Silicon Labs Si5xxUC-EVB User Manual

UG298: Si5xxUC-EVB

Universal Oscillator Evaluation Board

This document describes operation of the Silicon Laboratories Si5xxUC-EVB evaluation
board designed to evaluate any of Silicon Labs’ pin-controlled or I2C configurable Si5xx

XOs or VCXOs. Three device sites are available to support one of either 5mm x 7mm,

3.2mm x 5mm, or 2.5mm x 3.2mm devices in either 4, 6, or 8 pin configurations. Selec­tor switches make it easy to configure device control pins (pins 1, 2, 7, or 8) for proper
operation without the use of jumpers. Similarly, XO device VDD voltage (3.3V, 2.5V,

1.8V) can be selected via switches based on either external +5V (for stand-alone opera­tion) or micro USB sourced +5V USB operation. The EVB also features flexible output
termination circuits and PCB layout optimized for superior signal integrity.

Ext +5V

micro

USB

+VDD

GND

SDA

Vc_In

Power
Select
Switch

Silicon Labs

MCU

Pin 1

Signal

Selector

Switch

I2C Bus

Pin 1

SDA

SCL

Pin 1

Pin 2

Pin 7
Pin 8

Power
Supply

+VDD

XO

Location 1

(5mm x 7mm)

KEY FEATURES

• Evaluation of any Silicon Labs XO or
VCXO (Si51x, Si53x, Si54x, Si55x, Si56x,
Si57x, Si59x)

• AC coupled differential/single-ended output
clocks.

• Voltage control (Vc) port for VCXO
evalution.

• Switch selectable settings. No jumpers.

• External power or USB powered.

• Use stand-alone or with our Pro-

grammable Oscillator Calculator SW tool

Voltage

Selector

Switches

Output

Termination

CLK1_P

CLK1_N

+VDD

GND

SCL

+VDD

GND

SDA

+VDD

GND

SCL

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Pin 2

Signal

Selector

Switch

Pin 7

Signal

Selector

Switch

Pin 8

Signal

Selector

Switch

Pin 2

Pin 7

Pin 8

Pin 1

Pin 2

Pin 7
Pin 8

Pin 1

Pin 2

Pin 7
Pin 8

XO

Location 2

(3.2mm x 5mm)

XO

Location 3

(2.5mm x 3.2mm)

Output

Termination

Output

Termination

CLK2_P

CLK2_N

CLK3_P

CLK3_N

Table of Contents

1. Quick Start - Board Configuration Check List ...................3

2. Functional Description............................4

3. General Operational Restrictions ........................5

3.1 Evaluate Only a Single Device at a Time .....................5

4. Power Supply and I2C Bus Control .......................6

5. Control Signal Switch Settings.........................7

5.1 Oscillator Pin 1 Control DIP Switch (Pin_1_Ctrl) ...................8

5.2 Oscillator Pin 2 Control DIP Switch (Pin_2_Ctrl) ...................9

5.3 Oscillator Pin 7 Control DIP Switch (Pin_7_Ctrl) ...................10

5.4 Oscillator Pin 8 Control DIP Switch (Pin_8_Ctrl) ...................11

6. Supported Devices - Stand-Alone Mode ....................12

7. Supported Devices - Software Controlled Mode - I2C ...............15

8. USB Port and External Powering .......................16

9. Output Clock Terminations .........................17

10. EVB Test Points and LEDs .........................18

10.1 Test Points ...............................18

10.2 LEDs .................................18

11. VCXO Voltage Control Input Circuit .....................19

12. Programmable Oscillator Calculator Tool ...................20

13. Layout of Board .............................21

13.1 Si56x XO and VCXO 2.5x3.2mm Footprint Recommendation ..............22

14. Si5xxUC-EVB Schematic .........................23

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UG298: Si5xxUC-EVB

Quick Start - Board Configuration Check List

1. Quick Start - Board Configuration Check List

Mount your oscillator device on the board at appropriate oscillator site location (U1, U2, or U3, but on only one location) if a device is
not yet mounted.

