www.fairchildsemi.com
REV. 1.1.3 8/4/03
Features
• Can source and sink up to 2A continous, 3A peak
• No heatsink required
• Integrated Power MOSFETs
• Generates termination voltages for DDR SDRAM
•V
REF
input available for external voltage divider
• Separate voltages for V
CCQ
and PV
DD
• Buffered V
REF
output
•V
OUT
of ±3% or less at 2A
• Minimum external components
• 16-pin SOIC package
• -40°C to +85°C operating temperature range
• Shutdown for standby or suspend mode operation
• Thermal Shutdown
≈
130ºC
Description
The FAN6555 switching regulator is designed to convert
voltage supplies ranging from 2.3V to 4V into a desired out-
put voltage or termination voltage for DDR SDRAM mem-
ory. The FAN6555 can be implemented to produce regulated
output voltages in two different modes. In the default mode,
when the V
REF
pin is open, the FAN6555 output voltage is
50% of the voltage applied to V
CCQ
. The FAN6555 can also
be used to produce various user-defined voltages by forcing a
voltage on the VREF
IN
pin. In this case, the output voltage
follows the input VREF
IN
voltage. The switching regulator
is capable of sourcing or sinking up to 2A of current while
regulating an output V
TT
voltage to within 3% or less.
Transient output currents of ±3A can also be accommodated.
The FAN6555 can also be used in conjunction with series
termination resisitors to provide an excellent voltage source
for active termination schemes of high speed transmission
lines as those seen in high speed memory buses and distrib-
uted backplane designs.
Block Diagram
V
L2
AGND
13
VREF
IN
VREF
OUT
11
6
V
DD
1
SHDN
12
PV
DD2
PV
DD1
7
V
L1
3
+
–
–
+
AV
CC
V
CCQ
15
OSCILLATOR/
RAMP
GENERATOR
S
R
Q
Q
(V
OUT
)
(V
OUT
)
P
GND1
D
GND
V
FB
P
GND2
2
4 58
V
DD
9
14
10
V
REF
BUFFER
ERROR AMP
RAMP
COMPARATOR
+
–
16
200kΩ
200kΩ
FAN6555
2A DDR Bus Termination Regulator
