Si4455-C2A-GM_技术文档

Si4x55-C

EASY-TO-USE, LOW-CURRENT OOK/(G)FSK SUB-GHZ

TRANSCEIVER, TRANSMITTER, AND RECEIVER

Features



Frequency



Max data rate = 500 kbps

range = 284–960 MHz

Receive sensitivity = –116 dBm

Modulation

(G)FSK

OOK

Max output power = +13 dBm

Low active power consumption

10 mA RX

18 mA TX @ +10 dBm

Low standby current = 40 nA

Low shutdown current = 30 nA

Preamble sense mode

6 mA average RX current at

1.2 kbps

Power supply = 1.8 to 3.6 V

TX and RX 64 byte FIFOs

Automatic frequency control (AFC)

Automatic gain control (AGC)

Integrated battery voltage sensor

Packet handling including preamble,

sync word detection, and CRC

Low BOM



20-Pin 3x3 mm QFN package



Pin Assignments

Applications



Remote control

Home security and alarm

Telemetry



Remote keyless entry

Home automation

Industrial control

Sensor networks

Health monitors

GND

SDN

RXp

RXn

TX

1

2

3

4

5

6

20 19 18 17 16 nSEL

15 SDI



14 SDO

Si4455

Garage and gate openers

13 SCLK

12 nIRQ

Description

GND

7

8

9

10 11 GPIO1

Silicon Laboratories’ Si4455 is an easy-to-use, low current, sub-GHz

EZRadio^®transceiver. The Si4055 is a transmit-only device, and the Si4355

is a receiver-only device based on the Si4x55 architecture. This data sheet

covers all three products with the transmit descriptions being relevant for

Si4455 and Si4055 and the receive descriptions being relevant for Si4455

and Si4355. Covering all major bands, it combines plug-and-play simplicity

with the flexibility needed to handle a wide variety of applications. The

compact 3x3 mm package size combined with a low external BOM count

makes the Si4x55 both space efficient and cost effective. The +13 dBm

output power and excellent sensitivity of –116 dBm allows for a longer

operating range, while the low current consumption of 18 mA TX (at 10 dBm),

10 mA RX, and 40 nA standby, provides for superior battery life. By fully

integrating all components from the antenna to the GPIO or SPI interface to

the MCU, the Si4x55 makes it easy to realize this performance in an

application. Design simplicity is further exemplified in the Wireless

Development Suite (WDS) user interface software. WDS provides simplified

programming options for a broad range of applications in an easy-to-use

format that results in faster and lower risk development. The Si4x55 is

capable of supporting major worldwide regulatory standards, such as FCC,

ETSI, ARIB, and China regulatory standards.

Patents pending

Rev 1.0 10/14

Si4x55-C

Functional Block Diagram

GPIO3

GPIO2

XIN XOUT

Synthesizer

SDN

25-32MHz XO

Rx Chain

nSEL

SDI

RXp

RXn

Rx/Tx

Modem

PGA

LNA

ADC

SDO

SCLK

nIRQ

Battery

Voltage

Sensor

PA

Aux ADC

TX

GPIO1

VDD

GPIO0

2

Rev 1.0

Si4x55-C

TABLE OF CONTENTS

Section

Page

1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Typical Applications Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

3. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

3.1. Receiver Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

3.2. Receiver Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

3.3. Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

3.4. Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

3.5. Crystal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

3.6. Battery Voltage and Auxiliary ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4. Configuration Options and User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

4.1. Radio Configuration Application (RCA) GUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

4.2. Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

4.3. Configuration Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

5. Controller Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

5.1. Serial Peripheral Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

5.2. Operating Modes and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

5.3. Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

5.4. GPIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

6. Data Handling and Packet Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

6.1. RX and TX FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

6.2. Packet Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

6.3. Direct Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

7. Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

8. Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

9. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

10. PCB Land Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

11. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

11.1. Si4x55 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

11.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

Rev 1.0

3

Si4x55-C

1. Electrical Specifications

Table 1. DC Characteristics

Parameter

Symbol

Test Condition

Min Typ Max Unit

Supply Voltage

Range

V

1.8 3.3 3.6

V

DD

Power Saving

Modes

RC oscillator, main digital regulator, and low power digital

regulator OFF.

I

—

30

40

—

nA

mA

Shutdown

I

Register values maintained.

Standby

Crystal Oscillator and Main Digital Regulator ON,

all other blocks OFF.

I

1.8

1.5

Ready

I

SPI active state

SPI Active

TUNE Mode Cur-

rent

I

RX Tune

TX Tune

—

6.8

7.1

—

mA

Tune_RX

I

Tune_TX

RX Mode Current

TX Mode Current

I

Measured at 40 kbps, 20 kHz deviation, 315 MHz

10.9

RX

I

+10 dBm output power

Measured on direct tie RF evaluation board at 868 MHz

TX

—

19

24

—

mA

+13 dBm output power

Measured on direct tie RF evaluation board at 868 MHz

Note: All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and

from –40 to +85 °C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 °C unless otherwise stated.

