MHz 中頻:300 MHz LO頻率: 功率增益: P1dB: 工作電源電壓:1.8 V, 3.3 V 工作電源電流:120 mA 最大功率耗散:1 W 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFP-128 |
| RC2951MT | 功能描述:低壓差穩(wěn)壓器 - LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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