參數(shù)資料
型號(hào)： 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(yè)數(shù)： 26/26頁(yè)
文件大?。?/td> 296K
代理商： L4992
MOSFET’s (the so-called "logic-level" devices) is highly recommended.
The drivers are of "dynamic" type, which means they do not give origin to current consumption when
they are in static conditions (ON or OFF), but only during transitions. This feature is aimed at minimizing
the power consumption of the device even during stand-by when both low-side MOSFET’s are ON.
Protections
Each converter is fully protected against fault conditions. A monitoring system checks for overvoltages of
the output, quickly disabling both converters in case such an event occurs. This condition is latched and
to allow the device to start again either the supply voltage has to be removed or both RUN3 and RUN5
pins have to be driven low.
Undervoltage conditions are detected as well but do not cause interruption of the operation of the convert-
ers. Only PWROK signal (at pin 10) reveals the anomaly with a low output level.
If the chip overheats (above 135 °C typ.) the device stops operating as long as the temperature falls below a
safe value (105 °C typ.). The overtemperature condition is signalled by a low level on PWROK as well.
A current limitation comparator prevents from excessive current in case of overload or short-circuit. It in-
tervenes as the voltage VRsense exceeds 100 mV, turning off the high-side switch before the error sum-
ming does. By the way, this also gives the designer the ability to program the maximum operating current
by selecting an appropriate sense resistor.
This pulse-by-pulse limitation gives a quasi-constant current characteristic. If a "folded back" charac-
teristic, like the one shown in Fig. 4a, is desired the external circuit of Fig. 4b can be used. The circuits
acts on the current limitation and is extremely simple and cheap. The advantage of such a technique i
that a short circuit will cause a current much lower than the maximum to flow. Th e stress of the power
components will be very little and no overheating will occur. The part values shown in Fig. 4b produce
IFOLD = 1A in the Demo Board (see the relevant section).
Inrush current at start-up is reduced with soft-start. An external capacitor (one for each converter) is
charged by an internal 4
A current generator and its linearly ramping voltage increases the setpoint of
the current limit comparator, starting from zero up to the final value of 100 mV. Thus duty cycle reaches
gradually its steady-state value and dangerous current peaks as well as overshoots of the output voltage
are avoided.
+12 V LINEAR REGULATOR
The +12V Linear regulator is capable of delivering up to 120 mA to an external load through pin REG12.
It is supplied from pin V13IN which accepts voltages included in the range of 13 to 20V.
If the application works with input voltages included between 14 and 20V, the supply for the regulator
can be obtained directly from the input source. If such is not the case, the most convenient way to get
the supply is to use an auxiliary winding on the 3.3 V section inductor with a catch diode, Ds, and a filter
capacitor, Cs, as shown in fig. 5. This winding delivers energy to pin V13IN during the recirculation pe-
riod of each switching cycle with a voltage determined by the turns ratio n and little dependent on the in-
put voltage.
DETAILED FUNCTIONAL DESCRIPTION (continued)
L4992
31(26)
32(25)
Rsense
100
6.8K
(3.9K
)
CO
5V(3.3V)
D98IN815
L
30(27)
1N4148
12
6(19)
5(20)
VIN
(b)
IFOLD
Imax
VREF-VF-0.1
VO
IO
(a)
Figure 4.
L4992
9/26
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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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)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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