4

Rev 1.0

Si4x55-C

Table 2. Synthesizer AC Electrical Characteristics

Parameter

Symbol

Test Condition

Min

Typ

Max

Unit

Synthesizer Frequency

Range

F

SYN

284

—

350

MHz

350

850

—

525

960

MHz

Synthesizer Frequency

Resolution

F

—

114.4

57.2

—

Hz

RES-960

RES-525

RES-420

850–960 MHz

420–525 MHz

45.6

Hz

350–420 MHz

38.1

Hz

RES-350

283–350 MHz

Phase Noise

Lf(fm)

100

dBc/Hz

DF = 10 kHz, 915 MHz

102.1

123.5

136.6

Note: All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and

from –40 to +85 °C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 °C unless otherwise stated.

Rev 1.0

5

Si4x55-C

Table 3. Receiver AC Electrical Characteristics

Parameter

RX Frequency

Range

Symbol

Test Condition

Min

284

350

850

—

Typ

—

Max

350

525

960

—

Unit

MHz

dBm

F

RX

—

RX Sensitivity 915 MHz

P

(BER < 0.1%)

–115.0

RX-_2

(2.4 kbps, GFSK, BT = 0.5,

F = 30 kHz, 114 kHz Rx BW)

2

P

(BER < 0.1%)

(40 kbps, GFSK, BT = 0.5,

F = 25 kHz, 114 kHz Rx BW)

—

–107.6

–103.2

—

dBm

RX-_40

P

(BER < 0.1%)

(128 kbps, GFSK, BT = 0.5,

F = 70 kHz, 305 kHz Rx BW)

RX-_128

P

(BER < 0.1%, 1 kbps, 185 kHz Rx BW,

—

–113.5

–102.7

—

dBm

RX-_OOK

2

OOK, PN15 data)

(BER < 0.1%, 40 kbps, 185 kHz Rx BW,

2

OOK, PN15 data)

RX Channel Bandwidth

RSSI Resolution

BW

40

—

850

—

kHz

dB

RES

C/I

Valid from –110 dBm to –90 dBm

±0.5

–52

–56

RSSI

2

1-Ch Offset Selectivity

2-Ch Offset Selectivity

Desired Ref Signal 3 dB above sensitiv-

ity, BER < 0.1%. Interferer is CW and

desired modulated with 1.2 kbps,

F = 5.2 kHz, GFSK with BT = 0.5,

RX BW = 58 kHz

—

dB

1-CH

2-CH

C/I

—

dB

channel spacing = 100 kHz

2

200K

1M

Desired Ref Signal 3 dB above sensitiv-

ity, BER < 0.1%. Interferer is CW and

desired modulated with 1.2 kbps

F = 5.2 kHz GFSK with BT = 0.5,

RX BW = 58 kHz

—

–56

–71

–77

—

dB

Blocking 200 kHz–1 MHz

BLOCK

2

Blocking 1 MHz Offset

BLOCK

2

8M

Blocking 8 MHz Offset

2

Im

Rejection at the image frequency

IF = 468 kHz

—

40

—

dB

Image Rejection

REJ

Notes:

1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and

from –40 to +85 °C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 °C unless otherwise stated.

2. Conducted measurements on RF evaluation board. Specifications are dependent on frequency, matching components,

and board layout.

6

Rev 1.0

Si4x55-C

Table 4. Transmitter AC Electrical Characteristics¹

Parameter

Symbol

Test Condition

Min

Typ

Max

Unit

TX Frequency Range

F

TX

284

—

350

MHz

350

850

—

525

960

MHz

2

(G)FSK Data Rate

OOK Data Rate

DR

1.0

0.5

—

500

120

500

—

kbps

kHz

Hz

FSK

DR

f

OOK

960

525

350

Modulation Deviation

Range

—

850–960 MHz

350–525 MHz

284–350 MHz

850–1050 MHz

420–525 MHz

350–420 MHz

284–350 MHz

f

—

f

—

Modulation Deviation

Resolution

F

114.4

57.2

45.6

38.1

RES-960

RES-525

RES-420

RES-350

—

Hz

—

Hz

—

Hz

3

Output Power Range

Measured at 434 MHz, 3.3 V,

Class E match

P

–20

—

0.25

2.3

0.6

0.5

+13

—

dBm

dB

TX

3

Using switched current match within

6 dB of max power

TX RF Output Steps

P

RF_OUT

3

TX RF Output Level

–40 to +85 C

—

dB

RF_TEMP

Variation vs. Temperature

TX RF Output Level

P

Measured across 902–928 MHz

—

dB

3

RF_FREQ

Variation vs. Frequency

Transmit Modulation

Filtering

Gaussian Filtering Bandwith Time

Product

B*T

—

Notes:

1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and

from –40 to +85 °C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 °C unless otherwise stated.

2. The maximum data rate is dependent on the XTAL frequency and is calculated as per the formula: Maximum Symbol

Rate = Fxtal/60, where Fxtal is the XTAL frequency (typically 30 MHz).

3. Conducted measurements based on RF evaluation board. Output power and emissions specifications are dependent on

transmit frequency, matching components, and board layout.

Rev 1.0

7

Si4x55-C

Table 5. Auxiliary Block Specifications¹

Parameter

Symbol

XTAL

Test Condition

Min

Typ

Max

Unit

2

XTAL Range

25

—

32

—

MHz

µs

RANGE

30 MHz XTAL Start-Up

time

t

Using XTAL and board layout in

reference design. Start-up time

will vary with XTAL type and

board layout.

