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参数资料
| 型号： | LTC3786IMSE#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 11/34页 |
| 文件大小： | 397K |
| 代理商： | LTC3786IMSE#TRPBF |
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LTC3786
19
3786fa
applicaTions inForMaTion
A leaky diode DB in the boost converter can not only
prevent the top MOSFET from fully turning on but it can
also completely discharge the bootstrap capacitor CB and
create a current path from the input voltage to the BOOST
pin to INTVCC. This can cause INTVCC to rise if the diode
leakage exceeds the current consumption on INTVCC.
This is particularly a concern in Burst Mode operation
where the load on INTVCC can be very small. The external
Schottky or silicon diode should be carefully chosen such
that INTVCC never gets charged up much higher than its
normal regulation voltage.
Fault Conditions: Overtemperature Protection
At higher temperatures, or in cases where the internal
power dissipation causes excessive self heating on-chip
(such as an INTVCC short to ground), the overtemperature
shutdown circuitry will shut down the LTC3786. When the
junction temperature exceeds approximately 170°C, the
overtemperaturecircuitrydisablestheINTVCCLDO,causing
the INTVCC supply to collapse and effectively shut down
the entire LTC3786 chip. Once the junction temperature
drops back to approximately 155°C, the INTVCCLDOturns
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 won’t result in high power dissipation in
the body diodes of the top MOSFET. In this case, PGOOD
output may be used to turn the system load off.
Phase-Locked Loop and Frequency Synchronization
The LTC3786 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 to be locked to the rising
edgeofanexternalclocksignalappliedtothePLLIN/MODE
pin. The phase detector is an edge-sensitive digital type
thatprovideszerodegreesphaseshiftbetweentheexternal
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’sfrequency,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 PLLIN/MODE pin) input
highthresholdis1.6V,whiletheinputlowthresholdis1.2V.
Note that the LTC3786 can only be synchronized to an
external clock whose frequency is within range of the
LTC3786’s internal VCO, which is nominally 55kHz to
1MHz.Thisisguaranteedtobebetween75kHzand850kHz.
RapidphaselockingcanbeachievedbyusingtheFREQpin
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.
FREQ PIN RESISTOR (k)
15
FREQUENCY
(kHz) 600
800
1000
35 45 55
25
3786 F05
400
200
500
700
900
300
100
0
65 75 85 95 105 115 125
Figure 5. Relationship Between Oscillator Frequency
and Resistor Value at the FREQ Pin
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3786EMSE#TRPBF | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
| LTC3786EMSE#PBF | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
| LTC3786EUD#PBF | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC16 |
| LTC3787IGN#TRPBF | SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PDSO28 |
| LTC3787EGN#TRPBF | SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PDSO28 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3786IUD#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-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) |
| LTC3786IUD#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-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) |
| LTC3787EGN#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® 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 |
| LTC3787EGN#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 900kHz SSOP28 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 900kHz, SSOP28 |
| LTC3787EGN#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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