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参数资料
| 型号： | LTC3851EGN#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SSOP |
| 产品培训模块： | LTC3851 Single Output DC/DC Switching Regulator Controller |
| 特色产品： | Wide Input Voltage Range Synchronous Step-Down DC/DC Controller |
| 标准包装： | 100 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 790kHz |
| 占空比： | 99% |
| 电源电压： | 4 V ~ 38 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： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3851
APPLICATIONS INFORMATION
0V to 0.8V on the TK/SS pin. The total soft-start time can
be calculated as:
Output Voltage Tracking
The LTC3851 allows the user to program how its output
t SOFT-START = 0.8 ?
C SS
1.0μA
ramps up and down by means of the TK/SS pins. Through
this pin, the output can be set up to either coincidentally or
ratiometrically track with another supply’s output, as shown
V OUT R2 ? R3 + R4 ?
RegardlessofthemodeselectedbytheMODE/PLLINpin,
the regulator will always start in pulse-skipping mode up
to TK/SS = 0.64V. Between TK/SS = 0.64V and 0.72V, it
will operate in forced continuous mode and revert to the
selected mode once TK/SS > 0.72V. The output ripple
is minimized during the 80mV forced continuous mode
window.
When the regulator is con?gured to track another supply,
the feedback voltage of the other supply is duplicated by a
resistor divider and applied to the TK/SS pin. Therefore, the
voltage ramp rate on this pin is determined by the ramp rate
of the other supply’s voltage. Note that the small soft-start
capacitor charging current is always ?owing, producing
a small offset error. To minimize this error, one can select
the tracking resistive divider value to be small enough to
make this error negligible.
In order to track down another supply after the soft-start
phase expires, the LTC3851 must be con?gured for forced
continuous operation by connecting MODE/PLLIN to
INTV CC .
V MASTER
V OUT
in Figure 3. In the following discussions, V MASTER refers to
a master supply and V OUT refers to the LTC3851’s output
as a slave supply. To implement the coincident tracking
in Figure 3a, connect a resistor divider to V MASTER and
connect its midpoint to the TK/SS pin of the LTC3851. The
ratio of this divider should be selected the same as that of
the LTC3851’s feedback divider as shown in Figure 4a. In
this tracking mode, V MASTER must be higher than V OUT .
To implement ratiometric tracking, the ratio of the resistor
divider connected to V MASTER is determined by:
= ? ?
V MASTER R4 ? R1 + R2 ?
So which mode should be programmed? While either
mode in Figure 4 satis?es most practical applications,
the coincident mode offers better output regulation.
This concept can be better understood with the help of
Figure 5. At the input stage of the error ampli?er, two
common anode diodes are used to clamp the equivalent
reference voltage and an additional diode is used to match
the shifted common mode voltage. The top two current
sources are of the same amplitude. In the coincident
V MASTER
V OUT
TIME
TIME
3851 F03
(3a) Coincident Tracking
(3b) Ratiometric Tracking
Figure 3. Two Different Modes of Output Voltage Tracking
3851fb
15
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3851EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3851EMSE#PBF | 制造商:Linear Technology 功能描述:Switch Regulator IC 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN REGULATOR CTRL MSOP-16 |
| LTC3851EMSE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-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) |
| LTC3851EMSE-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3851EMSE-1#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-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) |
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