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| 型号： | LTC3891EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 835kHz |
| 占空比： | 99% |
| 电源电压： | 4 V ~ 60 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： | 20-TSSOP（0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3891
APPLICATIONS INFORMATION
The Typical Application on the first page is a basic LTC3891
application circuit. LTC3891 can be configured to use
either DCR (inductor resistance) sensing or low value
resistor sensing. The choice between 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 efficient, especially
in high current applications. However, current sensing
resistors provide the most accurate current limits for the
controller. Other external component selection is driven
by the load requirement, and begins with the selection of
R SENSE (if R SENSE is used) and inductor value. Next, the
power MOSFETs and Schottky diodes are selected. Finally,
input and output capacitors are selected.
Current Limit Programming
Filter components mutual to the sense lines should be
placed close to the LTC3891, and the sense lines should
run close together to a Kelvin connection underneath the
current sense element (shown in Figure 1). Sensing cur-
rent elsewhere can effectively add parasitic inductance
and capacitance to the current sense element, degrading
the information at the sense terminals and making the
programmed current limit unpredictable. If inductor DCR
sensing is used (Figure 2b), sense resistor R1 should be
placed close to the switching node, to prevent noise from
coupling into sensitive small-signal nodes.
TO SENSE FILTER,
NEXT TO THE CONTROLLER
C OUT
3891 F01
INDUCTOR OR R SENSE
Figure 1. Sense Lines Placement with Inductor or Sense Resistor
The I LIM pin is a tri-level logic input which sets the maximum
current limit of the controller. When I LIM is grounded, the
maximum current limit threshold voltage of the current
comparator is programmed to be 30mV. When I LIM is
floated, the maximum current limit threshold is 75mV.
When I LIM is tied to INTV CC , the maximum current limit
threshold is set to 50mV.
V IN
INTV CC
BOOST
TG
SW
LTC3891
BG
V IN
R SENSE
V OUT
C1* PLACE CAPACITOR NEAR
SENSE –
L
DCR
(R1||R2) ? C1 =
*PLACE C1 NEAR
R SENSE(EQ) = DCR
SENSE PINS
SENSE + andSENSE – Pins
The SENSE + and SENSE – pins are the inputs to the cur-
rent comparators. The common mode voltage range on
these pins is 0V to 28V (abs max), enabling the LTC3891
to regulate output voltages up to a nominal 24V (allowing
margin for tolerances and transients).
The SENSE + pin is high impedance over the full common
mode range, drawing at most ±1μA. This high impedance
allows the current comparators to be used in inductor
DCR sensing.
The impedance of the SENSE – pin changes depending on
the common mode voltage. When SENSE – is less than
INTV CC – 0.5V, a small current of less than 1μA flows out
of the pin. When SENSE – is above INTV CC + 0.5V, a higher
current (~700μA) flows into the pin. Between INTV CC – 0.5V
and INTV CC + 0.5V, the current transitions from the smaller
current to the higher current.
R1*
SENSE +
SENSE PINS
SGND
*R1 AND C1 ARE OPTIONAL
(2a) Using a Resistor to Sense Current
V IN V IN
INTV CC
BOOST INDUCTOR
TG
SW
LTC3891
BG
R1
SENSE +
C1* R2
SENSE –
SGND
L R2
DCR R1 + R2
(2b) Using the Inductor DCR to Sense Current
3891 F02a
V OUT
3891 F02b
Figure 2. Current Sensing Methods
3891fa
14
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相关代理商/技术参数 |
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| LTC3891EUDC#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN 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 |
| LTC3891EUDC#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 900kHz QFN20 |
| LTC3891EUDC#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN 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) |
| LTC3891HFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP 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: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 |
| LTC3891HFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP 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: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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