参数资料
| 型号： | LT1683EG#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/26页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 20-SSOP |
| 标准包装： | 66 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 46% |
| 电源电压： | 4 V ~ 20 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 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： | 20-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1328 (CN2011-ZH PDF) |
LT1683
APPLICATIONS INFORMATION
C T (nF) =
C T (nF) =
ReducingEMIfromswitchingpowersupplieshastradition-
ally invoked fear in designers. Many switchers are designed
solely on efficiency and as such produce waveforms filled
with high frequency harmonics that then propagate through
the rest of the system.
The LT1683 provides control over two of the more impor-
tant variables for controlling EMI with switching inductive
loads: switch voltage slew rate and switch current slew
rate. The use of this part will reduce noise and EMI over
conventional switch mode controllers. Because these
variables are under control, a supply built with this part
will exhibit far less tendency to create EMI and less chance
of encountering problems during production.
It is beyond the scope of this data sheet to get into EMI
fundamentals. Application Note 70 contains much informa-
tion concerning noise in switching regulators and should
be consulted.
Oscillator Frequency
The oscillator determines the switching frequency and
therefore the fundamental positioning of all harmonics.
The use of good quality external components is important
to ensure oscillator frequency stability. The oscillator is of
a sawtooth design. A current defined by external resistor,
R T , is used to charge and discharge the capacitor, C T . The
discharge rate is approximately ten times the charge rate.
By allowing the user to have control over both compo-
nents, trimming of oscillator frequency can be more easily
achieved.
The external capacitance C T is chosen by:
2180
f(kHz) ? R T (k ? )
where f is the desired oscillator frequency in kHz. For R T
equal to 16.9k, this simplifies to:
129
f(kHz)
Nominally R T should be 16.9k. Since it sets up current, its
temperature coefficient should be selected to compliment
the capacitor. Ideally, both should have low temperature
coefficients.
Oscillator frequency is important for noise reduction in
two ways. First the lower the oscillator frequency the
lower the waveform’s harmonics, making it easier to filter
them. Second the oscillator will control the placement of
the output voltage harmonics which can aid in specific
problems where you might be trying to avoid a certain
frequency bandwidth.
Oscillator Sync
If a more precise frequency is desired (e.g., to accurately
place harmonics) the oscillator can be synchronized to
an external clock. Set the RC timing components for an
oscillator frequency 10% lower than the desired sync
frequency.
Drive the SYNC pin with a square wave (with greater than
1.4V amplitude). The rising edge of the sync square wave
will initiate clock discharge. The sync pulse should have
a minimum pulse width of 0.5μs.
Be careful in sync’ing to frequencies much different
from the part since the internal oscillator charge slope
determines slope compensation. It would be possible to
get into subharmonic oscillation if the sync doesn’t al-
low for the charge cycle of the capacitor to initiate slope
compensation. In general, this will not be a problem until
the sync frequency is greater than 1.5 times the oscillator
free-run frequency.
Slew Rate Setting
The primary reason to use this part is to gain advantage
of lower EMI and noise due to slew control. The rolloff in
higher frequency harmonics has its theoretical basis with
two primary components. First, the clock frequency sets
the fundamental positioning of harmonics and second, the
associated normal frequency rolloff of harmonics.
e.g., C T = 1.29nF for f = 100kHz
1683fd
13
相关PDF资料 |
PDF描述 |
|---|---|
| LT1725IGN#TR | IC REG CTRLR FLYBK ISO CM 16SSOP |
| LT1737IGN#PBF | IC REG CTRLR FLYBK ISO CM 16SSOP |
| LT1738EG#PBF | IC REG CTRLR PWM CM 20-SSOP |
| LT1761IS5-2.5#TRMPBF | IC REG LDO 2.5V .1A TSOT23-5 |
| LT1762EMS8-3.3#TR | IC REG LDO 3.3V .15A 8MSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1683IG | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#PBF | 功能描述:IC REG CTRLR PWM CM 20-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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#TR | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#TRPBF | 功能描述:IC REG CTRLR PWM CM 20-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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1684 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Ring Tone Generator |
发布紧急采购，3分钟左右您将得到回复。