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參數(shù)資料
| 型號： | LTC3112EDHD#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 12 A SWITCHING REGULATOR, 825 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 5 X 4 MM, 0.75 MM HEIGHT, LEAD FREE, PLASTIC, MO-229WJGD-2, DFN-16 |
| 文件頁數(shù)： | 5/32頁 |
| 文件大小： | 651K |
| 代理商： | LTC3112EDHD#PBF |
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LTC3112
13
3112f
are pulse width modulated to produce the required duty
cycle to support the output regulation voltage.
As the input voltage nears the output voltage, switches
A and D are on for a greater portion of the switching
period, providing a direct current path from VIN to VOUT.
Switches B and C are turned on only enough to ensure
proper regulation and/or provide charging of the BST1
and BST2 capacitors. The internal control circuitry will
determine the proper duty cycle in all modes of operation,
which will vary with load current.
As the input voltage drops well below the output voltage, the
converteroperatessolelyinboostmode.SwitchAturnsonat
maximum duty cycle and switch B turns on just long enough
to refresh the voltage on the BST1 capacitor used to drive
A. Switches C and D are pulse width modulated to produce
the required duty cycle to regulate the output voltage.
This switching algorithm provides a seamless transition
between operating modes and eliminates discontinuities
in average inductor current, inductor current ripple, and
loop transfer function throughout the operational modes.
These advantages result in increased efciency and stab-
ility in comparison to the traditional 4-switch buck-boost
converter.
Powering VCC from an External Source
The LTC3112’s VCC regulator can be powered or back-fed
from an external source up to 5.5V. Advantages of back-
feeding VCC from a voltage above 4.2V include higher
efciency and improved maximum duty cycle at lower
input voltages. These advantages are shown in the Typical
Performance Characteristics curves “MOSFET Resistance
vs VCC” and “Minimum SW1 Low Times.” For 5VOUT
applications, VCC can be easily powered from VOUT using
an external low current Schottky diode as shown in several
applications circuits in the Typical Applications section.
Back-feeding VCC also improves a light load PWM mode
output voltage ripple that occurs when the inductor passes
through zero current. Back-feeding VCC reduces the switch
pin anti-cross conduction times, minimizing the VOUT
ripple during this light-load condition. One disadvantage
of powering VCC from VOUT is that no-load quiescent
current increases at low VIN in Burst Mode operation as
OPERATION
shown in the Typical Performance Characteristics curves
(compared to VCC powered from VIN).
Considerations for Boost Applications
In boost mode, the maximum output current that can be
supported at higher VOUT/VIN ratios is reduced. This ef-
fect is illustrated in the Maximum Output Current PWM
Mode curves in the Typical Performance Characteristics
section. For example at 12VOUT, the LTC3112 needs VIN > 4V
to support 1A. As described previously, powering VCC
from a 5V source (if available) can improve output current
capabilities at low input voltages.
At even lower input voltages (below 3.6V for 12VOUT), the
LTC3112 can run into duty cycle limitations. This occurs
since SW1 and SW2 maximum duty cycles are multiplied,
giving an approximate 70% maximum duty cycle at the
nominal 750kHz switching frequency. Reducing the
switching frequency with the PWM/SYNC pin will increase
the maximum duty cycle, allowing a higher boost ratio
to be achieved. Do not attempt operating the LTC3112
beyond the duty cycle limitations described as this may
result in unstable operation.
Burst Mode OPERATION
When the PWM/SYNC pin is held low, the buck-boost
converter operates utilizing a variable frequency switching
algorithm designed to improve efciency at light load
and reduce the standby current at zero load. In Burst
Mode operation, the inductor is charged with xed peak
amplitude current pulses and as a result only a fraction
of the maximum output current can be delivered when in
Burst Mode operation.
These current pulses are repeated as often as necessary
to maintain the output regulation voltage. The maximum
output current, IMAX, which can be supplied in Burst Mode
operation is dependent upon the input and output voltage
as approximated by the following formula:
IMAX =
0.5
V
IN
VIN + VOUT
(A)
If the buck-boost load exceeds the maximum Burst Mode
current capability, the output rail will lose regulation. In
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3112EFE#PBF | 功能描述:IC REG BUCK BOOST SYNC 20-TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LTC3112EFE#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 1.5MHz TSSOP20 |
| LTC3112EFE#TRPBF | 功能描述:IC REG BUCK BST SYNC ADJ 20TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LTC3112EFEPBF | 制造商:Linear Technology 功能描述:15V 2.5A Synch Buck-Boost DC/DC TSSOP20 |
| LTC3112IDHD#PBF | 功能描述:IC REG BUCK BST SYNC ADJ 16-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
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