參數(shù)資料
型號(hào)： LTC3731HUH#PBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： 5 A SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PQCC32
封裝： 5 X 5 MM, LEAD FREE, PLASTIC, MO-220WHHD, QFN-32
文件頁(yè)數(shù)： 11/34頁(yè)
文件大?。?/td> 427K
代理商： LTC3731HUH#PBF
LTC3731H
3731Hfb
applicaTions inForMaTion
Figure 8. Foldback Current Elimination
Current Foldback
In certain applications, it may be desirable to defeat the
internal current foldback function. A negative impedance
is experienced when powering a switching regulator. That
is, the input current is higher at a lower VIN and decreases
as VIN is increased. Current foldback is designed to ac-
commodate a normal, resistive load having increasing
current draw with increasing voltage. The EAIN pin should
be artificially held 70% above its nominal operating level
of 0.6V, or 0.42V in order to prevent the IC from “folding
back” the peak current level. A suggested circuit is shown
in Figure 8.
The emitter of Q1 will hold up the EAIN pin to a voltage in
the absence of VOUT that will prevent the internal sensing
circuitry from reducing the peak output current. Remov-
ing the function in this manner eliminates the external
MOSFET’sprotectivefeatureundershort-circuitconditions.
This technique will also prevent the short-circuit latchoff
function from turning off the part during a short-circuit
event and the peak output current will only be limited to
N 75mV/RSENSE.
Undervoltage Reset
In the event that the input power source to the IC (VCC)
drops below 4V, the RUN/SS capacitor will be discharged
toground.WhenVCCrisesabove4V,theRUN/SScapacitor
will be allowed to recharge and initiate another soft-start
turn-on attempt. This may be useful in applications that
switch between two supplies that are not diode connected,
but note that this cannot make up for the resultant inter-
ruption of the regulated output.
Phase-Locked Loop and Frequency Synchronization
The IC has a phase-locked loop comprised of an internal
voltagecontrolledoscillatorandphasedetector.Thisallows
the top MOSFET of output stage 1’s turn-on to be locked
to the rising edge of an external source. The frequency
range of the voltage controlled oscillator is ±50% around
the center frequency fO. A voltage applied to the PLLFLTR
pin of 1.2V corresponds to a frequency of approximately
400kHz. The nominal operating frequency range of the IC
is 225kHz to 680kHz.
The phase detector used is an edge sensitive digital type
thatprovideszerodegreesphaseshiftbetweentheexternal
and internal oscillators. This type of phase detector will
not lock the internal oscillator to harmonics of the input
frequency. The PLL hold-in range, fH, is equal to the
capture range, fC:
fH = fC = ±0.5 fO
The output of the phase detector is a complementary pair
of current sources charging or discharging the external
filter components on the PLLFLTR pin. A simplified block
diagram is shown in Figure 9.
If the external frequency (fPLLIN) is greater than the os-
cillator frequency, fOSC, current is sourced continuously,
pullingupthePLLFLTRpin.Whentheexternalfrequencyis
less than fOSC, current is sunk continuously, pulling down
VCC
3731H F08
CALCULATE FOR
0.42V TO 0.55V
VCC
EAIN
Q1
LTC3731H
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參數(shù)描述
LTC3731IG 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 36-Pin SSOP
LTC3731IG#PBF 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC3731IG#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC3731IUH 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 32-Pin QFN EP
LTC3731IUH#PBF 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
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