1. Start with EVB board powered down/off.

2. Set DIP switches (described in Section 5. Control Signal Switch Settings) for your specific device:

a. Look up your device as appropriate in the tables of Sections 6. Supported Devices - Stand-Alone Mode or 7. Supported Devi-

ces - Software Controlled Mode - I2C.

b. Make DIP switch settings per table entry for pins 1,2,7,8 as appropriate. See Sections 6. Supported Devices - Stand-Alone

Mode or 7. Supported Devices - Software Controlled Mode - I2C .

3. Verify output termination is appropriate for your device (see Section 9. Output Clock Terminations for more info).

4. Set +5V Select switch (SW5) based on how you will power the EVB, either via USB or via external +5V supply.

5. Connect power, either via USB port or external +5V power supply as chosen in previous step.

6. Output Clocks:

• For pin controlled oscillators, clock output should be available on output SMAs of DUT site in use.

• For I2C oscillators, run appropriate configuration software (e.g., Programmable Oscillator Software tool) and perform device
configuration to get desired output clock.

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UG298: Si5xxUC-EVB

Functional Description

2. Functional Description

The Si5xxUC-EVB is an evaluation board designed to support any Silicon Labs XO/VCXO device. The Si5xxUC-EVB is designed to
operate in one of two general operational modes:

• Stand-alone mode: The stand-alone mode is for evaluation of fixed output frequency or pin-controlled XO/VCXO devices
where I2C support is NOT required to operate or evaluate the device. Control of device pins, such as OE or FS, is done via on-board

switches. In Stand-alone mode the on-board switches must be set according to the requirements of the device installed on the
board. For example, if the installed device is a dual frequency part with output enable, the appropriate switches must be set to assert
output enable (OE) and the frequency select pin (FS) to give the desired output frequency. Device VDD voltage can be set via on-

board switches as well. Switch setting details for Stand-alone mode are shown in Section 4. Power Supply and I2C Bus Control (for
power supply) and Section 5. Control Signal Switch Settings (for device pins).

• Software controlled mode: The software controlled mode is for use with PC-based software tools (such as our Programmable Os-

cillator Calculator Tool) to control/configure the device being evaluated via the device I2C bus. The software controlled mode is pri-

marily intended for I2C controlled XO/VCXO devices. When using software controlled mode, some of the on-board switches must
be placed in specific default settings to allow the on-board MCU to perform I2C control. Other switches must still be used on certain

device signals, like output enable (OE). Switch setting details for software controlled mode are shown in Section 4. Power Supply

and I2C Bus Control (for power supply & I2C) and Section 5. Control Signal Switch Settings (for device pins).

For each of the 3 device locations on the Si5XXUC-EVB, separate sets of SMA outputs and terminations are provided per XO “Device
Under Test” (DUT) location even though only one device may be populated and used at a time (see Section 3. General Operational

Restrictions below). Separate outputs and terminations per device site provides the best possible clock signal integrity for each DUT

location.

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UG298: Si5xxUC-EVB

General Operational Restrictions

3. General Operational Restrictions

3.1 Evaluate Only a Single Device at a Time

Note: It is strongly recommended to populate only one device on the Si5xxUC-EVB board at a time. Carefully read the next paragraph

for important information.

The Si5xxUC-EVB supports evaluation of a single device in one of three different DUT locations. Device sizes supported are 5mm x
7mm, 3.2mm x 5mm, or 2.5mm x 3.2mm. All device locations can support 4, 6, or 8 pin configurations, but only one device at a time
should be installed in any one of the three locations on the Si5xxUC-EVB. This restriction is made to ensure no problems will occur due
to potential signal crosstalk, power supply over-loading/coupling, or signal contention/loading between multiple devices. Do not simply
remove power from a mounted device in an attempt to place it in an “unused”, but still mounted, state. Board control signals are wired in
parallel to all 3 locations and a non-powered device may load control signals to a powered device under test. Please follow this “one
device at a time” recommendation and only populate one device at a time.

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UG298: Si5xxUC-EVB

Power Supply and I2C Bus Control

4. Power Supply and I2C Bus Control

The power supply uses a linear voltage regulator to drop the +5 V input supply voltage to one of the supported nominal VDD voltages of
+3.3 V, +2.5 V, or +1.8 V. A switch is provided on the EVB (SW5) to select the +5 V source for the voltage regulator as either the USB
port +5V or an external +5 V source. The EVB power supply supports operation in one of 2 general modes that correspond to the two
operational EVB use cases.

