參數(shù)資料
型號(hào)： LM25005MHX
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 穩(wěn)壓器
英文描述： 42V, 2.5A STEP-DOWN SWITCHING REGULATOR
中文描述： 4.25 A SWITCHING REGULATOR, 525 kHz SWITCHING FREQ-MAX, PDSO20
封裝： TSSOP-20
文件頁(yè)數(shù)： 10/21頁(yè)
文件大?。?/td> 756K
代理商： LM25005MHX
Detailed Operating Description
The LM25005 switching regulator features all of the func-
tions necessary to implement an efficient high voltage buck
regulator using a minimum of external components. This
easy to use regulator integrates a 42V N-Channel buck
switch with an output current capability of 2.5 Amps. The
regulator control method is based on current mode control
utilizing an emulated current ramp. Peak current mode con-
trol provides inherent line voltage feed-forward, cycle-by-
cycle current limiting, and ease of loop compensation. The
use of an emulated control ramp reduces noise sensitivity of
the pulse-width modulation circuit, allowing reliable process-
ing of very small duty cycles necessary in high input voltage
applications. The operating frequency is user programmable
from 50kHz to 500kHz. An oscillator synchronization pin
allows multiple LM25005 regulators to self synchronize or be
synchronized to an external clock. The output voltage can be
set as low as 1.225V. Fault protection features include,
current limiting, thermal shutdown and remote shutdown
capability. The device is available in the TSSOP-20 package
featuring an exposed pad to aid thermal dissipation.
The functional block diagram and typical application of the
LM25005 are shown in
Figure 1
. The LM25005 can be
applied in numerous applications to efficiently step-down a
high, unregulated input voltage. The device is well suited for
telecom, industrial and automotive power bus voltage
ranges.
High Voltage Start-Up Regulator
The LM25005 contains a dual-mode internal high voltage
startup regulator that provides the Vcc bias supply for the
PWM controller and boot-strap MOSFET gate driver. The
input pin (Vin) can be connected directly to the input voltage,
as high as 42 Volts. For input voltages below 9V, a low
dropout switch connects Vcc directly to Vin. In this supply
range, Vcc is approximately equal to Vin. For Vin voltage
greater than 9V, the low dropout switch is disabled and the
Vcc regulator is enabled to maintain Vcc at approximately
7V. The wide operating range of 7V to 42V is achieved
through the use of this dual mode regulator.
The output of the Vcc regulator is current limited to 20mA.
Upon power up, the regulator sources current into the ca-
pacitor connected to the Vcc pin. When the voltage at the
Vcc pin exceeds the Vcc UVLO threshold of 6.3V and the SD
pin is greater than 1.225V, the output switch is enabled and
a soft-start sequence begins. The output switch remains
enabled until Vcc falls below 5.3V or the SD pin falls below
1.125V.
An auxiliary supply voltage can be applied to the Vcc pin to
reduce the IC power dissipation. If the auxiliary voltage is
greater than 7.3V, the internal regulator will essentially
shut off, reducing the IC power dissipation. The Vcc regula-
tor series pass transistor includes a diode between Vcc and
Vin that should not be forward biased in normal operation.
Therefore the auxiliary Vcc voltage should never exceed the
Vin voltage.
In high voltage applications extra care should be taken to
ensure the Vin pin does not exceed the absolute maximum
voltage rating of 45V. During line or load transients, voltage
ringing on the Vin line that exceeds the Absolute Maximum
Ratings can damage the IC. Both careful PC board layout
and the use of quality bypass capacitors located close to the
Vin and GND pins are essential.
20170004
FIGURE 2. Vin and Vcc Sequencing
L
www.national.com
10
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM25005MHX/NOPB 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
LM25007 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Boot Capacitor Regulation in LM25007 Constant-On-Time (COT) Converter
LM25007_08 制造商:NSC 制造商全稱:National Semiconductor 功能描述:42V, 0.5A Step-Down Switching Regulator
LM25007_11 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Boot Capacitor Regulation in LM25007 Constant-On-Time (COT) Converter
LM25007EVAL 功能描述:電源管理IC開發(fā)工具 LM25007 EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
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