參數(shù)資料
型號(hào)： TPS65251RHAT
廠(chǎng)商： TEXAS INSTRUMENTS INC
元件分類(lèi)： 穩(wěn)壓器
英文描述： SWITCHING REGULATOR, PQCC40
封裝： 6 X 6 MM, GREEN, PLASTIC, VQFN-40
文件頁(yè)數(shù)： 16/31頁(yè)
文件大?。?/td> 1827K
代理商： TPS65251RHAT
(
)
min
Vin
Vout
Icirms
Iout
Vin
-
=
×
max 0.25
Iout
Vin
Cin fsw
×
D
=
×
(
)
(
)
(
)
( )
Tss ms Iss uA
Css nF
Vref V
×
=
180
1(
)
1 1.3
RLIM
k
ILIM
W =
-
11
10
Vout Vref
R
Vref
-
=
www.ti.com
SLVSAA4B – JUNE 2010 – REVISED JANUARY 2011
(16)
The input capacitance value determines the input ripple voltage of the regulator. The input voltage ripple can be
calculated using Equation 17. Using the design example values, IOUTmax = 3 A, CIN = 10 F, fSW = 500 kHz, yields
an input voltage ripple of 150 mV.
(17)
Soft Start Capacitor
The soft start capacitor determines the minimum amount of time it will take for the output voltage to reach its
nominal programmed value during power up. This is useful 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 soft start capacitor value can be calculated using Equation 18. In this example, the converter’s soft start time
is 0.8 ms. In TPS65251, Iss is 5 A and Vref is 0.8 V. From Equation 18, the soft start capacitance is 5 nF. A
standard 4.7-nF ceramic capacitor is chosen in this design. In this example, C16 is 4.7nF
(18)
Bootstrap Capacitor Selection
A 0.047-F ceramic capacitor must be connected between the BST to LX pin for proper operation. It is
recommended to use a ceramic capacitor with X5R or better grade dielectric. The capacitor should have 10-V or
higher voltage rating.
Adjustable Current Limiting Resistor Selection
The converter uses the voltage drop on the high-side MOSFET to measure the inductor current. The over current
protection threshold can be optimized by changing the trip resistor. Equation 19 governs the threshold of over
current protection. In this example, the over current threshold is 3.5 A and the equation yields RLIM1 = 80 k
.
Due to the tolerance of the high-side current sensing, additional 30% is added to cover the upper tolerance. Thus
RLIM1 is determined to be 100 k
. In this example, R13 is 100 k.
(19)
Output Voltage and Feedback Resistors Selection
For the example design, 40.2 k
was selected for R10. Vout is 1.2 V, Vref = 0.8 V. Using Equation 20, R11 is
calculated as 80.4 k
. A standard 80.6-k resistor is chose in this design.
(20)
Copyright 2010–2011, Texas Instruments Incorporated
23
Product Folder Link(s): TPS65251
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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(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
TPS65253EVM 功能描述:電源管理IC開(kāi)發(fā)工具 TPS65253 Eval Mod 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
TPS65253RHDR 功能描述:PMIC 解決方案 4.5V-16Vin/2 Buck Converters RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
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