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參數(shù)資料
| 型號： | SP6121 |
| 英文描述： | Low Voltage, Synchronous Step Down PWM Controller Ideal for 2A to 10A, Small Footprint, DC-DC Power Converters |
| 中文描述： | 低電壓，為第2A同步降壓PWM控制器的理想下至10A，占地面積小，DC - DC電源轉(zhuǎn)換器 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 358K |
| 代理商： | SP6121 |
Date: 5/25/04
SP6121 Low Voltage, Synchronous Step Down PWM Controller Copyright 2004 Sipex Corporation
12
associated with the output capacitors and can be
determined by
f
Z(ESR)
1
=
π
C
OUT
R
ESR
Crossover frequency of 20kHz is a sound first
try if low ESR tantalum capacitors or poscaps
are used at the output. The next step is to calcu-
late the complex conjugate poles contributed by
the LC output filter,
f
P(LC)
= 1
2
π√
LC
OUT
The open loop gain of the whole system can be
divided into the gain of the error amplifier,
PWM modulator, buck converter, and feedback
resistor divider. In order to crossover at the
selected frequency fco, the gain of the error
amplifier has to compensate for the attenuation
caused by the rest of the loop at this frequency.
In the RC network shown in Figure 4, the product
of R1 and the error amplifier transconductance
determines this gain. Therefore, R1 can be deter-
mined from the following equation that takes
into account the typical error amplifier
transconductance, reference voltage and PWM
ramp built into the SP6121.
R1 = 975V
OUT
f
CO
f
Z(ESR)
V
IN
f
P(LC)2
In Figure 4, R1 and C1 provides a zero f
Z1
which
needs to be placed at or below f
P(LC)
. If f
Z1
is
made equal to f
P(LC)
for convenience, the value
of C1 can be calculated as
C1 =
1
2
π
f
P(LC)
R
1
The optional C2 generates a pole f
P1
with R1 to
cut down high frequency noise for reliable op-
eration. This pole should be placed one decade
higher than the crossover frequency to avoid
erosion of phase margin. Therefore, the value of
the C2 can be derived from
C2 =
1
20
π
f
CO
R
1
Figure 5 illustrates the overall loop frequency
response and frequency of each pole and zero.
To fine-tune the compensation, it is necessary to
physically measure the frequency response us-
ing a network analyzer.
Gain
-20db/dec
-40db/dec
-20db/dec
-20db/dec
-20db/dec
Error Amplifier
Loop
f
f
Figure 5. Frequency response of a stable system and its
error amplifier.
Overcurrent Protection
Over current protection on the SP6121 is imple-
mented through detection of an excess voltage
condition across the high side PMOS switch
during conduction. This is typically referred to
as high side R
DS(ON)
detection. By using the
R
DS(ON)
of Q1 to measure the output current, the
current limit circuit eliminates the sense resistor
that would otherwise be required and the corre-
sponding loss associated with it. This improves
the overall efficiency and reduces the number of
components in the power path benefiting size
and cost. R
DS(ON)
sensing is by default inaccu-
rate and is primarily meant to protect the power
supply during a fault condition. The overcurrent
trip point will vary from unit to unit as the
R
DS(ON)
of Q1 varies. The SP6121 provides a
built-in 160mV threshold between the I
SET
and
I
SENSE
pins. If a current limit threshold in excess
of 160mV is required, an external programming
resistor, R
SET
can be added between I
SET
pin and
V
IN
as shown in Figure 6.
APPLICATIONS INFORMATION: Continued
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP6121CN | Low Voltage, Synchronous Step Down PWM Controller Ideal for 2A to 10A, Small Footprint, DC-DC Power Converters |
| SP6121EB | Demo Board Manual |
| SP6132H | High Voltage, 300KHz Synchronous PWM Controller |
| SP6132HEU | High Voltage, 300KHz Synchronous PWM Controller |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP612-10 | 制造商:Delphi Corporation 功能描述:TORSION SPRING |
| SP6121CN | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Low Voltage, 8 Pin Synchronous, Cntrllr 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 |
| SP6121CN/TR | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Low Voltage, 8 Pin Synchronous, Cntrllr 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 |
| SP6121CN-L | 功能描述:電壓模式 PWM 控制器 Low Voltage, 8 Pin Synchronous, Cntrllr 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 |
| SP6121CN-L/TR | 功能描述:電壓模式 PWM 控制器 Low Voltage, 8 Pin Synchronous, Cntrllr 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 |
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