- 您现在的位置：买卖IC网 > PDF目录1823 > LT1940EFE#TRPBF (Linear Technology)IC REG BUCK ADJ 1.4A DL 16TSSOP PDF资料下载
参数资料
| 型号： | LT1940EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.4A DL 16TSSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 1.25 V ~ 22 V |
| 输入电压： | 3.6 V ~ 25 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1.1MHz |
| 电流 - 输出： | 1.4A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-TSSOP-EP |
LT1940/LT1940L
APPLICATIO S I FOR ATIO
The maximum input voltage is determined by the absolute
maximum ratings of the V IN and BOOST pins and by the
minimum duty cycle DC MIN = 0.15:
V INMAX = (V OUT + V D )/DC MIN – V D + V SW .
This limits the maximum input voltage to ~14V with
V OUT = 1.8V and ~19V with V OUT = 2.5V. Note that this is
a restriction on the operating input voltage; the circuit will
tolerate transient inputs up to the absolute maximum
rating. For the LT1940L, the maximum input voltage is 7V.
Inductor Selection and Maximum Output Current
A good first choice for the inductor value is:
L = (V OUT + V D )/1.2
where V D is the voltage drop of the catch diode (~0.4V) and
L is in μ H. With this value the maximum load current will
be ~1.4A, independent of input voltage. The inductor’s
RMS current rating must be greater than your maximum
load current and its saturation current should be about
30% higher. To keep efficiency high, the series resistance
(DCR) should be less than 0.1 ? . Table 1 lists several
vendors and types that are suitable.
Of course, such a simple design guide will not always
result in the optimum inductor for your application. A
larger value provides a slightly higher maximum load
current, and will reduce the output voltage ripple. If your
load is lower than 1.4A, then you can decrease the value of
the inductor and operate with higher ripple current. This
allows you to use a physically smaller inductor, or one with
a lower DCR resulting in higher efficiency. Be aware that if
the inductance differs from the simple rule above, then the
maximum load current will depend on input voltage. There
are several graphs in the Typical Performance Character-
istics section of this data sheet that show the maximum
load current as a function of input voltage and inductor
value for several popular output voltages. Also, low
inductance may result in discontinuous mode operation,
which is okay, but further reduces maximum load current.
For details of maximum output current and discontinuous
mode operation, see Linear Technology Application
Note 44. Finally, for duty cycles greater than 50%
(V OUT /V IN < 0.5), there is a minimum inductance required
to avoid subharmonic oscillations. See AN19. The discus-
sion below assumes continuous inductor current.
The current in the inductor is a triangle wave with an
average value equal to the load current. The peak switch
current is equal to the output current plus half the peak-to-
peak inductor ripple current. The LT1940 limits its switch
current in order to protect itself and the system from
overload faults. Therefore, the maximum output current
that the LT1940 will deliver depends on the current limit,
the inductor value, and the input and output voltages. L is
chosen based on output current requirements, output
voltage ripple requirements, size restrictions and effi-
ciency goals.
When the switch is off, the inductor sees the output
voltage plus the catch diode drop. This gives the peak-to-
peak ripple current in the inductor:
? I L = (1 – DC)(V OUT + V D )/(L ? f)
where f is the switching frequency of the LT1940 and L is
the value of the inductor. The peak inductor and switch
current is
I SWPK = I LPK = I OUT + ? I L /2.
To maintain output regulation, this peak current must be
less than the LT1940’s switch current limit I LIM . I LIM is at
least 1.8A at low duty cycle and decreases linearly to 1.5A
at DC = 0.8. The maximum output current is a function of
the chosen inductor value:
I OUTMAX = I LIM – ? I L /2 = 1.8A ? (1 – 0.21 ? DC) – ? I L /2
If the inductor value is chosen so that the ripple current is
small, then the available output current will be near the
switch current limit.
One approach to choosing the inductor is to start with the
simple rule given above, look at the available inductors,
and choose one to meet cost or space goals. Then use
these equations to check that the LT1940 will be able to
deliver the required output current. Note again that these
equations assume that the inductor current is continuous.
Discontinuous operation occurs when I OUT is less than
? I L /2 as calculated above.
1940fa
8
相关PDF资料 |
PDF描述 |
|---|---|
| LT1941EFE#TRPBF | IC REG MULTI CONFIG TRPL 28TSSOP |
| LT1942EUF#TRPBF | IC REG SW QUAD TFT LCD 24-QFN |
| LT1943EFE#TRPBF | IC REG SW QUAD TFT LCD 28-TSSOP |
| LT1944-1EMS#TR | IC REG BST ADJ 0.1A/175MA 10MSOP |
| LT1945IMS#TRPBF | IC REG MULTI CONFIG ADJ 10MSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1940LEFE | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP RoHS:否 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 |
| LT1940LEFE#PBF | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP 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 |
| LT1940LEFE#TR | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP RoHS:否 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 |
| LT1940LEFE#TRPBF | 功能描述:IC REG BUCK ADJ 1.4A DL 16TSSOP 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 |
| LT1940LEFEPBF | 制造商:Linear Technology 功能描述:Sw. Regulator Dual 1.4A 1.1MHz 7V TSSOP |
发布紧急采购，3分钟左右您将得到回复。