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參數(shù)資料
| 型號： | LM2591HVADJMWC |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, UUC |
| 封裝： | WAFER |
| 文件頁數(shù)： | 8/23頁 |
| 文件大?。?/td> | 722K |
| 代理商： | LM2591HVADJMWC |
Application Information (Continued)
sion. Since this regulator topology can produce an output
voltage that is either greater than or less than the input
voltage, the maximum output current greatly depends on
both the input and output voltage.
To determine how much load current is possible before the
internal device current limit is reached (and power limiting
occurs), the system must be evaluated as a buck-boost
configuration rather than as a buck. The peak switch current
in Amperes, for such a configuration is given as:
where L is in H and f is in Hz. The maximum possible load
current I
LOAD is limited by the requirement that IPEAK ≤ ICLIM.
While checking for this, take I
CLIM to be the lowest possible
current limit value (min across tolerance and temperature is
1.2A for the LM2591HV). Also to account for inductor toler-
ances, we should take the min value of Inductance for L in
the equation above (typically 20% less than the nominal
value). Further, the above equation disregards the drop
across the Switch and the diode. This is equivalent to as-
suming 100% efficiency, which is never so. Therefore expect
I
PEAK to be an additional 10-20% higher than calculated from
the above equation.
The reader is also referred to Application Note AN-1157 for
examples based on positive to negative configuration.
The maximum voltage appearing across the regulator is the
absolute sum of the input and output voltage, and this must
be limited to a maximum of 60V. For example, when convert-
ing +20V to 12V, the regulator would see 32V between the
input pin and ground pin. The LM2591HV has a maximum
input voltage spec of 60V.
Additional diodes are required in this regulator configuration.
Diode D1 is used to isolate input voltage ripple or noise from
coupling through the C
IN capacitor to the output, under light
or no load conditions. Also, this diode isolation changes the
topology to closley resemble a buck configuration thus pro-
viding good closed loop stability. A Schottky diode is recom-
mended for low input voltages, (because of its lower voltage
drop) but for higher input voltages, a fast recovery diode
could be used.
Without diode D3, when the input voltage is first applied, the
charging current of C
IN can pull the output positive by sev-
eral volts for a short period of time. Adding D3 prevents the
output from going positive by more than a diode voltage.
10129339
This circuit has hysteresis
Regulator starts switching at V
IN= 13V
Regulator stops switching at V
IN=8V
FIGURE 10. Undervoltage Lockout with Hysteresis for Inverting Regulator
10129340
C
IN
— 68 F/25V Tant. Sprague 595D
470 F/50V Elec. Panasonic HFQ
C
OUT
— 47 F/20V Tant. Sprague 595D
220 F/25V Elec. Panasonic HFQ
FIGURE 11. Inverting 5V Regulator with Delayed Startup
LM2591HV
www.national.com
16
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2591HVS-3.3 | 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 安裝風格:SMD/SMT |
| LM2591HVS-3.3/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 安裝風格:SMD/SMT |
| LM2591HVS-5.0 | 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 安裝風格:SMD/SMT |
| LM2591HVS-5.0/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 PWR CONVERTER 150KHz 1A ST-DOWN VLTG 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 安裝風格:SMD/SMT |
| LM2591HVS-5.0/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
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