參數(shù)資料
型號(hào)： LT1950
廠商： Linear Technology Corporation
英文描述： Single Switch PWM Controller with Auxiliary Boost Converter
中文描述： 單開(kāi)關(guān)PWM控制器，帶有輔助升壓轉(zhuǎn)換器
文件頁(yè)數(shù)： 14/20頁(yè)
文件大?。?/td> 285K
代理商： LT1950
LT1950
14
sn1950 1950fs
APPLICATIU
Programming Leading Edge Blank Time
For PWM controllers driving external MOSFETs, noise can
be generated during GATE rise time due to various para-
sitic effects. This noise can disturb the input to the current
sense comparator (I
SENSE
) and cause premature turn-off
of the external MOSFET. The LT1950 provides program-
mable leading edge blanking of the current sense com-
parator to avoid this effect.
Blanking is provided in 2 phases: The first phase is during
GATE rise time. GATE rise times vary depending on
MOSFET type. For this reason the LT1950 automatically
blanks the current comparator output until the “l(fā)eading
edge” of the GATE is detected. This occurs when the GATE
voltage has risen within 0.5V of the output driver supply
(V
IN2
) or has reached its clamp level of 13V. The second
phase of blanking starts immediately after “l(fā)eading edge”
has been detected. This phase is programmable using a
resistor (R
BLANK
) from the BLANK pin to ground. Typical
values for this portion of the blanking period are 110ns at
R
BLANK
= 0
up to 290ns at R
BLANK
= 75k. Figure 8 shows
blanking vs R
BLANK
. Blanking duration can be approxi-
mated as:
W
U
U
BLANKING EXTENDED
(
R
k
ns
BLANK
25
)
=
+
110
60
Figure 8. Blanking Timing Diagram
1950 F04
R
BLANK
= 0
0
< R
BLANK
< = 75k
60ns
(AUTOMATIC)
LEADING
EDGE
BLANKING
(DEFAULT)
EXTENDED
BLANKING
(PROGRAMMABLE)
EXTENDED
BLANKING
CURRENT
SENSE
DELAY
GATE
BLANKING
0
Xns
(X + 110)ns
[X + 110 + (60 R
BLANK
/25k)]ns
Programming Volt-Second Clamp
The V
SEC
pin is used to provide an adaptive maximum duty
cycle clamp for sophisticated control of the simplest
forward converter topology (single primary-side switch).
This adaptive maximum duty cycle clamp allows the use of
the smallest transformers, MOSFETs and output rectifiers
by addressing the biggest concern in single switch for-
ward converter topologies - transformer reset. The sec-
tion “Application Circuits-Forward Converter Applications”
covers transformer reset requirements and highlights the
advantages of the LT1950 adaptive maximum duty cycle
clamp. The programmable maximum duty cycle clamp is
controlled by the voltage on the V
SEC
pin. As voltage on the
V
SEC
pin increases within a specified range, maximum
duty cycle decreases. By deriving V
SEC
pin voltage from
the system input supply, a volt-second clamp is realized.
Maximum GATE output duty cycle follows a 1/X relation-
ship given by (105/V
SEC
)%. (see Maximum Duty Cycle vs
V
SEC
Voltage graph in the Typical Performance Character-
istics section). For example, if the minimum input supply
for a forward converter application is 36V, the V
SEC
pin can
be programmed with a maximum duty cycle of 75% at
1.4V. A movement of input voltage to 72V will lift the V
SEC
pin to 2.8V, resulting in a maximum duty cycle of 37.5%.
As the section on Forward Converter Applications will
show, transformer reset requirements are met with the
相關(guān)PDF資料
PDF描述
LT1950EGN Single Switch PWM Controller with Auxiliary Boost Converter
LT1950IGN Single Switch PWM Controller with Auxiliary Boost Converter
LT60400-1 Class T Fuse Blocks - 300 and 600 Volt
LT60600-1 Class T Fuse Blocks - 300 and 600 Volt
LT60030-1 Class T Fuse Blocks - 300 and 600 Volt
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT1950EGN 功能描述:IC REG CTRLR PWM CM 16-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LT1950EGN#PBF 功能描述:IC REG CTRLR PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LT1950EGN#TR 功能描述:IC REG CTRLR PWM CM 16-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LT1950EGN#TRPBF 功能描述:IC REG CTRLR PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LT1950IGN 功能描述:IC REG CTRLR PWM CM 16-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
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