- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄384596 > LM25010MHX (NATIONAL SEMICONDUCTOR CORP) 42V, 1.0A Step-Down Switching Regulator PDF資料下載
參數(shù)資料
| 型號(hào)： | LM25010MHX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 42V, 1.0A Step-Down Switching Regulator |
| 中文描述： | 1.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | PLASTIC, TSSOP-14 |
| 文件頁數(shù)： | 10/17頁 |
| 文件大?。?/td> | 776K |
| 代理商： | LM25010MHX |
Regulation Comparator
The feedback voltage at the FB pin is compared to the
voltage at the SS pin (2.5V,
±
2%). In normal operation an
on-time period is initiated when the voltage at FB falls below
2.5V. The buck switch conducts for the on-time programmed
by R
, causing the FB voltage to rise above 2.5V. After the
on-time period the buck switch remains off until the FB
voltage falls below 2.5V. Input bias current at the FB pin is
less than 5 nA over temperature.
Over-Voltage Comparator
The feedback voltage at FB is compared to an internal 2.9V
reference. If the voltage at FB rises above 2.9V the on-time
is immediately terminated. This condition can occur if the
input voltage, or the output load, changes suddenly. The
buck switch remains off until the voltage at FB falls below
2.5V.
ON-Time Control
The on-time of the internal buck switch is determined by the
R
ON
resistor and the input voltage (V
IN
), and is calculated as
follows:
(5)
The R
ON
resistor can be determined from the desired on-
time by re-arranging Equation 5 to the following:
(6)
To set a specific continuous conduction mode switching
frequency (Fs), the R
ON
resistor is determined from the
following:
(7)
In high frequency applications the minimum value for t
ON
is
limited by the maximum duty cycle required for regulation
and the minimum off-time of the LM25010 (260 ns,
±
15%).
The fixed off-time limits the maximum duty cycle achievable
with a low voltage at VIN. The minimum allowed on-time to
regulate the desired V
OUT
at the minimum V
IN
is determined
from the following:
(8)
Shutdown
The LM25010 can be remotely shut down by forcing the
RON/SD pin below 0.7V with a switch or open drain device.
See Figure 3. In the shutdown mode the SS pin is internally
grounded, the on-time one-shot is disabled, the input current
at VIN is reduced, and the V
CC
bypass switch is turned off.
The V
CC
regulator is not disabled in the shutdown mode.
Releasing the RON/SD pin allows normal operation to re-
sume. The nominal voltage at RON/SD is shown in the
Typical Performance Characteristics. When switching the
RON/SD pin, the transition time should be faster than one to
two cycles of the regulator’s nominal switching frequency.
Current Limit
Current limit detection occurs during the off-time by monitor-
ing the recirculating current through the internal current
sense resistor (R
). The detection threshold is 1.25A,
±
0.25A. Referring to the Block Diagram, if the current into
SGND during the off-time exceeds the threshold level the
current limit comparator delays the start of the next on-time
period. The next on-time starts when the current into SGND
is below the threshold
and
the voltage at FB is below 2.5V.
Figure 4 illustrates the inductor current waveform during
normal operation and during current limit. The output current
I
O
is the average of the inductor ripple current waveform.
The Low Load Current waveform illustrates continuous con-
duction mode operation with peak and valley inductor cur-
rents below the current limit threshold. When the load cur-
rent is increased (High Load Current), the ripple waveform
maintains the same amplitude and frequency since the cur-
rent falls below the current limit threshold at the valley of the
ripple waveform. Note the average current in the High Load
Current portion of Figure 4 is above the current limit thresh-
old. Since the current reduces below the threshold in the
normal off-time each cycle, the start of each on-time is not
delayed, and the circuit’s output voltage is regulated at the
correct value. When the load current is further increased
such that the lower peak would be above the threshold, the
off-time is lengthened to allow the current to decrease to the
threshold before the next on-time begins (Current Limited
portion of Figure 4). Both V
and the switching frequency
are reduced as the circuit operates in a constant current
20172718
FIGURE 3. Shutdown Implementation
L
www.national.com
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM25010SD | 42V, 1.0A Step-Down Switching Regulator |
| LM25010SDX | 42V, 1.0A Step-Down Switching Regulator |
| LM258P | LOW POWER DUAL OPERATIONAL AMPLIFIERS |
| LM2590HVT-ADJ | SIMPLE SWITCHER Power Converter 150 kHz 1A Step-Down Voltage Regulator, with Features |
| LM2590HV | Octal Buffers/Drivers With 3-State Outputs 20-SSOP -40 to 85 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM25010MHX/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 |
| LM25010Q0MH | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM25010Q0MH/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 |
| LM25010Q0MHX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:42V, 1.0A Step-Down Switching Regulator |
| LM25010Q0MHX/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 |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。