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| 型号： | LTC1772IS6#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 6/12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) |
LTC1772
OPERATIO
(Refer to Functional Diagram)
Slope Compensation and Inductor’s Peak Current
The inductor’s peak current is determined by:
110
100
90
I PK =
V ITH – 0 . 7
10 ( R SENSE )
80
70
60
when the LTC1772 is operating below 40% duty cycle.
However, once the duty cycle exceeds 40%, slope com-
pensation begins and effectively reduces the peak induc-
tor current. The amount of reduction is given by the curves
in Figure 2.
50
40
30
20
10
0
I RIPPLE = 0.4I PK
AT 5% DUTY CYCLE
I RIPPLE = 0.2I PK
AT 5% DUTY CYCLE
V IN = 4.2V
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
1772 F02
Figure 2. Maximum Output Current vs Duty Cycle
APPLICATIO N S I N FOR M ATIO N
R SENSE =
ThebasicLTC1772applicationcircuitisshownin Figure 1.
External component selection is driven by the load re-
quirement and begins with the selection of L1 and R SENSE
(= R1). Next, the power MOSFET, M1 and the output diode
D1 are selected followed by C IN (= C1) and C OUT (= C2).
R SENSE Selection for Output Current
R SENSE is chosen based on the required output current.
With the current comparator monitoring the voltage devel-
oped across R SENSE , the threshold of the comparator
determines the inductor’s peak current. The output cur-
rent the LTC1772 can provide is given by:
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 2, the value of R SENSE is:
SF
( 10 )( 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
I OUT =
0 . 12
R SENSE
I
2
ripple current. However, this is at the expense of efficiency
due to an increase in MOSFET gate charge losses.
The inductance value also has a direct effect on ripple
R SENSE =
for Duty Cycle < 40%
V IN ? V OUT ? V OUT + V D ?
? V IN D ?
I RIPPLE = ? ?
where I RIPPLE is the inductor peak-to-peak ripple current
(see Inductor Value Calculation section).
A reasonable starting point for setting ripple current is
I RIPPLE = (0.4)(I OUT ). Rearranging the above equation, it
becomes:
1
( 10 )( I OUT )
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:
f ( L ) + V
1772fb
6
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| LTC1773EMS | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
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| LTC1773EMS#TR | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
| LTC1773EMS#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
| LTC1775CGN | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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: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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