參數(shù)資料
型號(hào)： LM20323AMHE
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： 6 A SWITCHING REGULATOR, 570 kHz SWITCHING FREQ-MAX, PDSO20
封裝： TSSOP-20
文件頁(yè)數(shù)： 7/20頁(yè)
文件大?。?/td> 492K
代理商： LM20323AMHE
the synchronous MOSFET body diode and eliminating re-
verse recovery losses.
The external Schottky conducts currents for a very small por-
tion of the switching cycle, therefore the average current is
low. An external Schottky rated for 1A will improve efficiency
by several percent in some applications. A Schottky rated at
a higher current will not significantly improve efficiency and
may be worse due to the increased reverse capacitance. The
forward voltage of the synchronous MOSFET body diode is
approximately 700 mV, therefore an external Schottky with a
forward voltage less than or equal to 700 mV should be se-
lected to ensure the majority of the dead time current is carried
by the Schottky.
THERMAL CONSIDERATIONS
The thermal characteristics of the LM20323A are specified
using the parameter
θ
JA, which relates the junction tempera-
ture to the ambient temperature. Although the value of
θ
JA is
dependant on many variables, it still can be used to approxi-
mate the operating junction temperature of the device.
To obtain an estimate of the device junction temperature, one
may use the following relationship:
T
J = PD x θJA + TA
and
P
D = PIN x (1 - Efficiency) - 1.1 x (IOUT)
2
x DCR
Where:
T
J is the junction temperature in °C.
P
IN is the input power in Watts (PIN = VIN x IIN).
θ
JA is the junction to ambient thermal resistance for the
LM20323A.
T
A is the ambient temperature in °C.
I
OUT is the output load current.
DCR is the inductor series resistance.
It is important to always keep the operating junction temper-
ature (T
J) below 125°C for reliable operation. If the junction
temperature exceeds 170°C the device will cycle in and out
of thermal shutdown. If thermal shutdown occurs it is a sign
of inadequate heatsinking or excessive power dissipation in
the device.
Figure 8 and Figure 9 can be used as a guide to avoid ex-
ceeding the maximum junction temperature of 125°C provid-
ed an external 1A Schottky diode, such as Central
Semiconductor's CMMSH1-40-NST, is used to improve re-
verse recovery losses.
30077288
FIGURE 8. Safe Thermal Operating Areas (I
OUT = 3A)
30077290
FIGURE 9. Safe Thermal Operating Areas (I
OUT = 2.5A)
The dashed lines in Figure 8 and Figure 9 show an approxi-
mation of the minimum and maximum duty cycle limitations;
while, the solid lines define areas of operation for a given am-
bient temperature. This data for the figure was derived as-
suming the device is operating at 3A continuous output
current on a 4 layer PCB with an copper area greater than 4
square inches exhibiting a thermal characteristic less than 27
°C/W. Since the internal losses are dominated by the FETs a
slight reduction in current by 500mA allows for much larger
regions of operation, as shown in Figure 10.
Figure 10 provides a better approximation of the
θ
JA for a giv-
en PCB copper area. The PCB used in this test consisted of
4 layers: 1oz. copper was used for the internal layers while
the external layers were plated to 2oz. copper weight. To pro-
vide an optimal thermal connection, a 5 x 4 array of 12 mil
thermal vias located under the thermal pad was used to con-
nect the 4 layers.
15
www.national.com
LM20323A
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM20323AMHX 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:36V, 3A 500 kHz Synchronous Buck Regulator
LM20323EVAL 功能描述:電源管理IC開(kāi)發(fā)工具 LM20323 EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類(lèi)型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
LM20323MH 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 4.5V to 36V 20-Pin TSSOP EP Rail 制造商:Texas Instruments 功能描述:BUCK REG, 3A, 4V/36V, POWERWISE, 20TSSOP 制造商:Texas Instruments 功能描述:IC, DC-DC CONV; Primary Input Voltage:36V; No. of Outputs:1; Output Voltage:32V; Output Current:3A; No. of Pins:20; Operating Temperature Min:-40C; Operating Temperature Max:125C; Operating Temperature Range:-40C to +125C ;RoHS Compliant: Yes
LM20323MH/NOPB 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 36V,3A 500 KHZ SYNC BUCK REG RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)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
LM20323MHE 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 4.5V to 36V 20-Pin TSSOP EP T/R
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