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參數(shù)資料
| 型號： | LMZ10505EXTTZ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 8.7 A SWITCHING REGULATOR, 1160 kHz SWITCHING FREQ-MAX, PSSO7 |
| 封裝： | 10.16 X 13.77 MM, 4.57 MM HEIGHT, ROHS COMPLIANT, TO-PMOD, 7 PIN |
| 文件頁數(shù)： | 4/22頁 |
| 文件大小： | 1387K |
| 代理商： | LMZ10505EXTTZ |
Additional Features
ENABLE
The LMZ10505EXT features an enable (EN) pin and associ-
ated comparator to allow the user to easily sequence the
LMZ10505EXT from an external voltage rail, or to manually
set the input UVLO threshold. The turn-on or rising threshold
and hysteresis for this comparator are typically 1.23V and
0.15V respectively. The precise reference for the enable com-
parator allows the user to guarantee that the LMZ10505EXT
will be disabled when the system demands it to be.
The EN pin should not be left floating. For always-on opera-
tion, connect EN to VIN.
ENABLE AND UVLO
Using a resistor divider from VIN to EN as shown in the
schematic diagram below, the input voltage at which the part
begins switching can be increased above the normal input
UVLO level according to
For example, suppose that the required input UVLO level is
3.69V. Choosing R
enb = 10 k, then we calculate Rent = 20
k
.
30118344
Alternatively, the EN pin can be driven from another voltage
source to cater to system sequencing requirements common-
ly found in FPGA and other multi-rail applications. The fol-
lowing schematic shows an LMZ10505EXT that is sequenced
to start based on the voltage level of a master system rail
(V
OUT1).
30118345
SOFT-START
The LMZ10505EXT begins to operate when both the VIN and
EN, voltages exceed the rising UVLO and enable thresholds,
respectively. A controlled soft-start eliminates inrush currents
during startup and allows the user more control and flexibility
when sequencing the LMZ10505EXT with other power sup-
plies.
In the event of either VIN or EN decreasing below the falling
UVLO or enable threshold respectively, the voltage on the
soft-start pin is collapsed by discharging the soft-start capac-
itor by a 14 A (typ.) current sink to ground.
SOFT-START CAPACITOR
Determine the soft-start capacitance with the following rela-
tionship
where V
FB is the internal reference voltage (nominally 0.8V),
I
SS is the soft-start charging current (nominally 2 A) and
C
SS is the external soft-start capacitance.
Thus, the required soft-start capacitor per unit output voltage
startup time is given by
C
SS = 2.5 nF / ms
For example, a 4 ms soft-start time will yield a 10 nF capaci-
tance. The minimum soft-start capacitance is 680 pF.
TRACKING
The LMZ10505EXT can track the output of a master power
supply during soft-start by connecting a resistor divider to the
SS pin. In this way, the output voltage slew rate of the
LMZ10505EXT will be controlled by a master supply for loads
that require precise sequencing. When the tracking function
is used, a small value soft-start capacitor should be connect-
ed to the SS pin to alleviate output voltage overshoot when
recovering from a current limit fault.
30118357
TRACKING - EQUAL SOFT-START TIME
One way to use the tracking feature is to design the tracking
resistor divider so that the master supply output voltage,
V
OUT1, and the LMZ10505EXT output voltage, VOUT2, both
rise together and reach their target values at the same time.
This is termed ratiometric startup. For this case, the equation
governing the values of tracking divider resistors R
trkb and
R
trkt is given by
The above equation includes an offset voltage, of 200 mV, to
ensure that the final value of the SS pin voltage exceeds the
reference voltage of the LMZ10505EXT. This offset will cause
the LMZ10505EXT output voltage to reach regulation slightly
before the master supply. A value of 33 k
1% is recom-
mended for R
trkt as a compromise between high precision and
low quiescent current through the divider while minimizing the
effect of the 2 A soft-start current source.
www.national.com
12
LMZ10505EXT
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMZ10505EXTTZ/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 |
| LMZ10505EXTTZE | 制造商:Texas Instruments 功能描述:IC, BUCK, SYNC, ADJ, 5A, TO-PMOD-7 制造商:Texas Instruments 功能描述:IC, BUCK, SYNC, ADJ, 5A, TO-PMOD-7; Primary Input Voltage:5.5V; No. of Outputs:1; Output Current:5A; Voltage Regulator Case Style:TO-PMOD; No. of Pins:7; Operating Temperature Min:-55C; Operating Temperature Max:125C; MSL:MSL 3 - ;RoHS Compliant: Yes |
| LMZ10505EXTTZE/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 |
| LMZ10505EXTTZX | 制造商:TI 制造商全稱:Texas Instruments 功能描述:5A SIMPLE SWITCHER?? Power Module with 5.5V Maximum Input Voltage for Military and Rugged Applications |
| LMZ10505EXTTZX/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 |
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