300

30M

30 MHz XTAL Cap

Resolution

30M

RES

—

70

—

fF

POR Reset Time

t

—

6

ms

Hz

POR

Configurable to Fxtal or Fxtal

divided by 2, 3, 7.5, 10, 15, or 30

where Fxtal is the reference

XTAL frequency. In addition,

32.768 kHz is also supported.

Microcontroller Clock

Output Frequency Range

32.768 k

Fxtal

3

Notes:

1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and

from –40 to +85 °C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 °C unless otherwise stated.

2. XTAL Range tested in production using an external clock source (similar to using a TCXO).

3. Microcontroller clock frequency tested in production at 1 MHz, 30 MHz, 32 MHz, and 32.768 kHz. Other frequencies

tested by bench characterization.

8

Rev 1.0

Si4x55-C

Table 6. Digital IO Specifications (GPIO_x, SCLK, SDO, SDI, nSEL, nIRQ)¹

Parameter

Symbol

Test Condition

0.1 x V to 0.9 x V ,

DD

Min

Typ

Max

Unit

2,3

Rise Time

T

—

2.3

—

ns

RISE

DD

C = 10 pF, DRV<1:0> = LL

L

V

= 3.3 V

DD

3,4

Fall Time

0.9 x V to 0.1 x V

—

2

—

ns

FALL

DD

DD,

C = 10 pF, DRV<1:0> = LL

L

V

= 3.3 V

DD

Input Capacitance

C

V

—

2

—

pF

V

IN

Logic High Level Input Voltage

Logic Low Level Input Voltage

Input Current

V

x 0.7

—

IH

DD

V

—

–1

1

—

V

x 0.3

DD

V

IL

I

0 < V < V

DD

—

1

µA

mA

V

IN

Input Current if Pullup is Activated

I

V = 0 V

—

4

INP

IL

3

Drive Strength for Output Low

Level

I

DRV[1:0] = LL

—

6.66

5.03

3.16

1.13

5.75

4.37

2.73

0.96

2.53

2.21

1.70

0.80

—

OmaxLL

I

DRV[1:0] = LH

DRV[1:0] = HL

OmaxLH

OmaxHL

OmaxHH

3

I

DRV[1:0] = HH

3

Drive Strength for Output High

Level (GPIO1, GPIO2, GPIO3)

I

DRV[1:0] = LL

DRV[1:0] = LH

DRV[1:0] = HL

OmaxLL

OmaxLH

OmaxHL

OmaxHH

3

I

DRV[1:0] = HH

3

Drive Strength for Output High

Level (GPIO0)

I

DRV[1:0] = LL

DRV[1:0] = LH

DRV[1:0] = HL

OmaxLL

OmaxLH

OmaxHL

OmaxHH

3

I

DRV[1:0] = HH

3

Logic High Level Output Voltage

Logic Low Level Output Voltage

Notes:

V

DRV[1:0] = HL

V

x 0.8

DD

OH

3

V

—

V

x 0.2

DD

V

OL

1. All minimum and maximum values are guaranteed across the recommended operating conditions of supply voltage and

from –40 to +85 °C unless otherwise stated. All typical values apply at VDD = 3.3 V and 25 °C unless otherwise stated.

2. 6.7 ns is typical for GPIO0 rise time.

3. Assuming VDD = 3.3 V, drive strength is specified at Voh (min) = 2.64 V and Vol (max) = 0.66 V at room temperature.

4. 2.4 ns is typical for GPIO0 fall time.

Rev 1.0

9

Si4x55-C

Table 7. Thermal Characteristics

Parameter

Symbol

Max Value

71

Unit

Thermal Impedance Junction to Ambient*



°C/W

JA

Junction Temperature Maximum Value*

Operating Ambient Temperature Range

Storage Temperature Range

T

96

°C

J

C

–40 to +85

–55 to +150

A

T

C

STG

*Note: Thermal Impedance and Junction Temperature based on RF evaluation board measurements.

Table 8. Absolute Maximum Ratings

Parameter

Value

–0.3, +3.6

Unit

V

to GND

V

DD

Voltage on Digital Control Inputs

Instantaneous V to GND on TX Output Pin

–0.3, V + 0.3

DD

–0.3, V + 0.3

V

RF-peak

DD

Sustained V

to GND on TX Output Pin

–0.3, V + 8.0

V

RF-peak

DD

Voltage on Analog Inputs

RX Input Power

–0.3, V + 6.5

V

DD

+10

dBm

Note: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These

are stress ratings only and functional operation of the device at or beyond these ratings in the operational sections of

the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect

device reliability. The Power Amplifier may be damaged if switched on without proper load or termination connected.

TX matching network design will influence TX V_RF-peakon TX output pin. Caution: ESD sensitive device.

