参数资料
型号: LT1767EMS8#PBF
厂商: Linear Technology
文件页数: 9/16页
文件大小: 0K
描述: IC REG BUCK ADJ 1.5A 8MSOP
标准包装: 50
类型: 降压(降压)
输出类型: 可调式
输出数: 1
输出电压: 1.2 V ~ 20 V
输入电压: 3 V ~ 25 V
PWM 型: 电流模式
频率 - 开关: 1.25MHz
电流 - 输出: 1.5A
同步整流器:
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 8-TSSOP,8-MSOP(0.118",3.00mm 宽)
包装: 管件
供应商设备封装: 8-MSOP
产品目录页面: 1329 (CN2011-ZH PDF)
LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
APPLICATIO N S I N FOR M ATIO N
saturation of the inductor. In these applications, the
soft-start circuit shown in Figure 10 should be used.
2. Calculate peak inductor current at full load current to
ensure that the inductor will not saturate. Peak current
can be significantly higher than output current,
especially with smaller inductors and lighter loads, so
don’t omit this step. Powdered iron cores are forgiving
because they saturate softly, whereas ferrite cores
saturate abruptly. Other core materials fall somewhere
4. After making an initial choice, consider the secondary
things like output voltage ripple, second sourcing, etc.
Use the experts in the Linear Technology’s applica-
tions department if you feel uncertain about the final
choice. They have experience with a wide range of
inductor types and can tell you about the latest devel-
opments in low profile, surface mounting, etc.
CATCH DIODE
in between.
I PEAK = I OUT +
V OUT ( V IN ? V OUT
2 ( L )( f )( V IN )
)
The suggested catch diode (D1) is a UPS120 Schottky, or
its Motorola equivalent, MBRM120LTI/MBRM130LTI. It
is rated at 2A average forward current and 20V/30V
reverse voltage. Typical forward voltage is 0.5V at 1A. The
diode conducts current only during switch off time. Peak
V IN = Maximum input voltage
f = Switching frequency, 1.25MHz
reverse voltage is equal to regulator input voltage. Average
forward current in normal operation can be calculated
I D ( ) =
3.  Decideifthedesigncantoleratean“open”coregeom-
etry like a rod or barrel, which have high magnetic field
radiation, or whether it needs a closed core like a toroid
to prevent EMI problems. This is a tough decision
from:
AVG
I OUT ( V IN ? V OUT
V IN
)
because the rods or barrels are temptingly cheap and
small and there are no helpful guidelines to calculate
when the magnetic field radiation will be a problem.
Table 3
PART NUMBER  VALUE (uH)  I SAT (Amps)  DCR ( ? ) HEIGHT (mm)
Coiltronics
TP1-2R2 2.2 1.3 0.188 1.8
BOOST PIN
For most applications, the boost components are a 0.1 μ F
capacitor and a CMDSH-3 diode. The anode is typically
connected to the regulated output voltage to generate a
voltage approximately V OUT above V IN to drive the output
stage. The output driver requires at least 2.7V of head-
TP2-2R2
TP3-4R7
TP4- 100
2.2
4.7
10
1.5
1.5
1.5
0.111
0.181
0.146
2.2
2.2
3.0
room throughout the on period to keep the switch fully
saturated. However, the output stage discharges the boost
capacitor during the on time. If the output voltage is less
Murata
than 3.3V, it is recommended that an alternate boost
LQH1C1R0M04
LQH3C1R0M24
LQH3C2R2M24
LQH4C1R5M04
1.0
1.0
2.2
1.5
0.51
1.0
0.79
1.0
0.28
0.06
0.1
0.09
1.8
2.0
2.0
2.6
supply is used. The boost diode can be connected to the
input, although, care must be taken to prevent the 2x V IN
boost voltage from exceeding the BOOST pin absolute
maximum rating. The additional voltage across the switch
Sumida
driver also increases power loss, reducing efficiency. If
CD73- 100
CDRH4D18-2R2
CDRH5D18-6R2
CDRH5D28-100
10
2.2
6.2
10
1.44
1.32
1.4
1.3
0.080
0.058
0.071
0.048
3.5
1.8
1.8
2.8
available, an independent supply can be used with a local
bypass capacitor.
A 0.1 μ F boost capacitor is recommended for most appli-
cations. Almost any type of film or ceramic capacitor is
sn1767 1767fas
9
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