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參數(shù)資料
| 型號(hào)： | LM5010AHMHX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 1.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | TSSOP-14 |
| 文件頁(yè)數(shù)： | 2/18頁(yè) |
| 文件大小： | 399K |
| 代理商： | LM5010AHMHX |
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put 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 (VIN), 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 fre-
quency (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 LM5010A (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 regu-
late the desired V
OUT at the minimum VIN is determined from
the following:
(8)
Shutdown
The LM5010A 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. Re-
leasing the RON/SD pin allows normal operation to resume.
The nominal voltage at RON/SD is shown in the Typical Per-
formance 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.
20153818
FIGURE 3. Shutdown Implementation
Current Limit
Current limit detection occurs during the off-time by monitor-
ing the recirculating current through the internal current sense
resistor (R
SENSE). The detection threshold is 1.25A, ±0.25A.
Referring to the Block Diagram, if the current into SGND dur-
ing 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 illus-
trates 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 Cur-
rent waveform illustrates continuous conduction mode oper-
ation with peak and valley inductor currents below the current
limit threshold. When the load current is increased (High Load
Current), the ripple waveform maintains the same amplitude
and frequency since the current falls below the current limit
threshold at the valley of the ripple waveform. Note the aver-
age current in the High Load Current portion of Figure 4 is
above the current limit threshold. 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 fur-
ther 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
OUT and the
switching frequency are reduced as the circuit operates in a
constant current mode. The load current (I
OCL) is equal to the
current limit threshold plus half the ripple current (
ΔI/2). The
ripple amplitude (
ΔI) is calculated from:
(9)
The current limit threshold can be increased by connecting an
external resistor (R
CL) between SGND and ISEN. RCL typi-
cally is less than 1
, and the calculation of its value is ex-
plained in the Applications Information section. If the current
limit threshold is increased by adding R
CL, the maximum con-
tinuous load current should not exceed 1.5A, and the peak
current out of the SW pin should not exceed 2A.
www.national.com
10
LM5010A
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM5010AMH | 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 |
| LM5010AMH/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Hi Volt 1A Step Down Switching Reg 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 |
| LM5010AMHE | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 6V to 75V 14-Pin TSSOP EP T/R |
| LM5010AMHE/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 |
| LM5010AMHX | 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 |
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