EUTECH EUP7996

EUP7996
1.5A DDR Termination Regulator
DESCRIPTION
FEATURES
The EUP7996 is a high performance linear regulator
designed to provide power for termination of a DDR
memory bus. It significantly reduces parts count, board
space and overall system cost over previous switching
solutions.
The EUP7996 contains a high-speed operational amplifier
to provide excellent response to load transients. The
EUP7996 also incorporates a VSENSE pin to provide
superior load regulation and a VREF output as a reference
for chipset and DIMMs.
An additional feature found on the EUP7996 is an active
low shutdown (SD) pin. When SD is pulled low the VTT
output will Tri-state providing a high impedance output,
but, VREF will remain active. A power savings advantage
can be obtained in this mode through lower quiescent
current.
z
Extremely low quiescent current (305uA)
z
Fast transient response time
z
Capable of sourcing and sinking 1.5A for DDR-I
termination
z
Reference out for other memory and control
components
z
Low-current shutdown mode
z
Over-temperature protection
z
High accuracy output voltage at full-load
z
Low external component count
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Available in SOP-8, SOP(FD) package
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RoHS compliant and 100% lead (Pb)-free
APPLICATIONS
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The EUP7996, 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. A typical
DDR memory system is seen in Figure 1.
SIMPLIFIED SYSTEM DIRGRAM
Figure 1.
DS7996 Ver2.5
June.2005
1
DDR-I and DDR-II termination voltage
EUP7996
Pin Configurations
Package Type
Pin
Plastic SOP-8(FD)
*Thermal Pad
Configurations
(TOP VIEW)
*
Pin Description
PIN
SYMBOL
DESCRIPTION
1
GND
Ground
2
SD
Shutdown
3
VSENSE
Feedback pin for regulating VTT
4
VREF
Buffered internal reference voltage of VDDQ/2
5
VDDQ
Input for internal reference equal to VDDQ/2
6
AVIN
Analog input pin
7
PVIN
Power Input pin
8
VTT
Output voltage for connection to termination resistors
Typical Application Circuit
Figure 2. Recommended DDR-I Termination
DS7996 Ver2.5
June.2005
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EUP7996
Figure 3. Recommended DDR-II Termination
Ordering Information
Order Number
Package Type
EUP7996ADIR1
SOP-8
Xxxx
EUP7996
A
-40 °C to 125°C
EUP7996ADIR0
SOP-8
Xxxx
EUP7996
A
-40 °C to 125°C
EUP7996A □
Marking
□ □ □
Lead Free Code
1: Lead Free 0: Lead
Packing
R: Tape & Reel
Operating temperature range
I: Industry Standard
Package Type
D: SOP
DS7996 Ver2.5
June.2005
3
Operating Temperature range
EUP7996
Operating Range
Absolute Maximum Ratings
▓
▓
▓
▓
▓
▓
▓
▓
Input voltage - - - - - - - - - - - - - - - - - - 6V
Power dissipation - - - - - - - - - - - - - - - Internal limiting
ESD rating - - - - - - - - - - - - - - - - - - 3KV
Maximum junction temperature - - - - - 150 °C
Storage temperature range - - - - - - - - - -65°C to150°C
Lead temperature (soldering , 5 sec) - 260 °C
SOP-8 thermal resistance, θjA - - - - - - 67.9 °C/W
SOP-8(FD) thermal resistance, θjA - - -42.3 °C/W
▓
▓
▓
▓
Junction Temp. Range - - - - -40°C to 125°C
AVIN to GND - - - - - - - - - - -1.8V to 5.5V
PVIN,VDDQ to GND - - - - - 1.8V to AVIN
SD Input Voltage - - - - - - - - - - 0 to AVIN
Electrical Characteristics
Specifications with standard typeface are for TA=25 °C, unless otherwise specified, AVIN=2.5V
Symbol
Parameter
VREF
VREF Voltage
VTT
VOS
VTT Output Voltage
Output Offset Voltage
Conditions
IREF=0mA
PVIN=VDDQ=2.5V
PVIN=VDDQ=1.8V
PVIN=VDDQ=2.5V
IOUT = 0A
IOUT =±1.5A
PVIN=VDDQ=1.8V
IOUT =0A
IOUT =±0.9 A
PVIN=VDDQ=2.5V
IOUT=0A
IOUT=-1.5A
IOUT=+1.5A
PVIN=VDDQ=1.8V
IOUT=0A
IOUT=-1A
IOUT=+0.9A
Min
Typ
Max
Units
1.235
0.886
1.242
0.899
1.285
0.914
V
1.225
1.225
1.251
1.251
1.290
1.290
V
0.885
0.885
0.892
0.892
0.915
0.915
V
-20
-25
-25
0
0
0
20
25
25
mV
-15
-20
-20
0
0
0
15
20
20
mV
IQ
Quiescent Current (Note 2)
IOUT = 0A
200
305
500
µA
ISHDN
Quiescent Current in
Shutdown
SD = 0V
50
75
200
µA
ILKG_SD
Shutdown leakage current
SD = 0V
--
0.16
--
µA
IV
VTT Leakage Current in
Shutdown
SD = 0V,
VTT = 1.25V
--
0.13
--
µA
Guaranteed by design
--
155
--
°C
Guaranteed by design
--
30
--
°C
Output = High
1.8
--
--
Output = Low
--
--
0.6
Over Temperature Protection
Thermal Shutdown
Temperature
Thermal Shutdown
Hysteresis
TSD
TSD _HYS
Shutdown function
VIH
Shutdown Threshold Trigger
VIL
V
Note 1: VOS offset is the voltage measurement defined as VTT subtracted from VREF.
