RTG4 Board Level Considerations

Power Matters.TM
RTG4 Board Level Considerations
Microsemi Space Forum 2015
Bassam Youssef, Senior Staff Applications Engineer
Jim Steward, Application Engineering
© 2015 Microsemi Corporation. Company Proprietary.
1
Objectives
 Provide an overview of PCB design considerations for RTG4 designs
focusing on:
• Power Supplies
• Memory Controller Interfaces
• SERDES Interfaces
 Highlight information currently available in Microsemi documents
© 2015 Microsemi Corporation. Company Proprietary.
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Power Supplies
Supply
Voltage
Description
VDD
1.2 V
Core supply voltage
VPP
3.3 V
Power supply for
device charge pumps
VDDPLL
3.3 V
Power for eight corner
PLLs, PLLs in SERDES
PCIe/PCS blocks, and
FDDR PLL
VDDIx
1.2 V, 1.5 V,
1.8 V,
2.5 V, or 3.3 V
Bank supplies
VREFx
0.5 * VDDIx
SERDES_x_Lyz_VDDAIO
1.2 V
SERDES_x_Lyz_VDDAPLL
2.5 V
SERDES_VDDI
1.8 V, 2.5 V, or
3.3 V
FDDR reference
voltage
TX/RX analog I/O
voltage for SERDES
lanes.
Analog power for
SERDES TXPLL and
CDRPLL
Power for SERDES
reference clock
receiver supply.
SERDES_VREF
0.5 *
SERDES_VDDI
© 2015 Microsemi Corporation. Company Proprietary.
External differential
receiver reference
voltage for SERDES
Reference Clocks
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Analog Supplies
SERDES VDDAPLL Supply
2.5V
3.3W
SERDES_x_Lyz_VDDAPLL
33uF
0.1uF
SERDES_x_Lyz_REFRET
1.21KW
1%
SERDES_x_Lyz_REXT
FPGA PLL Supply
 External R-C filters provide filtering to
sensitive analog PLL supplies.
 SERDES PLL = 2.5V
• SERDES TXPLL and CDRPLL supply
• SERDES Calibration resistor(REXT). 1.21KW
– Impedance calibration (transmit, receive, and
receiver equalization)
 FPGA PLLs = 3.3V
 Place all passive components as
close to device as possible
3.3V
5W
VDDPLL
22uF
47uF
VSS
© 2015 Microsemi Corporation. Company Proprietary.
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Power Supplies Specifications
 Key power supplies must comply to the specifications including operating
range, POR trip points, and power supply ramping
 Monotonicity of VDD/VPP/VDDIx is required through its rise time
Preliminary Data
Symbol
Description
VDD
Core Supply Voltage
VPP
Flash operating voltage
VDDt
VPPt
Power ON Reset Threshold for VDD supply
Power ON Reset Threshold for VPP supply
VDD Power supply ramp rates ( from GND/0V) for all power
supplies
VDDr
Tvddpor
Power Up to Functional time (From VDD/VPP/VDDIx ramp to
beginning of device ready
© 2015 Microsemi Corporation. Company Proprietary.
Min
Typ
Max
Units
1.14
1.2
1.26
V
3
3.3
3.45
V
0.8
2.6
0.006
V
V
24
60
mV/ms
ms
Power Matters.TM
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Power-up/down Sequence
 There is no power-up/down sequence required for RTG4 if one of the
following conditions is met:
• All PLLs are held in reset until VDDPLL supply reaches its minimum recommended
Operating Conditions level (shown below)
• The device is held in reset by asserting DEVRST_N until VDDPLL supply reaches its
minimum recommended level as stated above
 If none of the above conditions is met, VDDPLL must start ramping up
and reach its minimum recommend level (as stated above) before VDD,
VPP, or VDDIx starts ramping up
• In other words, VDDPLL must not be the last supply to ramp up, and must reach its
minimum recommended level before the last supply starts ramping up
 All I/O banks supplies must be powered for the RTG4 to power up
• You can bring up the I/O banks in any order and before or after the core voltage
© 2015 Microsemi Corporation. Company Proprietary.
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Power Supply Decoupling Capacitors
 To reduce any potential fluctuation on the power supply lines, proper onboard power supply decoupling caps is required
• Keep decoupling caps close to pin (use 402’s where possible on underside of
device BGA)
• Distribute overall decoupling capacitance around the device perimeter
• Use blind vias to remove crosstalk risk and cap surface mount area
• Use larger power vias to reduce inductance- especially for high layer count
boards.
Pin
Name
 PME (Precious Metal Electrode)
decoupling caps within the package
enhance overall PCB decoupling
Internal PME capacitance
available for LG/CG1657
package
VDD
0.18uF/6.3V
VDDI0
0.18uF/6.3V
VDDI1
0.18uF/6.3V
VDDI2
0.18uF/6.3V
VDDI4
0.18uF/6.3V
VDDI5
0.18uF/6.3V
VDDI6
0.18uF/6.3V
VDDI7
0.18uF/6.3V
VDDI8
0.18uF/6.3V
VDDI9
0.18uF/6.3V
VDDPLL
0.8uF/6.3V
© 2015 Microsemi Corporation. Company Proprietary.
