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| 型号： | LT1952EGN#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR ISO PWM CM 16-SSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 560kHz |
| 占空比： | 90% |
| 电源电压： | 9.25 V ~ 25 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
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LT1952/LT1952-1
APPLICATIONS INFORMATION
current (460μA LT1952; 400μA LT1952-1) allows a large
resistor to be connected between system input supply and
V IN . Once the part is turned on, input current increases to
drive the IC (4.5mA) and the output drivers (I DRIVE ). A large
enough capacitor is chosen at the V IN pin to prevent V IN
falling below its turn off threshold before an auxiliary winding
in the converter takes over supply to V IN . This technique
allows a simple resistor/capacitor for start-up which draws
low power from the system supply to the converter. The
values for R START and C START are given by:
R START(MAX) = (V S(MIN) – V IN ON(max) )/I START(MAX)
C START(MIN) = (I Q(MAX) + I DRIVE(MAX) ) ? t START /
V IN HYST(MIN)
Example: (LT1952)
For V S(MIN) = 36V, V IN ON(MAX) = 15.75V,
I START(MAX) = 700μA, I Q(MAX) = 5.5mA,
I DRIVE(MAX) = 5mA, V IN HYST(MIN) = 3.75V
and t START = 100μs,
R START = (36 – 15.75)/700μA = 28.9k (choose 28.7k)
C START = (5.5mA + 5mA) ? 100μs/3.75V = 0.28μF
(typically choose ≥ 1μF)
possibly exceeding the rating for the V IN pin. The zener
voltage should obey V IN ON(MAX) < V Z < 25V.
Programming Oscillator Frequency
The oscillator frequency (f OSC ) of the LT1952/LT1952-1 is
programmed using an external resistor (R OSC ) connected
between the R OSC pin and ground. Figure 5 shows typical
f OSC vs R OSC resistor values. The LT1952/LT1952-1 free-
running oscillator frequency is programmable in the range
of 100kHz to 500kHz.
Stray capacitance and potential noise pickup on the R OSC
pin should be minimized by placing the R OSC resistor as
close as possible to the R OSC pin and keeping the area of
the R OSC node as small as possible. The ground side of
the R OSC resistor should be returned directly to the (analog
ground) GND pin. R OSC can be calculated by:
R OSC = 9.125k [(4100k/f OSC ) – 1]
500
450
400
350
For system input voltages exceeding the absolute maximum
rating of the LT1952/LT1952-1 V IN pin, an external zener
should be connected from the V IN pin to ground. This
covers the condition where V IN charges past V IN ON but
the part does not turn on because SD_V SEC < 1.32V. In this
condition V IN will continue to charge towards system V IN ,
300
250
200
150
100
50
100
150
200 250
R OSC (k )
300
350
400
SYSTEM
INPUT (V S )
FROM AUXILIARY WINDING
1952 F05
Figure 5. Oscillator Frequency (f OSC ) vs R OSC
R START
V IN
(14.25V ON, 8.75V OFF) LT1952
(7.75V ON, 6.5V OFF) LT1952-1
Programming Leading Edge Blank Time
D1*
C START
–
1.32V +
*FOR V S > 25V, ZENER D1 RECOMMENDED
(V IN ON(MAX) < V Z < 25V) 1952 F04
Figure 4. Low Power Start-Up
For PWM controllers driving external MOSFETs, noise
can be generated at the source of the MOSFET during
gate rise time and some time thereafter. This noise can
potentially exceed the OC and I SENSE pin thresholds of the
LT1952/LT1952-1 to cause premature turn off of SOUT and
OUT in addition to false trigger of soft-start. The LT1952/
LT1952-1 provide programmable leading edge blanking
of the OC and I SENSE comparator outputs to avoid false
current sensing during MOSFET switching.
19521fe
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1952IGN | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin SSOP N |
| LT1952IGN#PBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT1952IGN#TR | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin SSOP N T/R |
| LT1952IGN#TRPBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT1952IGN-1 | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin SSOP N |
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