Note 2: Quiescent current defined as the current flow into AVIN.
DS7996 Ver2.5
June.2005
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EUP7996
Typical Performance Characteristics
Vtt Vs. Itt
Vref vs. Iref
1.26
1.3
1.255
1.28
VTT(V)
Vref(V)
1.25
1.26
1.24
1.245
1.24
1.22
1.235
1.2
1.23
-30
-20
-10
0
Iref(uA)
10
20
30
-1.6
-1.2
-0.4
0
0.4
Load Current(A)
0.8
1.2
1.6
VTT vs VDDQ
Vref vs VDDQ
3
3
2.5
2.5
2
2
VTT(V)
Vref(V)
-0.8
1.5
1
1.5
1
0.5
0.5
0
0
1
2
3
4
5
0
6
0
VDDQ(V)
DS7996 Ver2.5
June.2005
1
2
3
VDDQ(V)
5
4
5
EUP7996
Maximum Sourcing Current vs. Avin
(VDDQ=2.5V , Pvin=2.5V)
1.4
2
1.2
1.9
1.0
1.8
Output(A)
Output(A)
Maximum Source Current vs Avin
(VDDQ=2.5V,PVIN=1.8V)
0.8
0.6
1.7
1.6
0.4
1.5
0.2
1.4
0.0
1.3
2.5
3.0
3.5
4.0
4.5
AVIN(V)
5.0
5.5
2.5
Maximum Sourcing Current vs AVIN
VDDQ=2.5V, PVIN=3.3V
3.4
3.0
Output(A)
Output(A)
3.2
2.8
2.6
2.4
2.2
2.0
3.5
4.0
4.5
AVIN(V)
5.0
4.0
4.5
AVIN(V)
5.0
5.5
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
5.5
2.2
Maximum Sourcing Current vs Avin
2.5
3.0
3.5
4.0
AVIN(V)
4.5
5.0
5.5
Maximum Sourcing Current vs. Avin
(VDDQ=1.8V , Pvin=3.3V)
VDDQ=1.8V, PVIN=1.8V
1.4
3.5
Maximum Sinking Current vs AVIN
(VDDQ=2.5V,PVIN=2.5V)
3.6
3.0
3.0
1.2
3.1
Output(A)
Output(A)
1.0
0.8
0.6
2.9
2.7
0.4
2.5
0.2
2.3
0.0
2.2
DS7996 Ver2.5
2.5
3.0
June.2005
3.5
4.0
AVIN(V)
4.5
5.0
5.5
3.0
6
3.5
4.0
4.5
AVIN(V)
5.0
5.5
EUP7996
1.25Vtt Transient Response
AVIN==PVIN=VDDQ=2.5V Cour=330uF/16V
Maximum Sinking Current vs. Avin
(VDDQ=1.8V , Pvin=2.5V)
2.6
Output(A)
2.4
2.2
2
1.8
1.6
2.5
3.0
3.5
4.0
4.5
AVIN(V)
5.0
5.5
0.9Vtt Transient Response
AVIN=2.5V, PVIN=VDDQ=1.8V Cour=330uF/16V
DS7996 Ver2.5
June.2005
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EUP7996
Block Diagram
Pin Functions
VREF
VREF provides the buffered output of the internal
reference voltage VDDQ/2. This output should be used
to provide the reference voltage for the Northbridge
chipset and memory. Since these inputs are typically
extremely high impedance, there should be little current
drawn from VREF. For improved performance, an output
bypass capacitor can be used, located close to the pin, to
help with noise. A ceramic capacitor in the range of
0.01uF to 0.1uF is recommended. This output remains
active during the shutdown state and thermal shutdown
events.
AVIN and PVIN
AVIN and PVIN are the input supply pins for the
EUP7996. AVIN is used to supply the internal control
circuitry. PVIN, however, is used exclusively to provide
the rail voltage for the output stage used to create VTT.
For SSTL-2 application, a good compromise would be to
connect the AVIN and PVIN directly together at 2.5V.
This eliminates the need for bypassing the two supply
pins separately. For SSTL-18 applications, it is
recommended to connect PVIN to 1.8V rail used for the
memory core and AVIN to a rail typically 2.5V supply.
The only limitation on input voltage selection is that
PVIN must be equal to or lower than AVIN.