10

Rev 1.0

Si4x55-C

2. Typical Applications Schematic

30 MHz

GP0

GP1

C6

GP2

GP3

GP4

GP5

GND

SDN

RXp

RXn

TX

SDI

1

2

3

15

14

13

SDO

SCLK

nIRQ

GPIO1

L6

L5

C2

Si4455

L4

L3

4

5

12

11

L2

C1

C4

C5

C3

L1

VDD

C7

C8

C9

100 p

100 n

1u

Figure 1. Si4455 Application Circuit

30 MHz

SDN

GP1

C2

GP2

GP3

GP4

GP5

GND

SDN

RXp

RXn

NC

SDI

1

2

3

15

14

13

SDO

SCLK

nIRQ

GPIO1

L2

C1

L1

Si4355

4

5

12

11

VDD

C3

100 p

C4

C5

100 n

1u

Figure 2. Si4355 Applications Circuit

Rev 1.0

11

Si4x55-C

3. Functional Description

GPIO3

GPIO2

XIN XOUT

Synthesizer

SDN

25-32MHz XO

Rx Chain

nSEL

SDI

RXp

LNA

RXn

Rx/Tx

Modem

PGA

ADC

SDO

SCLK

nIRQ

Battery

Voltage

Sensor

PA

Aux ADC

TX

GPIO1

VDD

GPIO0

Figure 3. Si4455 Functional Block Diagram

The Si4x55 is an easy-to-use, size efficient, low current wireless ISM device that covers the sub-GHz bands. The

wide operating voltage range of 1.8–3.6 V and low current consumption make the Si4x55 an ideal solution for

battery powered applications. The Si4455 operates as a time division duplexing (TDD) transceiver where the

device alternately transmits and receives data packets. The device uses a single-conversion mixer to downconvert

the FSK/GFSK or OOK modulated receive signal to a low IF frequency. Following a programmable gain amplifier

(PGA), the signal is converted to the digital domain by a high performance  ADC allowing filtering, demodulation,

slicing, and packet handling to be performed in the built-in digital modem, increasing the receiver’s performance

and flexibility versus analog based architectures. The demodulated signal is output to the system MCU through a

programmable GPIO or via the standard SPI bus by reading the 64-byte Rx FIFO.

A single high-precision local oscillator (LO) is used for both transmit and receive modes since the transmitter and

receiver do not operate at the same time. The LO signal is generated by an integrated VCO and  Fractional-N

PLL synthesizer. The synthesizer is designed to support configurable data rates up to 500 kbps. The Si4x55

operates in the frequency bands of 283–350, 350–525, and 850–960 MHz. The transmit FSK data is modulated

directly into the  data stream and can be shaped by a Gaussian low-pass filter to reduce unwanted spectral

content.

The device contains a power amplifier (PA) that supports output powers up to +13 dBm and is designed to support

single coin cell operation with current consumption of 18 mA for +10 dBm output power. The PA is single-ended to

allow for easy antenna matching and low BOM cost. The PA incorporates automatic ramp-up and ramp-down

control to reduce unwanted spectral spreading. Additional system features, such as 64-byte TX/RX FIFOs,

preamble detection, sync word detector, and CRC, reduce overall current consumption and allow for the use of

lower-cost system MCUs. Power-on-reset (POR) and GPIOs further reduce overall system cost and size. The

Si4x55 is designed to work with an MCU, crystal, and a few passives to create a very compact and low-cost

system.

12

Rev 1.0

Si4x55-C

3.1. Receiver Chain

The internal low-noise amplifier (LNA) is designed to be a wideband LNA that can be matched with three external

discrete components to cover any common range of frequencies in the sub-GHz band. The LNA has extremely low

noise to suppress the noise of the following stages and achieve optimal sensitivity; therefore, no external gain or

front-end modules are necessary. The LNA has gain control, which is controlled by the internal automatic gain

control (AGC) algorithm. The LNA is followed by an I-Q mixer, filter, programmable gain amplifier (PGA), and ADC.

The I-Q mixers downconvert the signal to an intermediate frequency. The PGA then boosts the gain to be within

dynamic range of the ADC. The ADC rejects out-of-band blockers and converts the signal to the digital domain

where filtering, demodulation, and processing is performed. Peak detectors are integrated at the output of the LNA

and PGA for use in the AGC algorithm.

The RX and TX pins can be directly tied externally on the Si4455 transceiver.

3.2. Receiver Modem

Using high-performance ADCs allows channel filtering, image rejection, and demodulation to be performed in the

digital domain, which allows for flexibility in optimizing the device for particular applications. The digital modem

performs the following functions:

Channel selection filter

Preamble detection

Invalid preamble detection

TX modulation

RX demodulation

Automatic Gain Control (AGC)

Automatic frequency compensation (AFC)

Radio signal strength indicator (RSSI)

Cyclic redundancy check (CRC)

The digital channel filter and demodulator are optimized for ultra-low-power consumption and are highly

configurable. Supported modulation types are GFSK, FSK, and OOK. The channel filter can be configured to

support bandwidths ranging from 850 kHz down to 40 kHz. A large variety of data rates are supported ranging from

0.5 kbps up to 500 kbps. The configurable preamble detector is used with the synchronous demodulator to improve

the reliability of the sync-word detection. Preamble detection can be skipped using only sync detection, which is a

valuable feature of the asynchronous demodulator when very short preambles are used. The received signal

strength indicator (RSSI) provides a measure of the signal strength received on the tuned channel. The resolution

of the RSSI is 0.5 dB. This high-resolution RSSI enables accurate channel power measurements for clear channel

assessment (CCA), carrier sense (CS), and listen before talk (LBT) functionality. A wireless communication

channel can be corrupted by noise and interference, so it is important to know if the received data is free of errors.

