參數(shù)資料
型號(hào)： L6997S
廠商： 意法半導(dǎo)體
英文描述： STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS
中文描述： 降壓控制器低電壓運(yùn)作
文件頁(yè)數(shù)： 8/30頁(yè)
文件大?。?/td> 515K
代理商： L6997S
L6997S
8/30
(6)
Where
V
OUT
is the output ripple and
V
INT
is the required ripple at the INT pin (100mV typ).
Figure 7. Integrator loop block diagram
Respect to a traditional PWM controller, that has an internal oscillator setting the switching frequency, in a hys-
teretic system the frequency can change with some parameters. For example, while in a standard fixed switch-
ing frequency topology, the increase of the losses (increasing the output current, for example) generates a
variation in the On Time and Off Time, in a fixed On Time topology , the increase of the losses generates only
a variation on the Off Time, changing the switching frequency. In the device is implemented the voltage feed-
forward circuit that allows constant switching frequency during steady-sate operation and withinthe input range
variation. Any way there are many factors affecting switching frequency accuracy in steady-state operation.
Some of these are internal as dead times, which depends on high side MOSFET driver. Others related to the
external components as high side MOSFET gate charge and gate resistance, voltage drops on supply and
ground rails, low side and high side RDSON and inductor parasitic resistance.
During a positive load transient, (the output current increases), the converter switches at its maximum frequency
(the period is TON+TOFFmin) to recover the output voltage drop. During a negative load transient, (the output
current decreases), the device stops to switch (high side MOSFET remains off).
4.3 Transition from PWM to PFM/PSK
To achieve high efficiency at light load conditions, PFM mode is provided. The PFM mode differs from the PWM
mode essentially for the off phase; the on phase is the same. In PFM after a On cycle the system turns-on the
low side MOSFET until the inductor current goes down zero, when the zero-crossing comparator turns off the
low side MOSFET. In PWM mode, after On cycle, the system keeps the low side MOSFET on until the next turn-
on cycle, so the energy stored in the output capacitor will flow through the low side MOSFET to ground. The
PFM mode is naturally implemented in an hysteretic controller enabling the zero current comparator by en-
abling, in fact in PFM mode the system reads the output voltage with a comparator and then turns on the high
side MOSFET when the output voltage goes down to reference value. The device works in discontinuous mode
C
C
INT1
---------------
V
V
INT
------------------
=
PCB TRACES
LOAD
From Vsense
Q
Cint1
R1
INT
Vref
FB
DS
R
S
Vout
Vin
HGATE
LGATE
Q
OSC
Vref
One-shot generator
FFSR
PWM comparator
Vsense
Gndsense
R2
Cint2
HS
LS
Integrator amplifier
+
-
-
+
+
-
相關(guān)PDF資料
PDF描述
L6997STR STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS
L702B 2A QUAD DARLINGTON SWITCH
L702N 2A QUAD DARLINGTON SWITCH
L7203 SMOOTH DRIVE SPINDLE MOTOR FOR OPTICAL DRIVE APPLICATION WITH POWER INTEGRATED
L7203S SMOOTH DRIVE SPINDLE MOTOR FOR OPTICAL DRIVE APPLICATION WITH POWER INTEGRATED
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L6997STR 功能描述:DC/DC 開(kāi)關(guān)控制器 3.0 to 5.5V Step-Dwn RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
L6998-0 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT
L6998-1 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT
L6998-5 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT
L6998-6 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*