参数资料
型号: MIC29303BU TR
厂商: Micrel Inc
文件页数: 20/25页
文件大小: 0K
描述: IC REG LDO ADJ 3A TO-263-5
标准包装: 750
稳压器拓扑结构: 正,可调式
输出电压: 1.25 V ~ 26 V
输入电压: 最高 26V
电压 - 压降(标准): 0.37V @ 3A
稳压器数量: 1
电流 - 输出: 3A
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: TO-263-6,D²Pak(5 引线+接片),TO-263BA
供应商设备封装: TO-263-5
包装: 带卷 (TR)
其它名称: MIC29303BUTR
MIC29303BUTR-ND
Micrel, Inc.
For example, given an expected maximum ambient
temperature (T A ) of 75 ° C with V IN = 3.3V, V OUT = 2.5V,
and I OUT = 1.5A, first calculate the expected P D using
Equation 3:
P D =(3.3V–2.5V)1.5A–(3.3V)(0.016A)=1.1472W
Eq. 3
Next, calcualte the junction temperature for the expected
power dissipation.
MIC29150/29300/29500/29750
Where the regulator is powered from a source with high
AC impedance, a 0.1μF capacitor connected between
Input and GND is recommended. This capacitor should
have good characteristics to above 250kHz.
Minimum Load Current
The MIC29150–29750 regulators are specified between
finite loads. If the output current is too small, leakage
currents dominate and the output voltage rises. The
following minimum load current swamps any expected
leakage current across the operating temperature range,
as shown in Table 2:
T J =( θ JA ×P D )+T A =(56 ° C/W×1.1472W)+75 ° C
=139.24 ° C
Eq. 4
Device
MIC29150
MIC29300
Minimum Load
5mA
7mA
Now determine the maximum power dissipation allowed
that would not exceed the IC’s maximum junction
MIC29500
MIC29750
10mA
10mA
temperature (125 ° C) without the useof a heat sink by:
Table 2. Minimum Load Currents
P D(MAX) = (T J(MAX) –T A )/ θ JA
= (125 ° C–75 ° C)/(56 ° C/W) = 0.893W
Capacitor Requirements
Eq. 5
Adjustable Regulator Design
The adjustable regulator versions, MIC29xx2 and
MIC29xx3, allow programming the output voltage
anywhere between 1.25V and the 25V. Two resistors are
used. The resistor values are calculated by Equation 6:
R 1 = R 2 × ? ? OUT ? 1 ? ?
For stability and minimum output noise, a capacitor on
the regulator output is necessary. The value of this
capacitor is dependent upon the output current; lower
currents allow smaller capacitors. The
? V ?
? 1.240 ?
Eq. 6
MIC29150/29300/29500/29750 regulators are stable
with the following minimum capacitor values at full load,
as noted in Table 1:
where V OUT is the desired output voltage. Figure 4 shows
component definition. Applications with widely varying
load currents may scale the resistors to draw the
Device
MIC29150
MIC29300
MIC29500
MIC29750
Full Load Capacitor
10μF
10μF
10μF
22μF
minimum load current required for proper operation (see
“Minimum Load Current” sub-section).
Table 1. Minimum Capacitor Values at Full Load
This capacitor need not be an expensive low ESR type:
aluminum electrolytics are adequate. In fact, extremely
low ESR capacitors may contribute to instability.
Tantalum capacitors are recommended for systems
where fast load transient response is important.
December 2012
20
M9999-122012-B
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