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参数资料
| 型号： | LM5041BSDX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 685 kHz SWITCHING FREQ-MAX, DSO16 |
| 封装： | 5 X 5 MM, LLP-16 |
| 文件页数： | 16/16页 |
| 文件大小： | 426K |
| 代理商： | LM5041BSDX |
Detailed Operating Description
The LM5041B PWM controller contains all of the features
necessary to implement either current-fed or voltage-fed
push-pull or bridge power converters. These “Cascaded”
topologies are well suited for multiple output and higher power
applications. The LM5041B includes these four control out-
puts: the buck stage controls (HD and LD) and the push-pull
control outputs (PUSH and PULL). Push-pull outputs are driv-
en at 50% nominal duty cycle at one half of the switching
frequency of the buck stage and can be configured for either
a guaranteed overlap time (for current-fed applications) or a
guaranteed non-overlap time (for voltage-fed applications).
Push-pull stage MOSFETs can be driven directly from the in-
ternal gate drivers while the buck stage requires an external
driver such as the LM5102. The LM5041B includes a high-
voltage start-up regulator that operates over a wide input
range of 15V to 100V. The PWM controller is designed for
high-speed capability including an oscillator frequency range
up to 1 MHz and total propagation delays of less than 100 ns.
Additional features include line Under-Voltage Lock-Out
(UVLO), Soft-Start, an error amplifier, precision voltage ref-
erence, and thermal shutdown.
High Voltage Start-Up Regulator
The LM5041B contains an internal high-voltage start-up reg-
ulator, thus the input pin (Vin) can be connected directly to the
line voltage. The regulator output is internally current limited
to 15 mA. When power is applied, the regulator is enabled
and sources current into an external capacitor connected to
the Vcc pin. The recommended capacitance range for the Vcc
regulator is 0.1F to 100 F. When the voltage on the Vcc pin
reaches the regulation point of 9V, the internal voltage refer-
ence (REF) reaches its regulation point of 5V, and the soft-
start capacitor is charged above its shutdown threshold, the
controller outputs are enabled. The Buck stage outputs will
remain enabled until Vcc falls below 7V, the REF pin voltage
falls below approximately 3V, the SS pin is forced below the
0.45V shutdown threshold or the line Under-Voltage Lock-Out
detector indicates that Vin is out of range. The push-pull out-
puts continue switching until the REF pin voltage falls below
approximately 3V. In typical applications, an auxiliary trans-
former winding is connected through a diode to the Vcc pin.
This winding must raise the Vcc voltage above 9.3V to shut
off the internal start-up regulator. Powering V
CC from an aux-
iliary winding improves efficiency while reducing the
controller's power dissipation. The recommended capaci-
tance range for the Vref regulator output is 0.1F to 10 F.
The external V
CC capacitor must be sized such that the ca-
pacitor maintains a V
CC voltage greater than 7V during the
initial start-up. During a fault mode when the converter auxil-
iary winding is inactive, external current draw on the V
CC line
should be limited so the power dissipated in the start-up reg-
ulator does not exceed the maximum power dissipation of the
controller.
An external start-up or other bias rail can be used instead of
the internal start-up regulator by connecting the V
CC and the
V
IN pins together and feeding the external bias voltage into
the two pins.
Line Under-Voltage Detector
The LM5041B contains a line Under-Voltage Lock-Out
(UVLO) circuit. An external set-point resistor divider from
V
IN to ground sets the operational range of the converter. The
divider must be designed such that the voltage at the UVLO
pin will be greater than 2.5V when V
IN is in the desired oper-
ating range. If the Under-Voltage threshold is not met, both
HD and LD will be forced to low state and VCC regulator will
be disabled while the push-pull outputs continue switching
until the REF pin voltage falls below approximately 3V.
ULVO hysteresis is accomplished with an internal 20 A cur-
rent source that is switched on or off into the impedance of
the set-point divider. When the UVLO threshold is exceeded,
the current source is activated to instantly raise the voltage at
the UVLO pin. When the UVLO pin falls below the 2.5V
threshold, the current source is turned off causing the voltage
at the UVLO pin to fall. The UVLO pin can also be used to
implement a remote enable / disable function. By shorting the
UVLO pin to ground, the converter can be disabled.
Buck Stage Control Outputs
The LM5041B Buck switch maximum duty cycle clamp en-
sures that there will be sufficient off time each cycle to
recharge the bootstrap capacitor used in the high side gate
driver. The Buck switch is guaranteed to be off, and the sync
switch on, for at least 250 ns per switching cycle. The Buck
stage control outputs (LD and HD) are CMOS buffers with
logic levels of 0 to 5V.
During any fault state or Under-Voltage off state, both HD and
LD state will be forced to low by the buck stage control.
Push-Pull Outputs
The push pull outputs operate continuously at a nominal 50%
duty cycle. A distinguishing feature of the LM5041B is the
ability to accurately configure either dead time (both-off) or
overlap time (both-on) on the complementary push-pull out-
puts. The overlap/dead time magnitude is controlled by a
resistor connected to the TIME pin on the controller. The TIME
pin holds one end of the resistor at 2.5V and the other end of
the resistor should be connected to either REF for dead time
control setting or to GND for overlap control. The polarity of
the current in the TIME is detected by the LM5041B The mag-
nitude of the overlap/dead time can be calculated as follows:
Overlap Time (ns) = (3.66 x R
SET) + 7
Overlap Time in ns, R
SET connected to GND, RSET in k
Dead Time (ns) = (3.69 x R
SET) + 21
Dead Time in ns, R
SET connected to REF, RSET in k
Recommended R
SET programming range: 10 k to 100 k
Current-fed designs require a period of overlap to insure there
is a continuous path for the buck inductor current. Voltage-fed
designs require a period of dead time to insure there is no
time when the push-pull transformer acts as a shorted turn to
the low impedance sourcing node. The push-pull outputs al-
ternate continuously under all conditions provided REF the
voltage is greater than 3V.
9
www.national.com
LM5041B
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM5041EVAL | 功能描述:BOARD EVALUATION LM5041 RoHS:否 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:PowerWise® 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| LM5041EVAL/NOPB | 功能描述:电源管理IC开发工具 LM5041 EVAL BOARD RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| LM5041MTC | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| LM5041MTC | 制造商:Texas Instruments 功能描述:PWM CONTROLLER POWERWISE TSSOP16 |
| LM5041MTC/NOPB | 功能描述:电流型 PWM 控制器 Cascaded Pwm Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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