參數(shù)資料
型號(hào)： L5985
廠商： 意法半導(dǎo)體
英文描述： 2A step-down switching regulator
中文描述： 第2A降壓型開關(guān)穩(wěn)壓器
文件頁(yè)數(shù)： 25/36頁(yè)
文件大小： 757K
代理商： L5985
L5985
Application informations
25/36
5.5
Thermal considerations
The thermal design is important to prevent the thermal shutdown of device if junction
temperature goes above 150°C. The three different sources of losses within the device are:
a)
conduction losses due to the not negligible R
DSON
of the power switch; these are
equal to:
Equation 27
Where D is the duty cycle of the application and the maximum R
DSON
is 300m
.
Note that the duty cycle is theoretically given by the ratio between V
OUT
an V
IN
, but actually
it is quite higher to compensate the losses of the regulator. So the conduction losses
increases compared with the ideal case.
b)
switching losses due to power MOSFET turn ON and OFF; these can be
calculated as:
Equation 28
Where T
RISE
and T
FALL
are the overlap times of the voltage across the power switch (V
DS
)
and the current flowing into it during turn ON and turn OFF phases, as shown in
Figure 16
.
T
SW
is the equivalent switching time. For this device the typical value for the equivalent
switching time is 50ns.
c)
Quiescent current losses, calculated as:
Equation 29
where I
Q
is the quiescent current. (I
Q
= 20uA)
The junction temperature T
J
can be calculated as:
Equation 30
Where T
A
is the ambient temperature and P
TOT
is the sum of the power losses just seen.
Rth
JA
is the equivalent thermal resistance juction to ambient of the device; it can be
calculated as the parallel of many paths of heat conduction from the junction to the ambient.
For this device the path through the exposed pad is the one conducting the largest amount
of heat. The Rth
JA
measured on the application demo board described in the following
paragraph is about 60°/W.
P
ON
R
DSON
I
OUT
(
)
2
D
=
P
SW
V
IN
I
OUT
T
------------------------------------------
Fsw
T
+
2
(
)
V
IN
I
OUT
T
SW
F
SW
=
=
P
Q
V
IN
I
Q
=
T
J
T
A
Rth
JA
P
TOT
+
=
相關(guān)PDF資料
PDF描述
L5985TR 2A step-down switching regulator
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L5991A PRIMARY CONTROLLER WITH STANDBY
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L5985_08 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:2 A step-down switching regulator
L5985TR 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2a Step-Down Switching Reg RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
L5986 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2.5 A buck switching regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
L5986A 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2.5 A STEP-DOWN SWITCH REG RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
L5986ATR 功能描述:直流/直流開關(guān)調(diào)節(jié)器 Step-down switch regulator, 2.5A RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
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