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參數(shù)資料
| 型號(hào)： | AAT1142ITP-1.8-T1 |
| 廠商： | Advanced Analog Technology,lnc. |
| 英文描述： | 800mA Voltage-Scaling Step-Down Converter |
| 中文描述： | 800mA的電壓縮放降壓轉(zhuǎn)換器 |
| 文件頁數(shù)： | 17/22頁 |
| 文件大?。?/td> | 982K |
| 代理商： | AAT1142ITP-1.8-T1 |
Component Selection
Inductor Selection
The step-down converter uses peak current mode
control with slope compensation to maintain stability
for duty cycles greater than 50%. The output induc-
tor value must be selected so the inductor current
down slope meets the internal slope compensation
requirements. The internal slope compensation for
the programmable AAT1142 is 0.61A/μsec. This
equates to a slope compensation that is 75% of the
inductor current down slope for a 1.8V output and
2.2μH inductor.
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 saturation 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 con-
sider the losses associated with the DCR and its
effect on the total converter efficiency when
selecting an inductor.
The 2.2μH CDRH2D14 series Sumida inductor has
a 94m
Ω
DCR and a 1.5A DC current rating. At full
800mA load, the inductor DC loss is 60mW which
gives a 4.8% loss in efficiency for an 800mA, 1.0V
output.
Input Capacitor
Select a 4.7μF to 10μF X7R or X5R ceramic capac-
itor for the input. To estimate the required input
capacitor size, determine the acceptable input rip-
ple level (V
PP
) and solve for C. The calculated
value varies with input voltage and is a maximum
when V
IN
is double the output voltage.
Always examine the ceramic capacitor DC voltage
coefficient characteristics when selecting the prop-
er value. For example, the capacitance of a 10
μ
F,
6.3V, X5R ceramic capacitor with 5.0V DC applied
is actually about 6μF.
The maximum input capacitor RMS current is:
The input capacitor RMS ripple current varies with
the input and output voltage and will always be less
than or equal to half of the total DC load current.
for V
IN
= 2 · V
O
The term
voltage ripple and input capacitor RMS current
equations and is a maximum when V
O
is twice V
IN
.
This is why the input voltage ripple and the input
capacitor RMS current ripple are a maximum at
50% duty cycle.
appears in both the input
The input capacitor provides a low impedance loop
for the edges of pulsed current drawn by the
AAT1142. Low ESR/ESL X7R and X5R ceramic
· 1
-
IN
O
V
O
V
IN
I
O
2
RMS(MAX)
I
=
· 1
-
= D
· (1 - D) = 0.5
2
=
V
IN
V
O
V
IN
O
1
2
I
RMS
= I
O
· · 1
-
V
IN
V
O
V
IN
C
IN(MIN)
=
1
- ESR
·
4
·
F
S
I
O
V
PP
· 1
-
= 1
IN
= 2 · V
O
V
IN
V
IN
O
V
O
4
· 1
-
V
O
V
IN
C
IN
=
V
O
V
IN
- ESR
·
F
S
V
PP
I
O
0.75
V
L
m = = 0.75
1.8V
2.2μH
A
μsec
AAT1142
800mA Voltage-Scaling Step-Down Converter
1142.2006.07.1.0
17
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AAT1142ITP-T1 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 800mA Volt. Scaling Step-Down Converter 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(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| AAT1142IWP-1.8-T1 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:800mA Voltage-Scaling Step-Down Converter |
| AAT1143 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:1MHz 400mA Step-Down Converter |
| AAT1143_06 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:1MHz 400mA Step-Down Converter |
| AAT1143IJS-0.6-T1 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:1MHz 400mA Step-Down Converter |
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