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參數(shù)資料
| 型號： | LTC4269IDKD-2#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 560 kHz SWITCHING FREQ-MAX, PDSO32 |
| 封裝： | 7 X 4 MM, PLASTIC, M0-229, DFN-32 |
| 文件頁數(shù)： | 16/34頁 |
| 文件大?。?/td> | 383K |
| 代理商： | LTC4269IDKD-2#TR |
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LTC4269-2
42692fb
Synchronizing
A SYNC pin allows the LTC4269-2 oscillator to be synchro-
nized to an external clock. The SYNC pin can be driven
from a logic-level output, requiring less than 0.8V for a
logic-level low and greater than 2.2V for a logic-level high.
Duty cycle should run between 10% and 90%. To avoid
lossofslopecompensationduringsynchronization,thefree
runningoscillatorfrequency,fOSC,shouldbeprogrammed
to 80% of the external clock frequency (fSYNC).TheRSLOPE
resistor chosen for nonsynchronized operation should be
increased by 1.25x (= fSYNC/fOSC).
Shutdown and Programming the Power Supply
Undervoltage Lockout
TheLTC4269-2hasanaccurate1.32Vshutdownthreshold
at the SD_VSEC pin. This threshold can be used in con-
junction with a resistor divider to define the power supply
undervoltagelockoutthreshold(UVLO)ofthepowersupply
inputvoltage(VS)(Figure9).Apincurrenthysteresis(11A
before part turn-on, 0A after part turn-on) allows power
supply UVLO hysteresis to be programmed. Calculation of
the on/off thresholds for the power supply input voltage
can be made as follows:
VS(OFF) Threshold = 1.32[1 + (R1/R2)]
VS(ON) Threshold = VS(OFF) + (11A R1)
Connect the PWRGD pin to the resistive divider network
at the SD_VSEC pin to prevent the DC/DC converter from
starting before the PD interface completely charges the
reservoir capacitor, C1 (Figure 9).
The SD_VSEC pin must not be left open since there must
be an external source current >11A to lift the pin past its
1.32V threshold for part turn-on.
Micropower Start-Up: Selection of Start-Up Resistor
and Capacitor for VIN
The LTC4269-2 uses turn-on voltage hysteresis at the VIN
pin and low start-up current to allow micropower start-up
(Figure 10). The LTC4269-2 monitors VIN pin voltage to
allow the part to turn-on at 14.25V and the part to turn-
off at 8.75V. Low start-up current (460A) allows a large
resistor to be connected between the power supply input
supply and VIN. Once the part is turned on, input current
applicaTions inForMaTion
Figure 9. Programming Power Supply
Undervoltage Lockout (UVLO)
1.32V
POWER SUPPLY
INPUT VOLTAGE (VS)
42692 F09
SD_VSEC
PWRGD
11A
LTC4269-2
R1
R2
+
–
Figure 10. Low Power Start-Up
1.32V
POWER SUPPLY
INPUT VOLTAGE (VS)
FROM AUXILIARY WINDING
*FOR VS > 25V, ZENER D1 RECOMMENDED
(VIN ON(MAX) < VZ < 25V)
42692 F10
VIN
LTC4269-2
CSTART
D1*
RSTART
+
–
increases to drive the IC (5.2mA) and the output drivers
(IDRIVE). A large enough capacitor is chosen at the VIN pin
to prevent VIN falling below its turn-off threshold before
a bias winding in the converter takes over supply to VIN.
This technique allows a simple resistor/capacitor for
start-up which draws low power from the system supply
to the converter.
Forsysteminputvoltagesexceedingtheabsolutemaximum
rating of the LTC4269-2 VIN pin, an external Zener should
be connected from the VIN pin to GND. This covers the
condition where VINchargespastVIN(ON)butthepartdoes
not turn on because SD_VSEC < 1.32V. In this condition,
VIN will continue to charge towards system VIN, possibly
exceeding the rating for the VIN pin. The Zener voltage
should obey VIN(ONMAX) < VZ < 25V.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC4269IDKD-2-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:IEEE 802.3at High Power PD and Synchronous Forward Controller with AUX Support |
| LTC4270 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:12-Port PoE/PoE+/LTPoE++ PSE Controller |
| LTC4270/ | 制造商:LINER 制造商全稱:Linear Technology 功能描述:8-Port PoE/PoE PSE Controller |
| LTC4270_12 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:12-Port PoE/PoE+/LTPoE++ PSE Controller |
| LTC4270AIUKG#PBF | 制造商:Linear Technology 功能描述:POE Controller 90W 52-Pin QFN EP 制造商:Linear Technology 功能描述:Bulk 制造商:Linear Technology 功能描述:IC POE LTPOE 12-PORT PSE 52-QFN 制造商:Linear Technology 功能描述:PSE CNTRL 12 PORT 90W 1MHZ 制造商:Linear Technology 功能描述:IC PSE CONTROLLER 3.3V QFN-52 制造商:Linear Technology 功能描述:IC, PSE CONTROLLER, 3.3V, QFN-52; Input Voltage:3.3V; Supply Current:10mA; UVLO:25V; Digital IC Case Style:QFN; No. of Pins:52; Frequency:1MHz; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:52-QFN ;RoHS Compliant: Yes |
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