參數(shù)資料
型號(hào)： L6726A
廠商： 意法半導(dǎo)體
英文描述： Single phase PWM controller
中文描述： 單相PWM控制器
文件頁(yè)數(shù)： 13/24頁(yè)
文件大?。?/td> 399K
代理商： L6726A
L6726A
Protections
13/24
7
Protections
7.1
Over current protection
The over current 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, R
dsON
. This method reduces cost and enhances converter efficiency by avoiding
the use of expensive and space-consuming sense resistors.
The low side R
dsON
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
Over Current Event is detected. If two Over Current Events are detected in two consecutive
switching cycles, the protection will be triggered and the device will turn off both LS and HS
MOSFETs in a latched condition.
To recover from Over Current Protection triggered, VCC power supply must be cycled.
7.1.1
Over current threshold setting
L6726A allows to easily program an Over Current Threshold ranging from 50mV to 550mV,
simply by adding a resistor (R
OCSET
) between LGATE and GND.
During a short period of time (5.5ms - 6.5ms) following VCC rising over UVLO threshold, an
internal 10μA current (I
OCSET
) is sourced from LGATE pin, determining a voltage drop
across R
OCSET
. This voltage drop will be sampled and internally held by the device as Over
Current Threshold. The OC setting procedure overall time length ranges from 5.5ms to
6.5ms, proportionally to the threshold being set.
Connecting a R
OCSET
resistor between LGATE and GND, the programmed threshold will be:
I
R
R
dsON
R
OCSET
values range from 5k
to 55k
.
If the voltage drop across R
OCSET
is too low, the system will be very sensitive to start-up
inrush current and noise. This can result in undesired OCP triggering. In this case, consider
increasing R
OCSET
value.
In case R
OCSET
is not connected, the device switches the OCP threshold to a 375mV default
value: an internal safety clamp on LGATE is triggered as soon as LGATE voltage reaches
700mV (typ), enabling the 375mV default threshold and suddenly ending OC setting phase.
See
Figure 6
for OC threshold setting procedure timings picture and oscilloscope sample
waveforms.
7.2
Feedback disconnection protection
In order to provide load protection even if FB pin is not connected, a 100nA bias current is
always sourced from this pin. If FB pin is not connected, bias current will permanently pull
up FB: this forces COMP pin low, avoiding output voltage rising to dangerous levels.
I
OCth
----------------------------------------------
=
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L6726A_07 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Single phase PWM controller
L6726A_10 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Single phase PWM controller
L6726ATR 功能描述:開(kāi)關(guān)變換器、穩(wěn)壓器與控制器 PWM Controler Single 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
L6726-D18-T 制造商:UTC-IC 制造商全稱:UTC-IC 功能描述:UNIVERSAL SPEECH CIRCUIT
L6726G-D18-T 制造商:UTC-IC 制造商全稱:UTC-IC 功能描述:UNIVERSAL SPEECH CIRCUIT
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