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参数资料
| 型号： | LTC3787EGN#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SSOP-28 |
| 文件页数： | 16/36页 |
| 文件大小： | 363K |
| 代理商： | LTC3787EGN#TRPBF |
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LTC3787
23
3787fb
APPLICATIONS INFORMATION
the entire LTC3787 chip. Once the junction temperature
drops back to approximately 155°C, the INTVCC LDO turns
back on. Long term overstress (TJ > 125°C) should be
avoided as it can degrade the performance or shorten
the life of the part.
Since the shutdown may occur at full load, beware that
the load current will result in high power dissipation in
the body diodes of the top MOSFETs. In this case, PGOOD
output may be used to turn the system load off.
Phase-Locked Loop and Frequency Synchronization
The LTC3787 has an internal phase-locked loop (PLL)
comprised of a phase frequency detector, a lowpass filter
and a voltage-controlled oscillator (VCO). This allows the
turn-on of the bottom MOSFET of channel 1 to be locked
to the rising edge of an external clock signal applied to
the PLLIN/MODE pin. The turn-on of channel 2’s bot-
tom 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.
If the external clock frequency is greater than the internal
oscillator’s frequency, fOSC,thencurrentissourcedcontinu-
ously from the phase detector output, pulling up the VCO
input. When the external clock frequency is less than fOSC,
current is sunk continuously, pulling down the VCO input.
If the external and internal frequencies are the same but
exhibit a phase difference, the current sources turn on for
an amount of time corresponding to the phase difference.
The voltage at the VCO input is adjusted until the phase
and frequency of the internal and external oscillators are
identical. At the stable operating point, the phase detector
output is high impedance and the internal filter capacitor,
CLP , holds the voltage at the VCO input.
Typically, the external clock (on the PLLIN/MODE pin) input
high threshold is 1.6V, while the input low threshold is 1.2V.
Note that the LTC3787 can only be synchronized to an
external clock whose frequency is within range of the
LTC3787’s internal VCO, which is nominally 55kHz to
1MHz. This is guaranteed to be between 75kHz and 850kHz.
Rapid phase locking can be achieved by using the FREQ pin
to set a free-running frequency near the desired synchro-
nization frequency. The VCO’s input voltage is prebiased
at a frequency corresponding to the frequency set by the
FREQ pin. Once prebiased, the PLL only needs to adjust
the frequency slightly to achieve phase lock and synchro-
nization. Although it is not required that the free-running
frequency be near external clock frequency, doing so will
prevent the operating frequency from passing through a
large range of frequencies as the PLL locks.
Figure 7. Relationship Between Oscillator
Frequency and Resistor Value at the FREQ Pin
FREQ PIN RESISTOR (k)
15
FREQUENCY
(kHz) 600
800
1000
35 45 55
25
3787 F07
400
200
500
700
900
300
100
0
65 75 85 95 105 115 125
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相关代理商/技术参数 |
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| LTC3787EUFD#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-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 |
| LTC3787EUFD#PBF | 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 900kHz, QFN28 |
| LTC3787EUFD#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 28-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 |
| LTC3787HGN#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP 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 |
| LTC3787HGN#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP 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 |
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