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參數(shù)資料
| 型號： | LP3907SQ-JIXI |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.5 A DUAL SWITCHING CONTROLLER, 2100 kHz SWITCHING FREQ-MAX, QCC24 |
| 封裝： | 4 X 4 MM, 0.8 MM HEIGHT, LLP-24 |
| 文件頁數(shù)： | 11/44頁 |
| 文件大?。?/td> | 3058K |
| 代理商： | LP3907SQ-JIXI |
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tions. When the output drops below the ‘low’ PFM threshold,
the cycle repeats to restore the output voltage to ~1.6% above
the nominal PWM output voltage.
If the load current should increase during PFM mode (see
figure below) causing the output voltage to fall below the
‘low2’ PFM threshold, the part will automatically transition into
fixed-frequency PWM mode.
SW1, SW2 OPERATION
SW1 and SW2 have selectable output voltages ranging from
0.8V to 3.5V (typ.). Both SW1 and SW2 in the LP3907 are
I2C register controlled and are enabled by default through the
internal state machine of the LP3907 following a Power-On
event that moves the operating mode to the Active state. (see
Power On Sequence). The SW1 and SW2 output voltages
revert to default values when the power on sequence has
been completed. The default output voltage for each buck
converter is factory programmable. (See Application Notes).
SW1, SW2 CONTROL REGISTERS
SW1, SW2 can be enabled/disabled through the correspond-
ing control register.
The Modulation mode PWM/PFM is by default automatic and
depends on the load as described above in the functional de-
scription. The modulation mode can be overridden by setting
I2C bit to a logic 1 in the corresponding buck control register,
forcing the buck to operate in PWM mode regardless of the
load condition.
30017814
SHUTDOWN MODE
During shutdown the PFET switch, reference, control and
bias circuitry of the converters are turned off. The NFET
switch will be on in shutdown to discharge the output. When
the converter is enabled, soft start is activated. It is recom-
mended to disable the converter during the system power up
and under voltage conditions when the supply is less than
2.8V.
SOFT START
The soft-start feature allows the power converter to gradually
reach the initial steady state operating point, thus reducing
start-up stresses and surges. The two LP3907 buck convert-
ers have a soft-start circuit that limits in-rush current during
start-up. During start-up the switch current limit is increased
in steps. Soft start is activated only if EN goes from logic low
to logic high after V
IN reaches 2.8V. Soft start is implemented
by increasing switch current limit in steps of 180mA, 300mA,
and 720mA for Buck1; 161mA, 300mA and 536mA for Buck2
(typ. Switch current limit). The start-up time thereby depends
on the output capacitor and load current demanded at start-
up.
LOW DROPOUT OPERATION
The LP3907 can operate at 100% duty cycle (no switching;
PMOS switch completely on) for low drop out support of the
output voltage. In this way the output voltage will be controlled
down to the lowest possible input voltage. When the device
operates near 100% duty cycle, output voltage ripple is ap-
proximately 25mV. The minimum input voltage needed to
support the output voltage is
V
IN, MIN = ILOAD * (RDSON, PFET + RINDUCTOR) + VOUT
— ILOAD
Load current
— RDSON, PFET
Drain to source resistance of
PFET switch in the triode region
— RINDUCTOR
Inductor resistance
19
www.national.com
LP3907
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP3907SQ-JXQX | 制造商:Texas Instruments 功能描述: |
| LP3907SQ-JXQX/NOPB | 功能描述:其他電源管理 RoHS:否 制造商:Texas Instruments 輸出電壓范圍: 輸出電流:4 mA 輸入電壓范圍:3 V to 3.6 V 輸入電流: 功率耗散: 工作溫度范圍:- 40 C to + 110 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel |
| LP3907SQ-JXQX/S7001874 | 制造商:Texas Instruments 功能描述:NSCLP3907SQ-JXQX@S7001874 1A&0.6A BUCKS |
| LP3907SQ-JXQXEV | 功能描述:LP3907 EVALUATION BOARD RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - DC/DC 與 AC/DC（離線）SMPS 系列:PowerWise® 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標準包裝:1 系列:True Shutdown™ 主要目的:DC/DC，步升 輸出及類型:1，非隔離 功率 - 輸出:- 輸出電壓:- 電流 - 輸出:1A 輸入電壓:2.5 V ~ 5.5 V 穩(wěn)壓器拓撲結(jié)構(gòu):升壓 頻率 - 開關(guān):3MHz 板類型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| LP3907SQ-JXQXEV/NOPB | 功能描述:BOARD EVAL FOR LP3907 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - DC/DC 與 AC/DC（離線）SMPS 系列:PowerWise® 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標準包裝:1 系列:True Shutdown™ 主要目的:DC/DC，步升 輸出及類型:1，非隔離 功率 - 輸出:- 輸出電壓:- 電流 - 輸出:1A 輸入電壓:2.5 V ~ 5.5 V 穩(wěn)壓器拓撲結(jié)構(gòu):升壓 頻率 - 開關(guān):3MHz 板類型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
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