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| 型号： | LTC3865EFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 24/38页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38TSSOP |
| 特色产品： | LTC3865 Dual Synchronous Controllers |
| 标准包装： | 50 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 880kHz |
| 占空比： | 95% |
| 电源电压： | 4.5 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 ~ 125°C |
| 封装/外壳： | 38-TFSOP （0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3865/LTC3865-1
APPLICATIONS INFORMATION
Fault Conditions: Current Limit and Current Foldback
The LTC3865/LTC3865-1 include current foldback to help
limit load current when the output is shorted to ground.
If the output 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 LTC3865 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 LTC3865/LTC3865-1 (≈ 90ns), the
input voltage and inductor value:
MOSFET of controller 1 to be locked to the rising edge of an
external clock signal applied to the MODE/PLLIN pin. The
turn-on of controller 2’s top MOSFET is thus 180 degrees
out-of-phase with the external clock. The phase detector
is an edge sensitive digital type that provides zero degrees
phase shift between the external and internal oscillators.
This type of phase detector does not exhibit false lock to
harmonics of the external clock.
The output of the phase detector is a pair of complementary
current sources that charge or discharge the internal ?lter
network. There is a precision 7.5μA of current ?owing out
of FREQ pin. This allows the user to use a single resistor
to SGND to set the switching frequency when no external
clock is applied to the MODE/PLLIN pin. The internal switch
between FREQ pin and the integrated PLL ?lter network is
Δ I L ( SC ) = t ON ( MIN ) ?
V IN
L
on, allowing the ?lter network to be at the same voltage
potential as of FREQ pin. The relationship between the volt-
The resulting short-circuit current is:
age on the FREQ pin and the operating frequency is shown
in Figure 10 and speci?ed in the Electrical Characteristic
– Δ I L ( SC )
I SC =
1 / 3 V SENSE ( MAX )
R SENSE
1
2
table. If an external clock is detected on the MODE/PLLIN
pin, the internal switch mentioned above will turn off and
isolate the in?uence of FREQ pin. Note that the LTC3865 can
Phase-Locked Loop and Frequency Synchronization
The LTC3865/LTC3865-1 have a phase-locked loop (PLL)
comprised of an internal voltage-controlled oscillator (V CO )
and a phase detector. This allows the turn-on of the top
only be synchronized to an external clock whose frequency
is within range of the LTC3865/LTC3865-1’s internal V CO .
This is guaranteed to be between 250kHz and 770kHz. A
simpli?ed block diagram is shown in Figure 11.
900
2.4V 5V
7.5μA
R SET
800
700
MODE/
FREQ
600
500
400
EXTERNAL
OSCILLATOR
PLLIN
DIGITAL
PHASE/
FREQUENCY
DETECTOR
SYNC
VCO
300
200
100
0
3865 F11
0
0.5
1 1.5
FREQ PIN VOLTAGE (V)
2
2.5
3865 F10
Figure 11. Phase-Locked Loop Block Diagram
Figure 10. Relationship Between Oscillator
Frequency and Voltage at the FREQ Pin
3865fb
24
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相关代理商/技术参数 |
参数描述 |
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| LTC3865EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3865EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-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) |
| LTC3865EUH-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3865EUH-1#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-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) |
| LTC3865IFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP 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) |
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