參數(shù)資料
型號(hào)： L7981TR
廠商： STMICROELECTRONICS
元件分類(lèi)： 穩(wěn)壓器
英文描述： SWITCHING REGULATOR, DSO8
封裝： 3 X 3 MM, 1.08 MM HEIGHT, ROHS COMPLIANT, VFQFP-8
文件頁(yè)數(shù)： 8/44頁(yè)
文件大小： 1315K
代理商： L7981TR
Application informations
L7981
16/44
Doc ID 15182 Rev 3
Given the physical dimension, ceramic capacitors can meet well the requirements of the
input filter sustaining an higher input RMS current than electrolytic / tantalum types. In this
case the equation of CIN as a function of the target VPP can be written as follows:
Equation 7
neglecting the small ESR of ceramic capacitors.
Considering
η=1, this function has its maximum in D=0.5, thus, given the maximum peak to
peak input voltage (VPP_MAX), the minimum input capacitor (CIN_MIN) value is:
Equation 8
Typically CIN is dimensioned to keep the maximum peak-peak voltage in the order of 1% of
VINMAX
In
Table 6. some multi layer ceramic capacitors suitable for this device are reported
A ceramic bypass capacitor, as close to the VCC and GND pins as possible, so that
additional parasitic ESR and ESL are minimized, is suggested in order to prevent instability
on the output voltage due to noise. The value of the bypass capacitor can go from 100 nF to
1 F.
6.2
Inductor selection
The inductance value fixes the current ripple flowing through the output capacitor. So the
minimum inductance value in order to have the expected current ripple has to be selected.
The rule to fix the current ripple value is to have a ripple at 20%-40% of the output current.
In the continuos current mode (CCM), the inductance value can be calculated by the
following equation:
Table 6.
Input MLCC capacitors
Manufacture
Series
Cap value (
μF)
Rated voltage (V)
Taiyo Yuden
UMK325BJ106MM-T
10
50
GMK325BJ106MN-T
10
35
Murata
GRM32ER71H475K
4.7
50
C
IN
I
O
V
PP
F
SW
---------------------------
1
D
η
----
–
D
η
----
1D
–
()
+
=
C
IN_MIN
I
O
2V
PP_MAX
F
SW
------------------------------------------------
=
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L7983 制造商:Leviton Manufacturing Co 功能描述:
L7985 功能描述:線(xiàn)性穩(wěn)壓器 - 標(biāo)準(zhǔn) 2A Step Down REG 4.5V to 38V 250 KHz RoHS:否 制造商:STMicroelectronics 輸出類(lèi)型: 極性: 輸出電壓:1.8 V 輸出電流:150 mA 負(fù)載調(diào)節(jié): 最大輸入電壓:5.5 V 線(xiàn)路調(diào)整率: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-323-5L
L7985A 功能描述:直流/直流開(kāi)關(guān)調(diào)節(jié)器 2A DC 4.5V to 38V 250 KHz Step-Down RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開(kāi)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
L7985ATR 功能描述:線(xiàn)性穩(wěn)壓器 - 標(biāo)準(zhǔn) 2A Step-Down REG 2A DC 4.5 to 38V RoHS:否 制造商:STMicroelectronics 輸出類(lèi)型: 極性: 輸出電壓:1.8 V 輸出電流:150 mA 負(fù)載調(diào)節(jié): 最大輸入電壓:5.5 V 線(xiàn)路調(diào)整率: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-323-5L
L7985TR 功能描述:線(xiàn)性穩(wěn)壓器 - 標(biāo)準(zhǔn) 2A Step-Down Reg 4.5V to 38V 250 KHz RoHS:否 制造商:STMicroelectronics 輸出類(lèi)型: 極性: 輸出電壓:1.8 V 輸出電流:150 mA 負(fù)載調(diào)節(jié): 最大輸入電壓:5.5 V 線(xiàn)路調(diào)整率: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-323-5L
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