參數(shù)資料
型號(hào)： NCP5218
廠商： ON SEMICONDUCTOR
英文描述： 2−in−1 Notebook DDR Power Controller
文件頁數(shù)： 19/31頁
文件大?。?/td> 463K
代理商： NCP5218
NCP5218
http://onsemi.com
19
APPLICATION INFORMATION
Input Capacitor Selection for V
DDQ
Buck Regulator
The input capacitor is important for proper regulation
operation of the buck regulator. It minimizes the input
voltage ripple and current ripple from the power source by
providing a local loop for switching current. The input
capacitor should be placed close to the drain of the
high
side MOSFET and source of the low
side MOSFET
with short, wide traces for connection. The input capacitor
must have large enough rms ripple current rating to
withstand the large current pulses present at the input of the
bulk regulator due to the switching current. The required
input capacitor rms ripple current rating can be estimated
by the following with minimum V
IN
:
ICIN(RMS)
IOUT
VOUT
VIN
VOUT
VIN
2
(eq. 1)
Besides, the voltage rating of the input capacitor should
be at least 1.25 times of the maximum input voltage.
Capacitance of around 20 F to 50 F should be sufficient
for most DDR applications. Ceramic capacitors are the
most suitable choice of input capacitor for notebook
applications due to their low ESR, high ripple current, and
high voltage rating. POSCAP or OS
CON capacitors can
also be used since they have good ESR and ripple current
rating, but they are larger in size and more expensive.
Aluminum electrolytic capacitors are also a choice for their
high voltage rating and low cost, but several aluminum
capacitors in parallel should be used for the required ripple
current. If ceramic capacitors are used, X5R and X7R types
are preferred rather than the Y5V type since the X5R and
X7R types are ceramic capacitors and have smaller
tolerance and temperature coefficient.
Output Capacitor Selection for V
DDQ
Buck Regulator
The output filter capacitor plays an important role in
steady state output ripple voltage, load transient
requirement, and loop compensation stability. The ESR
and the capacitance of the output capacitor are the most
important parameters needed to be considered. In general,
the output capacitor must have small enough ESR for
output ripple voltage and load transient requirement.
Besides, the capacitance of the output capacitor should be
large enough to meet the overshoot and undershoot during
load transient. Since steady state output ripple voltage,
transient load undershoot and overshoot are the largest at
maximum V
IN
, the ESR and capacitance of output
capacitor should be estimated at the maximum V
IN
condition.
For steady output ripple voltage, both ESR and
capacitance of the output capacitor are the contributing
factors, however, the capacitor ESR is the dominant factor.
The output ripple voltage is calculated as follows:
Vripple
IL(ripple)
ESR
IL(ripple)
COUT
ton
(eq. 2)
Vripple
IL(ripple)
ESR, for small tonand large COUT
(eq. 3)
where I
L(ripple)
is the inductor ripple current, t
on
is on
time,
and C
OUT
is the output capacitance.
The inductor ripple current can be calculated by the
equation:
(VIN
VOUT)
L
IL(ripple)
VOUT
VIN
fSW
(eq. 4)
where L is the inductance and f
SW
is the switching
frequency. The output ripple voltage can be reduced by
either using the inductor with larger inductance or the
output capacitor with smaller ESR. Thus, the ESR needed
to meet the ripple voltage requirement can be obtained by:
Vripple
(VIN
VOUT)
The inductor ripple current is typically 30% of the
maximum load current and the ripple voltage is typically
2% of the output voltage. Thus, the above inequality can be
simplified to:
0.02
0.3
For the load transient, the output capacitor contributes to
both the load
rise and the load
release responses. The
voltage undershoot during step
up load can be calculated
by the equation:
ESR
L
fSW
VIN
VOUT
(eq. 5)
ESR
VOUT
ILOAD(max)
(eq. 6)
Vundershoot
ILOAD
ESR
ILOAD
COUT
1
VOUT
fSW
VIN
(eq. 7)
where I
LOAD
is the change in output current. If the second
term is ignored, then it becomes the following inequality:
Vundershoot
ESR
ILOAD
(eq. 8)
The maximum ESR requires to meet voltage undershoot
requirement at step
up load transient can be estimated
from the above inequality.
Then, the required output capacitor capacitance can be
obtained by the following:
COUT
ILOAD
Vundershoot
ILOAD
ESR
1
VOUT
fSW
VIN
(eq. 9)
The output voltage overshoot during load
release is
because the excessive stored energy in the inductor is
absorbed by the output capacitor. The overshoot voltage
can be calculated by the following equation:
LI2STEP(peak)
Vovershoot
COUTV2OUT
COUT
VOUT
(eq. 10)
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NCP5218MNR2G 功能描述:電壓模式 PWM 控制器 2IN1 NOTEBK DDR CNTL RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
NCP5220 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:3−in−1 PWM Dual Buck and Linear Power Controller
NCP5220AMNR2 功能描述:DC/DC 開關(guān)控制器 3-in-1 PWM Dual Buck RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
NCP5220AMNR2G 功能描述:DC/DC 開關(guān)控制器 ANA DDR PWER CNTRLR RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
NCP5220MNR2 功能描述:DC/DC 開關(guān)控制器 3-in-1 PWM Dual Buck RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
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