RT9173D Ver la hoja de datos (PDF) - Richtek Technology
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RT9173D Datasheet PDF : 13 Pages
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RT9173D
Application Information
Consideration while designs the resistance of voltage
divider
Make sure the sinking current capability of pull-down NMOS
if the lower resistance was chosen so that the voltage on
VREFEN is below 0.2V.
In addition, the capacitor and voltage divider form the low-
pass filter. There are two reasons doing this design; one is
for output voltage soft-start while another is for noise
immunity.
How to reduce power dissipation on Notebook PC or
the dual channel DDR SDRAM application?
In notebook application, using RichTek's Patent
“Distributed Bus Terminator Topology” with choosing
RichTek's product is encouraged.
REFEN
Distributed Bus Terminating Topology
Terminator Resistor
R0
R1
VOUT
R2
RT9173D
R3
R4
R5
R6
VOUT
R7
RT9173D
R8
R9
BUS(0)
BUS(1)
BUS(2)
BUS(3)
BUS(4)
BUS(5)
BUS(6)
BUS(7)
BUS(8)
BUS(9)
VEXT
Figure 2
R(2N)
R(2N+1)
BUS(2N)
BUS(2N+1)
R1
VCNTL
VIN
RT9173D
REFEN
VOUT
R2
GND
VOUT
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10
Figure 3
General Regulator
The RT9173D could also serves as a general linear
regulator. The RT9173D accepts an external reference
voltage at REFEN pin and provides output voltage regulated
to this reference voltage as shown in Figure 3, where
VOUT = VEXT x R2/(R1+R2)
As other linear regulator, dropout voltage and thermal issue
should be specially considered. Figure 4 and 5 show the
RDS(ON) over temperature of RT9173D in PSOP-8 (Exposed
Pad) package. The minimum dropout voltage could be
obtained by the product of RDS(ON) and output current. For
thermal consideration, please refer to the relative sections.
RDS(ON) vs. Temperature
0.40
VCNTL = 3.3V
0.35
0.30
0.25
0.20
0.15
0.10
-50 -25
0
25 50 75
Temperature (°C)
Figure 4
100 125
RDS(ON) vs. Temperature
0.40
VCNTL = 5V
0.35
0.30
0.25
0.20
0.15
0.10
-50 -25
0
25 50 75
Temperature (°C)
Figure 5
100 125
DS9173D-05 September 2007
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