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參數(shù)資料
| 型號(hào)： | SPX2950ACN-3.3 |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | 150mA Low Dropout Voltage Regulators |
| 中文描述： | 150mA的低壓差穩(wěn)壓器 |
| 文件頁(yè)數(shù)： | 9/13頁(yè) |
| 文件大小： | 135K |
| 代理商： | SPX2950ACN-3.3 |
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9
Rev. 3/6/03
SPX2950/SPX2951 150mA Low Dropout Voltage Regulator
Copyright 2003 Sipex Corporation
PROGRAMMING THE OUTPUT
VOLTAGE OF SPX2951
The SPX2951 may be pin-strapped for 5V using
its internal voltage divider by tying Pin 1 (out-
put) to Pin 2 (sense) and Pin 7 (feedback) to Pin
6 (5V Tap). Also, it may be programmed for any
output voltage between its 1.235V reference
and its 30V maximum rating . As seen in Figure
2, an external pair of resistors is required. Refer
to the below equation for the programming of
the output voltage:
V
OUT
= V
REF
×
(1 + R
1
/R
2
)+ I
FB
R
1
The V
REF
is 1.235 and I
FB
is the feedback bias
current, nominally -20nA. The minimum rec-
ommended load current of 1
μ
A forces an upper
limit of 1.2M
on value of R
2
. If no load is
presented the I
FB
produces an error of typically
2% in V
OUT
which may be eliminated at room
temperature by trimming R
1
. To improve the
accuracy choose the value of R
2
= 100k this
reduces the error by 0.17% and increases the
resistor program current by 12
μ
A. Since the
SPX2951 typically draws 60
μ
A at no load with
Pin 2 open-circuited this is a small price to pay.
REDUCING OUTPUT NOISE
It may be an advantage to reduce the AC noise
present at the output. One way is to reduce the
regulator bandwidth by increasing the size of
the output capacitor. This is the only way that
noise can be reduced on the 3 lead SPX2950 but
is relatively inefficient, as increasing the ca-
pacitor from 1
μ
F to 220
μ
F only decreases the
noise from 430
μ
V to 160
μ
V
RMS
for a 100kHz
bandwidth at 5V output. Noise could also be
reduced fourfold by a bypass capacitor across
R
1
, since it reduces the high frequency gain from
4 to unity. Pick
C
BYPASS
(1 / 2
π
R
1
×
200 Hz)
or choose 0.01
μ
F. When doing this, the output
capacitor must be increased to 3.3
μ
F to main-
tain stability. These changes reduce the output
noise from 430
μ
V to 100
μ
V
for a 100kHz
bandwidth at 5V output. With the bypass ca-
pacitor added, noise no longer scales with out-
put voltage so that improvements are more dra-
matic at higher output voltages.
100K
OUTPUT
ERROR
ERROR
______
SD
V
OUT
GND
FB
+V
IN
+V
IN
1.23V
1.2 to30V
R
1
.01
μ
F
3.3
μ
F
R
2
V
REF
3
8
5
1
4
7
SHUTDOWN
INPUT
+
SPX2951
Figure 2. Adjustable Regulator
TYPICAL APPLICATIONS
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SPX2950ACN-5.0 | 150mA Low Dropout Voltage Regulators |
| SPX2950CN-3.0 | 150mA Low Dropout Voltage Regulators |
| SPX2951CS-3.0 | 150mA Low Dropout Voltage Regulators |
| SPX2951CS-3.3 | 150mA Low Dropout Voltage Regulators |
| SPX2954AN-3.3 | VARISTOR 14VRMS 0805 SMD AUTO |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SPX2950ACN-5.0 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:150mA Low Dropout Voltage Regulators |
| SPX2950ACN-L-3-3 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
| SPX2950ACN-L-5-0 | 制造商:Exar Corporation 功能描述: |
| SPX2950CN-3.0 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:150mA Low Dropout Voltage Regulators |
| SPX2950CN-3.3 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:150mA Low Dropout Voltage Regulators |
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