Renesas 8V19N850 User manual

Guide

8V19N850 HardwareDesign

X0120307 Rev.1.0

Mar 25, 2021

Page 1

This document contains general board-level hardware design information for the 8V19N850. It provides

recommendations for power rail handling, loop filter calculation,and input/output termination.

Contents

1. PowerRails.................................................................................................................................2

1.1 Bypass Capacitors................................................................................................................2

1.2 Power Supply Isolation..........................................................................................................3

1.3 Loop Filter...........................................................................................................................3

1.4 2nd Order Loop Filter.............................................................................................................3

1.5 Loop Filter Calculation Examples............................................................................................5

2. Input/Output Interface..................................................................................................................6

2.1 Input Termination for Reference Clock Input .............................................................................6

2.2 OX_DPLL Input (OCXO/TCXO) ..............................................................................................7

2.3 OSCI/OSCO Input (XTAL, XO, OCXO/TCXO)...........................................................................8

2.4 Output Terminations for QCLK and QREF Drivers .....................................................................9

2.4.1. LVPECL Type Driver Terminations .............................................................................9

2.4.2. LVDS Type Driver Terminations ...............................................................................14

3. Schematic Example ...................................................................................................................15

4. Revision History........................................................................................................................15

The simplified block diagramof 8V19N850 is shown in Figure 1. For a more detailed block diagram and in-depth

descriptions about the device, see the 8V19N850 Datasheet.

Figure 1. Simplified Block Diagram

A general reference schematic example is shown in Figure 2. A larger version can also be provided in a

separate document.In this schematic, the input and output interfaces are shown for illustration purposes.For

more examples, see the Input/Output Interface section.The input topology dependson the driver type, and the

output driver termination depends on the receiver specification and structure.

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 2

Figure 2. 8V19N850 Reference Schematic Example

1. Power Rails

1.1 Bypass Capacitors

To avoid signal interference, bypass capacitors are required to filter noise from switching power supplies and

other devices in the system. Figure 2 showsexamplesof bypass capacitors on the schematic. The type of

bypass capacitor will depend on the noise level and noise frequencies on the application board. The device

output driver switching can also cause power rail noise and interference with noise signalsfrom other devices on

the board, resulting in unwanted spurious tones in outputsignals. The bypass capacitors minimize these noise

sources.

The bypass capacitor values are usually in the range from 0.01µF to 0.1µF. Other values can also be used.

Typical capacitor sizes are 0603, 0402, or 0201 with a low Equivalent Series Resistance (ESR). The dielectric

types are typicallyX5R or X7R. A smaller size allows the capacitorto be placed closer to the powerpin ofthe

device with a reduced trace length.

