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參數資料
| 型號： | L6917D |
| 廠商： | STMICROELECTRONICS |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | SO-28 |
| 文件頁數： | 8/27頁 |
| 文件大?。?/td> | 411K |
| 代理商： | L6917D |
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L6917
16/27
with unity gain eliminating the errors. Keeping the FBR and FBG traces parallel and guarded by a power plane
results in common mode coupling for any picked-up noise.
If remote sense is not required, the output voltage is sensed by the VSEN pin connecting it directly to the output
voltage. In this case the FBG and FBR pins must be connected anyway to the regulated voltage.
Input Capacitor
The input capacitor has to sustain the ripple current produced during the on time of the upper MOSFETS. Con-
sidering the dual phase topology, the input rms current is highly reduced because of the peak current is one half
if compared with a single-phase solution.
Input capacitor must have a low ESR to minimize the losses. The rms value of this ripple is:
Where D is the duty cycle. The equation reaches its maximum value width D=0.5. The losses in worst case are:
Input bulk capacitor must be equally divided between high-side drain mosfets and placed as close as possible
to reduce switching noise above all during load transient. A symmetrical power path will help to improve tran-
sient response. Input coil may be used taking from this point the supply for the controller VCC and VCCDRV,
designing a ’star connection’.
IC’s power supplies filter capacitor must be placed as close as possible to VCC and VCCDRV pins; for the VCC
pins a typical value is of 1
F and must be used connected between VCC and SGND pins. For better noise fil-
tering a series resistor of a few tenth ohm is suggested since the device typically works with the same power
supply used for the power conversion (noisy because of the switching mosfet).
Capacitor on VCCDRV pin filter the low-side drivers power supply toward the PGND pin; 1
F capacitor is rec-
ommended.
The 12V input power bus can be used to supply the bootstrap capacitor alone or together with a 5.1V zener
diode in series and a 1
F capacitor for filtering. A gate-source voltage of 7V is so ready to switch on the high-
side mosfets with a good compromise of efficiency and controller power dissipation. Alternatively a linear regu-
lator can be used to produce the supply for high-side and low-side power mosfet drivers. This can help to opti-
mize the choose of switching frequency, controller power dissipation and overall efficiency.
Output Capacitor
Since the microprocessors require a current variation beyond 50A doing load transients, with a slope in the
range of tenth A/
s, the output capacitor is a basic component for the fast response of the power supply.
Dual phase topology reduces the amount of output capacitance needed because of faster load transient re-
sponse (switching frequency is doubled at the load connections). Current ripple cancellation due to the 180
°
phase shift between the two phases also reduces requirements on the output ESR to sustain a specified voltage
ripple.
When a load transient is applied to the converter’s output, for first few microseconds the current to the load is
supplied by the output capacitors. The controller recognizes immediately the load transient and increases the
duty cycle, but the current slope is limited by the inductor value.
The output voltage has a first drop due to the current variation inside the capacitor (neglecting the effect of the
ESL):
VOUT = IOUT ESR
A minimum capacitor value is required to sustain the current during the load transient without discharge it. The
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OU T
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相關代理商/技術參數 |
參數描述 |
|---|---|
| L6917DTR | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| L6918 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:5 BIT PROGRAMMABLE MULTIPHASE CONTROLLER |
| L6918A | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:5 BIT PROGRAMMABLE MULTIPHASE CONTROLLER |
| L6918AD | 功能描述:DC/DC 開關控制器 Prog Multi-Phase Cnt RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| L6918ADTR | 功能描述:DC/DC 開關控制器 Prog Multi-Phase Cnt RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
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