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參數(shù)資料
| 型號： | AAT1153 |
| 廠商： | Advanced Analogic Technologies, Inc. |
| 英文描述： | 2A Step-Down Converter |
| 中文描述： | 第2A降壓轉(zhuǎn)換器 |
| 文件頁數(shù)： | 12/20頁 |
| 文件大小： | 689K |
| 代理商： | AAT1153 |
AAT1153
2A Step-Down Converter
PRODUCT DATASHEET
12
1153.2007.11.1.1
w w w . a n a l o g i c t e c h . c o m
For output voltages above 2.0V, when light-load effi-
ciency is important, the minimum recommended induc-
tor is 2.2
μ
H.
Manufacturer’s specifications list both the inductor DC
current rating, which is a thermal limitation, and the
peak current rating, which is determined by the satura-
tion characteristics. The inductor should not show any
appreciable saturation under normal load conditions.
Some inductors may meet the peak and average current
ratings yet result in excessive losses due to a high DCR.
Always consider the losses associated with the DCR and
its effect on the total converter efficiency when selecting
an inductor. For optimum voltage-positioning load tran-
sients, choose an inductor with DC series resistance in
the 20m
Ω
to 100m
Ω
range. For higher efficiency at
heavy loads (above 200mA), or minimal load regulation
(but some transient overshoot), the resistance should be
kept below 100m
Ω
. The DC current rating of the induc-
tor should be at least equal to the maximum load cur-
rent plus half the ripple current to prevent core satura-
tion (2A + 600mA). Table 2 lists some typical surface
mount inductors that meet target applications for the
AAT1153.
For example, the 2.2
μ
H CDRH5D16-2R2 inductor select-
ed from Sumida has a 28.7m
Ω
DCR and a 3.0ADC cur-
rent rating. At full load, the inductor DC loss is 57mW
which gives a 1.6% loss in efficiency for a 1200mA, 1.8V
output.
Slope Compensation
The AAT1153 step-down converter uses peak current
mode control with slope compensation for stability when
duty cycles are greater than 50%. The slope compensa-
tion is set to maintain stability with lower value inductors
which provide better overall efficiency. The output induc-
tor value must be selected so the inductor current down
slope meets the internal slope compensation require-
ments. As an example, the value of the slope compensa-
tion is set to 1A/
μ
s which is large enough to guarantee
stability when using a 2.2
μ
H inductor for all output volt-
age levels from 0.6V to 3.3V.
The worst case external current slope (m) using the
2.2
μ
H inductor is when V
OUT
= 3.3V and is:
V
L
m = = = 1.5A/μs
3.3
2.2
To keep the power supply stable when the duty cycle is
above 50%, the internal slope compensation (mA)
should be:
1
2
m
a
≥
· m = 0.75A/μs
Therefore, to guarantee current loop stability, the slope
of the compensation ramp must be greater than one-half
of the down slope of the current waveform. So the inter-
nal slope compensated value of 1A/
μ
s will guarantee
stability using a 2.2
μ
H inductor value for all output volt-
ages from 0.6V to 3.3V.
Input Capacitor Selection
The input capacitor reduces the surge current drawn
from the input and switching noise from the device. The
input capacitor impedance at the switching frequency
should be less than the input source impedance to pre-
vent high frequency switching current passing to the
input. The calculated value varies with input voltage and
is a maximum when V
IN
is double the output voltage.
· 1
-
V
O
V
IN
C
IN
=
V
O
V
IN
- ESR
·
f
S
V
PP
I
O
C
IN(MIN)
=
1
- ESR
·
4
·
f
S
V
PP
I
O
A low ESR input capacitor sized for maximum RMS cur-
rent must be used. Ceramic capacitors with X5R or X7R
dielectrics are highly recommended because of their low
ESR and small temperature coefficients. A 22
μ
F ceram-
ic capacitor for most applications is sufficient. A large
value may be used for improved input voltage filtering.
The maximum input capacitor RMS current is:
I
RMS
= I
O
· · 1
-
V
IN
V
O
V
IN
相關(guān)PDF資料 |
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|---|---|
| AAT1153IDE-0.6-T1 | 2A Step-Down Converter |
| AAT1153IDE-1.8-T1 | 2A Step-Down Converter |
| AAT1154IAS-1.8-T1 | 1MHz 3A Buck DC/DC Converter |
| AAT1154 | 1MHz 3A Buck DC/DC Converter |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AAT1153_08 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:2A Step-Down Converter |
| AAT1153IDE-0.6-T1 | 功能描述:電源開關(guān) IC - 配電 2A Step Down Converter RoHS:否 制造商:Freescale Semiconductor 輸出端數(shù)量: 開啟電阻（最大值）: 開啟時間（最大值）: 關(guān)閉時間（最大值）: 工作電源電壓: 電源電流（最大值）: 最大工作溫度: 安裝風(fēng)格: 封裝 / 箱體: |
| AAT1153IDE-1.8-T1 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:2A Step-Down Converter |
| AAT1154 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:1MHz 3A Buck DC/DC Converter |
| AAT1154_06 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:1MHz 3A Step-Down DC/DC Converter |
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