參數(shù)資料
型號(hào)： L5985
廠商： STMICROELECTRONICS
元件分類： 穩(wěn)壓器
英文描述： 2 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
封裝： 3 X 3 MM, 1.08 MM HEIGHT, LEAD FREE, VFQFPN-8
文件頁(yè)數(shù)： 19/37頁(yè)
文件大?。?/td> 856K
代理商： L5985
Application information
L5985
26/37
Doc ID 13006 Rev 5
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 RDS(on) of the power switch; these are
equal to:
Equation 27
Where D is the duty cycle of the application and the maximum RDS(on) is 220 mΩ.
Note that the duty cycle is theoretically given by the ratio between VOUT an 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 28
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 50 ns.
c)
Quiescent current losses, calculated as:
Equation 29
where IQ is the quiescent current. (IQ = 2.4 mA)
The junction temperature TJ can be calculated as:
Equation 30
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
of heat. The RthJA measured on the application demonstration 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
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
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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