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RT9173D
Cost-Effective, Peak 3A Sink/Source Bus Termination Regulator
General Description
The RT9173D is a simple, cost-effective and high-speed linear regulator designed to generate termination voltage in double data rate (DDR) memory system to comply with the JEDEC SSTL_2 and SSTL_18 or other specific interfaces such as HSTL, SCSI-2 and SCSI-3 etc. devices requirements. The regulator is capable of actively sinking or sourcing continuous 2A or up to 3A transient peak current while regulating an output voltage to within 40mV. The output termination voltage cab be tightly regulated to track 1/2VDDQ by two external voltage divider resistors or the desired output voltage can be pro-grammed by externally forcing the REFEN pin voltage. The RT9173D also incorporates a high-speed differential amplifier to provide ultra-fast response in line/load transient. Other features include extremely low initial offset voltage, excellent load regulation, current limiting in bi-directions and on-chip thermal shut-down protection. The RT9173D are available in the SOP-8 (Exposed Pad) surface mount packages.
Features
Ideal for DDR-I, DDR-II and DDR-III VTT Applications Sink and Source Current 2A Continuous Current Peak 3A for DDRI and DDRII Peak 2.5A for DDRIII Integrated Power MOSFETs Generates Termination Voltage for SSTL_2, SSTL _18, HSTL, SCSI-2 and SCSI-3 Interfaces High Accuracy Output Voltage at Full-Load Output Adjustment by Two External Resistors Low External Component Count Shutdown for Suspend to RAM (STR) Functionality with High-Impedance Output Current Limiting Protection On-Chip Thermal Protection Available in SOP-8 (Exposed Pad) Packages VIN and VCNTL No Power Sequence Issue RoHS Compliant and 100% Lead (Pb)-Free
Applications
Desktop PCs, Notebooks, and Workstations Graphics Card Memory Termination Set Top Boxes, Digital TVs, Printers Embedded Systems Active Termination Buses DDR-I, DDR-II and DDR-III Memory Systems
Ordering Information
RT9173D Package Type SP : SOP-8 (Exposed Pad-Option 1) Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard)
Note : Richtek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating.
Pin Configurations
(TOP VIEW)
VIN GND REFEN VOUT 2 3 8 GND 6 9 4 5 7 NC NC VCNTL NC
SOP-8 (Exposed Pad)
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Typical Application Circuit
VCNTL = 3.3V VIN = 2.5V/1.8V/1.5V R1 VIN VCNTL CIN CCNTL RTT
2N7002 EN R2 CSS
RT9173D REFEN VOUT GND
COUT
GND
R1 = R2 = 100k, RTT = 50 / 33 / 25 COUT(MIN) = 10F (Ceramic) + 1000F under the worst case testing condition CSS = 1F, CIN = 470F (Low ESR), CCNTL = 47F
Test Circuit
2.5V/1.8V/1.5V 3.3V
VIN 1.25V/0.9V/0.75V
VCNTL VOUT
RT9173D REFEN VOUT GND
Figure 1. Test Circuit for Typical Operating Characteristics Curves
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Functional Pin Description
VIN (Pin 1) Input voltage which supplies current to the output pin. Connect this pin to a well-decoupled supply voltage. To prevent the input rail from dropping during large load transient, a large, low ESR capacitor is recommended to use. The capacitor should be placed as close as possible to the VIN pin. GND [Pin 2, Exposed pad (9)] Common Ground (Exposed pad is connected to GND). The GND pad area should be as large as possible and using many vias to conduct the heat into the buried GND plate of PCB layer. REFEN (Pin 3) Reference voltage input and active low shutdown control pin. Two resistors dividing down the VIN voltage on the pin to create the regulated output voltage. Pulling the pin to ground turns off the device by an open-drain, such as 2N7002, signal N-MOSFET. VOUT (Pin 4) Regulator output. VOUT is regulated to REFEN voltage that is used to terminate the bus resistors. It is capable of sinking and sourcing current while regulating the output rail. To maintain adequate large signal transient response, typical value of 1000F AL electrolytic capacitor with 10F ceramic capacitors are recommended to reduce the effects of current transients on VOUT. VCNTL (Pin 6) VCNTL supplies the internal control circuitry and provides the drive voltage. The driving capability of output current is proportioned to the VCNTL. Connect this pin to 3.3V bias supply to handle large output current with at least 10F capacitor from this pin to GND. NC (Pin 5, 7, 8) No Internal Connect.
