參數(shù)資料
型號(hào)： L6727
廠商： STMICROELECTRONICS
元件分類(lèi)： 穩(wěn)壓器
英文描述： 1.5 A SWITCHING CONTROLLER, 350 kHz SWITCHING FREQ-MAX, PDSO8
封裝： LEAD FREE, SOP-8
文件頁(yè)數(shù)： 5/34頁(yè)
文件大?。?/td> 974K
代理商： L6727
L6727
Overcurrent protection
Doc ID 12933 Rev 4
13/34
7
Overcurrent protection
The overcurrent feature protects the converter from a shorted output or overload, by sensing
the output current information across the low side MOSFET drain-source on-resistance,
RdsON. This method reduces cost and enhances converter efficiency by avoiding the use of
expensive and space-consuming sense resistors.
The low side RdsON current sense is implemented by comparing the voltage at the PHASE
node when LS MOSFET is turned on with the programmed OCP threshold voltage,
internally held. If the monitored voltage drop (GND to PHASE) exceeds this threshold, an
overcurrent event is detected. If two overcurrent events are detected in two consecutive
switching cycles, the protection will be triggered and the device will turn off both LS and HS
MOSFETs for 2048 clock cycles (plus internal SS remaining time, if triggered during a SS
phase); then it will begin a new soft-start.
If the overcurrent condition is not removed, the continuous fault will cause L6727 to go into a
hiccup mode with a typical period of 13.6 ms (Figure 5), guaranteeing safe load protection
and very low power dissipation.
7.1
Overcurrent threshold setting
When supplied with VCC = 5 V, L6727 allows to easily program an overcurrent threshold
ranging from 50 mV to 500 mV, simply by adding a resistor (ROCSET) between COMP and
VCC.
During a short period of time (5.5 ms - 6.5 ms) following the first enable (given VCC over
UVLO threshold), an internal 60A current (IOCSET) is sunk from COMP pin, determining a
voltage drop across ROCSET. This voltage drop, differentially sensed between VCC and
COMP, divided by a factor 3, will be sampled and internally held by the device as Over
Current Threshold until next VCC cycling. Differential sensing versus VCC allows OCSET
procedure to be fully independent from VIN rail. The OC setting procedure overall time
length ranges from 5.5 ms to 6.5 ms, proportionally to the threshold being set.
Connecting an ROCSET resistor between COMP and VCC, the programmed threshold will
be:
ROCSET values range from 2.5 kΩ to 25 kΩ.
If the voltage drop across ROCSET is too low, the system will be very sensitive to start-up
inrush current and noise. This can result in a continuous OCP triggering and hiccup mode.
In this case, consider to increase ROCSET value.
In case ROCSET is not connected (and VCC = 5 V), the device will set the maximum
threshold.
If the device is supplied with a VCC higher than 7 V, ROCSET must be not connected. In this
case, as soon as VCC rises over VCC_OC (8 V typ.), L6727 switches OC threshold to 400mV
(internally fixed value).
See Figure 5 for OC threshold setting and soft start oscilloscope sample waveforms.
I
OCth
1
3
---
I
OCSET
R
OCSET
R
dsON
--------------------------------------------
=
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L6727_10 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Single phase PWM controller
L6727TR 功能描述:開(kāi)關(guān)變換器、穩(wěn)壓器與控制器 Single PWM controler RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開(kāi)關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
L6728 功能描述:DC/DC 開(kāi)關(guān)控制器 Sngl phase PWM controller 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
L6728_0706 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Single phase PWM controller with Power Good
L6728A 功能描述:電壓模式 PWM 控制器 Hi-Freq. singl-phase PWM controller w/Po RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
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