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参数资料
| 型号： | LTC3788EGN-1#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | DUAL SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SSOP-28 |
| 文件页数： | 13/30页 |
| 文件大小： | 384K |
| 代理商： | LTC3788EGN-1#TRPBF |
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LTC3788-1
20
37881fb
applicaTions inForMaTion
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 LTC3788-1. When
the junction temperature exceeds approximately 170°C,
the overtemperature circuitry disables the INTVCC LDO,
causing the INTVCC supply to collapse and effectively shut
down the entire LTC3788-1 chip. Once the junction tem-
perature 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.
Phase-Locked Loop and Frequency Synchronization
The LTC3788-1 has an internal phase-locked loop (PLL)
comprised of a phase frequency detector, a low pass filter
and a voltage-controlled oscillator (VCO). This allows the
turn-on of the top MOSFET of controller 1 to be locked to
the rising edge of an external clock signal applied to the
PLLIN/MODEpin.Theturn-onofcontroller2’stopMOSFET
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’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 LTC3788-1 can only be synchronized to an
external clock whose frequency is within range of the
LTC3788-1’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.
Table 1 summarizes the different states in which the FREQ
pin can be used.
Table 1.
FREQ PIN
PLLIN/MODE PIN
FREQUENCY
0V
DC Voltage
350kHz
INTVCC
DC Voltage
535kHz
Resistor
DC Voltage
50kHz to 900kHz
Any of the Above
External Clock
Phase Locked to
External Clock
Figure 6. 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
37881 F06
400
200
500
700
900
300
100
0
65 75 85 95 105 115 125
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| LTC3789EGN#TRPBF | 0.1 A SWITCHING CONTROLLER, 710 kHz SWITCHING FREQ-MAX, PDSO28 |
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| LTC3788EUH#PBF | 功能描述:IC REG CTRLR BST 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:- 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 |
| LTC3788EUH#TRPBF | 功能描述:IC REG CTRLR BST 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:- 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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