A cyclic redundancy check (CRC) is used to detect the presence of erroneous bits in each packet. A CRC is

computed and appended at the end of each transmitted packet and verified by the receiver to confirm that no

errors have occurred. The packet handler and CRC can significantly reduce the load on the system microcontroller,

allowing for a simpler and cheaper microcontroller. The digital modem includes the TX modulator, which converts

the TX data bits into the corresponding stream of digital modulation values to be summed with the fractional input

to the sigma-delta modulator. This modulation approach results in highly accurate resolution of the frequency

deviation. A Gaussian filter is implemented to support GFSK, considerably reducing the energy in adjacent

channels. The default bandwidth-time (BT) product is 0.5 for all programmed data rates.

3.2.1. Received Signal Strength Indicator

The received signal strength indicator (RSSI) is an estimate of the signal strength in the channel to which the

receiver is tuned. The RSSI measurement is done after the channel filter, so it is only a measurement of the

desired or undesired in-band signal power. The Si4x55 uses a fast response register to read RSSI and so can

complete the read in 16 SPI clock cycles with no requirement to wait for CTS. The RSSI value reported by this API

command can be converted to dBm using the following equation:

Rev 1.0

13

Si4x55-C

RSSI_value

RSSI_dBm= -------------------------------- – 130

2

The value of 130 in the above formula is based on bench characterization of the EZRadio RF Pico boards

(evaluation boards). The RSSI value is latched at sync word detection and can be read via the fast response

register. The latched value of RSSI is available until the device re-enters Rx mode. In addition, the current value of

RSSI can be read out using the GET_MODEM_STATUS command. This can be used to implement CCA (clear

channel assessment) functionality. The user can set up an RSSI threshold value using the WDS Radio

Configuration Application GUI.

3.3. Synthesizer

The Si4x55 includes an integrated Sigma Delta () Fractional-N PLL synthesizer capable of operating over the

bands from 283–350, 350–525, and 850–960 MHz. The synthesizer has many advantages; it provides flexibility in

choosing data rate, deviation, channel frequency, and channel spacing. The transmit modulation is applied directly

to the loop in the digital domain through the fractional divider, which results in very precise accuracy and control

19

over the transmit deviation. The frequency resolution is (2/3)Freq_xo/(2 ) for 283–350 MHz, Freq_xo/(2 ) for

18

350–525 MHz, and Freq_xo/(2 ) for 850–960 MHz. The nominal reference frequency to the PLL is 30 MHz, but

any XTAL frequency from 25 to 32 MHz may be used. The modem configuration calculator in WDS will

automatically account for the XTAL frequency being used. The PLL utilizes a differential LC VCO with integrated

on-chip inductors. The output of the VCO is followed by a configurable divider, which will divide the signal down to

the desired output frequency band.

3.3.1. Synthesizer Frequency Control

The frequency is set by changing the integer and fractional settings to the synthesizer. The WDS calculator will

automatically provide these settings, but the synthesizer equation is shown below for convenience. Initial

frequency settings are configured in the EZConfig setup and can also be modified using the API commands:

FREQ_CONTROL_INTE,

FREQ_CONTROL_FRAC0.

FREQ_CONTROL_FRAC2,

FREQ_CONTROL_FRAC1,

and

4  freq_xo

------------------------------

fc_frac

2¹⁹





RF frequency = fc_inte + ------------------ 

Hz





outdiv

Note: The fc_frac/2¹⁹value in the above formula must be a number between 1 and 2. The LSB of fc_frac must be "1".

Table 9. Output Divider (Outdiv) Values

Outdiv

Lower (MHz)

Upper (MHz)

12

10

8

284

350

420

850

350

420

525

960

4

3.3.1.1. EZ Frequency Programming

EZ frequency programming allows for easily changing radio frequency using a single API command. The base

frequency is first set using the EZConfig setup. This base frequency will correspond to channel 0. Next, a channel

step size is also programmed within the EZConfig setup. The resulting frequency will be:

RF Frequency = Base Frequency + Channel  Step Size

The second argument of the START_RX or START_TX is CHANNEL, which sets the channel number for EZ

frequency programming. For example, if the channel step size is set to 1 MHz, the base frequency is set to

900 MHz, and a CHANNEL number of 5 is programmed during the START_TX command, the resulting frequency

will be 905 MHz. If no CHANNEL argument is written as part of the START_RX/TX command, it will default to the

previous value. The initial value of CHANNEL is 0 and so will be set to the base frequency if this argument is never

used.

14

Rev 1.0

Si4x55-C

3.4. Transmitter

The device contains a +13 dBm power amplifier that is capable of transmitting from –40 to +13 dBm. The output

power set size is dependent on the power level and can be seen in Figure 4. The PA power level is set using the

API command: PA_PWR_LVL. The power amplifier is single-ended to allow for easy antenna matching and low

BOM cost. For detailed matching values, BOM, and performance expectations, refer to "AN686: Antennas for the

Si4455/4355 RF ICs". Power ramp-up and ramp-down is automatically performed to reduce unwanted spectral

spreading.

