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| 型号： | LTC3851EGN#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/28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
The Typical Application on the ?rst page of this data sheet
is a basic LTC3851 application circuit. The LTC3851 can
V IN
INTV CC
V IN
be con?gured to use either DCR (inductor resistance)
sensing or low value resistor sensing. The choice of the
two current sensing schemes is largely a design trade-off
between cost, power consumption and accuracy. DCR
sensing is becoming popular because it saves expensive
current sensing resistors and is more power ef?cient,
especially in high current applications. However, current
sensing resistors provide the most accurate current limits
BOOST
TG
LTC3851
SW
BG
GND
SENSE +
SENSE –
R SENSE
V OUT
for the controller. Other external component selection
is driven by the load requirement, and begins with the
FILTER COMPONENTS
3851 F01
selection of R SENSE (if R SENSE is used) and the inductor
value. Next, the power MOSFETs and Schottky diodes are
selected. Finally, input and output capacitors are selected.
The circuit shown on the ?rst page can be con?gured for
operation up to 38V at V IN .
Current Limit Programming
The I LIM pin is a tri-level logic input to set the maximum
current limit of the controller. When I LIM is grounded, the
maximum current limit threshold of the current compara-
PLACED NEAR SENSE PINS
Figure 1. Using a Resistor to Sense Current with the LTC3851
The current comparator has a maximum threshold, V MAX ,
determined by the I LIM setting. The current comparator
threshold sets the maximum peak of the inductor current,
yielding a maximum average output current, I MAX , equal to
the maximum peak value less half the peak-to-peak ripple
current, ΔI L . Allowing a margin of 20% for variations in
the IC and external component values yields:
tor is programmed to be 30mV. When I LIM is ?oated, the
maximum current limit threshold is 50mV. When I LIM is
tied to INTV CC , the maximum current limit threshold is
set to 75mV.
R SENSE = 0.8 ?
V MAX
I MAX + Δ I L /2
SENSE + and SENSE – Pins
The SENSE + and SENSE – pins are the inputs to the current
comparators. The common mode input voltage range of
the current comparators is 0V to 5.5V. Both SENSE pins
are high impedance inputs with small base currents of
less than 1μA. When the SENSE pins ramp up from 0V
to 1.4V, the small base currents ?ow out of the SENSE
pins. When the SENSE pins ramp down from 5V to 1.1V,
the small base currents ?ow into the SENSE pins. The
high impedance inputs to the current comparators allow
accurate DCR sensing. However, care must be taken not
to ?oat these pins during normal operation.
Low Value Resistors Current Sensing
A typical sensing circuit using a discrete resistor is shown
in Figure 1. R SENSE is chosen based on the required output
current.
Inductor DCR Sensing
For applications requiring the highest possible ef?ciency,
the LTC3851 is capable of sensing the voltage drop across
the inductor DCR, as shown in Figure 2. The DCR of the
inductor represents the small amount of DC winding
resistance of the copper, which can be less than 1m Ω for
today’s low value, high current inductors. If the external
R1||R2 ? C1 time constant is chosen to be exactly equal
to the L/DCR time constant, the voltage drop across the
external capacitor is equal to the voltage drop across
the inductor DCR multiplied by R2/(R1 + R2). Therefore,
R2 may be used to scale the voltage across the sense
terminals when the DCR is greater than the target sense
resistance. Check the manufacturer’s data sheet for
speci?cations regarding the inductor DCR, in order to
properly dimension the external ?lter components. The
DCR of the inductor can also be measured using a good
RLC meter.
3851fb
12
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PDF描述 |
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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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