VTT
VTT is a regulated output that is used to terminate the bus
resistors. It is capable of sinking and sourcing current
while regulating the output precisely to VDDQ/2. The
EUP7996 is capable of sinking and sourcing 1.5A
continues current. If a transient above the maximum
continues current is expected for a significant amount of
time then the output capacitor should be sized large
enough to prevent an excessive voltage drop. If large
current are required for longer duration, then care should
be taken to ensure that the maximum junction
temperature is not exceeded. If the junction temperature
exceeds the thermal shutdown point than VTT will
tri-state until the part returns below the hysteretic
trip-point.
VDDQ
VDDQ is the input used to create the internal reference
voltage for regulating VTT. The reference voltage is
generated from a resistor divider of two internal 50KΩ
resistors. This guarantees that VTT will track VDDQ/2
precisely. For SSTL-2 applications, VDDQ should be a
2.5V. The optimal implementation of VDDQ is as
remote sense. This can be achieved by connecting
VDDQ directly to the 2.5V rail at DIMM instead of
AVIN and PVIN. This ensures that the reference voltage
tracks the DDR memory rails precisely without a large
voltage drop from the power lines. For SSTL-18
applications, VDDQ will be a 1.8V signal.
VSENSE
The purpose of the sense pin is to provide improved
remote load regulation. In most motherboard application
the termination resistors will connect to VTT in a long
plane. The VSENSE pin can be used by connecting it to the
middle of the bus. This will provide a better distribution
across the entire termination bus. When remote sense is
used, it may necessary to put a 0.1uf ceramic capacitor
beside the VSENSE pin to eliminate the noise that coupled
to VSENSE due to the long trace. VSENSE pin must be
connected to VTT if remote load regulation is not used.
DS7996 Ver2.5
June.2005
SD
SD can be used to put the regulator into low-power
mode. When SD is pulled low, the VTT power amplifier
is turned off and the VTT output is tri-state, but, VREF will
remain active, allowing those circuits requiring a
reference during the standby state to remain active.
8
EUP7996
Component Selection
INPUT CAPACITOR
The input capacitor should be located as close as
possible to the PVIN pin. Several recommendations
exist dependent on the application required. A typical
value recommended for AL electrolytic capacitors is
47uF. If the two supply rails (AVIN and PVIN) are
separated then the 47uF capacitor should be placed as
close to possible to PVIN rail. An additional 0.1uF
ceramic capacitor can be placed on the AVIN rail to
prevent excessive noise from coupling into the device.
When size and performance are critical, several hybrid
capacitors such OS-CON and SP that offer a large
capacitance while maintaining a low ESR are the better
solution.
PCB Layout Considerations
The EUP7996 regulator is packaged in plastic SOP-8
package. This small footprint package is unable to
convectively dissipate at high current levels. The
junction temperature should be kept well away from the
thermal shutdown temperature in normal operation. To
prevent damaging the part from exceeding the maximum
allowable junction temperature, care should be taken to
derate the part dependent on several variables: the
thickness of copper on PCB; the area of top side copper
used; and the airflow. Using large traces and more
copper on the top side of board with careful layout are
possible to reduce thermal resistance on the part.
OUTPUT CAPACITOR
As general recommendation, the output capacitor should
be sized above 220uF with a low ESR for SSTL
applications with DDR-SDRAM. The value of ESR
should be determined by maximum current spikes
expected from the DDR memory system to ensure VTT
staying within +/-40mV of VREF. Capacitor selection can
be varied depending on the number of lines terminated
and the maximum load transient.
With motherboards and other applications where VTT is
distributed across a long plane it is advisable to use
multiple bulk capacitors. Large aluminum electrolytic
capacitors can be used for their low ESR and low cost.
Additional 0.1uF ceramic capacitor is needed for high
frequency decoupling.
If the large ground trace around the IC is unavailable on
top, numerous vias to connect the part and dissipate heat
to the internal ground plane will help. The vias should
be small enough to retain solder when the board is
wave- soldered.
Additional improvements can be achieved with a
constant airflow across the package.
Test Circuit
Figure 2. Load transient (+1.5A ~ –1.5A) test circuit
DS7996 Ver2.5
June.2005
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EUP7996
Mechanical Information
X
Y
Z
Standard Solder Map
Bottom
Ues as much
copper area
as possible
Symbols
A
B
C
D
E
H
F
L1
L2
M
N
A1
B1
EXPOSED PAD
Dimension in Millimeters
Min.
Max.
4.80
5.00
5.80
6.20
3.80
4.00
1.194
1.346
1.45
1.55
0.00
0.10
0.33
0.51
0.19
0.25
0.40
1.27
0°
8°
40°
50°
2.6
2.8
2.4
2.6
Dimension in Inches
Min.
Max.
0.189
0.197
0.228
0.244
0.150
0.157
0.047
0.053
0.057
0.061
0.000
0.004
0.013
0.020
0.007
0.010
0.016
0.050
0°
8°
40°
50°
0.102
0.110
0.095
0.102
8 – Lead SOP(FD) Plastic Package
DS7996 Ver2.5
June.2005
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