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參數(shù)資料
| 型號： | LTC3728LZEUH |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A DUAL SWITCHING CONTROLLER, 590 kHz SWITCHING FREQ-MAX, PQCC28 |
| 封裝： | 5 X 5 MM, PLASTIC, MO-220WHHD, QFN-28 |
| 文件頁數(shù)： | 3/32頁 |
| 文件大?。?/td> | 467K |
| 代理商： | LTC3728LZEUH |
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LTC3728LZ
11
3728lzf
either output is not within ±7.5% of the nominal output
level as determined by the resistive feedback divider. When
both outputs meet the ±7.5% requirement, the MOSFET is
turned off within 10μs and the pin is allowed to be pulled
up by an external resistor to a source of up to 7V.
Foldback Current, Short-Circuit Detection and Short-
Circuit Latchoff
The RUN/SS capacitors are used initially to limit the inrush
current of each switching regulator. After the controller
has been started and been given adequate time to charge
up the output capacitors and provide full load current, the
RUN/SS capacitor is used in a short-circuit time-out circuit.
If the output voltage falls to less than 70% of its nominal
output voltage, the RUN/SS capacitor begins discharging
on the assumption that the output is in an overcurrent
and/or short-circuit condition. If the condition lasts for
a long enough period as determined by the size of the
RUN/SS capacitor, the controller will be shut down until
the RUN/SS pin(s) voltage(s) are recycled. This built-in
latchoff can be overridden by providing a >5A pull-up
at a compliance of 6V to the RUN/SS pin(s). This current
shortens the soft start period but also prevents net dis-
charge of the RUN/SS capacitor(s) during an overcurrent
and/or short-circuit condition. Foldback current limiting
is also activated when the output voltage falls below
70% of its nominal level whether or not the short-circuit
latchoff circuit is enabled. Even if a short is present and
the short-circuit latchoff is not enabled, a safe, low output
current is provided due to internal current foldback and
actual power wasted is low due to the efcient nature of
the current mode switching regulator.
THEORY AND BENEFITS OF 2-PHASE OPERATION
The LTC3728 family of dual high efciency DC/DC control-
lers brings the considerable benets of 2-phase operation
to portable applications for the rst time. Notebook comput-
ers, PDAs, handheld terminals and automotive electronics
will all benet from the lower input ltering requirement,
reduced electromagnetic interference (EMI) and increased
efciency associated with 2-phase operation.
When constant-frequency dual switching regulators oper-
ated both channels in phase (i.e., single-phase operation),
both switches turned on at the same time, causing cur-
rent pulses of up to twice the amplitude of those for one
regulator to be drawn from the input capacitor and battery.
These large amplitude current pulses increase the total
RMS current owing from the input capacitor, requiring
the use of more expensive input capacitors and increasing
both EMI and losses in the input capacitor and battery.
With 2-phase operation, the two channels of the dual-
switching regulator are operated 180 degrees out of phase.
This effectively interleaves the current pulses drawn by the
switches, greatly reducing the overlap time where they add
together. The result is a signicant reduction in total RMS
input current, which in turn allows less expensive input
capacitors to be used, reduces shielding requirements for
EMI and improves real world operating efciency.
Figure 3 compares the input waveforms for a representative
single-phase dual switching regulator to the LTC3728LZ
2-phase dual switching regulator. An actual measure-
ment of the RMS input current under these conditions
shows that 2-phase operation dropped the input current
from 2.53ARMS to 1.55ARMS. While this is an impressive
reduction in itself, remember that the power losses are
proportional to IRMS
2,meaningthattheactualpowerwasted
is reduced by a factor of 2.66. The reduced input ripple
voltage also means less power is lost in the input power
path, which could include batteries, switches, trace/con-
nector resistances and protection circuitry. Improvements
in both conducted and radiated EMI also directly accrue as
a result of the reduced RMS input current and voltage.
Of course, the improvement afforded by 2-phase opera-
tion is a function of the dual switching regulator’s relative
duty cycles which, in turn, are dependent upon the input
voltage VIN (Duty Cycle = VOUT/VIN). Figure 4 shows how
the RMS input current varies for single-phase and 2-phase
operation for 3.3V and 5V regulators over a wide input
voltage range.
It can readily be seen that the advantages of 2-phase opera-
tion are not just limited to a narrow operating range, but
in fact extend over a wide region. A good rule of thumb
for most applications is that 2-phase operation will reduce
the input capacitor requirement to that for just one channel
operating at maximum current and 50% duty cycle.
OPERATION (Refer to Functional Diagram)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LTC3728LZEUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3728LZEUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3729EG | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3729EG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LTC3729EG#PBF-ND | 制造商: 功能描述: 制造商:undefined 功能描述: |
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