Function Block Diagram
VCNTL VIN
Current Limit Thermal Protection
REFEN
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+ -
EA
VOUT
GND
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Absolute Maximum Ratings
(Note 1) Input Voltage, VIN ------------------------------------------------------------------------------------------------------ 6V Control Voltage, VCNTL ----------------------------------------------------------------------------------------------- 6V Power Dissipation, PD @ TA = 25C SOP-8 (Exposed Pad) ----------------------------------------------------------------------------------------------- 1.33W Package Thermal Resistance (Note 4) SOP-8 (Exposed Pad), JA ------------------------------------------------------------------------------------------ 75C/W SOP-8 (Exposed Pad), JC ----------------------------------------------------------------------------------------- 28C/W Junction Temperature ------------------------------------------------------------------------------------------------- 125C Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260C Storage Temperature Range ---------------------------------------------------------------------------------------- -65C to 150C ESD Susceptibility (Note 2) HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 3)
Input Voltage, VIN ------------------------------------------------------------------------------------------------------ 2.5V to 1.5V 3% Control Voltage, VCNTL ----------------------------------------------------------------------------------------------- 5V or 3.3V 5% Ambient Temperature Range ---------------------------------------------------------------------------------------- -40C to 85C Junction Temperature Range ---------------------------------------------------------------------------------------- -40C to 125C
Electrical Characteristics
(VIN = 2.5V/1.8V/1.5V, VCNTL = 3.3V, VREFEN = 1.25V/0.9V/0.75V, COUT = 10F (Ceramic), TA = 25C, unless otherwise specified)
Parameter Input VCNTL Operation Current Standby Current (Note 7) Output (DDR / DDR II / DDR III) Output Offset Voltage (Note 5) Load Regulation (Note 6) Protection Current limit
Symbol ICNTL ISTBY IOUT = 0A
Test Conditions
Min ---
Typ 1 50
Max Units 2.5 90 mA A
VREFEN < 0.2V (Shutdown), RLOAD = 180 IOUT = 0A IOUT = +2A IOUT = -2A VIN = 2.5V/1.8V/1.5V 3.3V VCNTL 5V 3.3V VCNTL 5V Enable Shutdown
VOS VLOAD
-20 -20
---
+20 +20
mV mV
ILIM TSD VIH VIL
-125 -0.6 --
3.4 170 35 ---
----0.2
A C C
Thermal Shutdown Temperature TSD Thermal Shutdown Hysteresis REFEN Shutdown Shutdown Threshold
V
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Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2. Devices are ESD sensitive. Handling precaution recommended. Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. JA is measured in the natural convection at TA = 25C on a high effective thermal conductivity test board (4 Layers, 2S2P) of JEDEC 51-7 thermal measurement standard. The case point of JC is on the expose pad for SOP-8 (Exposed Pad) package. Note 5. VOS offset is the voltage measurement defined as VOUT subtracted from VREFEN. Note 6. Regulation is measured at constant junction temperature by using a 5ms current pulse. Devices are tested for load regulation in the load range from 0A to 2A. Note 7. Standby current is the input current drawn by a regulator when the output voltage is disabled by a shutdown signal on REFEN pin (VIL < 0.2V). It is measured with VIN = VCNTL = 5V.