LVDS Style Termination Ex ample

C22 0.1uF

Zo = 50

QCLK_D13

VDDO_R4

1.0uF

C95

100pF

5.1k

R28 1

VDD_OSC

nQREF_R03

nQREF_R13

R24

100

C70

0.1uF

C56

100pF

C43

0.1uF

nCLK1 2

C48 100pF

C59

10uF

C53

10uF

QREF_R53

C34 10uF

C49

10uF

C41

100pF

R20

VDDO_R23

VDDO_Dx

R27

R30

Keep close to DUT

Loop Filter - Keep close to DUT

C5 0.1uF

L18

220

C84 0.1uF

100

QCLK_R0

C30 10uF

L17

220

C47 0.1uF

C80 0.1uF

SDO_SDA 5

C23

10uF

R26

Keep close to DUT

L8220

C38

0.1uF

C9 0.1uF

C72

10uF

C96

0.1uF

QREF_R33

C15

0.1uF

L5 220

C20 0.1uF

C50

100pF

QCLK_R2

C1310uF

VDD_INP

GPIO_2

VDDO_REF

nQCLK_D23

VDD_APLL

C55 0.1uF

QCLK_D03

VDD_DPLL0

C74

0.1uF

C10

22uF

R13

510

C93 0.1uF

nQCLK_D03

SPI_SEL2

R18

220

C42

0.1uF

C37 100pF

5.1K

SDI 5

QREF_R13

SCLK_SCL 5

C18

10uF

L7 220

C68 0.1uF

VDD_XO

CLK1 2

C82 100pF

8V19N850

VDD_DPLL0

VDDO_REF_2

QREF_R0

nQREF_R0

QREF_R1

nQREF_R1

QREF_R2

nQREF_R2

QREF_R3

nQREF_R3

QREF_R4

nQREF_R4

QREF_R5

nQREF_R5

VDDO_REF_15

CAP_APLL

VDD_APLL

CP_APLL

GPIO_0

GPIO_1

GPIO_2

GPIO_3

VDD_GPIO

QCLK_D0

SPI_SEL

36 VDDO_D3

35 nQCLK_D3

34 QCLK_D3

33 VDDO_D2

32 nQCLK_D2

31 QCLK_D2

30 VDDO_D1

29 nQCLK_D1

28 QCLK_D1

27 VDDO_D0

26 nQCLK_D0

nQCLK_R4 48

VDDO_R4_47 47

DNU-46 46

DNU_45 45

VDD_RFVCO

44 CAP_RFPLL

43 CP_RFPLL

42 VDD_RFPLL

41 VDDO_R5_40

40 nQCLK_R5

39 QCLK_R5

38 VDDO_R5

QCLK_R4 49

VDDO_R4_50 50

VDDO_R23_51 51

nQCLK_R3 52

QCLK_R3 53

nQCLK_R2 54

QCLK_R2 55

VDDO_R23_56 56

VDDO_R01_57 57

nQCLK_R1 58

QCLK_R1 59

nQCLK_R0 60

QCLK_R0 61

VDDO_R01_62 62

VDD_DPLL1 63

CP_DPLL1 64

CAP_DPLL1 65

VDD_DC01 66

VDD_INP 67

nCLK1 68

CLK1 69

nCLK0 70

CLK0 71

VDD_SPI 72

nCS/ADR0 73

SCLK/SCL 74

SDO/SDA 75

SDI/ADR1 76

EXT_SYS 77

SCL_M 78

SDA_M 79

OSCO 80

OSCI 81

VREG_OSC_CAP 82

VDD_OSC 83

nXO_DPLL 84

XO_DPLL 85

VDD_XO 86

CP_DPLL0 87

CAP_DPLL0 88

EP 89

L1220

C3 0.1uF

VDD_GPIO

L6 220

C46 0.1uF

C69

33pF

VDD_RFPLL

C61 10uF

R17

L2 220

C65

10uF

C7 0.1uF

C77

10uF

QCLK_R53

C88

0.1uF

L21 220 C97

0.1uF

nQREF_R43

nQCLK_R3

R21

300

VDDO_Dx

100

C63

22uF

VCC=3.3V

L20

220

C92 0.1uF

GPIO_0

C25 0.1uF

QCLK_D23

C86 100pF

C58

0.1uF

GPIO_1

3C52

0.1uF

CLK

nCLK

nQREF_R23

R321

nQCLK_R1

C36 0.1uF

L14 220

C66 0.1uF

VDD_DPLL1

nCS 5

nQCLK_R0

C32

10uF

Keep close to DUT

VDDO_Dx

C83 10uF

C31 0.1uF

C79 10uF

L13

220

SDA_M 5

R10 1

C27

22uF

OCXO/TCXO LVCMOS

L12220

C39

10uF

C71

0.1uF

L19

220 C89

0.1uF

C87

100pF

C21 10uF

Zo = 50

C140.1uF

R23 1

VDDO_Dx

C26

33pF

C54

33pF

QREF_R43

EXT_SYS 2

VCC=3.3V

VDD

C24

470pF

QCLK_R3

R33

nQCLK_D33

R29

QREF_R03

Keep close to DUT

C44

10uF

C57

0.1uF

L11

220

C51

0.1uF

VDDO_REF

C19

0.1uF

C35 0.1uF

R19

JP2

GPIO_1

Loop Filter - Keep close to DUT

C4 10uF

QREF_R23

XO/OCXO/TCXO LVCMOS

QCLK_R1

100

C33 0.1uF

C29 0.1uF

C94 100pF

nQCLK_D13

C45 10uF

C62 0.1uF

JP1

GPIO_0

R14 1

C8 10uF

C76

0.1uF

L16

220 C73

0.1uF

C98

10uF

C16

22uF

LVDS Driver

L3220

C120.1uF

R311

nQCLK_R53

SCL_M 5

VDDO_R01

VDDO_R5

C64

0.1uF

R16

C75

22uF

C11

0.1uF

nQREF_R53

R12

100

C91 10uF

VDD_DCO1

Update pin name

100

Zo = 50

L4220

C17

0.1uF

C67 10uF

VDD_SPI

QCLK_D33

Loop Filter - Keep

close to DUT

GPIO_3

nQREF_R33

C85 0.1uF

nQCLK_R2

L10

220

R22

R25

200

C81 0.1uF

C60 0.1uF

VDD_RFVCO

C28

0.1uF

VDD_XO

L15

220

C40

0.1uF

C78

0.1uF

C90

10uF

R11

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 3

To minimize ESR between power pins and the bypasscapacitors,it is recommended to place at least one