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Radiation Tolerant Power Supplies
 Microsemi provides many Radiation-Tolerant components that can be
used with RTG4 PCB designs
 Engineers should consider the following when selecting power supply
components
• Calculate required power of the RTG4 device
– Power Calculator spreadsheet
– SmartPower tool in Libero SoC
• Select an appropriate Radiation-Tolerant regulator that can supply the required power
and meet all the unique power requirements of the FPGA, using either of the below:
– Radiation-Tolerant Linear-Regulator (Microsemi)
– Radiation-Tolerant Switching regulator (Microsemi)
© 2015 Microsemi Corporation. Company Proprietary.
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DDR3 Memory Interface
 DDR3 Characteristics
• SSTL15 interface
• RTG4 On-Die termination
• RTG4 IMP_CALIB resistor
•
•
•
•
•
– 240W
CMD/ADDR require external
termination to VTT(0.75V)
CLK_P/CLK_N requires
differential resistor at memory
clk input
Match ADDR/CMD/CTRL to CLK
Tightly match DQ/DM/DQS
delays
TMATCH DQS compensation
© 2015 Microsemi Corporation. Company Proprietary.
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DDR2 Memory Interface
 DDR2 Characteristics
• SSTL18
• RTG4 On-Die termination
• RTG4 IMP_CALIB resistor
– 150W
• CMD/ADDR require external
•
•
•
•
•
termination to VTT(0.9V)
CLK_P/CLK_N requires
differential resistor at memory clk
input
Match ADDR/CMD/CTRL to CLK
Tightly matched DQ/DM/DQS
delays
Loosely match DQS to CLK
TMATCH DQS compensation
© 2015 Microsemi Corporation. Company Proprietary.
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LPDDR Memory Interface
 LPDDR Characteristics
•
•
•
•
•
LVCMOS18
Match ADDR/CMD/CTRL to CLK
Tightly matched DQ/DM/DQS
Loosely match DQS to CLK
TMATCH DQS compensation
© 2015 Microsemi Corporation. Company Proprietary.
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SERDES Routing
 Proper differential pair routing is needed for proper common-mode rejection
and noise immunity
•
Pair-to-pair spacing is 2X greater than trace-to-trace spacing
 Avoid Routing Discontinuities:
•
•
No Plane Split Crossing
Do not route High-Speed signals close to the edge of a plane
© 2015 Microsemi Corporation. Company Proprietary.
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SERDES Differential Skew
 "Differential skew" refers to the time difference between the two singleended signals in a differential pair (LANE)
 Skew limits the bandwidth, adds data-dependent jitter, and limits the
possibility of properly equalizing lanes
© 2015 Microsemi Corporation. Company Proprietary.
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SERDES Skew Matching
 P & N trace skew matching “meandering” is used to balance the
skew of the pair, it should be distributed throughout the trace length
Immediately compensating will
result in better skew
distribution
 Keep traces matched throughout routing, not at the end
© 2015 Microsemi Corporation. Company Proprietary.
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AC-Coupling
 RTG4 requires AC-Coupling for all SERDES applications including
PCI Express for link detection
 AC-coupling provides common-mode independence
Tx
Rx
 Use symmetrical routing and placement for best performance.
Creates wider trace spacing
resulting in more discontinuity
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15
AC-Coupling
 Minimize reflections from the mounting structures with cut-outs in the
reference plane
 Clearing of the reference plane underneath the ac-coupling cap
produces less discontinuities of the routing path
© 2015 Microsemi Corporation. Company Proprietary.
Power Matters.TM
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SpaceWire: ES/MS to PROTO/Flight Silicon
 RTG4 ES device supports 12 SpaceWire ports
• RTG4 ES Dev board supports 12 SpaceWire ports
 The SpaceWire package pin assignment will be updated in the next
silicon revision for PROTO and flight units to support 16 SpaceWire ports
• RTG4 Production Dev board will support 13 SpaceWire ports
 Going from the current silicon revision to the next silicon revision, refer to
the pin mapping of the device on the Dev board
SpaceWire Pin Mapping from RTG4 ES/MS Silicon to PROTO/Flight Silicon for RTG4
Development Kit
© 2015 Microsemi Corporation. Company Proprietary.
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CG1657 Package Pins
 Two devices are available in Libero SoC Software
• RT4G150_ES CG1657
• RT4G150 (production) CG1657
 Software generated package pins for RT4G150_ES are not compatible
with pins generated for RT4G150 device
• Due to SpaceWire enhancements
 The following pin mapping tables are provided to help you start
designing your board
SpaceWire Pin Mapping from RTG4 ES/MS Silicon to PROTO/Flight Silicon
SpaceWire Pin Mapping from RTG4 ES/MS Silicon to PROTO/Flight Silicon for RTG4
Development Kit
© 2015 Microsemi Corporation. Company Proprietary.
Power Matters.TM
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Take-Aways
 Understand key points of the RTG4 power supplies and requirements
 Recognize the different PCB topologies and features for the memory
controllers available with the RTG4
 Awareness of SERDES layout methods needed for PCB first-time
success
© 2015 Microsemi Corporation. Company Proprietary.
Power Matters.TM
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Appendix
© 2015 Microsemi Corporation. Company Proprietary.
Power Matters.TM
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Thank You
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