• Stand-alone mode: Power can be sourced from either external supply or USB port, but software is not required and no EVB software
tool should be actively connected to Si5XXUC-EVB when being used in Stand-alone mode. In Stand-alone mode the oscillator de­vice VDD voltage is set via the “VDD_DUT_SEL” switch according to the voltage select table shown below. By default this switch is

set to 1.8 V and will need to be changed if evaluating a non-I2C oscillator with 2.5 V or 3.3 V VDD.

• Software controlled mode: Power can be sourced from either external power supply or USB port, but the Programmable Oscillator
Software tool can be used to set the VDD voltage to the oscillator. In software controlled mode, “VDD_DUT_SEL” switches should
remain set to 1.8 V setting regardless of the desired VDD voltage.

The I2C Disable switch is typically set to the “Off” setting (to enable the on-board MCU to drive the I2C bus) unless the user is attempt­ing to connect an external I2C master to communicate with the oscillator device. The I2C Disable control allows for disabling the on­board I2C buffer to disconnect the oscillator from the on-board MCU. This disconnection is useful if the user wishes to connect an exter­nal I2C bus master to communicate with the DUT.

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UG298: Si5xxUC-EVB

Control Signal Switch Settings

5. Control Signal Switch Settings

Four of the 5 on-board DIP switches (SW1, 2, 3, 4) are used for configuration of the EVB oscillator locations to match any standard
oscillator pin-out. Using this DIP switch arrangement, the Si5xxUC-EVB can be configured to support all Silicon Labs oscillator devices.
The oscillator device pins that can vary in function, depending on the device variant, are pins 1, 2, 7, and 8 as shown in the Device Pin­out Mapping table below. Pins 3, 4, 5, and 6 are typically fixed function pins that do not change with device variant.

Note: All device locations on the Si5xxUC-EVB can support up to 8 pin variant devices. Devices with fewer pins (4, 6 pin) can be instal­led in the same location and will fit within the 8 pin footprint.

Device Pin-out Mapping

4 pin

Device

6 pin

Device

8 pin

Device

DIP Switch

Function

Options

1 1 1 Pin_1_Ctrl (SW1) FS/OE/SDA/Vc

- 2 2 Pin_2_Ctrl (SW2) FS/OE/SCL

2 3 3 - GND

3 4 4 - Output

- 5 5 - Output

4 6 6 - VDD

1

1

1

1

- - 7 Pin_7_Ctrl (SW3) FS/SDA

- - 8 Pin_8_Ctrl (SW4) FS/SCL

Note:

1. Fixed function pins

Configuration details of each of the 4 variable pin function DIP switches is described in following sections. For devices that may not
utilize all 4 of the variable pin function switches, the corresponding unused DIP switch can be set to the NC setting (all Off position).
Make sure to make the following switch settings with the Si5xxUC-EVB powered down. Once all are set appropriately, the board may
be powered on.

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UG298: Si5xxUC-EVB

Control Signal Switch Settings

5.1 Oscillator Pin 1 Control DIP Switch (Pin_1_Ctrl)

The pin 1 control DIP switch allows oscillator pin 1 to be driven from any of these 4 sources.

1. High (VDD) level

2. Low (GND) level

3. I2C bus SDA signal

4. External control voltage Vc (for VCXO applications)

Note: The 4 signal sources listed above are connected on separate pins on left side of the switch and all pins on right side are tied
together (common) and then connect to pin 1 of the oscillator. This means that only one (1) of the switches in this DIP switch bank
can be in the ON position at a time. Switching more than 1 switch to the on position at a time may cause undesired behavior. All
switches can be set to OFF position to effectively isolate pin 1 from any signal source and is the No Connect (NC) state.

To determine the required Pin 1 switch settings for your specific device, please refer to the Supported Device Tables in Chapter

6. Supported Devices - Stand-Alone Mode and Chapter 7. Supported Devices - Software Controlled Mode - I2C.

Pin 1 DIP Switch (4, 6, or 8 pin DUT)

1 2 3 4 Pin 1 Signal

Off Off Off Off NC

On Off Off Off FS/OE high

Off On Off Off FS/OE low

Off Off On Off SDA

Off Off Off On Vc

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