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參數(shù)資料
| 型號： | FAN6520AMX |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Single Synchronous Buck PWM Controller |
| 中文描述： | 1 A SWITCHING CONTROLLER, 340 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | MS-012AA, SOIC-8 |
| 文件頁數(shù)： | 9/15頁 |
| 文件大?。?/td> | 580K |
| 代理商： | FAN6520AMX |
PRODUCT SPECIFICATION
FAN6520A
REV. 1.0.2 8/26/04
9
Figure 8. Asymptotic Bode Plot of Converter Gain
An output capacitor is required to filter the output and supply
the load transient current. The filtering requirements are a
function of the switching frequency and the ripple current.
The load transient requirements are a function of the slew
rate (di/dt) and the magnitude of the transient load current.
These requirements are generally met with a mix of capaci-
tors and careful layout.
Component Selection
Output Capacitors (C
OUT
)
Modern components and loads are capable of producing
transient load rates above 1A/ns. High frequency capacitors
initially supply the transient and slow the current load rate
seen by the bulk capacitors. Effective Series Resistance
(ESR) and voltage rating are typically the prime consider-
ations for the bulk filter capacitors, rather than actual capaci-
tance requirements. High-frequency decoupling capacitors
should be placed as close to the power pins of the load as
physically possible. Be careful not to add inductance in the
circuit board wiring that could cancel the performance of
these low inductance components. Consult with the load
manufacturer on specific decoupling requirements. Use only
specialized low-ESR capacitors intended for switching-
regulator applications for the bulk capacitors. The bulk
capacitor’s ESR will determine the output ripple voltage and
the initial voltage drop after a high slew-rate transient. An
aluminum electrolytic capacitor’s ESR value is related to the
case size with lower ESR available in larger case sizes. How-
ever, the Equivalent Series Inductance (ESL) of these capac-
itors increases with case size and can reduce the usefulness
of the capacitor to high slew-rate transient loading. Unfortu-
nately, ESL is not a specified parameter. Work with your
capacitor supplier and measure the capacitor’s impedance
with frequency to select a suitable component. In most cases,
multiple electrolytic capacitors of small case size
perform better than a single large case capacitor.
Output Inductor (L
OUT
)
The output inductor is selected to meet the output voltage
ripple requirements and minimize the converter’s response
time to the load transient. The inductor value determines the
converter’s ripple current and the ripple voltage is a function
of the ripple current. The ripple voltage (
V) and current
(
I) are approximated by the following equations:
Increasing the inductance value reduces the ripple current
and voltage. However, a large inductance value reduces the
converter’s ability to quickly respond to a load transient. One
of the parameters limiting the converter’s response to a load
transient is the time required to change the inductor current.
Given a sufficiently fast control loop design, the FAN6520A
will provide either 0% or 100% duty cycle in response to a
load transient. The response time is the time required to
slew the inductor current from an initial current value to the
transient current level. During this interval the difference
between the inductor current and the transient current level
must be supplied by the output capacitor. Minimizing the
response time can minimize the output capacitance required.
Depending upon the whether there is a load application or a
load removal, the response time to a load transient (I
STEP
) is
different. The following equations give the approximate
response time interval for application and removal of a
transient load:
where T
RISE
is the response time to the application of a
positive I
STEP
, and T
FALL
is the response time to a load
removal (negative I
STEP
). The worst case response time can
be either at the application or removal of load. Be sure to
check both of these equations at the minimum and maximum
output levels for the worst case response time.
Input Capacitor Selection
Use a mix of input bypass capacitors to control the voltage
overshoot across the MOSFETs. Use small ceramic capaci-
tors for high-frequency decoupling and bulk capacitors to
supply the current needed each time Q1 turns on. Place the
small ceramic capacitors physically close to the MOSFETs
and between the drain of Q1 and the source of Q2. The
important parameters for the bulk input capacitor are the
voltage rating and the RMS current rating. For reliable
operation, select the bulk capacitor with voltage and current
ratings above the maximum input voltage and the largest
100
80
60
40
20
0
-20
-40
-60
10
100
1K
10K
100K
FREQUENCY (Hz)
OPEN LOOP
ERROR AMP GAIN
COMPENSATION
GAIN
CLOSED LOOP
GAIN
MODULATOR
GAIN
20LOG
(V
IN
/DV
OSC
)
20LOG
(R
2
/R
1
)
F
Z1
F
Z2
F
P1
F
LC
F
ESR
F
P2
G
1M
10M
I
V
SW
V
OUT
L
×
–
----F
=
V
≈
ESR
×
I (1)
T
RISE
L
I
V
OUT
–
V
IN
-----------------------------
=
T
FALL
L
------------------------
I
V
OUT
=
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FAN6520AMX_Q | 功能描述:電壓模式 PWM 控制器 Single Synchronous Buck PWM Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(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 |
| FAN6520AMXCT | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| FAN6520B | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Single Synchronous Buck PWM Controller |
| FAN6520BIM | 功能描述:電壓模式 PWM 控制器 ANG FG SynchBuck Regulator- 8ld RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(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 |
| FAN6520BIMX | 功能描述:電壓模式 PWM 控制器 ANG FG SynchBuck Regulator- 8ld RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(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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