參數(shù)資料
型號: LTC3833EUDC#TRPBF
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PQCC20
封裝: 3 X 3 MM, LEAD FREE, PLASTIC, QFN-20
文件頁數(shù): 6/36頁
文件大?。?/td> 513K
代理商: LTC3833EUDC#TRPBF
LTC3833
14
3833f
APPLICATIONS INFORMATION
point that is to be accurately regulated through remote
differential sensing.
Switching Frequency Programming
The choice of operating frequency is a trade-off between
efficiencyandcomponentsize.Loweringtheoperatingfre-
quencyimprovesefficiencybyreducingMOSFETswitching
losses but requires larger inductance and/or capacitance
to maintain low output ripple voltage. Conversely, raising
the operating frequency degrades efficiency but reduces
component size.
The switching frequency of the LTC3833 can be pro-
grammed from 200kHz to 2MHz by connecting a resistor
from the RT pin to signal ground. The value of this resistor
is given by the following empirical formula:
RT k
[ ]= 41550
f kHz
[ ]
– 2.2
Not counting resistor tolerances, the switching fre-
quency could still have a ±10% deviation from the ideal
programmed value. The internal PLL has a synchroniza-
tion range of ±30% around this programmed frequency.
Therefore, during external clock synchronization be sure
that the external clock frequency is within this ±30% range
of the RT programmed frequency. It is advisable that the
RT programmed frequency be equal to the external clock
for maximum synchronization margin. Refer to Phase and
Frequency Synchronization for further details.
Inductor Selection
The operating frequency and inductor selection are inter-
relatedinthathigheroperatingfrequenciesallowtheuseof
smaller inductor and capacitor values. A higher frequency
generally results in lower efficiency because of MOSFET
gate charge losses and top MOSFET transition losses.
In addition to this basic trade-off, the effect of inductor
value on ripple current and low current operation must
also be considered.
The inductor value has a direct effect on ripple current.
The inductor ripple current,
IL, decreases with higher
inductance or frequency and increases with higher VIN:
IL =
VOUT
f L
1–
VOUT
VIN
Accepting larger values of
IL allows the use of low induc-
tances, but results in higher output voltage ripple, higher
ESRlossesintheoutputcapacitor,andgreatercorelosses.
A reasonable starting point for setting ripple current is
IL = 0.4 IOUT(MAX) where IOUT(MAX) is the maximum
output current for the application. The maximum
IL
occurs at the maximum input voltage. To guarantee that
RFB1
MB
RFB2
MT
L
CIN
VIN
COUT1
COUT2
3833 F02
ILOAD
OTHER CURRENTS
FLOWING IN
SHARED GROUND
PLANE
POWER TRACE
PARASITICS
±VDROP(PWR)
+–
GROUND TRACE
PARASITICS
±VDROP(GND)
ILOAD
LTC3833
VOSNS+
VOSNS–
Figure 2: Differential Output Sensing Used to Correct Line Loss Variations in a
High Power Distributed System with a Shared Ground Plane
相關(guān)PDF資料
PDF描述
LTC3833EUDC#PBF SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PQCC20
LTC3833IFE#PBF SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PDSO20
LTC3835IGN-1#TR 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO16
LTC3835EDHC-1#TRPBF 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO16
LTC3835IGN-1 3 A SWITCHING CONTROLLER, 580 kHz SWITCHING FREQ-MAX, PDSO16
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