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Typical Operating Characteristics
Output Voltage vs. Temperature
0.77 0.765
Output Voltage vs. Temperature
0.92 0.915
VIN = 1.5V
VIN = 1.8V
Output Voltage (V)
-50 -25 0 25 50 75 100 125
Output Voltage (V)
0.76 0.755 0.75 0.745 0.74
0.91 0.905 0.9 0.895 0.89 -50 -25 0 25 50 75 100 125
Temperature (C)
Temperature (C)
Output Voltage vs. Temperature
1.27 1.265
Shutdown Threshold vs. Temperature
0.6 0.55
VIN = 2.5V
VCNTL = 5V, Turn On VCNTL = 5V, Turn Off
Shutdown Threshold (V)
Output Voltage (V)
1.26 1.255 1.25 1.245 1.24 -50 -25 0 25 50 75 100 125
0.5 0.45 0.4 0.35
VCNTL = 3.3V, Turn On VCNTL = 3.3V, Turn Off
0.3 0.25 -50 -25 0 25 50 75 100 125
Temperature (C)
Temperature (C)
VIN Current vs. Temperature
5 4.5
Vcntl Current vs. Temperature
0.6 0.55
VIN = 1.8V, VCNTL = 3.3V VIN = 1.8V, VCNTL = 5V VIN = 2.5V, VCNTL = 3.3V
Vcntl Current (mA)
V IN Current (mA)
4 3.5 3
VIN = 2.5V, VCNTL = 5V
0.5 0.45 0.4 0.35 0.3
VIN
VIN = 1.8V, VCNTL = 3.3V VIN = 1.8V, VCNTL = 5V VIN = 2.5V, VCNTL = 3.3V = 2.5V, VCNTL = 5V
VIN = 1.5V, VCNTL = 5V
2.5 2 -50 -25 0 25 50 75 100 125
VIN = 1.5V, VCNTL = 5V VIN = 1.5V, VCNTL = 3.3V
VIN = 1.5V, VCNTL = 3.3V
-50
-25
0
25
50
75
100
125
Temperature (C)
Temperature (C)
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Source Current Limit vs. Temperature
4.5
Sink Current Limit vs. Temperature
4.5
Source Current Limit (A)
Sink Current Limit (A)
4
3.5
VIN = 1.8V, VCNTL = 5V VIN = 1.8V, VCNTL = 3.3V VIN = 2.5V, VCNTL = 5V VIN = 2.5V, VCNTL = 3.3V
4
VIN
3.5
VIN = 1.8V, VCNTL = 3.3V VIN = 2.5V, VCNTL = 3.3V VIN = 2.5V, VCNTL = 5V = 1.8V, VCNTL = 5V
3
VIN = 1.5V, VCNTL = 5V VIN = 1.5V, VCNTL = 3.3V
3
2.5
2.5
VIN = 1.5V, VCNTL = 5V VIN = 1.5V, VCNTL = 3.3V
2 -50 -25 0 25 50 75 100 125
2 -50 -25 0 25 50 75 100 125
Temperature (C)
Temperature (C)
0.9VTT @ 2A Transient Response
Output Voltage Transient (mV) Output Voltage Transient (mV)
VIN = 1.8V, VCNTL = 3.3V, VOUT = 0.9V Sink
0.9VTT @ 2A Transient Response
VIN = 1.8V, VCNTL = 3.3V, VOUT = 0.9V Source
40 20 0 -20 2 1 0
Swing Frequency : 1kHz
40 20 0 -20 2 1 0
Swing Frequency : 1kHz
Output Current (A)
Time (250s/Div)
Output Current (A)
Time (250s/Div)
0.75VTT @ 2A Transient Response
Output Voltage Transient (mV)
0.75VTT @ 2A Transient Response
Output Voltage Transient (mV)
VIN = 1.5V, VCNTL = 3.3V, VOUT = 0.75V Source
VIN = 1.5V, VCNTL = 3.3V, VOUT = 0.75V
Sink
40 20 0 -20 2 1 0
Swing Frequency : 1kHz
40 20 0 -20 2 1 0
Swing Frequency : 1kHz
Output Current (A)
Time (250s/Div)
Output Current (A)
Time (250s/Div)
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1.25VTT @ 2A Transient Response
Output Voltage Transient (mV) Output Voltage Transient (mV)
VIN = 2.5V, VCNTL = 3.3V, VOUT = 1.25V Sink
1.25VTT @ 2A Transient Response
VIN = 2.5V, VCNTL = 3.3V, VOUT = 1.25V Source
40 20 0 -20 2 1 0
Swing Frequency : 1kHz
40 20 0 -20 2 1 0
Swing Frequency : 1kHz
Output Current (A)
Time (250s/Div)
Output Current (A)
Time (250s/Div)
Output Short-Circuit Protection
12
Output Short Circuit (A)
VIN = 1.5V, VCNTL = 3.3V Sink
Output Short-Circuit Protection
12
Output Short Circuit (A)
VIN = 1.5V, VCNTL = 3.3V Source
10 8 6 4 2 0
10 8 6 4 2 0
Time (1ms/Div)
Time (1ms/Div)
Output Short-Circuit Protection
12
Output Short Circuit (A)
VIN = 1.8V, VCNTL = 3.3V Sink
