參數(shù)資料
型號: LTC3786EUD#PBF
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC16
封裝: 3 X 3 MM, LEAD FREE, PLASTIC, MO-220WEED-2,QFN-16
文件頁數(shù): 16/34頁
文件大小: 397K
代理商: LTC3786EUD#PBF
LTC3786
23
3786fa
applicaTions inForMaTion
PC Board Layout Debugging
It is helpful to use a DC-50MHz current probe to monitor
the current in the inductor while testing the circuit. Moni-
tor the output switching node (SW pin) to synchronize
the oscilloscope to the internal oscillator and probe the
actual output voltage. Check for proper performance over
the operating voltage and current range expected in the
application. The frequency of operation should be main-
tained over the input voltage range down to dropout and
until the output load drops below the low current opera-
tion threshold— typically 10% of the maximum designed
current level in Burst Mode operation.
Thedutycyclepercentageshouldbemaintainedfromcycle
to cycle in a well designed, low noise PCB implementation.
Variation in the duty cycle at a subharmonic rate can sug-
gest noise pick-up at the current or voltage sensing inputs
or inadequate loop compensation. Overcompensation of
the loop can be used to tame a poor PC layout if regulator
bandwidth optimization is not required.
Reduce VIN from its nominal level to verify operation with
high duty cycle. Check the operation of the undervoltage
lockout circuit by further lowering VIN while monitoring
the outputs to verify operation.
Investigate whether any problems exist only at higher out-
put currents or only at higher input voltages. If problems
coincide with high input voltages and low output currents,
look for capacitive coupling between the BOOST, SW, TG,
and possibly BG connections and the sensitive voltage
and current pins. The capacitor placed across the current
sensing pins needs to be placed immediately adjacent to
the pins of the IC. This capacitor helps to minimize the
effects of differential noise injection due to high frequency
capacitive coupling.
An embarrassing problem, which can be missed in an
otherwise properly working switching regulator results
when the current sensing leads are hooked up backwards.
The output voltage under this improper hook-up will still
bemaintained,buttheadvantagesofcurrentmodecontrol
will not be realized. Compensation of the voltage loop will
be much more sensitive to component selection. This
behavior can be investigated by temporarily shorting out
the current sensing resistor—don’t worry, the regulator
will still maintain control of the output voltage.
相關PDF資料
PDF描述
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LTC3787EUFD#PBF SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PQCC28
LTC3787IGN#PBF SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PDSO28
LTC3788EUH#TRPBF DUAL SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC32
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