- 您现在的位置：买卖IC网 > PDF目录79926 > LTC3872ETS8#PBF (LINEAR TECHNOLOGY CORP) SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8 PDF资料下载
参数资料
| 型号： | LTC3872ETS8#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | 1 MM HEIGHT, LEAD FREE, PLASTIC, MO-193, TSOT-23, 8 PIN |
| 文件页数： | 21/22页 |
| 文件大小： | 245K |
| 代理商： | LTC3872ETS8#PBF |
LTC3872
8
3872fb
Output Voltage Programming
The output voltage is set by a resistor divider according
to the following formula:
VO =1.2V 1+
R2
R1
The external resistor divider is connected to the output
as shown in the Typical Application on the front page,
allowing remote voltage sensing.
Application Circuits
A basic LTC3872 application circuit is shown on the front
page of this datasheet. External component selection is
drivenbythecharacteristicsoftheloadandtheinputsupply.
Duty Cycle Considerations
For a boost converter operating in a continuous conduc-
tion mode (CCM), the duty cycle of the main switch is:
D
=
VO + VD – VIN
VO + VD
where VD is the forward voltage of the boost diode. For
converters where the input voltage is close to the output
voltage,thedutycycleislowandforconvertersthatdevelop
a high output voltage from a low voltage input supply, the
duty cycle is high. The LTC3872 has a built-in circuit that
allows the extension of the maximum duty cycle while
keeping the minimum switch off time unchanged. This
is accomplished by reducing the clock frequency when
the duty cycle is close to 80%. This function allows the
user to obtain high output voltages from low input supply
voltages. The shift of frequency with duty cycle is shown
in the Typical Performance Characteristics section.
The Peak and Average Input Currents
The control circuit in the LTC3872 is measuring the input
current (either by using the RDS(ON) of the power MOSFET
or by using a sense resistor in the MOSFET source), so
the output current needs to be reflected back to the input
in order to dimension the power MOSFET properly. Based
on the fact that, ideally, the output power is equal to the
input power, the maximum average input current is:
IIN(MAX) =
IO(MAX)
1– DMAX
The peak input current is:
IIN(PEAK) = 1+
χ
2
IO(MAX)
1– DMAX
Ripple Current IL and the c Factor
The constant c in the equation above represents the
percentage peak-to-peak ripple current in the inductor,
relative to its maximum value. For example, if 30% ripple
current is chosen, then c = 0.30, and the peak current is
15% greater than the average.
For a current mode boost regulator operating in CCM,
slope compensation must be added for duty cycles above
50% in order to avoid subharmonic oscillation. For the
LTC3872, this ramp compensation is internal. Having an
internally fixed ramp compensation waveform, however,
does place some constraints on the value of the inductor
and the operating frequency. If too large an inductor is
used, the resulting current ramp (IL) will be small relative
to the internal ramp compensation (at duty cycles above
50%), and the converter operation will approach voltage
mode (ramp compensation reduces the gain of the current
loop). If too small an inductor is used, but the converter is
still operating in CCM (continuous conduction mode), the
internal ramp compensation may be inadequate to prevent
subharmonicoscillation.Toensuregoodcurrentmodegain
andavoidsubharmonicoscillation,itisrecommendedthat
the ripple current in the inductor fall in the range of 20%
to 40% of the maximum average current. For example, if
the maximum average input current is 1A, choose an IL
between 0.2A and 0.4A, and a value cbetween 0.2 and 0.4.
Inductor Selection
Givenanoperatinginputvoltagerange,andhavingchosen
the operating frequency and ripple current in the inductor,
applicaTions inForMaTion
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3850EGN | 0.1 A DUAL SWITCHING CONTROLLER, 860 kHz SWITCHING FREQ-MAX, PDSO28 |
| LT1933HS6#TR | 1.05 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO6 |
| LC016AJ | 2-OUTPUT 16 W DC-DC REG PWR SUPPLY MODULE |
| LTC4224CMS-2#PBF | 2-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO10 |
| LTC4224IMS-1#PBF | 2-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO10 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3872HDDB#TRMPBF | 功能描述:IC REG CTRLR BST PWM CM 8-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3872HDDB#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 8-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3872HTS8#PBF | 制造商:Linear Technology 功能描述:DP-SWREG/Controller, CUT TAPE No Rsense, Current Mode Boost DC/DC Controller |
| LTC3872HTS8#TRMPBF | 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3872HTS8#TRPBF | 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
发布紧急采购，3分钟左右您将得到回复。