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參數(shù)資料
| 型號： | TPS65251RHAR |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, PQCC40 |
| 封裝： | 6 X 6 MM, GREEN, PLASTIC, VQFN-40 |
| 文件頁數(shù)： | 15/31頁 |
| 文件大小： | 1827K |
| 代理商： | TPS65251RHAR |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁當前第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁
ind
Vin Vout
Vout
Lo
Io K
Vin fsw
-
=
×
Vin Vout
Vout
Iripple
Lo
Vin fsw
-
=
×
2
1
(
max
)
12
max
Vo Vin
Vo
ILrms
Io
Vin
Lo fsw
×
-
=
+
×
÷
×
è
2
Iripple
ILpeak
Iout
=
+
2
OUT
o
out
I
L
Co
V
Vout
D
×
>
× D
1
8
Co
Vripple
fsw
Iripple
>
×
SLVSAA4B – JUNE 2010 – REVISED JANUARY 2011
www.ti.com
frequency allows for lower valued inductors and smaller output capacitors compared to a power supply that
switches at a lower frequency. However, the highest switching frequency causes extra switching losses, which
hurt the converter’s performance. The converter is capable of running from 300 kHz to 2.2 MHz. Unless a small
solution size is an ultimate goal, a moderate switching frequency of 500 kHz is selected to achieve both a small
solution size and a high efficiency operation. Using Figure 21, R1 is determined to be 383 k
Output Inductor Selection
To calculate the value of the output inductor, use Equation 10. KIND is a coefficient that represents the amount
of inductor ripple current relative to the maximum output current. In general, KIND is normally from 0.1 to 0.3 for
the majority of applications.
For this design example, use KIND = 0.2 and the inductor value is calculated to be 3.6 H. For this design, a
nearest standard value was chosen: 4.7 H. For the output filter inductor, it is important that the RMS current
and saturation current ratings not be exceeded. The RMS and peak inductor current can be found from
(10)
(11)
(12)
(13)
Output Capacitor
There are two primary considerations for selecting the value of the output capacitor. The output capacitors are
selected to meet load transient and output ripple’s requirements.
Equation 14 gives the minimum output capacitance to meet the transient specification. For this example,
LO = 4.7 H, ΔIOUT = 1.5 A – 0.75 A = 0.75 A and ΔVOUT = 120 mV. Using these numbers gives a minimum
capacitance of 18 F. A standard 22-F ceramic capacitor is chose in the design.
(14)
Equation 15 calculates the minimum output capacitance needed to meet the output voltage ripple specification.
Where fsw is the switching frequency, VRIPPLE is the maximum allowable output voltage ripple, and IRIPPLE is the
inductor ripple current. In this case, the maximum output voltage ripple is 30 mV. From Equation 11, the output
current ripple is 0.46 A. From Equation 15, the minimum output capacitance meeting the output voltage ripple
requirement is 1.74 F.
(15)
Additional capacitance de-rating for aging, temperature and DC bias should influence this minimum value. For
this example, one 22-F, 6.3-V X7R ceramic capacitor with 3 m
of ESR will be used.
Input Capacitor
A minimum 10-F X7R/X5R ceramic input capacitor is recommended to be added between VIN and GND. These
capacitors should be connected as close as physically possible to the input pins of the converters as they handle
the RMS ripple current shown in Equation 16. For this example, IOUT = 3 A, VOUT = 1.2 V, VINmin = 9.6 V, from
Equation 16, the input capacitors must support a ripple current of 0.99 A RMS.
22
Copyright 2010–2011, Texas Instruments Incorporated
Product Folder Link(s): TPS65251
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| TPS65251RHAT | 功能描述:PMIC 解決方案 PMU with 3 DC/DC Converters RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| TPS65252EVM | 功能描述:電源管理IC開發(fā)工具 TPS65252 Eval Mod RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| TPS65252RHDR | 功能描述:PMIC 解決方案 4.5-16V Inp w/ 2 BUCK CONVERTER RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| TPS65252RHDT | 功能描述:PMIC 解決方案 4.5-16V Inp w/ 2 BUCK CONVERTER RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| TPS65253EVM | 功能描述:電源管理IC開發(fā)工具 TPS65253 Eval Mod RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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