參數(shù)資料
型號(hào): LP3984IBPX-2.0
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: Solid-State Panel Mount Relay; Output Device:MOSFET; Output Voltage Max:500VDC; Control Voltage Max:32VDC; Control Voltage Min:3.5VDC; Load Current Max:7A; Switching:DC Switch RoHS Compliant: Yes
中文描述: 2 V FIXED POSITIVE LDO REGULATOR, 0.12 V DROPOUT, PBGA4
封裝: 0.995 MM HEIGHT, MICRO, BUMP, SMD-4
文件頁數(shù): 9/11頁
文件大小: 293K
代理商: LP3984IBPX-2.0
Application Hints
External Capacitors
Like any low-dropout regulator, the LP3984 requires external
capacitors for regulator stability. The LP3984 is specifically
designed for portable applications requiring minimum board
space and smallest components. These capacitors must be
correctly selected for good performance.
Input Capacitor
An input capacitance of
)
1μF is required between the
LP3984 input pin and ground (the amount of the capacitance
may be increased without limit).
This capacitor must be located a distance of not more than
1cm from the input pin and returned to a clean analog
ground.Any good quality ceramic, tantalum, or film capacitor
may be used at the input.
Important:
Tantalum capacitors can suffer catastrophic fail-
ures
due
to
surge
current
low-impedance source of power (like a battery or a very
large capacitor). If a tantalum capacitor is used at the input,
it must be guaranteed by the manufacturer to have a surge
current rating sufficient for the application.
There are no requirements for the ESR on the input capaci-
tor, but tolerance and temperature coefficient must be con-
sidered when selecting the capacitor to ensure the capaci-
tance will be
)
1μF over the entire operating temperature
range.
when
connected
to
a
Output Capacitor
The LP3984 is designed specifically to work with tantalum
output capacitors. A tantalum capacitor in 1 to 22 μF range
with 2
to 10
ESR range is suitable in the LP3984 appli-
cation circuit.
It may also be possible to use film capacitors at the output,
but these are not as attractive for reasons of size and cost.
The output capacitor must meet the requirement for mini-
mum amount of capacitance and also have an ESR (Equiva-
lent Series Resistance) value which is within a stable range
(2
to 10
).
No-Load Stability
The LP3984 will remain stable and in regulation with no
external load. This is specially important in CMOS RAM
keep-alive applications.
On/Off Input Operation
The LP3984 is turned off by pulling the V
EN
pin low, and
turned on by pulling it high. If this feature is not used, the V
EN
pin should be tied to V
IN
to keep the regulator output on at all
time. To assure proper operation, the signal source used to
drive the V
EN
input must be able to swing above and below
the specified turn-on/off voltage thresholds listed in the Elec-
trical Characteristics section under V
IL
and V
IH
.
Fast On-Time
The LP3984 utilizes a speed up circuitry to ramp up the
internal V
voltage to its final value to achieve a fast
output turn on time.
Micro SMD Mounting
The micro SMD package requires specific mounting tech-
niques which are detailed in National Semiconductor Appli-
cation Note (AN-1112). Referring to the section Surface
Mount Technology (SMT) Assembly Considerations it
should be noted that the pad style which must be used with
the 5 pin package is NSMD (non-solder mask defined) type.
For best results during assembly, alignment ordinals on the
PC board may be used to facilitate placement of the micro
SMD device.
Micro SMD Light Sensitivity
Exposing the micro SMD device to direct sunlight will cause
misoperation of the device. Light sources such as Halogen
lamps can effect electrical performance if brought near to the
device.
The wavelengths which have most detrimental effect are
reds and infra-reds, which means that the fluorescent light-
ing used inside most buildings has very little effect on per-
formance. A micro SMD test board was brought to within
1cm of a fluorescent desk lamp and the effect on the regu-
lated output voltage was negligible, showing a deviation of
less than 0.1% from nominal.
L
www.national.com
9
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