Figure 4. Tx Power vs PA_PWR_LVL and VDD

Rev 1.0

15

Si4x55-C

3.5. Crystal Oscillator

The Si4x55 includes an integrated crystal oscillator with a fast start-up time of less than 250 µs. The design is

differential with the required crystal load capacitance integrated on-chip to minimize the number of external

components. By default, all that is required off-chip is the crystal. The default crystal is 30 MHz, but the circuit is

designed to handle any XTAL from 25 to 32 MHz, set in the EZConfig setup. The crystal load capacitance can be

digitally programmed to accommodate crystals with various load capacitance and to adjust the frequency of the

crystal oscillator. The tuning of the crystal load capacitance is programmed through the GLOBAL_XO_TUNE API

property. The total internal capacitance is 11 pF and is adjustable in 127 steps (70 fF/step). The crystal frequency

adjustment can be used to compensate for crystal production tolerances. The frequency offset characteristics of

the capacitor bank are demonstrated in Figure 5.

Figure 5. Capacitor Bank Frequency Offset Characteristics

An external signal source can easily be used in lieu of a conventional XTAL and should be connected to the XIN

pin. The incoming clock signal is recommended to be ac-coupled to the XIN pin since the dc bias is controlled by

the internal crystal oscillator buffering circuitry. The input swing range should be between 600 mV–1.8 V

peak-to-peak. If external drive is desired, the incoming signal amplitude should not go below 0 V or exceed 1.8 V.

The best dc bias should be approximately 0.7 V. However, if the signal swing exceeds 1.4 Vpp, the dc bias can be

set to 1/2 the peak-to-peak voltage swing. The XO capacitor bank should be set to 0 whenever an external drive is

used on the XIN pin. In addition, the POWER_UP command should be invoked with the TCXO option whenever

external drive is used.

3.6. Battery Voltage and Auxiliary ADC

The Si4x55 contains an integrated auxiliary 11-bit ADC used for the internal battery voltage detector or an external

component via GPIO. The Effective Number of Bits (ENOB) is 9 bits. When measuring external components, the

input voltage range is 1 V, and the conversion rate is between 300 Hz to 2.44 kHz. The ADC value is read by first

sending the GET_ADC_READING command and enabling the desired inputs. When the conversion is finished and

all the data is ready, CTS will go high, and the data can be read out. For details on this command and the formulas

needed to interpret the results, refer to the EZRadio API documentation zip file available from www.silabs.com.

16

Rev 1.0

Si4x55-C

4. Configuration Options and User Interface

4.1. Radio Configuration Application (RCA) GUI

The Radio Configuration Application (RCA) GUI is part of the Wireless Development Suite (WDS) program. This

setup interface provides an easy path to quickly selecting and loading the desired configuration for the device. The

RCA allows for two different methods for device setup. One option is the configuration table, which provides a list of

preloaded, common configurations. A second option allows for custom configurations to be loaded. After the

desired configuration is selected, the RCA automatically creates the EZConfig configuration array that will be

passed to the chip for setup. The program then gives the option to load a sample project with the selected

configuration onto the evaluation board or launch IDE with the new configuration array preloaded into the user

program. For more information on EZConfig usage, refer to application note, “AN692: Si4355/Si4455 Programming

Guide”.

Figure 6. Device Configuration Options

Rev 1.0

17

Si4x55-C

4.1.1. Radio Configuration Application

The Radio Configuration Application provides an intuitive interface for directly modifying the device configuration.

Using this control panel, the device parameters such as modulation type, data rate, frequency deviation, and any

packet related settings can be set. The program then takes these parameters and automatically determines the

appropriate device settings. This method allows the user to have complete flexibility in determining the

configuration of the device without the need to translate the system requirements into device specific properties.

The resulting configuration array is automatically generated and available for use in the user's program. The

resulting configuration array is obfuscated; therefore, its content changes every time a new array is generated,

even if the input parameters are the same.

4.2. Configuration Options

4.2.1. Frequency Band

The Si4455 can operate in the 283–350 MHz, 350–525 MHz, or 850–960 MHz bands. One of these three bands

will be selected during the configuration setup and then the specific transmission frequency that will be used within

this band can be selected.

4.2.2. Modulation Type

The Si4x55 can operate using On/Off Keying (OOK), Frequency Shift Keying (FSK), or Gaussian Frequency Shift

Keying (GFSK). OOK modulation is the most basic modulation type available. It is the most power-efficient method

and does not require as high oscillator accuracy as FSK. FSK provides the best sensitivity and range performance,

but generally requires more precision from the oscillator used. GFSK is a version of FSK where the signal is

passed through a Gaussian filter, limiting its spectral width. As a result, the out-of-band components of the signal

are reduced.

The Si4x55 also has an option for Manchester coding. This method provides a state transition at each bit and so

allows for more reliable clock recovery. Manchester code is available only when using the packet handler option

and, if selected, will be applied to the entire packet (the preamble pattern is set to continuous “1” if the Manchester

mode is enabled; therefore, the chip rate of the resulting preamble pattern is the same as for the rest of the packet).

The polarity can be configured to a “10” or “01”.

