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| 型号： | LT1912EDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2A 10DFN |
| 标准包装： | 121 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.79 V ~ 20 V |
| 输入电压： | 3.6 V ~ 36 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz ~ 500kHz |
| 电流 - 输出： | 2A |
| 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： | 管件 |
| 供应商设备封装： | 10-DFN（3x3） |
| 产品目录页面： | 1329 (CN2011-ZH PDF) |
LT1912
APPLICATIONS INFORMATION
R1 = R2 ? OUT – 1 ?
f SW ( MAX ) =
V IN ( MIN ) =
– V D + V SW
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 ?
? 0.79V ?
Reference designators refer to the Block Diagram.
Setting the Switching Frequency
The LT1912 uses a constant frequency PWM architecture
that can be programmed to switch from 200kHz to 500kHz
by using a resistor tied from the R T pin to ground. A table
showing the necessary R T value for a desired switching
frequency is in Figure 1.
SWITCHING FREQUENCY (kHz) R T VALUE (kΩ)
200 187
300 121
400 88.7
500 68.1
Figure 1. Switching Frequency vs R T Value
Operating Frequency Trade-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 D + V OUT
t ON ( MIN ) ( V D + V IN – V SW )
where V IN is the typical input voltage, V OUT is the output
voltage, V D is the catch diode drop (~0.5V) and V SW is the
internal switch drop (~0.5V at max load). This equation
shows that slower switching frequency is necessary to
safely accommodate high V IN /V OUT ratio. Also, as shown
in the next section, lower frequency allows a lower dropout
voltage. The reason input voltage range depends on the
switching frequency is because the LT1912 switch has
finite minimum on and off times. The switch can turn on
for a minimum of ~150ns and turn off for a minimum of
~150ns. Typical minimum on time at 25°C is 80ns. This
means that the minimum and maximum duty cycles are:
DC MIN = f SW t ON ( MIN )
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 (~150ns), and the t OFF(MIN) is
the minimum switch off time (~150ns). 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
The maximum input voltage for LT1912 applications
depends on switching frequency, the Absolute Maximum
Ratings of the V IN and BOOST pins, and the operating mode.
While the output is in start-up, short-circuit, or other
overload conditions, the switching frequency should be
chosen according to the following equation.
V OUT + V D
1– f SW t OFF ( MIN )
where V IN(MAX) is the maximum operating input voltage,
V OUT is the output voltage, V D is the catch diode drop
(~0.5V), V SW is the internal switch drop (~0.5V at max
load), f SW is the switching frequency (set by R T ), and
t ON(MIN) is the minimum switch on time (~150ns). Note that
a higher switching frequency will depress the maximum
operating input voltage. Conversely, a lower switching
frequency will be necessary to achieve safe operation at
high input voltages.
If the output is in regulation and no short-circuit, start-
up, or overload events are expected, then input voltage
transients of up to 36V are acceptable regardless of the
switching frequency. In this mode, the LT1912 may enter
1912fa
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1912EDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 2A, 500kHz Step-Down Switching Regulator |
| LT1912EMSE#PBF | 功能描述:IC REG BUCK ADJ 2A 10MSOP 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:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT1912EMSE#TRPBF | 功能描述:IC REG BUCK ADJ 2A 10MSOP 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 |
| LT1912EMSEPBF | 制造商:Linear Technology 功能描述:2A, 500kHz Step-Down Regulator LT1912EM |
| LT1912EMSE-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 2A, 500kHz Step-Down Switching Regulator |
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