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| 型号： | LTC3861EUHE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/38页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 36-QFN |
| 标准包装： | 61 |
| 系列： | PolyPhase® |
| PWM 型： | 电压模式 |
| 输出数： | 2 |
| 频率 - 最大： | 2.1MHz |
| 占空比： | 91.5% |
| 电源电压： | 3 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： | 36-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3861
APPLICATIONS INFORMATION
Since the temperature coefficient of the inductor’s DCR is
3900ppm/°C, first order compensation of the filter time
constant is possible by using filter resistors with an equal
but opposite (negative) TC, assuming a low TC capacitor is
used. That is, as the inductor’s DCR rises with increasing
temperature, the L/DCR time constant drops. Since we
want the filter RC time constant to match the L/DCR time
constant, we also want the filter RC time constant to drop
with increasing temperature. Typically, the inductance will
also have a small negative TC.
The ISNSP and ISNSN pins are the inputs to the current
comparators. The common mode range of the current
comparators is –0.3V to V CC – 0.5V. Continuous linear
operation is provided throughout this range, allowing
output voltages between 0.6V (the reference input to the
error amplifiers) and V CC – 0.5V. The maximum output
voltage is lower than V CC to account for output ripple and
output overshoot. The maximum differential current sense
input (V ISNSP – V ISNSN ) is 50mV.
The high impedance inputs to the current comparators
allow accurate DCR sensing. However, care must be taken
not to float these pins during normal operation.
Filter components mutual to the sense lines should be
placed close to the LTC3861, and the sense lines should
run close together to a Kelvin connection underneath the
current sense element (shown in Figure 7). 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 low value
(<5mΩ) sense resistors are used, verify that the signal
across C F resembles the current through the inductor,
TO SENSE FILTER,
NEXT TO THE CONTROLLER
C OUT
INDUCTOR OR R SENSE 3861 F07
Figure 7. Sense Lines Placement with Inductor or Sense Resistor
and reduce R F to eliminate any large step associated with
the turn-on of the primary switch. If DCR sensing is used
(Figure 6b), sense resistor R1 should be placed close to
the switching node, to prevent noise from coupling into
sensitive small-signal nodes. The capacitor C1 should be
placed close to the IC pins.
Multiphase Operation
When the LTC3861 is used in a single output, multiphase
application, the slave error amplifiers must be disabled
by connecting their FB pins to V CC . All current limits
should be set to the same value using only one resistor
to SGND per IC. I LIM2 should then be connected to V CC .
These connections are shown in Table 4. In a multiphase
application all COMP, RUN and TRACK/SS pins must be
connected together.
Table 4. Multiphase Configurations
CH1 CH2 FB1 FB2 I LIM1 I LIM2
Master Slave On Off Resistor V CC
(FB = V CC ) to GND
Slave Slave Off Off Resistor V CC
(FB = V CC ) (FB = V CC ) to GND
Slave Additional Off On Resistor Resistor
Output (FB = V CC ) to GND to GND
For output loads that demand high current, multiple
LTC3861s can be daisychained to run out of phase to
provide more output current without increasing input and
output voltage ripple. The CLKIN pin allows the LTC3861
to synchronize to the CLKOUT signal of another LTC3861.
The CLKOUT signal can be connected to the CLKIN pin of
the following LTC3861 stage to line up both the frequency
and the phase of the entire system. Tying the PHSMD pin to
V CC , SGND or floating it generates a phase difference
(between CLKIN and CLKOUT) of 240°, 60° or 90° respec-
tively, and a phase difference (between CH1 and CH2) of
120°, 180° or 180°. Figure 8 shows the PHSMD connections
necessary for 3-, 4-, 6- or 12-phase operation. A total of
twelve phases can be daisychained to run simultaneously
out of phase with respect to each other.
22
For more information www.linear.com/LTC3861
3861fa
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相关代理商/技术参数 |
参数描述 |
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| LTC3861IUH-1#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Sync Step Down 3V to 24V Input 32-Pin QFN EP 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 制造商:Linear Technology 功能描述:BUCK CNTRL DUAL 12PH 2.25MHZ 32QFN 制造商:Linear Technology 功能描述:BUCK, CNTRL, DUAL, 12PH, 2.25MHZ, 32QFN 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual-Phase/Dual-Channel Step-Down Voltage Mode Controller w 制造商:Linear Technology 功能描述:PWM CONTROLLER, BUCK, 2.25MHZ, 24V, QFN-32, Input Voltage:24V, Output Voltage:5.5V, Output Current:60A, Supply Voltage Min:3V, Supply Voltage Max:5.5V, Digital IC Case Style:QFN, No. of Pins:32, Frequency:2.25MHz , RoHS Compliant: Yes |
| LTC3861IUH-1#TRPBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN |
| LTC3861IUHE#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 36-QFN RoHS:是 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: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) |
| LTC3861IUHE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 36-QFN RoHS:是 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: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) |
| LTC3862EFE#PBF | 功能描述:IC REG CTRLR BST PWM CM 24-TSSOP 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 |
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