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參數(shù)資料
| 型號： | SP6120 |
| 英文描述： | Fixed Frequency, Voltage Mode, Synchronous PWM Controller(固定頻率，電壓模式同步PWM（脈寬調(diào)制控制器）) |
| 中文描述： | 固定頻率，電壓模式，同步PWM控制器（固定頻率，電壓模式同步的PWM（脈寬調(diào)制控制器）） |
| 文件頁數(shù)： | 16/20頁 |
| 文件大?。?/td> | 187K |
| 代理商： | SP6120 |
16
Rev. 2/15/01
SP6120 Low Voltage, AnyFET
TM
, Synchronous, Buck Controller Copyright 2001 Sipex Corporation
P
2
)
(
)
(
1
1300
LC
P
IN
ESR
Z
CO
OUT
f
V
f
f
V
R
=
In Figure 7, 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
1
)
(
1
2
1
R
f
C
LC
P
π
=
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
1
2
20
1
f
R
C
co
π
=
Figure 8 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
f
Z1
f
P(LC)
f
Z(ESR)
f
CO
f
P1
Figure 8. Frequency response of a stable system and its
error amplifier.
Current Sense
The SP6120 allows sensing current using the
inductor, PCB trace or current-sense resistor.
Inductor-sense utilizes the voltage drop across
the ESR of the inductor, while PCB trace and
current-sense resistor introduce additional re-
sistance in series with the inductor. The resis-
tance of the sense element determines the
overcurrent protection threshold as follows,
I
LIM
= 40mV
R
SEN
R
SEN
= current-sense resistance which can be
implemented as ESR of the inductor, trace or
discrete resistor.
The maximum power dissipation on the current-
sense element is:
I
P
=
SEN
OUT
SEN
R
2
(max)
For the inductor-sense scheme shown in the
application circuit, Rs and Cs are used to repli-
cate the signal across the ESR of the inductor. Rs
and Cs can be looked at as a low pass filter
whose output represents the DC differential
voltage between the switch node and the output.
At steady state, this voltage happens to be the
output current times the ESR of the inductor. In
addition, if the following relationship is satisfied,
L
=
S
S
C
R
ESR
the output of the RsCs filter represents the exact
voltage across the ESR, including the ripple.
Since the SP6120’s hiccup overcurrent protec-
tion scheme is intended to safeguard sustained
overload conditions, the DC portion of the cur-
rent signal is more of interest. Therefore, design-
ing the RsCs time constant higher than L/ESR
provides reliable current sense against any pre-
mature triggering due to noise or any transient
conditions. Pick Rs between 10k and 100k, and
Cs can be determined by:
S
S
C
ESR
L
C
1
2
=
Here the time constant of RsCs is twice the value
of L/ESR.
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相關(guān)代理商/技術(shù)參數(shù) |
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| SP6120_05 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Voltage, AnyFETTM, Synchronous,Buck Controller Ideal for 2A to 10A, High Performance, DC-DC Power Converters |
| SP612-05 | 制造商:Delphi Corporation 功能描述:WIRE STOP |
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| SP612-08 | 制造商:Delphi Corporation 功能描述:PIVOT PIN |
| SP6120B | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Voltage, AnyFETTM, Synchronous ,Buck Controller Ideal for 2A to 10A, High Performance, DC-DC Power Converters |
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