Output Short-Circuit Protection
12
Output Short Circuit (A)
VIN = 1.8V, VCNTL = 3.3V Source
10 8 6 4 2 0
10 8 6 4 2 0
Time (1ms/Div)
Time (1ms/Div)
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Output Short-Circuit Protection
12
Output Short Circuit (A)
VIN = 2.5V, VCNTL = 3.3V Sink
Output Short-Circuit Protection
12
Output Short Circuit (A)
VIN = 2.5V, VCNTL = 3.3V Source
10 8 6 4 2 0
10 8 6 4 2 0
Time (1ms/Div)
Time (1ms/Div)
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RT9173D
Application Information
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 VREFEN is below 0.2V. In addition, the capacitor and voltage divider form the lowpass filter. There are two reasons doing this design; one is for output voltage soft-start while another is for noise immunity. How to reduce power dissipation on Notebook PC or the dual channel DDR SDRAM application? In notebook application, using RichTek's Patent "Distributed Bus Terminator Topology" with choosing RichTek's product is encouraged.
Distributed Bus Terminating Topology
Terminator Resistor
General Regulator The RT9173D could also serves as a general linear regulator. The RT9173D accepts an external reference voltage at REFEN pin and provides output voltage regulated to this reference voltage as shown in Figure 3, where VOUT = VEXT x R2/(R1+R2) As other linear regulator, dropout voltage and thermal issue should be specially considered. Figure 4 and 5 show the RDS(ON) over temperature of RT9173D in PSOP-8 (Exposed Pad) package. The minimum dropout voltage could be obtained by the product of RDS(ON) and output current. For thermal consideration, please refer to the relative sections.
RDS(ON) vs. Temperature
0.40 0.35 0.30 0.25 0.20 0.15 0.10 -50 -25 0 25 50 75 100 125
VCNTL = 3.3V
BUS(0) BUS(1)
R1 VOUT R2 R3 R4 REFEN R5 R6 BUS(6) RT9173D VOUT R7 R8 R9 BUS(7) BUS(8) BUS(9)
RT9173D
BUS(2) BUS(3) BUS(4) BUS(5)
R DS(ON) ()
R0
Temperature (C)
Figure 4
RDS(ON) vs. Temperature
0.40
R(2N) R(2N+1) BUS(2N)
VCNTL = 5V
0.35
BUS(2N+1)
VEXT VCNTL VIN VOUT
R DS(ON) ()
Figure 2
0.30 0.25 0.20 0.15 0.10 -50 -25 0 25 50 75 100 125
R1
RT9173D REFEN VOUT GND
R2
Temperature (C)
Figure 3
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Figure 5
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Input Capacitor and Layout Consideration Place the input bypass capacitor as close as possible to the RT9173D. A low ESR capacitor larger than 470uF is recommended for the input capacitor. Use short and wide traces to minimize parasitic resistance and inductance. Inappropriate layout may result in large parasitic inductance and cause undesired oscillation between RT9173D and the preceding power converter. Thermal Consideration RT9173D regulators have internal thermal limiting circuitry designed to protect the device during overload conditions. For continued operation, do not exceed maximum operation junction temperature 125C. The power dissipation definition in device is: PD = (VIN - VOUT) x IOUT + VIN x IQ The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and temperature difference between junction to ambient. The maximum power dissipation can be calculated by following formula: PD(MAX) = ( TJ(MAX) -TA ) /JA Where T J(MAX) is the maximum operation junction temperature 125C, TA is the ambient temperature