?/DIV>
=
R
DS(ON)
= 130m&
According to the above calculation, the minimum R
DS(ON)
is 130m& for a 2.5V to 1.8V LDO with 5A of output
current. For this design, the R
DS(ON)
for the FETs should
maintain   better   than   130m&   over   the   required
temperature, current, and voltage conditions.
Placing two or more P-Channel FETs in parallel can
reduce the total R
DS(ON)
of the regulator. This also aids
thermal dissipation by sharing the current and heat
between the multiple FETs.
Thermal Considerations
Linear   regulators   are   simple   to   use.   The   most
complicated design parameters to consider are thermal
characteristics. Since the MIC5159 offers no thermal
protection,   thermal   design   requires   the   following
application-specific parameters:
"    Maximum ambient temperature (T
A
)
"    Output current (I
OUT
)
"    Output voltage (V
OUT
)
"    Input voltage (V
IN
)
First, calculate the maximum power dissipation of the
regulator:
P
D
= (V
IN
V
OUT
) ?I
OUT
Ground current can generally be ignored. The amount of
power dissipated by ground current and input voltage is
minimal.   Minimum   ?/DIV>
JA
  for   the   MOSFET   can   be
calculated using the following formula:
)
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
=
D
A
J(MAX)
JA
P
T
T
?/DIV>
Where T
J(max)
is equal to the maximum die temperature
of the P-Channel.
?/DIV>
JA
= ?/DIV>
JC
+ ?/DIV>
CS
+ ?/DIV>
SA
Example
For the same regulator, 2.5V
IN
to 1.8V
OUT
at 5A with an
ambient temperature of 60癈:
P
D
= (2.5V1.8V) ?5A
P
D
= 3.5W
Where V
IN
is the maximum V
IN
and I
OUT
is the maximum
I
OUT
.
The P-Channel MOSFET must be able to dissipate
3.5W. The minimum ?/DIV>
JA
to maintain a maximum T
J
of
150癈 (max.) T
J
according to a typical MOSFET data
sheet is as follows:
)
3.5W
C
60
C
150
?/DIV>
JA
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
MIC5159YM6 |
制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Programmable Current Limit μCap LDO Regulator Controller |
MIC5159YM6 TR |
功能描述:低壓差控制器 - LDO Progr. Ilim LDO Controller(Lead Free)
RoHS:否 制造商:Micrel 最大輸入電壓:5.5 V 輸出電壓:Adjustable 輸出電流:10 mA 負(fù)載調(diào)節(jié): 輸出類型:Adjustable, Fixed 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-6 |
MIC5159YM6TR |
制造商:Micrel 功能描述:LDO Regulator 1.235V to 5.5V |
MIC5159YM6-TR |
功能描述:Linear Regulator Controller IC Positive Adjustable 1 Output SOT-23-6 制造商:microchip technology 系列:- 包裝:剪切帶(CT) 零件狀態(tài):有效 類型:正,可調(diào)式 輸出數(shù):1 電流 - 電源:10mA 電壓 - 輸入:1.65 V ~ 5.5 V 工作溫度:-40°C ~ 125°C 封裝/外殼:SOT-23-6 供應(yīng)商器件封裝:SOT-23-6 標(biāo)準(zhǔn)包裝:1 |
MIC5162 |
制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Dual Regulator Controller for DDR3 GDDR3/4/5 Memory and High-Speed Bus Termination |
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