參數(shù)資料
型號： MP2105
廠商： Monolithic Power Systems, Inc.
英文描述： 1MHz, 800mA Synchronous Step-Down Converter
中文描述： 1MHz的，800mA的同步降壓轉(zhuǎn)換器
文件頁數(shù)： 6/8頁
文件大小： 275K
代理商： MP2105
MP2105 – 1MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER
MP2105 Rev. 1.2
8/19/2005
www.MonolithicPower.com
6
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
2005 MPS. All Rights Reserved.
TM
Current Mode PWM Control
Slope compensated current mode PWM control
provides stable switching and cycle-by-cycle
current limit for superior load and line response
and protection of the internal main switch and
synchronous rectifier. The MP2105 switches at a
constant frequency (1MHz) and regulates the
output voltage. During each cycle the PWM
comparator modulates the power transferred to the
load by changing the inductor peak current based
on the feedback error voltage. During normal
operation, the main switch is turned on for a certain
time to ramp the inductor current at each rising
edge of the internal oscillator, and switched off
when the peak inductor current is above the error
voltage. When the main switch is off, the
synchronous rectifier will be turned on immediately
and stay on until either the next cycle starts.
Dropout Operation
The MP2105 allows the main switch to remain on
for more than one switching cycle and increases
the duty cycle while the input voltage is dropping
close to the output voltage. When the duty cycle
reaches 100%, the main switch is held on
continuously to deliver current to the output up to
the PFET current limit. The output voltage then is
the input voltage minus the voltage drop across
the main switch and the inductor.
Short Circuit Protection
The MP2105 has short circuit protection. When
the output is shorted to ground, the oscillator
frequency is reduced to prevent the inductor
current from increasing beyond the PFET current
limit. The PFET current limit is also reduced to
lower the short circuit current. The frequency and
current limit will return to the normal values once
the short circuit condition is removed and the
feedback voltage reaches 0.6V.
Maximum Load Current
The MP2105 can operate down to 2.5V input
voltage; however the maximum load current
decreases at lower input due to large IR drop on
the main switch and synchronous rectifier. The
slope compensation signal reduces the peak
inductor current as a function of the duty cycle to
prevent sub-harmonic oscillations at duty cycles
greater than 50%. Conversely the current limit
increases as the duty cycle decreases.
APPLICATION INFORMATION
Output Voltage Setting
The external resistor divider sets the output
voltage (see Figure 3). The feedback resistor R1
also sets the feedback loop bandwidth with the
internal compensation capacitor (see Figure 1).
Choose R1 around 500k
for optimal transient
response. R2 is then given by:
1
V
6
V
1
R
2
R
OUT
=
Table 1—Resistor Selection vs. Output
Voltage Setting
V
OUT
R1
R2
1.2V
499k
(1%)
499k
(1%)
499k
(1%)
499k
(1%)
499k
(1%)
332k
(1%)
249k
(1%)
158k
(1%)
1.5V
1.8V
2.5V
Inductor Selection
A 1μH to 10μH inductor with DC current rating at least
25% higher than the maximum load current is
recommended for most applications. For best
efficiency, the inductor DC resistance shall be
<200m
. See Table 2 for recommended inductors
and manufacturers. For most designs, the inductance
value can be derived from the following equation:
(
OUT
V
×
)
OSC
L
IN
OUT
V
IN
I
f
V
V
L
×
×
=
where
I
L
is Inductor Ripple Current. Choose inductor
ripple current approximately 30% of the maximum
load current, 800mA.
The maximum inductor peak current is:
2
I
I
I
L
LOAD
)
MAX
(
L
+
=
Under light load conditions below 100mA, larger
inductance is recommended for improved efficiency.
Table 3 lists inductors recommended for this purpose.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MP2105_06 制造商:MPS 制造商全稱:Monolithic Power Systems 功能描述:1MHz, 800mA Synchronous Step-Down Converter
MP2105DJ 制造商:MPS 制造商全稱:Monolithic Power Systems 功能描述:800mA Synchronous Buck Step-Down Converter
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MP2105DJLFZ 制造商:Monolithic Power Systems 功能描述: 制造商:MPS 功能描述:
MP2105DJ-LF-Z 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 0.8A/6V Synch Step-Down RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
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