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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)： | 20/31頁 |
| 文件大小： | 463K |
| 代理商： | NCP5218 |
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NCP5218
http://onsemi.com
20
Then the required output capacitor capacitance can be
estimated by:
I2STEP(peak)
(Vovershoot
COUT
L
VOUT)2
V2OUT
(VIN
VOUT)
2L
fSW
(eq. 11)
ISTEP(peak)
ILOAD
VOUT
VIN
(eq. 12)
where I
STEP(peak)
is the load current step plus half of the
ripple current at the load release and I
LOAD
is the change
in the output load current.
Besides, the ESR and the capacitance of the output filter
capacitor also contribute to double pole and ESR zero
frequencies of the output filter, and the poles and zeros
frequencies of the compensation network for close loop
stability. The compensation network will be discussed in
more detail in the Loop Compensation section.
Other parameters about output filter capacitor that
needed to be considered are the voltage rating and ripple
current rating. The voltage rating should be at least
1.25 times the output voltage and the rms ripple current
rating should be greater than the inductor ripple current.
Thus, the voltage rating and ripple current rating can be
obtained by:
Vrating
1.25
VOUT
(eq. 13)
ICOUT(RMS)
IL(ripple)
(VIN
VOUT)
L
VOUT
VIN
fSW
(eq. 14)
SP
Cap, POSCAP and OS
CON capacitors are suitable
for the output capacitor since their ESR is low enough to
meet the ripple voltage and load transient requirements.
Usually, two or more capacitors of the same type,
capacitance and ESR can be used in parallel to achieve the
required ESR and capacitance without change the ESR
zero position for maintaining the same loop stability. Other
than the performance point of view, the physical size and
cost are also the concerned factors for output capacitor
selection.
Inductor Selection
The inductor should be chosen according to the inductor
ripple current, inductance, maximum current rating,
transient load release, and DCR.
In general, the inductor ripple current is 20% to 40% of
the maximum load current. A ripple current of 30% of the
maximum load current can be used as a typical value. The
required inductance can be estimated by:
(VIN
VOUT)
0.3
ILOAD(max)
L
VOUT
VIN
fSW
(eq. 15)
where I
LOAD(max)
is the maximum load current.
The DC current rating of the inductor should be about 1.2
times of the peak inductor current at maximum output load
current. Therefore, the maximum DC current rating of the
inductor can be obtained by:
IL(rating)
1.2
IL(peak)
(eq. 16)
where I
L(peak)
is the peak inductor current at maximum load
current which is determined by:
IL(peak)
ILOAD(max)
IL(ripple)
2
(VIN
VOUT)
2
L
(eq. 17)
ILOAD(max)
VOUT
VIN
fSW
Since the excessive energy stored in the inductor
contributed to the output voltage overshoot during load
release, the following inequality can be used to ensure that
the selected inductance value can meet the voltage
overshoot requirement at load release:
(
(Vovershoot
I2STEP(peak)
L
COUT
VOUT)2
V2OUT
)
(eq. 18)
In addition, the inductor also needs to have low enough
DCR to obtain good conversion efficiency. In general,
inductors with about 2.0 m to 3.0 m per
inductance can be used. Besides, larger inductance value
can be selected to achieve higher efficiency as long as it
still meets the targeted voltage overshoot at load release
and inductor DC current rating. Moreover, it should be
noted that using too small inductance value will cause very
large inductor ripple current in CCM in S0 mode and
extremely large peak inductor current in DCM in
power
saving mode during S3 mode. For both cases,
output capacitors with smaller ESR and larger capacitance
are required to keep the output ripple voltage small. It
should also be noted that the peak inductor current under
DCM light
load condition in power
saving mode in S3
mode will be larger than the peak inductor current under
heavy
load condition in S0 mode when very small
inductance value is used. Besides, using smaller
inductance
will
achieve
require larger minimum load to maintain nominal voltage
regulation in power
saving mode in S3 state. Therefore, it
is recommended that the inductance value should be at
least 0.56 H or above to obtain optimum performance.
H of
lower
efficiency
and
MOSFET Selection
External N
channel MOSFETs are used as the switching
elements of the buck controller. Both high
side and
low
side MOSFETs must be logic
level MOSFETs which
can be fully turned on at 5.0 V gate
drive voltage.
On
resistance (R
DS(on)
), maximum drain
to
source
voltage (V
DSS
), maximum drain current rating, and gate
charges (Q
G
, Q
GD
, Q
GS
) are the key parameters to be
considered when choosing the MOSFETs.
For on
resistance, it should be the lower; the better is the
performance in terms of efficiency and power dissipation.
Check the MOSFET’s rated R
DS(on)
at V
GS
= 4.5 Vwhen
selecting the MOSFETs. The low
side MOSFET should
have lower R
DS(on)
than the high
side MOSFET since the
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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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