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參數(shù)資料
| 型號： | LM4128BMFX-2.5 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | SOT-23 Precision Micropower Series Voltage Reference |
| 中文描述： | 1-OUTPUT THREE TERM VOLTAGE REFERENCE, 2.5 V, PDSO5 |
| 封裝： | SOT-23, 5 PIN |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 280K |
| 代理商： | LM4128BMFX-2.5 |
Application Information
THEORY OF OPERATION
The foundation of any voltage reference is the band-gap cir-
cuit. While the reference in the LM4128 is developed from the
gate-source voltage of transistors in the IC, principles of the
band-gap circuit are easily understood using a bipolar exam-
ple. For a detailed analysis of the bipolar band-gap circuit,
please refer to Application Note AN-56.
SUPPLY AND ENABLE VOLTAGES
To ensure proper operation, V
and V
must be within a
specified range. An acceptable range of input voltages is
V
IN
> V
REF
+ 400 mV (I
LOAD
≤
10 mA)
The enable pin uses an internal pull-up current source
(I
2 μA) that may be left floating or triggered by an
external source. If the part is not enabled by an external
source, it may be connected to V
. An acceptable range of
enable voltages is given by the enable transfer characteris-
tics. See the Electrical Characteristics section and Enable
Transfer Characteristics figure for more detail. Note, the part
will not operate correctly for V
EN
> V
IN
.
COMPONENT SELECTION
A small ceramic (X5R or X7R) capacitor on the input must be
used to ensure stable operation. The value of C
must be
sized according to the output capacitor value. The value of
C
must satisfy the relationship C
≥
C
. When no output
capacitor is used, C
must have a minimum value of 0.1 μF.
Noise on the power-supply input may affect the output noise.
Larger input capacitor values (typically 4.7 μF to 22 μF) may
help reduce noise on the output and significantly reduce over-
shoot during startup. Use of an additional optional bypass
capacitor between the input and ground may help further re-
duce noise on the output. With an input capacitor, the LM4128
will drive any combination of resistance and capacitance up
to V
REF
/20 mA and 10 μF respectively.
The LM4128 is designed to operate with or without an output
capacitor and is stable with capacitive loads up to 10 μF.
Connecting a capacitor between the output and ground will
significantly improve the load transient response when
switching from a light load to a heavy load. The output ca-
pacitor should not be made arbitrarily large because it will
effect the turn-on time as well as line and load transients.
While a variety of capacitor chemistry types may be used, it
is typically advisable to use low esr ceramic capacitors. Such
capacitors provide a low impedance to high frequency sig-
nals, effectively bypassing them to ground. Bypass capacitors
should be mounted close to the part. Mounting bypass ca-
pacitors close to the part will help reduce the parasitic trace
components thereby improving performance.
SHORT CIRCUITED OUTPUT
The LM4128 features indefinite short circuit protection. This
protection limits the output current to 75 mA when the output
is shorted to ground.
TURN ON TIME
Turn on time is defined as the time taken for the output voltage
to rise to 90% of the preset value. The turn on time depends
on the load. The turn on time is typically 33.2 μs when driving
a 1μF load and 78.8 μs when driving a 10 μF load. Some users
may experience an extended turn on time (up to 10 ms) under
brown out conditions and low temperatures (-40°C).
THERMAL HYSTERESIS
Thermal hysteresis is defined as the change in output voltage
at 25oC after some deviation from 25oC. This is to say that
thermal hysteresis is the difference in output voltage between
two points in a given temperature profile. An illustrative tem-
perature profile is shown in
Figure 1
.
20211038
FIGURE 1. Illustrative Temperature Profile
This may be expressed analytically as the following:
Where
V
HYS
= Thermal hysteresis expressed in ppm
V
REF
= Nominal preset output voltage
V
REF1
= V
REF
before temperature fluctuation
V
REF2
= V
REF
after temperature fluctuation.
The LM4128 features a low thermal hysteresis of 190 μV from
-40°C to 125°C.
TEMPERATURE COEFFICIENT
Temperature drift is defined as the maximum deviation in out-
put voltage over the operating temperature range. This devi-
ation over temperature may be illustrated as shown in
Figure
2
.
20211039
FIGURE 2. Illustrative Temperature Coefficient Profile
Temperature coefficient may be expressed analytically as the
following:
www.national.com
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相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4128BMFX-3.0 | SOT-23 Precision Micropower Series Voltage Reference |
| LM4128BMFX-3.3 | SOT-23 Precision Micropower Series Voltage Reference |
| LM4128BMFX-4.1 | SOT-23 Precision Micropower Series Voltage Reference |
| LM4128CMF-1.8 | SOT-23 Precision Micropower Series Voltage Reference |
| LM4128CMF-2.0 | SOT-23 Precision Micropower Series Voltage Reference |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4128BMFX-3.0 | 功能描述:基準(zhǔn)電壓& 基準(zhǔn)電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓?fù)浣Y(jié)構(gòu):Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準(zhǔn)確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
| LM4128BMFX-3.0/NOPB | 功能描述:基準(zhǔn)電壓& 基準(zhǔn)電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓?fù)浣Y(jié)構(gòu):Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準(zhǔn)確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
| LM4128BMFX-3.3 | 功能描述:基準(zhǔn)電壓& 基準(zhǔn)電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓?fù)浣Y(jié)構(gòu):Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準(zhǔn)確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
| LM4128BMFX-3.3/NOPB | 功能描述:基準(zhǔn)電壓& 基準(zhǔn)電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓?fù)浣Y(jié)構(gòu):Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準(zhǔn)確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
| LM4128BMFX-4.1 | 功能描述:基準(zhǔn)電壓& 基準(zhǔn)電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓?fù)浣Y(jié)構(gòu):Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準(zhǔn)確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
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