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參數(shù)資料
| 型號： | LT1761 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | 100mA, Low Noise, LDO Micropower Regulators in SOT-23(可調(diào)輸出,100mA,低噪聲，低壓差穩(wěn)壓器（SOT-23封裝）) |
| 中文描述： | 100mA的，低噪聲，LDO穩(wěn)壓器采用SOT微功耗穩(wěn)壓- 23（可調(diào)輸出，100mA的，低噪聲，低壓差穩(wěn)壓器（采用SOT - 23封裝）） |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 197K |
| 代理商： | LT1761 |
12
LT1761 Series
APPLICATIO
S I
N
FOR
ATIO
U
Adjustable Operation
The adjustable version of the LT1761 has an output
voltage range of 1.22V to 20V. The output voltage is set by
the ratio of two external resistors as shown in Figure 1. The
device servos the output to maintain the ADJ pin voltage
at 1.22V referenced to ground. The current in R1 is then
equal to 1.22V/R1 and the current in R2 is the current in R1
plus the ADJ pin bias current. The ADJ pin bias current,
30nA at 25
°
C, flows through R2 into the ADJ pin. The
output voltage can be calculated using the formula in
Figure 1. The value of R1 should be no greater than 250k
to minimize errors in the output voltage caused by the ADJ
pin bias current. Note that in shutdown the output is turned
off and the divider current will be zero. Curves of ADJ
Pin Voltage vs Temperature and ADJ Pin Bias Current
vs Temperature appear in the Typical Performance
Characteristics.
W
U
Bypass Capacitance and Low Noise Performance
The LT1761 regulators may be used with the addition of a
bypass capacitor from V
OUT
to the BYP pin to lower output
voltage noise. A good quality low leakage capacitor is
recommended. This capacitor will bypass the reference of
the regulator, providing a low frequency noise pole. The
noise pole provided by this bypass capacitor will lower the
output voltage noise to as low as 20
μ
V
RMS
with the
addition of a 0.01
μ
F bypass capacitor. Using a bypass
capacitor has the added benefit of improving transient
response. With no bypass capacitor and a 10
μ
F output
capacitor, a 10mA to 100mA load step will settle to within
1% of its final value in less than 100
μ
s. With the addition
of a 0.01
μ
F bypass capacitor, the output will stay within
1% for a 10mA to 100mA load step (see LT1761-5
Transient Reponse in Typical Performance Characteris-
tics section). However, regulator start-up time is inversely
proportional to the size of the bypass capacitor, slowing to
15ms with a 0.01
μ
F bypass capacitor and 10
μ
F output
capacitor.
Output Capacitance and Transient Response
The LT1761 regulators are designed to be stable with a
wide range of output capacitors. The ESR of the output
capacitor affects stability, most notably with small capaci-
tors. A minimum output capacitor of 1
μ
F with an ESR of
3
or less is recommended to prevent oscillations. The
LT1761-X is a micropower device and output transient
response will be a function of output capacitance. Larger
values of output capacitance decrease the peak deviations
and provide improved transient response for larger load
current changes. Bypass capacitors, used to decouple
individual components powered by the LT1761-X, will
increase the effective output capacitor value. With larger
capacitors used to bypass the reference (for low noise
operation), larger values of output capacitors are needed.
For 100pF of bypass capacitance, 2.2
μ
F of output capaci-
tor is recommended. With a 330pF bypass capacitor or
larger, a 3.3
μ
F output capacitor is recommended. The
shaded region of Figure 2 defines the region over which
the LT1761 regulators are stable. The minimum ESR
needed is defined by the amount of bypass capacitance
used, while the maximum ESR is 3
.
IN
1761 F01
R2
LT1761
OUT
V
IN
V
OUT
ADJ
GND
R1
+
V
V
R
R
I
R
V
V
I
nA
OUT
ADJ
ADJ
ADJ
OUTPUT RANGE = 1.22V TO 20V
=
+
+
(
1
)( )
=
=
1 22
1
2
2
1 22
30
AT 25 C
Figure 1. Adjustable Operation
The adjustable device is tested and specified with the ADJ
pin tied to the OUT pin for an output voltage of 1.22V.
Specifications for output voltages greater than 1.22V will
be proportional to the ratio of the desired output voltage to
1.22V: V
OUT
/1.22V. For example, load regulation for an
output current change of 1mA to 100mA is –1mV typical
at V
OUT
= 1.22V. At V
OUT
= 12V, load regulation is:
(12V/1.22V)(–1mV) = –9.8mV
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT1761-1.8 | 100mA, Low Noise, LDO Micropower Regulators in SOT-23(1.8V輸出，100mA,低噪聲，低壓差穩(wěn)壓器（SOT-23封裝）) |
| LT1761-2 | 100mA, Low Noise, LDO Micropower Regulators in SOT-23(2V輸出，100mA,低噪聲，低壓差穩(wěn)壓器（SOT-23封裝）) |
| LT1761-2.5 | 100mA, Low Noise, LDO Micropower Regulators in SOT-23(2.5V輸出，100mA,低噪聲，低壓差穩(wěn)壓器（SOT-23封裝）) |
| LT1761-3 | 100mA, Low Noise, LDO Micropower Regulators in SOT-23(3V輸出，100mA,低噪聲，低壓差穩(wěn)壓器（SOT-23封裝）) |
| LT1761-3.3 | 100mA, Low Noise, LDO Micropower Regulators in SOT-23(3.3V輸出，100mA,低噪聲，低壓差穩(wěn)壓器（SOT-23封裝）) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1761_1 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:100mA, Low Noise,LDO Micropower Regulators in SOT-23 |
| LT1761_10 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:100mA, Low Noise, LDO Micropower Regulators in TSOT-23 |
| LT1761CS5-2.5 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Positive Fixed Voltage Regulator |
| LT1761CS5-3 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Positive Fixed Voltage Regulator |
| LT1761CS5-3.3 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Positive Fixed Voltage Regulator |
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