bypass capacitor at each VDD power pin, with a placement as near as possible to therespective power pin of

the device. A thick trace width between the bypasscapacitor and power pin helps to reduce ESR. It is

recommended to combine multiple capacitors atdifferent resonance frequenciesto achieve band pass filter

characteristics at the critical noise frequencies.

1.2 Power Supply Isolation

The power rails should be as noise-free as possible to support the low phase noise performance of the device

PLLs. The 8V19N850 also integratesLDOs for additional noise filtering. An external ultra-low noise LDO may not

be required but it is recommended for further reducing power supply noise. AnLDO should have a noise level of

less than 6.5uVrms from 10Hz to100kHz. The Renesas RAA214020 is a suitable LDO.

It is recommended to isolate the analog power rail from other high noise power rails, VDDO_x and VDD_INPUT.

The isolation can be implemented through an RC low pass filter.The larger RCcomponent values can further

reduce the cutoff frequency and clean up lower frequency noise. For the outputsupplies VDDO_x, to reduce

output frequency interference, the powerrails between the output banksthat operate at different output

frequencies can be isolated using separate LDOs or using 1 to 2 ohm resistors if they share the same power

source. Additionalsmaller value capacitors(e.g., 100pF) in parallel with theexisting 0.1µF near the power pins

can provide additional higher frequency noise filtering.

1.3 Loop Filter

1.4 2nd Order Loop Filter

The 8V19N850 contains four Analog PLLs: APLL0,APLL1, APLL2,and RFPLL. These analog PLLsrequire

board-level 2nd order loop filter. The approximate VCO frequency and VCO gains for each APLL isdisplayed in

Table 1. The VCO gain Kvco depend on the operating region.

Table 1. 2nd Order LoopFilter

APLL

ApproximateVCO

Frequency(GHz) Kvco (MHz/V)

APLL0

2.5

APLL1

3.93216

APLL2

3.75

RFPLL

2.94912

The following section provides a general design of a 2nd order loop filter for PLL. A typical 2nd order loop filter is

shown in Figure 3. The design shows a step-by-step calculation todetermine Rs, Cs,and Cp values. The

required parameters for this part are also provided. A spreadsheet or software tool for calculating the loop filter

values are also available.

Figure 3. Typical 2nd Order Loop Filter

Charge Pump Driver

Loop Filter Return

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 4

1. Determine desired loop bandwidth fc. The fc must satisfy the following condition:

Fpd

Where, Fpd is phase detector input frequency.

2. Calculate Rs

 =2∗π∗fc ∗N

Icp ∗Kvco

Where,

Icpis charge pump current.

Kvcois VCO gain.

N is effective feedback divider.

Fpd

Fvco

Fvco is vco frequency.

Fpd is the phase detector input frequency.

3. Calculate Cs

 =α

2∗∗ ∗

Where,

α is ratio between loop bandwidth and the zero frequency at zero, α = fc / fz, recommend α greater than 3.

fz is frequency at zero.

4. Calculate Cp

 =Cs

α ∗ β

Where,

βis ratio between frequency at pole and loop bandwidth, β = fp / fc, recommend β greater than 3.

fp is frequency at pole.

5. Verify maximum Phase Margin, PM

)

arctan( b

PM −

Where,

b = 1 + 



PM should be greater than 50 degrees.

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 5

1.5 Loop Filter Calculation Examples

This section provides calculation examplesfor APLL0 loop filter value for loop bandwidth of ~150kHz. In this

example, the reference OCXO input frequency = 48MHz after multiplied by 2, the phase detectorinput frequency

Fpd = 96MHz. This satisfies the condition of Fpd/Fc>> 20.

The APLL0 VCO frequency, Fvco = 2500MHz, the effective feedback divider.

N = Mv= Fvcxo/ Fpd ~ 26

Rs can be calculated from the equation,

 =2∗π∗fc ∗N

Icp ∗Kvco

The APLL0 VCO gain, Kvco ~30MHz/V.

The charge pump current is set as 1.7mAin thisexample.

