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参数资料
| 型号： | LTC1772BIS6#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO6 |
| 封装： | LEAD FREE, PLASTIC, MO-193, SOT-23, 6 PIN |
| 文件页数： | 13/16页 |
| 文件大小： | 223K |
| 代理商： | LTC1772BIS6#PBF |
LTC1772B
6
1772bfa
OPERATION
Main Control Loop
The LTC1772B is a constant frequency current mode
switching regulator. During normal operation, the external
P-channel power MOSFET is turned on each cycle when
the oscillator sets the RS latch (RS1) and turned off when
the current comparator (ICMP) resets the latch. The peak
inductor current at which ICMP resets the RS latch is
controlled by the voltage on the ITH/RUN pin, which is the
output of the error amplier EAMP. An external resistive
divider connected between VOUT and ground allows the
EAMP to receive an output feedback voltage VFB. When
the load current increases, it causes a slight decrease in
VFB relative to the 0.8V reference, which in turn causes the
ITH/RUN voltage to increase until the average inductor
current matches the new load current.
The main control loop is shut down by pulling the ITH/RUN
pin low. Releasing ITH/RUNallowsaninternal0.5μAcurrent
source to charge up the external compensation network.
When the ITH/RUN pin reaches 0.35V, the main control
loop is enabled with the ITH/RUN voltage then pulled up
to its zero current level of approximately 0.85V. As the
external compensation network continues to charge up,
the corresponding output current trip level follows, allow-
ing normal operation.
Comparator OVP guards against transient overshoots
> 7.5% by turning off the external P-channel power
MOSFET and keeping it off until the fault is removed.
Low Load Current Operation
Under very light load current conditions, the ITH/RUN pin
voltage will be very close to the zero current level of 0.85V.
As the load current decreases further, an internal offset at
the current comparator input will assure that the current
comparator remains tripped (even at zero load current) and
the regulator will start to skip cycles, as it must, in order
to maintain regulation. This behavior allows the regulator
to maintain constant frequency down to very light loads,
resulting in less low frequency noise generation over a
wide load current range.
Figure 2 illustrates this result for the circuit of Figure 1
using both an LTC1772 in Burst Mode operation and an
LTC1772B (non-Burst Mode operation). At an output cur-
rent of 100mA, the Burst Mode operation part exhibits
an output ripple of approximately 60mVP-P, whereas the
non-Burst Mode operation part has an output ripple of only
20mVP-P. At lower output current levels, the improvement
is even greater. This comes at a tradeoff of lower efciency
for the non-Burst Mode operation part (see Figure 1). Also
notice the constant frequency operation of the LTC1772B,
even at 5% of maximum output current.
Dropout Operation
When the input supply voltage decreases towards the
output voltage, the rate of change of inductor current
during the ON cycle decreases. This reduction means
Figure 2. Output Ripple Waveforms for the Circuit of Figure 1.
VOUT Ripple for Figure 1 Circuit Using
LTC1772 Burst Mode Operation.
VOUT Ripple for Figure 1 Circuit Using
LTC1772B Non-Burst Mode Operation.
VIN = 3.6V
VOUT = 2.5V
IOUT = 100mA
5μs/DIV
20mVAC/DIV
1772 F02a
VIN = 3.6V
VOUT = 2.5V
IOUT = 100mA
5μs/DIV
20mVAC/DIV
1772 F02b
(Refer to Functional Diagram)
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1772CS6 | 制造商:Linear Technology 功能描述:Swithed-Mode Power Supply Controller, Current Mode Type, 3 Pin, Plastic, TO-236 |
| LTC1772CS6#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.5V to 9.8V Input 6-Pin TSOT-23 制造商:Linear Technology 功能描述:BUCK 2.8 - 20V 5A 1.23-18V 6SOT23 制造商:Linear Technology 功能描述:BUCK, 2.8 - 20V, 5A, 1.23-18V, 6SOT23 |
| LTC1772CS6#TR | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 RoHS:否 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) |
| LTC1772CS6#TRM | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 RoHS:否 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) |
| LTC1772CS6#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 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) |
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