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參數(shù)資料
| 型號： | L5980TR |
| 廠商： | 意法半導體 |
| 英文描述： | 0.7A step-down switching regulator |
| 中文描述： | 0.7A的降壓開關(guān)穩(wěn)壓器 |
| 文件頁數(shù)： | 26/37頁 |
| 文件大?。?/td> | 959K |
| 代理商： | L5980TR |
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Application informations
L5980
26/37
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 26
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 27
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 28
where I
Q
is the quiescent current
(I
Q
=20uA).
The junction temperature T
J
can be calculated as:
Equation 29
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 junction 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
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
+
=
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| L5991AD | PRIMARY CONTROLLER WITH STANDBY |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| L5980TR-CUT TAPE | 制造商:ST 功能描述:L5980 Series 15 V 250 kHz 0.7 A Step Down Switching Regulator - VFQFPN-8 |
| L5981 | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1A 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| L5981_08 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:1 A step-down switching regulator |
| L5981TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1a 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| L5983 | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.5A STEP-DOWN 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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