Description
The SE9174 regulator is designed to convert
voltage supplies ranging from 1.6V to 6V into a
desired output voltage, which is adjusted by two
external voltage divider resistors. The regulator is
capable of sourcing or sinking up to 2.0A of current
while regulating an output voltage to within 2%
(DDR 1 or DDR 2) or less.
The SE9174, used in conjunction with series
termination resistors, provides an excellent voltage
source for active termination schemes of high
speed transmission lines as those seen in high
speed memory buses and distributed back-plane
designs. The voltage output of the regulator can be
used as a termination voltage for DDR SDRAM.
Current limits in both sourcing and sinking
mode, plus on-chip thermal shutdown make the
circuit tolerant of the output fault conditions.
Features
Support Both DDR 1 (1.25V
TT
) and DDR 2
(0.9V
TT
) Requirements
SOP-8 Packages
Capable of Sourcing and Sinking Current 2.0A
Current-limiting Protection
Thermal Protection
Current-shoot-through protection
Integrated Power MOSFETs
Generates Termination Voltages for SSTL-2
High Accuracy Output Voltage at Full-Load
Adjustable Vout by External Resistors
Minimum External Components
Shutdown for Standby or Suspend Mode
Operation with High-impedance Output
Application
DDR Memory Termination
Active Termination Buses
Supply Splitter
Pin Configuration
Pin Description
Pin Name
V
IN
GND
V
CNTL
REFEN
Pin function
Power Input
Ground
Gate Drive Voltage
Reference Voltage input and
Chip Enable
V
OUT
Output Voltage
Block Diagram
VCNTL
Current
Limiting Sensor
VIN
REFEN
Thermal
CNTL
VOUT
GND
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© Seaward Electronics Inc., 2005. • www.seawardinc.com • Page 1
Absolute Maximum Rating
(1)
Parameter
Input Voltage
Power Dissipation
ESD Rating
Storage Temperature
Range
Lead Temperature
(Soldering, 5 sec.)
Package Thermal
Resistance
Symbol
V
IN
P
D
--
T
S
T
LEAD
Θ
JC
Value
6
Internally Limited
3
-65 to 150
Unit
V
--
KV
°C
260
°C
15.7
ºC/W
Electrical Characteristics
V
IN
=2.5V, V
CNTL
=3.3V, V
REFEN
=1.25V, C
OUT
=10µF (Ceramic)), T
A
=25ºC, unless otherwise specified
Parameter
Output Offset Voltage
(2)
Load Regulation
(DDR 1/2)
Input Voltage Range
(DDR 1/2)
Current In Shutdown
Mode
Symbol
V
OS
|∆V
LOAD
|
V
IN
V
CNTL
I
SHDN
Test Conditions
I
OUT
= 0A
I
L
: 0A→2.0A
I
L
: 0A→-2.0A
Keep V
CNTL
≥V
IN
on
operation power on and
power off sequences
V
REFEN
＜0.2V,
R
L
= 180Ω
Short Circuit Protection
Min
-20
--
--
1.6
--
Typ
-5
0.5
0.5
2.5/1.8
3.3
Max
20
2
2
--
6
Units
mV
%
V
--
1
90
µA
Current limit
Quiescent Current
I
LIMIT
I
Q
I
L
=2.0A
Over Temperature Protection
--
--
2.5
1.4
--
3
A
mA
Thermal Shutdown
Temperature
Thermal Shutdown
Hysterresis
T
CASE
3.3V
≤
V
CNTL
≤5
V
Guaranteed by design
Shutdown Function
--
100
--
ºC
--
30
--
Shutdown Threshold
Trigger
Output=High
Output=Low
0.8
--
--
--
--
0.2
V
Note 1:
Exceeding the absolute maximum rating may damage the device.
Note 2:
V
OS
offset is the voltage measurement defined as V
OUT
subtracted from V
REFEN
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© Seaward Electronics Inc., 2005. • www.seawardinc.com • Page 2
Application Information
Internal parasitic diode
Avoid forward-bias internal parasitic diode,
V
OUT
to V
CNTL
, and V
OUT
to V
IN
, the V
OUT
should not
be forced same voltage respect to ground on this
pin while the V
CNTL
or V
IN
is disappeared.
