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| 型号： | LTC3853EUJ#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 40-QFN |
| 产品培训模块： | LTC3853 Multiphase Switching Controller |
| 标准包装： | 61 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 3 |
| 频率 - 最大： | 830kHz |
| 占空比： | 98% |
| 电源电压： | 4.5 V ~ 24 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： | 40-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3853
APPLICATIONS INFORMATION
R B C FF
D V OUT ≈ I RIPPLE ? ESR +
D I L(SC) = t ON(MIN) ?
I SC =
– D I L(SC)
V OUT = 0.8V ? ? 1 + B ?
time.ThetotalRMSpowerlostislowerwhenmorethan
one controller is operating due to the reduced overlap of
current pulses required through the input capacitor’s ESR.
This is why the input capacitor’s requirement calculated
above for the worst-case controller is adequate for the
dual or triple controller design. Also, the input protection
fuse resistance, battery resistance, and PC board trace
resistance losses are also reduced due to the reduced
peak currents in a 3-phase system. The overall benefit of
a multiphase design will only be fully realized when the
source impedance of the power supply/battery is included
in the efficiency testing. The sources of the top MOSFETs
should be placed within 1cm of each other and share a
common C IN (s). Separating the sources and C IN may pro-
duce undesirable voltage and current resonances at V IN .
A small (0.1μF to 1μF) bypass capacitor between the chip
V IN pin and ground, placed close to the LTC3853, is also
suggested. A 2.2Ω to 10Ω resistor placed between C IN
(C1) and the V IN pin provides further isolation between
the channels.
The selection of C OUT is driven by the effective series
resistance (ESR). Typically, once the ESR requirement
is satisfied, the capacitance is adequate for filtering. The
output ripple ( D V OUT ) is approximated by:
? 1 ?
?
? 8fC OUT ?
where f is the operating frequency, C OUT is the output
capacitance and I RIPPLE is the ripple current in the induc-
tor. The output ripple is highest at maximum input voltage
since I RIPPLE increases with input voltage.
Setting Output Voltage
The LTC3853 output voltages are each set by an external
feedback resistive divider carefully placed across the
output, as shown in Figure 9. The regulated output volt-
age is determined by:
? R ?
? R A ?
V OUT
1/3 LTC3853
V FB
R A
3853 F09
Figure 9. Setting Output Voltage
To improve the frequency response, a feed-forward ca-
pacitor, C FF , may be used. Great care should be taken to
route the V FB line away from noise sources, such as the
inductor or the SW line.
Fault Conditions: Current Limit and Current Foldback
The LTC3853 includes current foldback to help limit load
current when the output is shorted to ground. If the out-
put falls below 50% of its nominal output level, then the
maximum sense voltage is progressively lowered from its
maximum programmed value to one-third of the maximum
value. Foldback current limiting is disabled during the
soft-start or tracking up. Under short-circuit conditions
with very low duty cycles, the LTC3853 will begin cycle
skipping in order to limit the short-circuit current. In this
situation the bottom MOSFET will be dissipating most of
the power but less than in normal operation. The short-
circuit ripple current is determined by the minimum on-
time t ON(MIN) of the LTC3853 (≈ 90ns), the input voltage
and inductor value:
V IN
L
The resulting short-circuit current is:
1/3 V SENSE(MAX) 1
R SENSE 2
Phase-Locked Loop and Frequency Synchronization
The LTC3853 has a phase-locked loop (PLL) comprised of
an internal voltage-controlled oscillator (VCO) and a phase
detector. This allows the turn-on of the top MOSFET of
3853fa
22
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相关代理商/技术参数 |
参数描述 |
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| LTC3853IUJ#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-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: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 |
| LTC3853IUJ#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-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: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 |
| LTC3854EDDB#PBF | 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Cut Tape Small Footprint, Low Pin Count Synchronous Step-Do |
| LTC3854EDDB#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM 12-DFN 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) |
| LTC3854EDDB#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 12-DFN 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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