at9173eg

Manufacturer Part Numberat9173eg
DescriptionBus Termination Regulator
ManufacturerAME, Inc.
at9173eg datasheet
 
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AME, Inc.
AT9173
n Application Information
V
= 3.3V
CNTL
V
= 1.8V
IN
R
1
2N7002
EN
R
2
R
= R
= 100KO, R
= 50O / 33O / 25O
1
2
TT
C
= 10uF (Ceramic) + 1000uF under the worst case testing condition
OUT(MIN)
R
= 1KO as for V
discharge when V
DUMMY
OUT
C
= 1uF, C
= 470uF (Low ESR), C
SS
IN
n Application Circuit
Typical application circuit is used as a regulator to provide
termination voltage in double data rate (DDR) memory
system. The regulator could source and sink up to 2A peak
current. The output voltage will follow REFEN which
generated by two external dividing resistors down from V
or to the desired output voltage set externally by forcing a
voltage level to REFEN pin. To add a shutdown function ,
connect a small transistor to REFEN pin. To perform
shutdown function , put a logic high 5V signal to EN yield a
low (0V) to REFEN pin thus force output voltage to zero
voltage. The capacitor Css is used to softstart the output
voltage since V
will follow REFEN.
OUT
Time constant for this circuit is Css*(R1//R2). The Css
could also used as the bypass capacitor to filter out noise in
REFEN pin. So carefully layout should put Css close to
REFEN pin to maintain noise immunity. The C
used as power decoupling capacitor. C
10uF ceramic plus 1000uF electrolyte capacitors. The first
one is to used as high frequency filter and the second one is
used to reduce voltage drop during load regulating.
Rev. C.05
VCNTL
VIN
AT9173
REFEN
VOUT
GND
C
SS
is not presented but V
IN
= 47uF
CNTL
n General Regulator
The AT9173 can be used as a general regulator.
To get a desired output voltage, put a reference
voltage to REFEN pin or dividing resistors down a
input voltage source. To drive inside N-Channel
MOSFET the V
IN
enough driving voltage. The minimum dropout
voltage could be I
current.
n Layout issue
Place a bypass capacitor as close as possible to
V
IN
capacitor is recommended
an C
is
capacitor. Use wide and short PCB traces to
IN
CNTL
connect in between V
is composed of
OUT
reduce PCB resistance thus to reduce undesired
power dissipation.
Bus Termination Regulator
C
C
IN
CNTL
R
C
DUMMY
OUT
is presented
CNTL
should be larger than V
CNTL
*0.1, where I
OUT
OUT
and V
pin is necessary. A low ESR
CNTL
for this bypass
power source V
IN
R
TT
to get
IN
is the output
to
OUT
7