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 V
REFEN
is below 0.2V.
In addition to item1, 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.
Thermal Consideration
SE9174 regulators have internal thermal
limiting circuitry designed to protect the device
during overload conditions. For continuous normal
load conditions however, the maximum junction
temperature rating of 150°C must not be exceeded.
Higher continuous currents or ambient temperature
require additional heatsinking. Heat sinking to the
IC package must consider the worst case power
dissipation which may occur.
It should also be noted that with the V
CNTL
equal to 5V, the point of thermal shutdown will be
degraded by approx. 20°C compared to the V
CNTL
equipped with 3.3V. It is highly recommended that
to use the 3.3V rail acting as the V
CNTL
so as to
minimize the thermal concern of the SE9174 in the
SOP-8 package.
Layout Consideration
The
SE9174
regulator
is
packaged
in
thermally enhanced plastic SOP-8 package. This
small footprint package is unable to convectively
dissipate the heat generated when the regulator is
operating at high current levels. In order to control
die operating temperatures, the PC board layout
should allow for maximum possible copper area at
the V
CNTL
pins of the SE9174.
The multiple V
CNTL
pins on the SOP-8 package
are internally connected, but lowest thermal
resistance will result if these pins are tightly
connected on the PC board. This will also aid heat
dissipation at high power levels.
If
the
large
copper around
the IC
is
unavailable, a buried layer may be used as a heat
spreader, Use via to conduct the heat into the
buried or backside of PCB layer. The via should be
small enough to retain solder when the board is
wave-soldered.
Terminator Resis
R0
BUS(0)
BUS(1)
BUS(2)
BUS(3)
BUS(4)
BUS(5)
BUS(6)
BUS(7)
BUS(8)
BUS(9)
SE9174
REFEN
VOUT
R1
R2
R3
R4
R5
SE9174
VOUT
R6
R7
R8
R9
RN
RN1
BUS(N+1)
BUS(N)
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© Seaward Electronics Inc., 2005. • www.seawardinc.com • Page 3
Application Diagram
R
1
= R
2
= 100KΩ, R
TT
= 50Ω/33Ω/25Ω
C
OUT, min
= 10µF(Ceramic) + 1000µF under the worst case testing condition
R
DUMMY
= 1KΩ as for V
OUT
discharge when V
IN
is not present but V
CNTL
is present
C
SS
= 1µF, C
IN
= 470µF(Low ESR), C
CNTL
= 47µF
All contents are subject to change without prior notice
© Seaward Electronics Inc., 2005. • www.seawardinc.com • Page 4
Outline Drawing SOP-8
DIMENSIONS
INCHES
MM
MIN MAX MIN MAX
0.0532 0.0688
0.0040 0.0098
0.0130 0.0200
0.050 BSC
0.0075 0.0098
0.1890 0.1968
0.2284 0.2440
0.1497 0.1574
1.35
1.75
0.10
0.25
0.33
0.51
1.27 BSC
0.19
0.25
4.80
5.00
5.80
6.20
3.80
4.00
1
2
D
8
7
6
B1
B
DIM
N
A
A1
B
B1
C
D
H
E
3
4
5
A1
E
H
A
C
Contact Information
Seaward Electronics Incorporated – China
Room 1605, Building 1, International Pioneering Park, #1 Shangdi Xinxi Rd.
Haidian District, Beijing 100085, China
Tel: 86-10-8289-5700/01/05
Fax: 86-10-8289-5706
Email: sales@seawardinc.com.cn
Seaward Electronics Corporation – Taiwan
2F, #181, Sec. 3, Min Quan East Rd.
Taipei, Taiwan R.O.C
Tel: 886-2-2712-0307
Fax: 886-2-2712-0191
Email: sales@seawardinc.com.tw
Seaward Electronics Incorporated – North America
49 Showers Dr. J126
Mountain View, CA 94040, USA
Tel: 1-408-821-6600
Last Updated - 3/21/2005
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© Seaward Electronics Inc., 2005. • www.seawardinc.com • Page 5
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