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參數(shù)資料
| 型號： | TPS5420MDREP |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 5.2 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | GREEN, PLASTIC, MS-012AA, SOIC-8 |
| 文件頁數(shù)： | 4/23頁 |
| 文件大?。?/td> | 658K |
| 代理商： | TPS5420MDREP |
www.ti.com
I
CIN +
I
OUT(MAX)
2
(3)
LMIN =
()
VOUT
IN(MAX)
OUT
V
-
VIN(max)
IND
OUT
SW
K
I
F
0.8
(4)
I
L(RMS) +
I2
OUT(MAX) )
1
12
V
OUT
V
IN(MAX) *
V
OUT
V
IN(MAX)
L
OUT
F
SW
0.8
2
(5)
IL(PK) =I
+
OUT(MAX)
()
V
OUT
IN(MAX)
OUT
-
1.6
V
L
F
IN(MAX)
OUT
SW
(6)
SLVS717 – DECEMBER 2006
The maximum RMS ripple current also needs to be checked. For worst-case conditions, this is approximated by
In this example, the calculated input ripple voltage is 118 mV and the RMS ripple current is 1.0 A. The maximum
voltage across the input capacitors would be VIN max plus delta VIN/2. The chosen input decoupling capacitors
are rated for 50 V, and the ripple current capacity for each is 3 A at 500 kHz, providing ample margin. The actual
measured input ripple voltage may be larger than the calculated value, due to the output impedance of the input
voltage source and parasitics associated with the layout.
CAUTION:
The maximum ratings for voltage and current are not to be exceeded under any
circumstance.
Additionally, some bulk capacitance may be needed, especially if the TPS5420 circuit is not located within
approximately 2 in from the input voltage source. The value for this capacitor is not critical, but it should be rated
to handle the maximum input voltage, including ripple voltage, and should filter the output so that input ripple
voltage is acceptable.
Output Filter Components
Two components need to be selected for the output filter, L1 and C2. Since the TPS5420 is an internally
compensated device, a limited range of filter component types and values can be supported.
Inductor Selection
To calculate the minimum value of the output inductor, use Equation 4:
KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum output current.
Three things need to be considered when determining the amount of ripple current in the inductor: the
peak-to-peak ripple current affects the output ripple voltage amplitude, the ripple current affects the peak switch
current, and the amount of ripple current determines at what point the circuit becomes discontinuous. For
designs using the TPS5420, KIND of 0.2 to 0.3 yields good results. Low output ripple voltages are obtained when
paired with the proper output capacitor, the peak switch current is below the current limit set point, and low load
currents can be sourced before discontinuous operation.
For this design example, use KIND = 0.2, and the minimum inductor value is 31 H. The next highest standard
value used in this design is 33
H.
For the output filter inductor, it is important that the RMS current and saturation current ratings not be exceeded.
The RMS inductor current can be found from Equation 5:
and the peak inductor current can be determined using Equation 6:
For this design, the RMS inductor current is 2.002 A, and the peak inductor current is 2.16 A. The chosen
inductor is a Coilcraft MSS1260-333 type. The nominal inductance is 33
H. It has a saturation current rating of
2.2 A and an RMS current rating of 2.7 A, which meets the requirements. Inductor values for use with the
TPS5420 are in the range of 10
H to 100 H.
12
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| TPS5420MDREPG4 | 功能描述:直流/直流開關調節(jié)器 EP 2A Wide-Inp-Range StepDwn SWIFT Cnvrtr RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關頻率: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 |
| TPS5420-Q1 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:2-A WIDE-INPUT-RANGE STEP-DOWN SWIFTa?￠ CONVERTER |
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