Clock

Data

1

0

1

0

1

Manchester

Figure 7. Manchester Code Example

18

Rev 1.0

Si4x55-C

4.2.3. Frequency Deviation

If FSK or GFSK modulation is selected, then a frequency deviation will also need to be selected. The frequency

deviation is the maximum instantaneous difference between the FM modulated frequency and the nominal carrier

frequency. The Si4x55 can operate across a wide range of data rates and frequency deviations. If a frequency

deviation needs to be selected, the following guideline might be helpful to build a robust link. A proper frequency

deviation is linked to the frequency error between transmitter and receiver. The frequency error can be calculated

using the crystal tolerance parameters and the RF operating frequency: (ppm_tx+ppm_rx)*Frf/1E-6. For frequency

errors below 50 kHz, the deviation can be about the same as the frequency error. For frequency errors exceeding

50 kHz, the frequency deviation can be set to about 0.75 times the frequency error. It is advised to position the

modulation index (= 2*freq_dev/data_rate) into a range between 1 and 100 for Packet Handling mode and 2 to 100

for direct mode (non-standard preamble). For example, when in Packet Handling mode and the frequency error is

smaller than data_rate/2, the frequency deviation is set to about data_rate/2. When the frequency error exceeds

100xdata_rate/2, the frequency deviation is preferred to be set to 100xdata_rate/2.

4.2.4. Channel Bandwidth

The channel bandwidth sets the bandwidth for the receiver. Since the receiver bandwidth is directly proportional to

the noise allowed in the system, this will normally be set as low as possible. The specific channel bandwidth used

will usually be determined based upon the precision of the oscillator and the frequency deviation of the transmitted

signal. The RCA can provide the recommended channel bandwidth based upon these two parameters to help

optimize the system.

4.2.5. Preamble Length

A preamble is a defined simple bit sequence used to notify the receiver that a data transmission is imminent. The

length of this preamble will normally be set as short as possible to minimize power while insuring that it will be

reliably detected given the receiver characteristics, such as duty cycling and packet error rate performance. The

Si4x55 allows the preamble length to be set between 0 to 255 bytes in length with a default length of 4 bytes. The

preamble pattern for the Si4x55 will always be 55h with a first bit of “0” if the packet handler capability is used.

4.2.6. Sync Word Length and Pattern

The sync word follows the preamble in the packet structure and is used to identify the start of the payload data and

to synchronize the receiver to the transmitted bit stream. The Si4x55 allows for sync word lengths of 1 to 4 bytes

and the specific pattern can be set within the RCA program. The default is a 2 byte length 2d d4 pattern.

4.2.7. Cyclic Redundancy Check

Cyclic Redundancy Check (CRC) is used to verify that no errors have occurred during transmission and the

received packet has exactly the same data as it did when transmitted. If this function is enabled in the Si4x55, the

last byte of transmitted data must include the CRC generated by the transmitter. The Si4x55 then performs a CRC

calculation on the received packet and compares that to the transmitted CRC. If these two values are the same, the

Si4455 will set an interrupt indicating a valid packet has been received and is waiting in the Rx FIFO. If these two

CRC values differ, the Si4455 will flag an interrupt indicating that a packet error occurred. The Si4x55 uses

CRC(16)-IBM: x16+x15+x2+1 with a seed of 0xFFFF as well as a 16-bit ITU-T CRC as specified in the IEEE

802.15.4g standard.

4.2.8. Preamble Sense Mode

This mode of operation is suitable for extremely low power applications where power consumption is important.

The preamble sense mode (PSM) takes advantage of the Digital Signal Arrival detector (DSA), which can detect a

preamble within eight bit times with no sensitivity degradation. This fast detection of an incoming signal can be

combined with duty cycling of the receiver during the time the device is searching or sniffing for packets over the

air. The average receive current is lowered significantly when using this mode. In applications where the timing of

the incoming signal is unknown, the amount of power savings is primarily dependent on the data rate and preamble

length as the Rx inactive time is determined by these factors. In applications where the sleep time is fixed and the

timing of the incoming signal is known, the average current also depends on the sleep time. The PSM mode is

similar to the low duty cycle mode but has the benefit of faster signal detection and autonomous duty cycling of the

receiver to achieve even lower average receive currents.

Rev 1.0

19

Si4x55-C

Noiseꢀ(noꢀsignal,ꢀgoꢀbackꢀtoꢀreadyꢀstate)

ValidꢀPacketꢀ(PMꢀdetected,ꢀstayꢀinꢀRx)

10.9mA

Receive

1.8ꢀmA

Ready

Sleep

740ꢀnA

t

Figure 8. Preamble Sense Mode

Table 10. Data Rates*

Data Rate

9.6 kbps

1.2 kbps

5.8

50 kbps

7.6

100 kbps

PM length = 4 bytes

PM length = 8 bytes

6.1

3.7

9.3

5.0

mA

3.6

4.3

*Note: Typical values. Active RX current is 10.9 mA.

20

Rev 1.0

Si4x55-C

4.3. Configuration Commands

The RCA provides all of the code needed for basic radio configuration. Once the setup is completed in the GUI, the

program outputs configuration array(s) that can be sent to the radio via the SPI interface. No additional setup

coding is needed. The configuration command process is shown in Figure 9. As shown below, the configuration is

sent to the device in two EZCONFIG_ARRAY_WRITE commands with a NOP between them. The second

EZCONFIG_ARRAY_WRITE can be sent after CTS is received for the NOP command. The NOP can be sent

immediately after the first EZCONFIG_ARRAY_WRITE command. EZCONFIG_ARRAY_WRITE uses the same

command code as WRITE_TX_FIFO (0x66). The EZCONFIG_SETUP passes the configuration array to the device

and the EZCONFIG_CHECK insures that all of the configuration data was written correctly. For more information

on the setup commands, refer to “AN692: Si4355/Si4455 Programming Guide” and the EZRadio API

Documentation zip file available from www.silabs.com.