Rs = 510 Ohm

Cs can be calculated from the following equation,

 =α

2∗∗ ∗

For α = 10, Cs is calculated to be ~20 nF. Csgreater than this value can be used to assure that the α is greater

than 10. For example, the actual chosen value can be 100 nF from a standard capacitor value to allow room for

charge pump current adjustment.

Cp can be calculated from the equation,

 =Cs

α ∗ β

For β = 3, Cp is calculated to be ~650pF. Less than thisvalue can be used for Cp to assure that the β is greater

than 3 (e.g., the actual selected value Cp can be 470 nF).

Phase margin = 67 degrees

The following table shows Loop Filter Value Examples for APLL0, APLL1,APLL2, and RFPLL.The loop filter

values will vary based on the application requirement. Other loop values can also be used as long as the PLLs

operate at the stable region.

Table 2. 8V19N850 Analog PLLs Loop Filter Values Examples

APLL0

APLL1

APLL2

RFPLL

LoopBandwidth(Hz)

150k

600k

80k

PDF

96MHz

96Mhz

78.125MHz

245.76MHz

Feedbackdivider, N

Charge Pumpcurrent

setting

Can be setbetw een0.7mA

to 2.2mA

1.7mA

Rs (Ohm )

510

300

200

100nF

470pF

~33pF

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 6

2. Input/Output Interface

2.1 Input Termination for Reference Clock Input

The 8V19N850 reference clock input CLK/nCLK is a high impedance differential receiver. The inverting input

nCLK has weak bias to ~1.65V. The input can accepta signal from a standard 3.3VLVPECL or an LVDS driver

directly in DC coupling. The board-level termination at the CLK/nCLK inputis determined by the driver type.

Figure 4 and Figure 5 provide examples of input interface without AC coupling.Figure 6 and Figure 7 provide

examples ofinput driven by a differential driver with AC coupling. This section provides only few examples.

Other termination topologiescan also be used.Forsingle-ended driving the differential input, please refer to the

example in the OX_DPLL Input (OCXO/TCXO) input section.

Figure 4. Input TerminationExample – 8V19N850 Reference Clock Input CLK/nCLK, Driven by a 3.3V LVPECL Driver

Figure 5. Input TerminationExample – 8V19N850 Reference Clock Input CLK/nCLK Driven by a 3.3V LVDS Driver

Clock Input

CLK

nCLK

VCC=3.3V

82.5

133

VCC=3.3V

Zo = 50

LVPECL Driver

VCC=3.3V

Zo = 50

LVDS Driver

VCC=3.3V

100 Clock Input

CLK

nCLK

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 7

Figure 6. 8V19N850 Reference Clock Input CLK/nCLK AC Coupling Termination– Example 1

Figure 7. 8V19N850 Reference Clock Input CLK/nCLK AC Coupling Termination– Example 2

2.2 OX_DPLL Input (OCXO/TCXO)

The XO_DPLL input receives a stable frequency source from OCXO/TCXO mainly for SysAPLL and SysDPLL.

This input can also be used for APLL0, APLL1,and APLL2 phase frequencydetector input. The limitation of

frequency range is provided in the 8V19N850 datasheet. When the XO_DPLL input is only used for SysAPLLor

SysDPLL, a stable frequency TCXO/OCXO is required. Low frequency (e.g., 10MHz to 20MHz) is fine. Phase

noise performance is not critical.When the TCXO/OCXO is used for both SysAPLL/SysDPLL and APLL0,

APLL1, both stable frequency and good phase noiseperformance are required. Higher frequency (e.g.,~ 38MHz

to 54MHz) is recommended for better phase noise performance.

XO_DPLL/nXO_DPLL is a differential high-impedance input with built-in weak pull-up and pull-down resistors.

The input termination is dictated by the signal source driver type. Ifthe driver is a differential driver, see the

examples provided in “Input Termination for Reference Clock Input”. Since most OCXO/TCXO drivers are single-

ended drivers, Figure 8 provides an example of single-ended to XO_DPLL input layout. Not all componentsin

the footprint are required to be populated because ofthe varying strength ofthe driver and trace length in the

layout.

