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參數(shù)資料
| 型號： | LTC3880IUJ-1#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40 |
| 封裝： | 6 X 6 MM, LEAD FREE, PLASTIC, WJJD-2, QFN-40 |
| 文件頁數(shù)： | 52/112頁 |
| 文件大?。?/td> | 2182K |
| 代理商： | LTC3880IUJ-1#PBF |
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LTC3880/LTC3880-1
44
3880fa
APPLICATIONS INFORMATION
the end of the fall time interval. If the TOFF_FALL time is
set shorter than the time required to discharge the load
capacitance, the output will not reach the desired zero volt
state. At the end of TOFF_FALL, the controller will cease
to sink current and VOUT will decay at the natural rate
determined by the load impedance. If the controller is in
discontinuous mode, the controller will not pull negative
current and the output will be pulled low by the load, not
the power stage. The maximum fail time is limited to 1.3
seconds. The shorter TOFF_FALL time is set, the more
jagged the TOFF_FALL ramp will appear. The number of
steps in the ramp is equal to TOFF_FALL/0.1ms.
INTVCC REGULATOR
The LTC3880 features an NPN linear regulator that sup-
plies power to INTVCC from the VIN supply. INTVCC powers
the gate drivers, VDD33 and much of the LTC3880 internal
circuitry. The linear regulator produces the voltage at the
INTVCC pin to nominally 5V when VIN is greater than 6.5V.
Theregulatorcansupplyapeakcurrentof100mAandmust
be bypassed to ground with a minimum of 1F ceramic
capacitor or low ESR electrolytic capacitor. No matter what
type of bulk capacitor is used, an additional 0.1F ceramic
capacitor placed directly adjacent to the INTVCCandPGND
pins is highly recommended. Good bypassing is needed to
supplythehightransientcurrentsrequiredbytheMOSFET
gate drivers and to prevent interaction between the chan-
nels. The NPN linear regulator on the LTC3880-1 is not
present and an external 5V supply is needed.
High input voltage application in which large MOSFETs
are being driven at high frequencies may cause the maxi-
mum junction temperature rating for the LTC3880 to be
exceeded. The INTVCC current, of which a large percent-
age is due to the gate charge current, may be supplied by
either the internal 5V linear regulator or from an external
5V regulator on the LTC3880-1. If the LTC3880 is used
with the internal regulator activated, the power through
the IC is equal to VIN IINTVCC. The gate charge current
is dependent on operating frequency as discussed in the
Efficiency Considerations section. The junction tempera-
ture can be estimated by using the equations in Note 2 of
the Electrical Characteristics. For example, the LTC3880
INTVCC current is limited to less than 69mA from a 24V
supply:
TJ = 70°C + 69mA 24V 33°C/W = 125°C
To prevent the maximum junction temperature from being
exceeded, a LTC3880-1 can be used. In the LTC3880-1,
the INTVCC linear regulator is disabled and approximately
2mA of current is supplied internally from VIN. Significant
system efficiency and thermal gains can be realized by
powering the EXTVCC pin from a switching 5V regulator.
The VIN current resulting from the gate driver and control
circuitry will be scaled by a factor of:
VEXTVCC
VIN
1
Efficiency
Tying the EXTVCC pin to a 5V supply (LTC3880-1 only)
reduces the junction temperature in the previous example
from125°C to:
TJ = 70°C + 69mA 5V 33°C/W + 2mA 24V 33°C/W
= 83°C
Do not tie INTVCC on the LTC3880 to an external supply
because INTVCC will attempt to pull the external supply
high and hit current limit, significantly increasing the die
temperature.
ForapplicationswhereVINis5V,tietheVINandINTVCCpins
together and tie the combined pins to the 5V input with a
1Ωor2.2ΩresistorasshowninFigure23.Tominimizethe
voltage drop caused by the gate charge current a low ESR
capacitor must be connected to the VIN/INTVCC (EXTVCC)
pins. This configuration will override the INTVCC(EXTVCC)
linear regulator and will prevent INTVCC (EXTVCC) from
dropping too low. Make sure the INTVCC(EXTVCC) voltage
exceeds the RDS(ON)testvoltagefortheMOSFETswhichis
Figure 23. Setup for a 5V Input
RVIN
1
CIN
3880 F23
5V
CINTVCC
4.7F
+
INTVCC/EXTVCC
LTC3880
LTC3880-1
VIN
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| LTC3883EUH#PBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 制造商:Linear Technology 功能描述:BUCK CNTRL 24V 1MHZ 0.5/5.5V 32QFN 制造商:Linear Technology 功能描述:BUCK, CNTRL, 24V, 1MHZ, 0.5/5.5V, 32QFN 制造商:Linear Technology 功能描述:PWM CONTROLLER, BUCK, 1MHZ, 24V, QFN-32, Input Voltage:24V, Output Voltage:5.5V, Output Current:30A, Supply Voltage Min:4.5V, Supply Voltage Max:24V, Digital IC Case Style:QFN, No. of Pins:32, Frequency:1MHz, MSL:MSL 1 - Unlimited , RoHS Compliant: Yes 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Digitally Programmable, Multiphase Step-Down DC/DC Controll |
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