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参数资料
| 型号： | LTC3727AIG-1#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 5.30 MM, PLASTIC, SSOP-28 |
| 文件页数： | 5/32页 |
| 文件大小： | 328K |
| 代理商： | LTC3727AIG-1#TR |
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LTC3727A-1
13
3727a1fa
Figure 1 on the rst page is a basic LTC3727A-1 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 LTC3727A-1 current comparator has a maximum
threshold of 135mV/RSENSE and an input common mode
range of SGND to 14V. 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 LTC3727A-1 and
external component values yields:
R
mV
I
SENSE
MAX
=
90
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 reducton
in peak output current level depending upon the operating
duty factor.
Operating Frequency
The LTC3727A-1 uses a constant frequency phase-lockable
architecture 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
Information 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
APPLICATIONS INFORMATION
Figure 5. PLLFLTR Pin Voltage vs Frequency
OPERATING FREQUENCY (kHz)
200
250
300
350
550
400
450
500
PLLFLTR
PIN
VOLTAGE
(V)
3727 F05
2.5
2.0
1.5
1.0
0.5
0
is increased the gate charge losses will be higher, reducing
efciency (see Efciency Considerations). The maximum
switching frequency is approximately 550kHz.
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:
ΔI
fL
V
L
OUT
IN
=
1
()( )
–
Accepting larger values of
ΔIL allows the use of low
inductances, 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.
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| LTC3727EG | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3727EG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3727EG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3727EG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3727EG-1 | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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