VCC=3.3V

Clock Input

CLK

nCLK

10K

5.1K

VCC=3.3V

Differential Signal

2 x Zo

VCC=3.3V

Clock Input

CLK

nCLK

DifferentialSignal

R4 10K

R3 5.1K

VCC=3.3V

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 8

Figure 8. GeneralLayout Example for Single-endedLVCMOStoXO_DPLL

2.3 OSCI/OSCO Input (XTAL, XO, OCXO/TCXO)

The OSCIinput receives a signal from a crystal. It can be overdriven by oscillation sourceslike XO, OCXO, and

TCXO. The limitation of the frequency range is provided in the datasheet. The OSCI input mainly provides a

signal source for APLL0, APLL1, and APLL2. The OCSI source can also be usedto SysAPLL. The OCSI source

cannot be used for SysDPLL. The OCSI signal source phase noise needsto have good performance so that it

provides a good close-end phase noise performance at the 8V19N850output. The OCSI signal source can be

XO, OCXO, or TCXO.

When an XO to OSCI is used in conjunctionwith an OCXO at the XO_DPLL input, the XO is used for APLL0,

APLL1, or APLL2. This OCSI input must be a good phase noise performance and higher frequency (~38MHz to

54MHz). The OCXO to the XO_DPLL to the SysDPLL/SysDPLL must be frequency stable but it doesnot need to

have as good phase noise performance as the XO to the OSCI. The OCXO can be lower frequency (e.g.,

10MHz to 20MHz).

The OCSI/OSCO input containsan oscillation circuitand can interface with a crystal. Figure 9 provides an

example ofa parallel resonant crystal to OCSI/OSCOinput interface. The OCSIinput can also be overdriven by

an oscillator with a single-ended driver. Figure 10 shows an example of a single-ended oscillator overdrive OSCI

input with AC coupling. The unused OCSO can be left floating.

Figure 9. Crystal to OSCI input interface Example

VCC=3.3V

5.1k

XO_DPLL Input

OCXO/TCXO LVCMOS

5.1K

100

CL1

8V19N850 OSCI input

OSCI

OSCO

CL2

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 9

Figure 10. Single-endedOscillator Overdrive OSCI Example

Notes:

1. When OSCIor XO_DPLL is used forinput ofAPLL0 or APLL1 with DPLL0 or DPLL1 active, the selected

frequency cannot cause the APLL0 or APLL1 feedback divider to set to an integer. For example, ifAPLL0

VCO= 2.5GHz, OSCI = 50MHz,the APLL0 PDF =2x50MHz =100MHz, the APLL0 feedbackmust be set to

25. The feedback divider = 25 is an integer. IfDPLL0 is not active, there is no issue. IfDPLL0 is active, this

will create a problem and cause DPLL0 to be unstable; therefore, a 50MHzoscillator cannotbe used under

this condition.

2. When both XO_DPLL and OCSIare used, the two frequencies should not be close to each other.

The following list shows a few examples of OCXO:

■Rakon U7842 or different frequency in the same product family.

■TXC OG48070001 or different frequency in the same product family.

■CTS17 or different frequency in the same product family.

2.4 Output Terminations for QCLK and QREF Drivers

The output stage of the 8V19N850 QCLK drivers can be configured to be LVPECL style driver or LVDS style

driver.

2.4.1. LVPECL Type Driver Terminations

When the 8V19N850 output is configured to LVPECL, the driver is an open emitter type that requires a DC

current path to the termination voltage VTT through the pull-down resistor. A standard LVPECL driver termination

is shown in Figure 10, and Figure 12 to Figure 14 show alternative terminations. The LVPECL output driver is

configurable and the applicable termination voltage VTT depends on the output amplitude setting and output

supply voltage VDDO_v. Refer to the VTT and termination resistor value tables beloweach diagram.

100

8V19N850 OSCI input

OSCI

OSCO

VDD

OCXO/TCXO LVCMOS

8V19N850 Hardware Design Guide

X0120307 Rev.1.0

Mar 25, 2021

Page 10

Figure 11. LVPECL Style Termination

Table 3. VTValues for Output Termination inFigure 11

Output SupplyVoltage

Output Amplitude

DDO_V

=1.8V

350mV

DDO_v

–1.50V

500mV

DDO_v

–1.75V

DDO_V

=2.5V

350mV

DDO_v

–1.50V

500mV

DDO_v

–1.75V

DDO_V

=3.3V

350mV

DDO_v

–1.50V

500mV

DDO_v

–1.75V

750mV

DDO_v

–2.0V

1000mV

DDO_v

–2.25V

High Impedance Input

Zo = 50 R1

50 No Built-in Termination

VDDO_v

VTT

Zo = 50

LVPECL Driver R2

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