参数资料
型号: LMR10510YSDE/NOPB
厂商: National Semiconductor
文件页数: 10/26页
文件大小: 0K
描述: IC REG BUCK ADJ 1A 6LLP
特色产品: SIMPLE SWITCHER? DC/DC Converters
标准包装: 1
系列: SIMPLE SWITCHER®
类型: 降压(降压)
输出类型: 可调式
输出数: 1
输出电压: 0.6 V ~ 4.5 V
输入电压: 3 V ~ 5.5 V
PWM 型: 电流模式
频率 - 开关: 3MHz
电流 - 输出: 1A
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: 6-WDFN 裸露焊盘
包装: 标准包装
供应商设备封装: 6-LLP-EP(3x3)
其它名称: LMR10510YSDE/NOPBDKR
SNVS727B – OCTOBER 2011 – REVISED APRIL 2013
Design Guide
INDUCTOR SELECTION
The Duty Cycle (D) can be approximated quickly using the ratio of output voltage (V O ) to input voltage (V IN ):
D=
V OUT
V IN
The catch diode (D1) forward voltage drop and the voltage drop across the internal PMOS must be included to
calculate a more accurate duty cycle. Calculate D by using the following formula:
D=
V OUT + V D
V IN + V D - V SW
V SW can be approximated by:
V SW = I OUT x R DSON
The diode forward drop (V D ) can range from 0.3V to 0.7V depending on the quality of the diode. The lower the
V D , the higher the operating efficiency of the converter. The inductor value determines the output ripple current.
Lower inductor values decrease the size of the inductor, but increase the output ripple current. An increase in the
inductor value will decrease the output ripple current.
One must ensure that the minimum current limit (1.2A) is not exceeded, so the peak current in the inductor must
be calculated. The peak current (I LPK ) in the inductor is calculated by:
I LPK = I OUT + Δ i L
' i L
I OUT
V IN - V OUT
L
V OUT
L
DT S
T S
t
Figure 23. Inductor Current
V IN - V OUT
L
=
2 ' i L
DT S
In general,
Δ i L = 0.1 x (I OUT ) → 0.2 x (I OUT )
If Δ i L = 20% of 1A, the peak current in the inductor will be 1.2A. The minimum specified current limit over all
operating conditions is 1.2A. One can either reduce Δ i L , or make the engineering judgment that zero margin will
be safe enough. The typical current limit is 1.75A.
The LMR10510 operates at frequencies allowing the use of ceramic output capacitors without compromising
transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing output ripple.
See the OUTPUT CAPACITOR section for more details on calculating output voltage ripple. Now that the ripple
current is determined, the inductance is calculated by:
L=
DT S
2 ' i L
x (V IN - V OUT )
where
?
T S =
1
f S
10
Product Folder Links: LMR10510
Copyright ? 2011–2013, Texas Instruments Incorporated
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