and the JA is the junction to ambient thermal resistance. The junction to ambient thermal resistance (JA is layout dependent) for SOP-8 package (Exposed Pad) is 75C/W on standard JEDEC 51-7 (4 layers, 2S2P) thermal test board. The maximum power dissipation at TA = 25C can be calculated by following formula: PD(MAX) = (125C - 25C) / 75C/W = 1.33W Figure 6 show the package sectional drawing of SOP-8 (Exposed Pad). Every package has several thermal dissipation paths. As show in Figure 7, the thermal resistance equivalent circuit of SOP-8 (Exposed Pad). The path 2 is the main path due to these materials thermal conductivity. We define the exposed pad is the case point of the path 2. The thermal resistance JA of SOP-8 (Exposed Pad) is determined by the package design and the PCB design. However, the package design has been decided. If possible, it's useful to increase thermal performance by the PCB design. The thermal resistance can be decreased by adding copper under the expose pad of SOP-8 package. About PCB layout, the Figure 8 show the relation between thermal resistance JA and copper area on a standard JEDEC 51-7 (4 layers, 2S2P) thermal test board at TA = 25C.We have to consider the copper couldn't stretch infinitely and avoid the tin overflow. We use the "dog-bone" copper patterns on the top layer as Figure 9. As shown in Figure 10, the amount of copper area to which the SOP-8 (Exposed Pad) is mounted affects thermal performance. When mounted to the standard SOP-8 (Exposed Pad) pad of 2 oz. copper (Figure 10.a), JA is 75C/W. Adding copper area of pad under the SOP-8 (Exposed Pad) (Figure 10.b) reduces the JA to 64C/W. Even further, increasing the copper area of pad to 70mm2 (Figure 10.e) reduces the JA to 49C/W.
Junction
Ambient Molding Compound Gold Line Lead Frame
Die Pad
Case (Exposed Pad)
Figure 6. SOP-8 (Exposed Pad) Package Sectional Drawing
RGOLD-LINE path 1 RDIE
RLEAD FRAME
RPCB
RDIE-ATTACH RDIE-PAD path 2
RPCB
Case (Exposed Pad)
Ambient
RMOLDING-COMPOUND path 3
Figure 7. Thermal Resistance Equivalent Circuit
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RT9173D
JA vs. Copper Area
100 90 80
JA (C/W)
70 60 50 40 30 0 10 20 30 40 50
2
Figure 10 (b). Copper Area = 10mm2, JA = 64C/W
60
70
Copper Area (mm )
Figure 8
Exposed Pad
Figure 10 (c). Copper Area = 30mm2, JA = 54C/W
W2.28mm
Figure 9.Dog-Bone layout
Figure 10 (d). Copper Area = 50mm2, JA = 51C/W
Figure 10 (a). Minimum Footprint, JA = 75C/W
Figure 10 (e). Copper Area = 70mm2, JA = 49C/W Figure 10. Thermal Resistance vs. Different Cooper Area Layout Design
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Outline Information
A H M EXPOSED THERMAL PAD (Bottom of Package) Y J X B
F
C I D
Symbol A B C D F H I J M Option 1 X Y X Y
Dimensions In Millimeters Min 4.801 3.810 1.346 0.330 1.194 0.170 0.000 5.791 0.406 2.000 2.000 2.100 3.000 Max 5.004 4.000 1.753 0.510 1.346 0.254 0.152 6.200 1.270 2.300 2.300 2.500 3.500
Dimensions In Inches Min 0.189 0.150 0.053 0.013 0.047 0.007 0.000 0.228 0.016 0.079 0.079 0.083 0.118 Max 0.197 0.157 0.069 0.020 0.053 0.010 0.006 0.244 0.050 0.091 0.091 0.098 0.138
Option 2
8-Lead SOP (Exposed Pad) Plastic Package
Richtek Technology Corporation
Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
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