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參數(shù)資料
| 型號： | LP5951MF-3.0 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Micropower, 150mA Low-Dropout CMOS Voltage Regulator |
| 中文描述： | 3 V FIXED POSITIVE LDO REGULATOR, 0.25 V DROPOUT, PDSO5 |
| 封裝： | SOT-23, 5 PIN |
| 文件頁數(shù)： | 9/10頁 |
| 文件大小： | 608K |
| 代理商： | LP5951MF-3.0 |
Application Hints
(Continued)
The ceramic capacitor’s capacitance can vary with tempera-
ture. The capacitor type X7R, which operates over a tem-
perature range of -55C to +125C, will only vary the capaci-
tance to within
±
15%. The capacitor type X5R has a similar
tolerance over a reduced temperature range of -55C to
+85C. Many large value ceramic capacitors, larger than 1μF
are manufactured with Z5U or Y5V temperature characteris-
tics. Their capacitance can drop by more than 50% as the
temperature varies from 25C to 85C. Therefore X7R is
recommended over Z5U and Y5V in applications where the
ambient temperature will change significantly above or be-
low 25C.
Tantalum capacitors are less desirable than ceramic for use
as output capacitors because they are more expensive when
comparing equivalent capacitance and voltage ratings in the
1μF to 4.7μF range.
Another important consideration is that tantalum capacitors
have higher ESR values than equivalent size ceramics. This
means that while it may be possible to find a tantalum
capacitor with an ESR value within the stable range, it would
have to be larger in capacitance (which means bigger and
more costly) than a ceramic capacitor with the same ESR
value. It should also be noted that the ESR of a typical
tantalum will increase about 2:1 as the temperature goes
from 25C down to -40C, so some guard band must be
allowed.
NO-LOAD STABILITY
The LP5951 will remain stable and in regulation with no
external load. This is an important consideration in some
circuits, for example CMOS RAM keep-alive applications.
ENABLE OPERATION
The LP5951 may be switched ON or OFF by a logic input at
the Enable pin, V
. A logic high at this pin will turn the
device on. When the enable pin is low, the regulator output is
off and the device typically consumes 5nA.
If the application does not require the Enable switching
feature, the V
pin should be tied to V
IN
to keep the
regulator output permanently on.
To ensure proper operation, the signal source used to drive
the V
input must be able to swing above and below the
specified turn-on/off voltage thresholds listed in the Electrical
Characteristics section under Enable Control Characteris-
tics, V
IL
and V
IH
.
FAST TURN OFF AND ON
The controlled switch-off feature of the device provides a fast
turn off by discharging the output capacitor via an internal
FET device. This discharge is current limited by the RDSon
of this switch.
Fast turn-on is guaranteed by an optimized architecture
allowing a very fast ramp of the output voltage to reach the
target voltage.
SHORT-CIRCUIT PROTECTION
The LP5951 is short circuit protected and in the event of a
peak over-current condition, the output current through the
PMOS will be limited.
If the over-current condition exists for a longer time, the
average power dissipation will increase depending on the
input to output voltage difference until the thermal shutdown
circuitry will turn off the PMOS.
Please refer to the section on thermal information for power
dissipation calculations.
THERMAL-OVERLOAD PROTECTION
Thermal-Overload Protection limits the total power dissipa-
tion in the LP5951. When the junction temperature exceeds
T
= 160C typ., the shutdown logic is triggered and the
PMOS is turned off, allowing the device to cool down. After
the junction temperature dropped by 20C (temperature hys-
teresis), the PMOS is activated again. This results in a
pulsed output voltage during continuous thermal-overload
conditions.
The Thermal-Overload Protection is designed to protect the
LP5951 in the event of a fault condition. For normal, continu-
ous operation, do not exceed the absolute maximum junc-
tion temperature rating of T
J
= +150C (see Absolute Maxi-
mum Ratings).
REVERSE CURRENT PATH
The internal MOSFET in LP5951 has an inherent parasitic
body diode. During normal operation, the input voltage is
higher than the output voltage and the parasitic diode is
reverse biased. However, if the output is pulled above the
input in an application, then current flows from the output to
the input as the parasitic diode gets forward biased. The
output can be pulled above the input as long as the current
in the parasitic diode is limited to 50mA.
For currents above this limit an external Schottky diode must
be connected from V
OUT
to V
IN
(cathode on V
IN
, anode on
V
OUT
).
20136206
FIGURE 1. Graph Showing A Typical Variation In
Capacitance vs DC Bias
L
www.national.com
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP5951MFX-1.3 | 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 |
| LP5951MFX-1.3/NOPB | 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 |
| LP5951MFX-1.5 | 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 |
| LP5951MFX-1.5/NOPB | 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 |
| LP5951MFX-1.8 | 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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