參數(shù)資料
型號(hào)： FSDH0270RNB
廠商： FAIRCHILD SEMICONDUCTOR CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： Green Mode Fairchild Power Switch (FPSTM)
中文描述： 8 A SWITCHING REGULATOR, 108 kHz SWITCHING FREQ-MAX, PDIP8
封裝： MS-001BA, DIP-8
文件頁(yè)數(shù)： 10/19頁(yè)
文件大?。?/td> 608K
代理商： FSDH0270RNB
10
www.fairchildsemi.com
FSDH0170RNB/FSDH0270RNB/FSDH0370RNB Rev. 1.0.2
F
Figure 6. Over Load Protection (OLP)
4.2 Thermal Shutdown (TSD)
: The Sense FET and the
control IC are integrated, making it easier for the control
IC to detect the temperature of the Sense FET. When
the temperature exceeds approximately 140
°
C, thermal
shutdown is activated.
4.3 Over Voltage Protection (OVP):
In the event of a
malfunction in the secondary side feedback circuit, or an
open feedback loop caused by a soldering defect, the
current through the optocoupler transistor becomes
almost zero (refer to Figure 5). Then, V
FB
climbs up in a
similar manner to the overload situation, forcing the
preset maximum current to be supplied to the SMPS
until the overload protection is activated. Because
excess energy is provided to the output, the output
voltage may exceed the rated voltage before the
overload protection is activated, resulting in the
breakdown of the devices in the secondary side. In order
to prevent this situation, an Over Voltage Protection
(OVP) circuit is employed. In general, V
CC
is proportional
to the output voltage and the FPS uses V
CC
instead of
directly monitoring the output voltage. If V
CC
exceeds
19V, OVP circuit is activated resulting in termination of
the switching operation. In order to avoid undesired
activation of OVP during normal operation, Vcc should
be designed to be below 19V.
5. Soft Start
: The FPS has an internal soft start circuit
that slowly increases the Sense FET current after startup
as shown in Figure 7. The typical soft start time is 10ms,
where progressive increments of the Sense FET current
are allowed during the start-up phase. The pulse width to
the power switching device is progressively increased to
establish the correct working conditions for transformers,
inductors, and capacitors. The voltage on the output
capacitors is progressively increased with the intention
of smoothly establishing the required output voltage.
This also helps to prevent transformer saturation and
reduce the stress on the secondary diode during startup.
Figure 7. Soft Start Function
6. Burst Operation:
In order to minimize power
dissipation in standby mode, the FPS enters burst mode
operation. Feedback voltage decreases as the load
decreases and as shown in Figure 8, the device
automatically enters burst mode when the feedback
voltage drops below V
BURH
(typically 600mV). Switching
still continues until the feedback voltage drops below
V
BURL
(typically 400mV). At this point switching stops
and the output voltage start to drop at a rate dependent
on the standby current load. This causes the feedback
voltage to rise. Once it passes V
BURH
, switching
resumes. The feedback voltage then falls and the
process is repeated. Burst mode operation alternately
enables and disables switching of the Sense FET and
reduces switching loss in standby mode.
Figure 8. Burst Operation Function
7. Frequency Modulation
: Modulating the switching
frequency of a switched power supply can reduce EMI.
Frequency modulation can reduce EMI by spreading the
energy over a wider frequency range than the bandwidth
measured by the EMI test equipment. The amount of
EMI reduction is directly related to the depth of the
reference frequency. As can be seen in Figure 9, the
frequency changes from 97KHz to 103KHz in 4ms for
the 700V FPS series. Frequency modulation allows the
use of a cost effective inductor instead of an AC input
mode choke to satisfy the requirements of world wide
EMI limits.
V
FB
t
3V
6V
Over Load Protection
t
12
= C
FB
×
(V(t
2
)-V(t
1
)) / I
DELAY
t
1
t
2
V
t
V
V
t
V
A
I
I
t
V
t
V
C
t
DELAY
DELAY
FB
6
)
(
,
3
)
(
,
5
;
)
(
)
(
2
1
1
2
12
=
=
=
=
μ
DRAIN
GND
R
sense
#6,7,8
#1
I
LIM
5V
V
BURH
Switching
OFF
Current
Waveform
Burst
Operation
Normal
Operation
V
FB
V
BURL
Switching
OFF
Burst
Operation
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
FSDH0370RNB 功能描述:電源開(kāi)關(guān) IC - 配電 FPS FOR DVDP/STB RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5
FSDH0565 制造商:FAIRCHILD 制造商全稱(chēng):Fairchild Semiconductor 功能描述:Green Mode Fairchild Power Switch (FPSTM)
FSDH321 功能描述:電源開(kāi)關(guān) IC - 配電 FPS for DVDP/STB RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5
FSDH321_04 制造商:FAIRCHILD 制造商全稱(chēng):Fairchild Semiconductor 功能描述:Green Mode Fairchild Power Switch
FSDH321L 功能描述:電源開(kāi)關(guān) IC - 配電 FPS for DVDP/STB RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5
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