at9173eg AME, Inc., at9173eg Datasheet - Page 7

• Manufacturer Part Number: at9173eg
• Description: Bus Termination Regulator
• Manufacturer: AME, Inc.

n Application Information
n Application Circuit
AT9173
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
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.
Typical application circuit is used as a regulator to provide
Time constant for this circuit is Css*(R1//R2). The Css
Rev. C.05
V
V
R
C
R
C
CNTL
IN
1
OUT(MIN)
DUMMY
SS
= 1.8V
= R
= 3.3V
= 1uF, C
EN
2
= 1KO as for V
= 100KO, R
= 10uF (Ceramic) + 1000uF under the worst case testing condition
2N7002
AME, Inc.
OUT
IN
= 470uF (Low ESR), C
will follow REFEN.
TT
= 50O / 33O / 25O
OUT
R
R
discharge when V
1
2
C
SS
CNTL
OUT
REFEN
VIN
is composed of
= 47uF
IN
IN
is not presented but V
an C
AT9173
GND
CNTL
is
IN
VCNTL
n 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
enough driving voltage. The minimum dropout
voltage could be I
current.
n Layout issue
VOUT
V
capacitor is recommended
capacitor. Use wide and short PCB traces to
connect in between V
reduce PCB resistance thus to reduce undesired
power dissipation.
The AT9173 can be used as a general regulator.
Place a bypass capacitor as close as possible to
IN
and V
CNTL
Bus Termination Regulator
CNTL
is presented
CNTL
C
pin is necessary. A low ESR
IN
OUT
should be larger than V
*0.1, where I
C
OUT
IN
C
power source V
CNTL
R
DUMMY
for this bypass
OUT
is the output
R
TT
IN
OUT
to get
to
7