參數(shù)資料
型號(hào)： LM2746
廠商： National Semiconductor Corporation
英文描述： Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
中文描述： 低壓N溝道MOSFET同步降壓穩(wěn)壓控制器
文件頁(yè)數(shù)： 9/24頁(yè)
文件大?。?/td> 1087K
代理商： LM2746
Block Diagram
20147703
Application Information
THEORY OF OPERATION
The LM2746 is a voltage-mode, high-speed synchronous
buck regulator with a PWM control scheme. It is designed for
use in set-top boxes, thin clients, DSL/Cable modems, and
other applications that require high efficiency buck convert-
ers. It has output shutdown (SD), input undervoltage lock-out
(UVLO) mode and power good (PWGD) flag (based on
overvoltage and undervoltage detection). The overvoltage
and undervoltage signals are logically OR’ed to drive the
power good signal and provide a logic signal to the system if
the output voltage goes out of regulation. Current limit is
achieved by sensing the voltage V
DS
across the low side
MOSFET.
START UP/SOFT-START
When V
CC
exceeds 2.76V and the shutdown pin (SD) sees
a logic high, the soft-start period begins. Then an internal,
fixed 10 μA source begins charging the soft-start capacitor.
During soft-start the voltage on the soft-start capacitor C
is
connected internally to the non-inverting input of the error
amplifier. The soft-start period lasts until the voltage on the
soft-start capacitor exceeds the LM2746 reference voltage
of 0.6V. At this point the reference voltage takes over at the
non-inverting error amplifier input. The capacitance of C
determines the length of the soft-start period, and can be
approximated by:
Where C
SS
is in μF and t
SS
is in ms.
During soft start the Power Good flag is forced low and it is
released when the FB pin voltage reaches 70% of 0.6V. At
this point the chip enters normal operation mode, and the
output overvoltage and undervoltage monitoring starts.
NORMAL OPERATION
While in normal operation mode, the LM2746 regulates the
output voltage by controlling the duty cycle of the high side
and low side MOSFETs (see Typical Application Circuit).The
equation governing output voltage is:
The PWM frequency is adjustable between 50 kHz and 1
MHz and is set by an external resistor, R
, between the
FREQ pin and ground. The resistance needed for a desired
frequency is approximately:
L
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相關(guān)PDF資料
PDF描述
LM2746MXA Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
LM2746MXAX Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
LM2753SD High Power Switched Capacitor Voltage Convertor/Flash LED Driver
LM2753 High Power Switched Capacitor Voltage Convertor/Flash LED Driver
LM2753SDX High Power Switched Capacitor Voltage Convertor/Flash LED Driver
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2746MXA 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
LM2746MXA/NOPB 功能描述:IC REG CTRLR BUCK PWM VM 14TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR)
LM2746MXAX 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
LM2746MXAX/NOPB 功能描述:IC REG CTRLR BUCK PWM VM 14TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:100% 電源電壓:8.2 V ~ 30 V 降壓:無(wú) 升壓:無(wú) 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:是 工作溫度:0°C ~ 70°C 封裝/外殼:8-DIP（0.300"，7.62mm） 包裝:管件 產(chǎn)品目錄頁(yè)面:1316 (CN2011-ZH PDF)
LM2747 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Synchronous Buck Controller with Pre-bias Startup, and Optional Clock Synchronization
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