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參數(shù)資料
| 型號： | TPS54418RTER |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 6.4 A SWITCHING REGULATOR, 2000 kHz SWITCHING FREQ-MAX, PQCC16 |
| 封裝： | 3 X 3 MM, GREEN, PLASTIC, WQFN-16 |
| 文件頁數(shù)： | 14/35頁 |
| 文件大小： | 1356K |
| 代理商： | TPS54418RTER |
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Voripple
Resr <
Iripple
-
Vout
(Vinm ax
Vout)
Icorm s =
12
Vinm ax
L1
sw
(
)
Vinm in
Vou t
Vout
Icirm s = Io ut
Vinm in
Vin min
-
Ioutmax
0.25
Vin =
Cin
sw
D
Tss(ms)
Iss( A)
Css(nF) =
Vref(V)
m
www.ti.com
SLVS946A – MAY 2009 – REVISED MAY 2010
Equation 24 calculates the maximum ESR an output capacitor can have to meet the output voltage ripple
specification. Equation 24 indicates the ESR should be less than 26 m
. In this case, the ESR of the ceramic
capacitor is much less than 26 m
.
Additional capacitance de-ratings for aging, temperature and DC bias should be factored in which increases this
minimum value. For this example, two 22 mF 10 V X5R ceramic capacitors with 3 m of ESR are used.
Capacitors generally have limits to the amount of ripple current they can handle without failing or producing
excess heat. An output capacitor that can support the inductor ripple current must be specified. Some capacitor
data sheets specify the RMS (Root Mean Square) value of the maximum ripple current. Equation 25 can be used
to calculate the RMS ripple current the output capacitor needs to support. For this application, Equation 25 yields
333 mA.
(24)
(25)
INPUT CAPACITOR
The TPS54418 requires a high quality ceramic, type X5R or X7R, input decoupling capacitor of at least 4.7 mF of
effective capacitance and in some applications a bulk capacitance. The effective capacitance includes any DC
bias effects. The voltage rating of the input capacitor must be greater than the maximum input voltage. The
capacitor must also have a ripple current rating greater than the maximum input current ripple of the TPS54418.
The input ripple current can be calculated using Equation 26.
The value of a ceramic capacitor varies significantly over temperature and the amount of DC bias applied to the
capacitor. The capacitance variations due to temperature can be minimized by selecting a dielectric material that
is stable over temperature. X5R and X7R ceramic dielectrics are usually selected for power regulator capacitors
because they have a high capacitance to volume ratio and are fairly stable over temperature. The output
capacitor must also be selected with the DC bias taken into account. The capacitance value of a capacitor
decreases as the DC bias across a capacitor increases.
For this example design, a ceramic capacitor with at least a 10 V voltage rating is required to support the
maximum input voltage. For this example, one 10 mF and one 0.1 mF 10 V capacitors in parallel have been
selected. The input capacitance value determines the input ripple voltage of the regulator. The input voltage
ripple can be calculated using Equation 27. Using the design example values, Ioutmax=4 A, Cin=10 mF, Fsw=1
MHz, yields an input voltage ripple of 99 mV and a rms input ripple current of 1.96 A.
(26)
(27)
SLOW START CAPACITOR
The slow start capacitor determines the minimum amount of time it takes for the output voltage to reach its
nominal programmed value during power up. This is useful if a load requires a controlled voltage slew rate. This
is also used if the output capacitance is very large and would require large amounts of current to quickly charge
the capacitor to the output voltage level. The large currents necessary to charge the capacitor may make the
TPS54418 reach the current limit or excessive current draw from the input power supply may cause the input
voltage rail to sag. Limiting the output voltage slew rate solves both of these problems.
The slow start capacitor value can be calculated using Equation 28. For the example circuit, the slow start time is
not too critical since the output capacitor value is 44 mF which does not require much current to charge to 1.8 V.
The example circuit has the slow start time set to an arbitrary value of 4ms which requires a 10 nF capacitor. In
TPS54418, Iss is 2 mA and Vref is 0.8 V.
(28)
Copyright 2009–2010, Texas Instruments Incorporated
21
Product Folder Link(s): TPS54418
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| TPS54426PWP | 7.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO14 |
| TPS54429PWP | 0.01 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO14 |
| TPS5450MDDAREP | 11.7 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO8 |
| TPS54519RTER | 8 A SWITCHING REGULATOR, 2000 kHz SWITCHING FREQ-MAX, PQCC16 |
| TPS54612MPWPREP | 12 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO28 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS54418RTERG4 | 制造商:Texas Instruments 功能描述: |
| TPS54418RTET | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2.95-6Vin 4A 2MHz Synch St Down 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 |
| TPS54424RNVT | 功能描述:4.5V TO 17V INPUT, CURRENT MODE, 制造商:texas instruments 系列:SWIFT?? 包裝:剪切帶（CT） 零件狀態(tài):在售 功能:降壓 輸出配置:正 拓?fù)?降壓 輸出類型:可調(diào)式 輸出數(shù):1 電壓 - 輸入（最小值）:4.5V 電壓 - 輸入（最大值）:17V 電壓 - 輸出（最小值/固定）:0.6V 電壓 - 輸出（最大值）:12V 電流 - 輸出:4A 頻率 - 開關(guān):200kHz ~ 1.6MHz 同步整流器:是 工作溫度:-40°C ~ 150°C（TJ） 安裝類型:表面貼裝 封裝/外殼:18-VFQFN 供應(yīng)商器件封裝:18-VQFN-HR（3.5x3.5） 標(biāo)準(zhǔn)包裝:1 |
| TPS54425 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:4-A OUTPUT SINGLE SYNCHRONOUS STEP DOWN SWITCHER WITH INTEGRATED FET ( SWIFT?) |
| TPS54425_10 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:4-A OUTPUT SINGLE SYNCHRONOUS STEP DOWN SWITCHER WITH INTEGRATED FET ( SWIFT?) |
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