參數(shù)資料
型號： L7980
廠商： STMICROELECTRONICS
元件分類： 穩(wěn)壓器
英文描述： 3.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
封裝： 3 X 3 MM, 1.08 MM HEIGHT, ROHS COMPLIANT, VFQFPN-8
文件頁數(shù)： 21/44頁
文件大小： 1247K
代理商： L7980
Application informations
L7980
28/44
Doc ID 15181 Rev 3
6.5
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 RDSon of the power switch; these are
equal to:
Equation 29
Where D is the duty cycle of the application and the maximum RDSon over temperature is
220 m
Ω. Note that the duty cycle is theoretically given by the ratio between V
OUT and VIN,
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 30
Where TRISE and TFALL are the overlap times of the voltage across the power switch (VDS)
and the current flowing into it during turn ON and turn OFF phases, as shown in Figure 16.
TSW is the equivalent switching time. For this device the typical value for the equivalent
switching time is 30 ns.
c)
Quiescent current losses, calculated as:
Equation 31
where IQ is the quiescent current (IQ=2.4 mA).
The junction temperature TJ can be calculated as:
Equation 32
Where TA is the ambient temperature and PTOT is the sum of the power losses just seen.
RthJA 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
RISE
T
FALL
+
()
2
------------------------------------------- Fsw
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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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L7980A 制造商:STMicroelectronics 功能描述:Conv DC-DC Single Step Down 4.5V to 28V 8-Pin HSOP EP Tube 制造商:STMicroelectronics 功能描述:POWER CONVERSION - Rail/Tube 制造商:STMicroelectronics 功能描述:2A Step-Down Reg 2.5A 4.5 28V 250kHz 制造商:STMicroelectronics 功能描述:BUCK, 4.5-28V, 2A, 1MHZ, 0.6-28V, 8HSOP; Primary Input Voltage:28V; No. of Outputs:1; Output Current:2A; Voltage Regulator Case Style:HSOP; No. of Pins:8; Operating Temperature Min:-25C; Operating Temperature Max:125C; MSL:MSL 3 - ;RoHS Compliant: Yes 制造商:ST 功能描述:0
L7980ATR 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 2 A Step-Down Reg 4.5V to 28V 250 kHz RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
L7980TR 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 2A DC 4.5 V to 28 V Adj 0.6V 250 kHz RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
L7981 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3A Step-Down Reg 3A DC 4.5-28V 250Khz 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
L7981A 制造商:STMicroelectronics 功能描述:POWER CONVERSION - Rail/Tube 制造商:STMicroelectronics 功能描述:3A Step-Down Reg 3.7A 4.5 to 28V 1MHz 制造商:ST 功能描述:3A STEP-DOWN SWITCHING REGULATOR
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