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| 型号： | LTC3634EUFD#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 5.5 A DUAL SWITCHING CONTROLLER, 4600 kHz SWITCHING FREQ-MAX, PQCC28 |
| 封装： | 4 X 5 MM, LEAD FREE, PLASTIC, MO-220, QFN-28 |
| 文件页数： | 2/28页 |
| 文件大小： | 359K |
| 代理商： | LTC3634EUFD#TRPBF |
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LTC3634
10
3634f
operaTion
The LTC3634 is a dual-channel, current mode monolithic
step-down regulator designed to provide high efficiency
power conversion for DDR memory supplies and bus ter-
mination.Itsuniquecontrolledon-timearchitectureallows
extremely low step-down ratios while maintaining a fast,
constant switching frequency. Each channel is enabled by
raising the voltage on the RUN pin above 1.22V nominally.
Main Control Loop
In normal operation, the internal top power MOSFET is
turned on for a fixed interval determined by a one-shot
timer (ON signal in the Block Diagram). When the top
powerMOSFETturnsoff,thebottompowerMOSFETturns
on until the current comparator ICMP trips, thus restarting
the one-shot timer and initiating the next cycle. Inductor
current is measured by sensing the voltage drop across
the bottom power MOSFET. The voltage on the ITH pin
sets the comparator threshold corresponding to induc-
tor valley current. The error amplifier EA adjusts this ITH
voltage by comparing the feedback signal VFB (derived
from the output voltage) to an internal 0.6V reference
voltage (channel 1) or the VTTR voltage (channel 2). If the
load current increases, it causes a drop in the feedback
voltage relative to the reference voltage. The ITH voltage
then rises until the average inductor current matches that
of the load current.
The switching frequency is determined by the value of the
RT resistor, which programs the current for the internal
oscillator. An internal phase-locked loop servos the one-
shot timer (ON signal) such that the internal oscillator
edge phase-locks to the SW node edge, thus forcing a
constant switching frequency. This unique controlled
on-time architecture also allows the switching frequency
to be synchronized to an external clock source when it
is applied to the MODE/SYNC pin. Channel 1 defaults to
forcedcontinuousoperationoncetheclocksignalisapplied
(channel 2 is always in forced continuous operation).
VTTR Output Buffer
The VTTR pin outputs a voltage equal to one half of
VDDQIN. It is capable of sourcing/sinking 10mA and driv-
ing capacitive loads up to 0.01F. The error amplifier for
channel 2 uses this voltage as its reference voltage.
High Efficiency Burst Mode Operation
At light load currents, the inductor current can drop to zero
and become negative. In Burst Mode operation (available
only on channel 1), a current reversal comparator (IREV)
detects the negative inductor current and shuts off the
bottom power MOSFET, resulting in discontinuous opera-
tion and increased efficiency. Both power MOSFETs will
remainoffuntiltheITHvoltagerisesabovethezerocurrent
level to initiate another cycle. During this time, the output
capacitor supplies the load current and the part is placed
into a low current sleep mode. Burst Mode operation is
disabled by tying the MODE/SYNC pin to ground, which
forces continuous synchronous operation regardless of
output load current.
Power Good Status Output
The PGOOD open-drain output will be pulled low if the
regulatoroutputexitsa±8%windowaroundtheregulation
point. This threshold has 15mV of hysteresis relative to
the VFB pin. To prevent unwanted PGOOD glitches during
transients or dynamic VOUTchanges,theLTC3634PGOOD
falling edge includes a filter time of approximately 40μs.
For the VTT output (channel 2), VTTR is the regulation
point. The PGOOD2 pin will always be low when the VTTR
output voltage is less than 300mV.
VIN Overvoltage Protection
In order to protect the internal power MOSFET devices
against long transient voltage events, the LTC3634 con-
stantly monitors each VIN pin for an overvoltage condi-
tion. When VIN rises above 17.5V, the regulator suspends
operation by shutting off both power MOSFETs on the
corresponding channel. Once VIN drops below 16.5V, the
regulator immediately resumes normal operation. The
regulator does not execute its soft-start function when
exiting an overvoltage condition.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3634HFE#PBF | 制造商:Linear Technology 功能描述:IC CONV DDR DDR2 DDR3 28TSSOP 制造商:Linear Technology 功能描述:BUCK 15V 3A 500KHZ-4MHZ TS 制造商:Linear Technology 功能描述:DP-SWREG/Monolithic, 15V Dual 3A Monolithic Step Down Regulator for DDR Power 制造商:Linear Technology 功能描述:DC-DC REGULATOR, BUCK, ADJ, TSSOP-28, Primary Input Voltage:15V, No. of Outputs:2, Output Current:3A, No. of Pins:28, Operating Temperature Min:-40C, Operating Temperature Max:150C, MSL:MSL 1 - Unlimited, Package / Case:28-TSSOP , RoHS Compliant: Yes |
| LTC3634HFE#TRPBF | 制造商:Linear Technology 功能描述:IC REG 15V 3A STEP DOWN 28-TSSOP |
| LTC3634HUFD#PBF | 制造商:Linear Technology 功能描述:IC CONV DDR DDR2 DDR3 28-QFN 制造商:Linear Technology 功能描述:BUCK 15V 3A 500KHZ-4MHZ QF 制造商:Linear Technology 功能描述:DC-DC REGULATOR, BUCK, ADJ, QFN-28, Primary Input Voltage:15V, No. of Outputs:2, Output Current:3A, No. of Pins:28, Operating Temperature Min:-40C, Operating Temperature Max:150C, MSL:MSL 1 - Unlimited, Package / Case:28-QFN , RoHS Compliant: Yes |
| LTC3634HUFD#TRPBF | 制造商:Linear Technology 功能描述:IC REG 15V 3A STEP DOWN 28-QFN 制造商:Linear Technology 功能描述:DC-DC REGULATOR, BUCK, ADJ, QFN-28, Primary Input Voltage:15V, No. of Outputs:2, Output Current:3A, No. of Pins:28, Operating Temperature Min:-40C, Operating Temperature Max:150C, MSL:-, Package / Case:28-QFN , RoHS Compliant: Yes |
| LTC3634IFE#PBF | 功能描述:IC CONV DDR DDR2 DDR3 28TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
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