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参数资料
| 型号： | LTC1772BES6#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM SOT23-6 |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 650kHz |
| 占空比： | 100% |
| 电源电压： | 2.5 V ~ 9.8 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 ~ 85°C |
| 封装/外壳： | SOT-23-6 细型，TSOT-23-6 |
| 包装： | 带卷 (TR) |
LTC1772B
APPLICATIONS INFORMATION
The basic LTC1772B application circuit is shown in Figure 1.
External component selection is driven by the load require-
ment and begins with the selection of L1 and R SENSE (= R1).
Next, the power MOSFET, M1 and the output diode D1 is
selected followed by C IN (= C1)and C OUT (= C2).
The inductance value also has a direct effect on ripple
current. The ripple current, I RIPPLE , decreases with higher
inductance or frequency and increases with higher V IN or
V OUT . The inductor’s peak-to-peak ripple current is given
by:
R SENSE Selection for Output Current
I RIPPLE =
V IN V OUT V OUT + V D
f ( L ) V IN + V D
R SENSE is chosen based on the required output current.
With the current comparator monitoring the voltage de-
veloped across R SENSE , the threshold of the comparator
determines the inductor’s peak current. The output current
the LTC1772B can provide is given by:
where f is the operating frequency. Accepting larger values
of I RIPPLE 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
? RIPPLE
I OUT =
0 . 105
R SENSE
I
2
I RIPPLE = 0.4(I OUT(MAX) ). Remember, the maximum I RIPPLE
occurs at the maximum input voltage.
The ripple current is normally set such that the induc-
where I RIPPLE is the inductor peak-to-peak ripple current
(see Inductor Value Calculation section).
tor current is continuous down to approximately 1/4 of
maximum load current. This results in:
A reasonable starting point for setting ripple current is
I RIPPLE = (0.4)(I OUT ). Rearranging the above equation, it
becomes:
I RIPPLE ≤
0 . 03
R SENSE
L MIN =
0.03 V IN + V D
( )
0.0875
R SENSE = for Duty Cycle < 40%
I OUT
However, for operation that is above 40% duty cycle, slope
compensation effect has to be taken into consideration to
select the appropriate value to provide the required amount
of current. Using Figure 3, the value of R SENSE is:
(0.0875)SF
R SENSE =
I OUT 100
Inductor Value Calculation
The operating frequency and inductor selection are inter-
related in that higher operating frequencies permit the use
of a smaller inductor for the same amount of inductor ripple
current. However, this is at the expense of ef?ciency due
to an increase in MOSFET gate charge losses.
This implies a minimum inductance of:
V IN V OUT V OUT + V D
f
R SENSE
(Use V IN(MAX) = V IN )
A smaller value than L MIN could be used in the circuit;
however, the inductor current transitioning from continuous
to discontinuous will occur at a higher load current.
Power MOSFET Selection
An external P-channel power MOSFET must be selected
for use with the LTC1772B. The main selection criteria for
the power MOSFET are the threshold voltage V GS(TH) and
the “on” resistance R DS(ON) , reverse transfer capacitance
C RSS and total gate charge.
1772bfa
8
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相关代理商/技术参数 |
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| LTC1772BIS6#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 |
| LTC1772BIS6#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM TSOT23-6 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) |
| LTC1772BIS6#TRPBF | 功能描述:IC REG CTRLR BUCK PWM TSOT23-6 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) |
| 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 |
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