參數(shù)資料
型號(hào)： L6732TR
廠商： STMICROELECTRONICS
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16
封裝： LEAD FREE, HTSSOP-16
文件頁(yè)數(shù)： 14/37頁(yè)
文件大小： 898K
代理商： L6732TR
L6732
Device description
21/37
5.12
Bootstrap anti-discharging system
This built-in system avoids that the voltage across the bootstrap capacitor becomes less
than 3.3 V. An internal comparator senses the voltage across the external bootstrap
capacitor keeping it charged, eventually turning-on the low-side MOSFET for approximately
200 ns. If the bootstrap capacitor is not enough charged the high-side MOSFET cannot be
effectively turned-on and it will present a higher RDS(on). In some cases the OCP can be
also triggered. The bootstrap capacitor can be discharged during the soft-start in case of
very long soft-start time and light loads. It's also possible to mention one application
condition during which the bootstrap capacitor can be discharged:
5.12.1
Fan's power supply
In many applications the FAN is a DC MOTOR driven by a voltage-mode DC/DC converter.
Often only the speed of the MOTOR is controlled by varying the voltage applied to the input
terminal and there's no control on the torque because the current is not directly controlled.
In order to vary the MOTOR speed the output voltage of the converter must be varied. The
L6732 has a dedicated pin called EAREF (see the related section) that allows providing an
external reference to the non-inverting input of the error-amplifier.
In these applications the duty cycle depends on the MOTOR's speed and sometimes 100 %
has to be set in order to go at the maximum speed. Unfortunately in these conditions the
bootstrap capacitor can not be recharged and the system cannot work properly. Some PWM
controller limits the maximum duty-cycle to 80-90 % in order to keep the bootstrap cap
charged but this make worse the performance during the load transient. Thanks to the
“bootstrap anti-discharging system” the L6732 can work at 100 % without any problem. The
following picture shows the device behavior when input voltage is 5 V and 100 % is set by
the external reference.
Figure 16.
100 % duty cycle operation
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L6733 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Advanced modular synchronous PWM controller
L6733TR 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Advanced modular synchronous PWM controller
L6738 功能描述:電流型 PWM 控制器 Single-Phase SD Cont 5V to 12V bus 1.5V RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
L6738A 功能描述:電流型 PWM 控制器 Single-phase PWM Light Load EFF RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
L6738ATR 功能描述:電流型 PWM 控制器 Single Phase PWM CNTRL Light-Load EFF RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
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