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參數(shù)資料
| 型號： | L4992 |
| 廠商： | STMICROELECTRONICS |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 300 kHz SWITCHING FREQ-MAX, PQFP32 |
| 封裝： | TQFP-32 |
| 文件頁數(shù)： | 9/26頁 |
| 文件大小： | 296K |
| 代理商： | L4992 |
turbing the circuit. These points are the reference voltage VREF, the IC supply pin VIN, the REG5 line
and the alternative supply pin V5SW. Use film capacitors suitable for AC decoupling.
+12 V LINEAR REGULATOR
Catch Diode
The diode which steers the current generated by the secondary winding of the +3.3V transformer should
be a p-n fast-recovery one, with a breakdown voltage greater than:
VRR = (Vinlin - 3.3) + n
(V in max - 3.3)
with a certain safety margin. The diode has to withstand a pulsed current whose peak value is approxi-
mately:
I13pk
Iout12
Vin min
3.3
,
while its RMS value is given by:
I13RMS
= Iout12
√
Vin min
3.3
The DC value is obviously Iout12.
Filter Capacitors
The most stringent requirement on the input filter capacitor (connected between V13IN and ground) is its
RMS ripple current rating, which should be at least:
I13AC
= Iout12
√
3.3
Vin min
3.3
The working voltage should be higher than the voltage generated when the regulator is lightly loaded.
Also for this part the use of high quality electrolytic or OS-CON capacitors is advised.
LAYOUT AND GROUNDING
The electrical design is only the first step in the development of a switching converter. Since currents
ranging from
Amperes to some Amperes, both DC and switched, live together on the same circuit-
board, the PCB layout is vital for a correct operation of the circuit but is not an easy task.
A proper layout process generally includes careful component placing, proper grounding, correct traces
routing, and appropriate trace widths. Fortunately, since low voltages are involved in this kind of applica-
tions, isolation requirements are of no concern.
Referring to literature for a detailed analysis of this matter, only few important points will be here reminded.
1) All current returns (signal ground, power ground, etc.) should be mutually isolated and should be con-
nected only at a single ground point. Ground planes may be extremely useful both to arrange properly
current returns and to minimize radiation (see next 2 points), even though they cannot solve every
problem
2) Noise coupling between adjacent circuitry can be reduced minimizing the area of the loop where cur-
rent flows. This is particularly important where there are high pulsed currents, that is the circuit includ-
ing the input filter capacitor, the power switch, the synchronous rectifier and the output capacitor. The
next priority should be given to the gate drive circuits.
3) Magnetic field radiation (and stray inductance) can be reduced by keeping all traces which carry
switched currents as short as possible.
4) The Kelvin-connected traces of current sense should be kept short and close together.
5) For high current paths, the traces could be doubled on the other side of the PCB whenever possible:
this will reduce both the resistance and the inductance of the wiring.
6) In general, traces carrying signal currents should run far from traces carrying pulsed currents or with
quickly swinging voltages. From this viewpoint, particular care should be taken of the high impedance
paths (feedback input, current sense traces...). It could be a good idea to route signal traces on one
DESIGN PROCEDURE (continued)
L4992
17/26
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| L4993 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Low drop voltage regulator |
| L4993D | 功能描述:低壓差穩(wěn)壓器 - LDO Low drop voltage regulator RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4993DTR | 功能描述:低壓差穩(wěn)壓器 - LDO Low drop voltage regulator RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4993MD | 功能描述:低壓差穩(wěn)壓器 - LDO Low drop voltage regulator RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4993MDTR | 功能描述:低壓差穩(wěn)壓器 - LDO 5V 150mA LW DROP VLT REGULATOR RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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