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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)： | 5/32頁 |
| 文件大?。?/td> | 467K |
| 代理商： | LTC3728LZEUH |
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LTC3728LZ
13
3728lzf
Figure 1 on the rst page is a basic LTC3728LZ application
circuit. External component selection is driven by the load
requirement, and begins with the selection of RSENSE and
the inductor value. Next, the power MOSFETs and D1 are
selected. Finally, CIN and COUT are selected. The circuit
shown in Figure 1 can be congured for operation up to an
input voltage of 28V (limited by the external MOSFETs).
RSENSE Selection For Output Current
RSENSE is chosen based on the required output current.
The current comparator has a maximum threshold of
75mV/RSENSE and an input common mode range of SGND
to 1.1(INTVCC). The current comparator threshold sets the
peak of the inductor current, yielding a maximum average
output current IMAX equal to the peak value less half the
peak-to-peak ripple current, ΔIL.
Allowing a margin for variations in the IC and external
component values yields:
R
mV
I
SENSE
MAX
=
50
When using the controller in very low dropout conditions,
the maximum output current level will be reduced due to the
internal compensation required to meet stability criterion
for buck regulators operating at greater than 50% duty
factor. A curve is provided to estimate this reduction in
peak output current level depending upon the operating
duty factor.
Operating Frequency
The IC uses a constant frequency phase-lockable ar-
chitecture with the frequency determined by an internal
capacitor. This capacitor is charged by a xed current plus
an additional current which is proportional to the voltage
applied to the PLLFLTR pin. Refer to Phase-Locked Loop
and Frequency Synchronization in the Applications Infor-
mation section for additional information.
A graph for the voltage applied to the PLLFLTR pin vs
frequency is given in Figure 5. As the operating frequency
is increased the gate charge losses will be higher, reducing
efciency (see Efciency Considerations). The maximum
switching frequency is approximately 550kHz.
APPLICATIONS INFORMATION
Inductor Value Calculation
The operating frequency and inductor selection are inter-
related in that higher operating frequencies allow the use
of smaller inductor and capacitor values. So why would
anyone ever choose to operate at lower frequencies with
larger components? The answer is efciency. A higher
frequency generally results in lower efciency because
of MOSFET gate charge losses. In addition to this basic
trade-off, the effect of inductor value on ripple current and
low current operation must also be considered.
The inductor value has a direct effect on ripple current.
The inductor ripple current ΔIL decreases with higher
inductance or frequency and increases with higher VIN:
I
fL
V
L
OUT
IN
=
1
()( )
–
Accepting larger values of ΔIL allows the use of low in-
ductances, but results in higher output voltage ripple and
greater core losses. A reasonable starting point for setting
ripple current is ΔIL=0.3(IMAX). The maximum ΔIL occurs
at the maximum input voltage.
Figure 5. PLLFLTR Pin Voltage vs Frequency
OPERATING FREQUENCY (kHz)
200
300
400
500
600
PLLFLTR
PIN
VOLTAGE
(V)
3728LZ F05
2.5
2.0
1.5
1.0
0.5
0
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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® 標準包裝: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® 標準包裝: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® 標準包裝: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 |
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| LTC3729EG#PBF-ND | 制造商: 功能描述: 制造商:undefined 功能描述: |
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