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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： | 15/16页 |
| 文件大小： | 223K |
| 代理商： | LTC1772BIS6#PBF |
LTC1772B
8
1772bfa
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 RSENSE(= R1).
Next, the power MOSFET, M1 and the output diode D1 is
selected followed by CIN (= C1)and COUT(= C2).
RSENSE Selection for Output Current
RSENSE is chosen based on the required output current.
With the current comparator monitoring the voltage de-
veloped across RSENSE, the threshold of the comparator
determines the inductor’s peak current. The output current
the LTC1772B can provide is given by:
I
R
I
OUT
SENSE
RIPPLE
=
0 105
2
.
where IRIPPLE is the inductor peak-to-peak ripple current
(see Inductor Value Calculation section).
A reasonable starting point for setting ripple current is
IRIPPLE = (0.4)(IOUT). Rearranging the above equation, it
becomes:
R
I
SENSE
OUT
=
0 0875
.
for Duty Cycle < 40%
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 RSENSE is:
R
SF
I
SENSE
OUT
=
()
(.
)
0 0875
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 efciency due
to an increase in MOSFET gate charge losses.
The inductance value also has a direct effect on ripple
current. The ripple current, IRIPPLE, decreases with higher
inductance or frequency and increases with higher VIN or
VOUT. The inductor’s peak-to-peak ripple current is given
by:
IRIPPLE =
VIN VOUT
fL
( )
VOUT + VD
VIN + VD
where f is the operating frequency. Accepting larger values
of IRIPPLE 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
IRIPPLE = 0.4(IOUT(MAX)). Remember, the maximum IRIPPLE
occurs at the maximum input voltage.
The ripple current is normally set such that the induc-
tor current is continuous down to approximately 1/4 of
maximum load current. This results in:
I
R
RIPPLE
SENSE
≤
003
.
This implies a minimum inductance of:
LMIN =
VIN VOUT
f
0.03
RSENSE
VOUT + VD
VIN + VD
(Use VIN(MAX) = VIN)
A smaller value than LMIN 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 VGS(TH) and
the “on” resistance RDS(ON), reverse transfer capacitance
CRSS and total gate charge.
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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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