- 您现在的位置：买卖IC网 > PDF目录14021 > LT3990IDD#TRPBF (Linear Technology)IC REG BUCK ADJ 0.35A 10DFN PDF资料下载
参数资料
| 型号： | LT3990IDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/22页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.35A 10DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.21 V ~ 25 V |
| 输入电压： | 4.2 V ~ 62 V |
| PWM 型： | 电流模式，Burst Mode? |
| 频率 - 开关： | 210kHz ~ 2.3MHz |
| 电流 - 输出： | 350mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
LT3990/LT3990-3.3/LT3990-5
APPLICATIONS INFORMATION
R1 = R2 ? OUT – 1 ?
FBResistorNetwork
The output voltage is programmed with a resistor divider
between the output and the FB pin. Choose the 1% resis-
tors according to:
? V ?
? 1.21 ?
Reference designators refer to the Block Diagram. Note
that choosing larger resistors will decrease the quiescent
current of the application circuit.
Setting the Switching Frequency
The LT3990 uses a constant frequency PWM architecture
that can be programmed to switch from 200kHz to 2.2MHz
by using a resistor tied from the RT pin to ground. A table
showing the necessary R T value for a desired switching
frequency is in Table 1.
where V IN is the typical input voltage, V OUT is the output
voltage, V D is the integrated catch diode drop (~0.7V),
and V SW is the internal switch drop (~0.5V at max load).
This equation shows that slower switching frequency is
necessary to accommodate high V IN /V OUT ratio.
Lower frequency also allows a lower dropout voltage.
The input voltage range depends on the switching fre-
quency because the LT3990 switch has finite minimum
on and off times. The switch can turn off for a minimum
of ~160ns but the minimum on-time is a strong function
of temperature. Use the minimum switch on-time curve
(see Typical Performance Characteristics) to design for
an application’s maximum temperature, while adding
about 30% for part-to-part variation. The minimum and
maximum duty cycles that can be achieved taking these
on and off times into account are:
DC MIN = f SW ? t ON(MIN)
Table 1. Switching Frequency vs R T Value
SWITCHING FREQUENCY (MHz)
0.2
0.3
0.4
0.5
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
R T VALUE (kΩ)
787
511
374
287
232
169
127
102
84.5
69.8
59
51.1
44.2
DC MAX = 1 – f SW ? t OFF(MIN)
where f SW is the switching frequency, the t ON(MIN) is the
minimum switch on-time, and the t OFF(MIN) is the minimum
switch off-time (~160ns). These equations show that
duty cycle range increases when switching frequency is
decreased.
A good choice of switching frequency should allow ad-
equate input voltage range (see next section) and keep
the inductor and capacitor values small.
Input Voltage Range
f SW(MAX) =
V OUT + V D
V IN(MIN) = – V D + V SW
OperatingFrequencyTrade-Offs
Selection of the operating frequency is a trade-off between
efficiency, component size, minimum dropout voltage and
maximum input voltage. The advantage of high frequency
operation is that smaller inductor and capacitor values may
be used. The disadvantages are lower efficiency, lower
maximum input voltage, and higher dropout voltage. The
highest acceptable switching frequency (f SW(MAX) ) for a
given application can be calculated as follows:
V OUT + V D
t ON(MIN) ( V IN – V SW + V D )
The minimum input voltage is determined by either the
LT3990’s minimum operating voltage of 4.2V or by its
maximum duty cycle (as explained in previous section).
The minimum input voltage due to duty cycle is:
1– f SW ? t OFF(MIN)
where V IN(MIN) is the minimum input voltage, V OUT is the
output voltage, V D is the catch diode drop (~0.7V), V SW
is the internal switch drop (~0.5V at max load), f SW is
the switching frequency (set by RT), and t OFF(MIN) is the
minimum switch off-time (160ns). Note that higher switch-
ing frequency will increase the minimum input voltage.
3990fa
10
相关PDF资料 |
PDF描述 |
|---|---|
| MAX6718AUKRFD3+T | IC SUPERVISOR MPU SOT23-5 |
| MAX6718AUKRFD5+T | IC SUPERVISOR MPU SOT23-5 |
| MAX6718AUKRFD2+T | IC SUPERVISOR MPU SOT23-5 |
| MAX6718AUKRDD5+T | IC SUPERVISOR MPU SOT23-5 |
| MAX6718AUKRVD1+T | IC SUPERVISOR MPU SOT23-5 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3990IMS | 制造商:LINER 制造商全称:Linear Technology 功能描述:60V, 350mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes |
| LT3990IMSE#PBF | 功能描述:IC REG BUCK ADJ 0.35A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3990IMSE#TRPBF | 功能描述:IC REG BUCK ADJ 0.35A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3990IMSE-3.3#PBF | 功能描述:IC REG BUCK ADJ 0.35A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:MIC23xxx HyperLight Load™ Regulators 标准包装:5,000 系列:HyperLight Load® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.8V 输入电压:2.7 V ~ 5.5 V PWM 型:混合物 频率 - 开关:4MHz 电流 - 输出:2A 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘，8-MLF? 包装:带卷 (TR) 供应商设备封装:8-MLF?（2x2） 产品目录页面:1094 (CN2011-ZH PDF) 其它名称:576-3303-2 |
| LT3990IMSE-3.3#TRPBF | 功能描述:IC REG BUCK ADJ 0.35A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
发布紧急采购，3分钟左右您将得到回复。