欧美成人免费电影,国产欧美一区二区三区精品酒店,精品国产a毛片,色网在线免费观看

參數(shù)資料
型號: FAN5234
廠商: Fairchild Semiconductor Corporation
英文描述: Terminal Block; Pitch Spacing:0.197"; Mounting Type:PC Board RoHS Compliant: Yes
中文描述: 移動友好的PWM / PFM控制器
文件頁數(shù): 7/15頁
文件大小: 537K
代理商: FAN5234
FAN5234
PRODUCT SPECIFICATION
REV. 1.0.10 5/3/04
7
Figure 4. Current Limit / Summing Circuits
LDRV
PGND
ISNS
in +
in –
2.5V
ILIM det.
R
SENSE
SS
1.5M
C
SS
VSEN
V to I
Reference and
Soft Start
17pf
ISNS
S/H
TO PWM COMP
4.14K
300K
ISNS
0.17pf
I2 =
ILIM*11.2
ILIM
0.9V
R
ILIM
ILIM
The hysteretic comparator causes HDRV turn-on when the
output voltage (at VSEN) falls below the lower threshold
(10mV below VREF) and terminates the PFM signal when
VSEN rises over the higher threshold (5mV above VREF).
The switching frequency is primarily a function of:
1.
Spread between the two hysteretic thresholds
2.
I
LOAD
Output Inductor and Capacitor ESR
3.
A transition back to PWM (Continuous Conduction Mode or
CCM) mode occurs when the inductor current rises suffi-
ciently to stay positive for 8 consecutive cycles. This occurs
when:
where
V
HYSTERESIS
= 15mV and ESR is the equivalent
series resistance of C
OUT
.
Because of the different control mechanisms, the value of the
load current where transition into PWM operation takes
place is typically higher compared to the load level at which
transition into hysteretic mode occurs. Hysteretic mode
can be disabled by setting the FPWM pin HIGH.
Current Processing Section
The following discussion refers to Figure 4.
The current through R
SENSE
resistor (ISNS) is sampled
shortly after Q2 is turned on. That current is held, and
summed with the output of the error amplifier. This effec-
tively creates a current mode control loop. The resistor con-
nected to ISNS pin (R
SENSE
) sets the gain in the current
feedback loop. For stable operation, the voltage induced by
the current feedback at the PWM comparator input should be
set to 30% of the ramp amplitude at maximum load currrent
and line voltage. The following expression estimates the rec-
ommended value of R
SENSE
as a function of the maximum
load current (I
LOAD(MAX)
) and the value of the MOSFET’s
R
DS(ON)
:
R
SENSE
must, however, be kept higher than:
Setting the Current Limit
A ratio of ISNS is also compared to the current established
when a 0.9 V internal reference drives the ILIM pin:
Since the tolerance on the current limit is largely dependent
on the ratio of the external resistors it is fairly accurate if the
voltage drop on the Switching Node side of R
SENSE
is an
accurate representation of the load current. When using the
MOSFET as the sensing element, the variation of R
DS(ON)
causes proportional variation in the ISNS. This value not
only varies from device to device, but also has a typical
junction temperature coefficient of about 0.4%/°C (consult
the MOSFET datasheet for actual values), so the actual
current limit set point will decrease propotional to increasing
MOSFET die temperature. A factor of 1.6 in the current
limit setpoint should compensate for all MOSFET R
DS(ON)
variations, assuming the MOSFET’s heat sinking will keep
its operating die temperature below 125°C.
I
LOAD CCM
)
V
----------2 ESR
=
(3)
R
SENSE
I
)
R
DS ON
V
IN MAX
)
×
4.1K
×
0.125
×
)
×
--------30%
100
=
(4a)
R
SENSE
I
--------------------150
R
)
×
μ
A
100
=
(4b)
(5)
R
ILIM
I
LIMIT
---11.2
100
-------------+
R
R
DS ON
(
)
)
×
=
相關(guān)PDF資料
PDF描述
FAN5235 System Electronics Regulator for Mobile PCs
FAN5236MTC Dual Mobile-Friendly DDR / Dual-output PWM Controller
FAN5236MTCX Dual Mobile-Friendly DDR / Dual-output PWM Controller
FAN5236QSC Dual Mobile-Friendly DDR / Dual-output PWM Controller
FAN5236QSCX Dual Mobile-Friendly DDR / Dual-output PWM Controller
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
FAN5234_10 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Dual Mobile-Friendly PWM / PFM Controller
FAN5234MTC 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 PWM Controller 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
FAN5234MTC_Q 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 PWM Controller 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
FAN5234MTCX 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 PWM Controller 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
FAN5234QSC 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 PWM Controller 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
主站蜘蛛池模板: 永寿县| 安远县| 军事| 洪雅县| 阳曲县| 新沂市| 唐河县| 武鸣县| 宁国市| 克东县| 宜君县| 威远县| 阿城市| 沙河市| 远安县| 武邑县| 天气| 阳信县| 大兴区| 城口县| 巴彦县| 于都县| 临清市| 永德县| 阿拉善盟| 日喀则市| 鄂托克旗| 余庆县| 澎湖县| 静安区| 通榆县| 太和县| 邯郸市| 五台县| 迭部县| 蒲江县| 张家港市| 衡水市| 沅江市| 岑溪市| 呼伦贝尔市|