參數(shù)資料
型號： LP3972SQ-5810
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 電源管理
英文描述： 1-CHANNEL POWER SUPPLY SUPPORT CKT, QCC40
封裝： 5 X 5 MM, LLP-40
文件頁數(shù)： 13/60頁
文件大小： 1171K
代理商： LP3972SQ-5810
up times with
10 μF output capacitor and 1000 mA load
current is 390
μs and with 1 mA load current it is 295 μs.
LDO - LOW DROP OUT OPERATION
The LP3972 can operate at 100% duty cycle (no switching;
PMOS switch completely on) for low drop out support of the
output voltage. In this way the output voltage will be controlled
down to the lowest possible input voltage. When the device
operates near 100% duty cycle, output voltage ripple is ap-
proximately 25 mV. The minimum input voltage needed to
support the output voltage is
V
IN, MIN = ILOAD * (RDSON, PFET + RINDUCTOR) + VOUT
I
LOAD
Load Current
R
DSON, PFET
Drain to source resistance of PFET
switch in the triode region
R
INDUCTOR
Inductor resistance
SPREAD SPECTRUM FEATURE
Periodic switching in the buck regulator is inherently a noisier
function block compared to an LDO. It can be challenging in
some critical applications to comply with stringent regulatory
standards or simply to minimize interference to sensitive cir-
cuits in space limited portable systems. The regulator’s
switching frequency and harmonics can cause “noise” in the
signal spectrum. The magnitude of this noise is measured by
its power spectral density. The power spectral density of the
switching frequency, F
C, is one parameter that system de-
signers want to be as low as practical to reduce interference
to the environment and subsystems within their products. The
LP3972 has a user selectable function on chip, wherein a
noise reduction technique known as “spread spectrum” can
be employed to ease customer’s design and production is-
sues.
The principle behind spread spectrum is to modulate the
switching frequency slightly and slowly, and spread the signal
frequency over a broader bandwidth. Thus, its power spectral
density becomes attenuated, and the associated interference
electro-magnetic energy is reduced. The clock used to mod-
ulate the LP3972 buck regulator can be used as a spread
spectrum clock via 2 I2C control register (System Control
Register 1 (SCR1) 8h’80) bits bk_ssen, and slomod. With this
feature enabled, the intense energy of the clock frequency
can be spread across a small band of frequencies in the
neighborhood of the center frequency. The results in a re-
duction of the peak energy!
The LP3972 spread spectrum clock uses a triangular modu-
lation profile with equal rise and fall slopes. The modulation
has the following characteristics:
The center frequency:
F
C = 2 MHz, and
The modulating frequency,
f
M = 6.8 kHz or 12 kHz.
Peak frequency deviation:
Δ_f = ±100 kHz (or ±5%)
Modulation index
β = Δ_f/f
M = 14.7 or 8.3
Switching Energy RBW = 300 Hz
20207641
www.national.com
20
LP3972
相關PDF資料
PDF描述
LP3972SQXE514 1-CHANNEL POWER SUPPLY SUPPORT CKT, QCC40
LPB48DP 2-OUTPUT 75 W DC-DC REG PWR SUPPLY MODULE
LPB24DP 2-OUTPUT 75 W DC-DC REG PWR SUPPLY MODULE
LPB15SP 1-OUTPUT 75 W DC-DC REG PWR SUPPLY MODULE
LPB24SP 1-OUTPUT 75 W DC-DC REG PWR SUPPLY MODULE
相關代理商/技術參數(shù)
參數(shù)描述
LP3972SQ-5810/NOPB 功能描述:監(jiān)控電路 Pwr Mgmt Unit RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監(jiān)視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel
LP3972SQ-A413 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
LP3972SQ-A413/NOPB 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
LP3972SQ-A514 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
LP3972SQ-A514/NOPB 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
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