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参数资料
| 型号： | LTC3801BES6#TRM |
| 厂商： | Linear Technology |
| 文件页数： | 7/12页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM TSOT23-6 |
| 标准包装： | 500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 650kHz |
| 占空比： | 100% |
| 电源电压： | 2.4 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) |
| 其它名称： | LTC3801BES6 LTC3801BES6-ND |
LTC3801/LTC3801B
OPERATIO
(Refer to the Functional Diagram)
inductor current. The amount of reduction is given by the
curve in Figure 3.
115
105
LTC3801
100
90
Soft-Start
An internal default soft-start circuit is employed at power-
95
85
75
LTC3801B
80
70
up and/or when coming out of shutdown. The soft-start
circuit works by internally clamping the voltage at the
I TH /RUN pin to the corresponding zero current level and
gradually raising the clamp voltage such that the minimum
time required for the programmed switch current to reach
its maximum is approximately 0.6ms. After the soft-start
65
55
45
35
20
V IN = 4.2V
T A = 25 ° C
30 40
50 60 70
DUTY CYCLE (%)
80
90
60
50
40
30
100
circuit has timed out, it is disabled until the part is put in
shutdown again or the input supply is cycled.
APPLICATIO S I FOR ATIO
The basic LTC3801/LTC3801B application circuit is shown
on the front page of this data sheet. External component
selection is driven by the load requirement and begins with
the selection of the inductor and R SENSE . Next, the power
MOSFET and the output diode are selected followed by the
3801 F03
Figure 3. Maximum Current Limit Trip Voltage vs Duty Cycle
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:
input bypass capacitor C IN and output bypass capacitor
C OUT .
R SENSE =
SF
( 10 )( I OUT )( 100 )
? RIPPLE
I OUT =
V IN ? V OUT ? V OUT + V D ?
? V IN + V D ?
R SENSE Selection for Output Current
R SENSE is chosen based on the required output current.
With the current comparator monitoring the voltage
developed across R SENSE , the threshold of the compara-
tor determines the inductor’s peak current. The output
current the LTC3801 can provide is given by:
0 . 117 I
R SENSE 2
where I RIPPLE is the inductor peak-to-peak ripple current
(see Inductor Value Calculation section). For the LTC3801B
use 104mV in the previous equation and follow through
the analysis using that number.
A reasonable starting point for setting ripple current is
I RIPPLE = (0.4)(I OUT ). Rearranging the above equation, it
becomes:
where SF is the “Slope Factor.”
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 efficiency
due to an increase in MOSFET gate charge losses.
The inductance value also has a direct effect on ripple cur-
rent. The ripple current, I RIPPLE , decreases with higher in-
ductance or frequency and increases with higher V IN or
V OUT . The inductor’s peak-to-peak ripple current is given by:
I RIPPLE = ? ?
f ( L )
where f is the operating frequency. Accepting larger values
R SENSE =
1
( 10 )( I OUT )
for Duty Cycle < 40%
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
sn3801 3801fs
7
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| LTC3801ES6#TR | 功能描述:IC REG CTRLR BUCK PWM TSOT23-6 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) |
| LTC3801ES6#TRM | 功能描述:IC REG CTRLR BUCK PWM TSOT23-6 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) |
| LTC3801ES6#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) |
| LTC3801ES6#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) |
| LTC3802EGN | 功能描述:IC REG CTRLR BUCK PWM VM 28-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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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