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参数资料
| 型号： | L6726ATR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 1.5 A SWITCHING CONTROLLER, 297 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | SOP-8 |
| 文件页数： | 5/35页 |
| 文件大小： | 986K |
| 代理商： | L6726ATR |
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L6726A
Protections
Doc ID 12754 Rev 4
13/35
7
Protections
7.1
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 in a latched condition.
To recover from over current protection triggered, VCC power supply must be cycled.
7.1.1
Overcurrent threshold setting
L6726A allows to easily program an overcurrent threshold ranging from 50 mV to 550 mV,
simply by adding a resistor (ROCSET) between LGATE and GND.
During a short time following VCC rising over UVLO threshold, an internal 10A current
(IOCSET) is sourced from LGATE pin, determining a voltage drop across ROCSET. This
voltage drop will be sampled and internally held by the device as overcurrent Threshold. The
OC setting procedure overall time length ranges from 5.5 ms to 6.5 ms, proportionally to the
threshold being set.
Connecting a ROCSET resistor between LGATE and GND, the programmed threshold will be:
ROCSET values range from 5 kΩ to 55 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 undesired OCP triggering. In this case, consider
increasing ROCSET value.
In case ROCSET is not connected, the device switches the OCP threshold to a 400 mV
default value: an internal safety clamp on LGATE is triggered as soon as LGATE voltage
reaches 700 mV (typ), enabling the 400 mV 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 100 nA 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
I
OCSET
R
OCSET
R
dsON
--------------------------------------------
=
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| L6726-D18-T | 制造商:UTC-IC 制造商全称:UTC-IC 功能描述:UNIVERSAL SPEECH CIRCUIT |
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| L6726G-S18-R | 制造商:UTC-IC 制造商全称:UTC-IC 功能描述:UNIVERSAL SPEECH CIRCUIT |
| L6726G-S18-T | 制造商:UTC-IC 制造商全称:UTC-IC 功能描述:UNIVERSAL SPEECH CIRCUIT |
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