EZCONFIG_ARRAY_WRITE

NOP

EZCONFIG_ARRAY_WRITE

EZCONFIG_CHECK

Figure 9. Configuration Command Flowchart

Rev 1.0

21

Si4x55-C

5. Controller Interface

5.1. Serial Peripheral Interface

The Si4x55 communicates with the host MCU over a standard 4-wire serial peripheral interface (SPI): SCLK, SDI,

SDO, and nSEL. The SPI interface is designed to operate at a maximum of 10 MHz. The SPI timing parameters

are listed in Table 11. The host MCU writes data over the SDI pin and can read data from the device on the SDO

output pin. Figure 10 shows an SPI write command. The nSEL pin should go low to initiate the SPI command. The

first byte of SDI data will be one of the API commands followed by n bytes of parameter data which will be variable

depending on the specific command. The rising edges of SCLK should be aligned with the center of the SDI data.

Table 11. Serial Interface Timing Parameters

Symbol

Parameter

Min

(ns)

Max

(ns)

Diagram

t

Clock high time

Clock low time

40

20

CH

t

CL

DS

DH

DD

SCLK

SDI

t_SS

t_CL

t_CH

t_DSt_DH

t_DD

t_SHt_DE

t

Data setup time

t

Data hold time

Output data delay time

Output disable time

Select setup time

Select hold time

Select high period

43

45

t

DE

SDO

t

20

50

80

SS

SH

t_SW

t

nSEL

t

SW

*Note: CL = 10 pF; VDD = 1.8 V; SDO Drive strength setting = 10.

nSEL

SDO

SDI

API Command

ParamByte 0

ParamByte n

SCLK

Figure 10. SPI Write Command

22

Rev 1.0

Si4x55-C

The Si4x55 contains an internal MCU which controls all the internal functions of the radio. For SPI read commands,

a typical communication flow of checking clear-to-send (CTS) is used to make sure the internal MCU has executed

the command and prepared the data to be output over the SDO pin. Figure 11 demonstrates the general flow of an

SPI read command. Once the CTS value reads FFh, then the read data is ready to be clocked out to the host MCU.

The typical time for a valid FFh CTS reading is 20 µs. Figure 12 demonstrates the remaining read cycle after CTS

is set to FFh. The internal MCU will clock out the SDO data on the negative edge so the host MCU should process

the SDO data on the rising edge of SCLK.

0xFF

Retrieve

Response

Send Command

Read CTS

CTS Value

0x00

nSEL

SDO

SDI

CTS

ReadCmdBuff

SCLK

Figure 11. SPI Read Command—Check CTS Value

nSEL

SDO

SDI

Response Byte 0

Response Byte n

SCLK

Figure 12. SPI Read Command—Clock Out Read Data

Rev 1.0

23

Si4x55-C

5.2. Operating Modes and Timing

The primary states of the Si4x55 are shown in Figure 13. The shutdown state completely shuts down the radio,

minimizing current consumption and is controlled using the SDN (pin 2). All other states are controlled using the

API commands START_RX, START_TX and CHANGE_STATE. Table 12 shows each of the operating modes with

the time required to reach either RX or TX state as well as the current consumption of each state. The times in

Table 12 are measured from the rising edge of nSEL until the chip is in the desired state. This information is

included for reference only since an automatic sequencer moves the chip from one state to another and so it is not

necessary to manually step through each state. Figure 14 and Figure 15 demonstrate this timing and the current

consumption for each radio state as the chip moves from shutdown or standby to TX and back. Most applications

will utilize the standby mode since this provides the fastest transition response time, maintains all register values,

and results in nearly the same current consumption as shutdown.

Standby

Shutdown

SPI Active

Config

Ready

Tx Tune

Tx

Rx Tune

Rx

Figure 13. State Machine Diagram

24

Rev 1.0

Si4x55-C

Table 12. Operating State Response Time and Current Consumption

State / Mode

Response Time to

Current in State / Mode

Tx

Rx

Shutdown

Standby

SPI Active

Ready

Tx Tune

Rx Tune

Tx

30 ms

504 μs

288 μs

108 μs

60 μs

30 ms

516 μs

296 μs

120 μs

30 nA

40 nA

1.5 mA

1.8 mA

6.8 mA

84 μs

132 μs

108 μs

7.1 mA

18 mA @ +10 dBm

10.9 mA

Rx

120 μs

TX = 19 mA

Tune = 100 us@7.1 mA

POR = 1 ms@1.25 mA

Ready = 300 us@1.8 mA

Reg Inrush = 5 us@2 mA

Standby = 10 us@40 nA

POWER_UP / CONFIG_SETUP =

29 ms@2 mA

Shutdown = 30 nA

Figure 14. Start-Up Timing and Current Consumption using Shutdown State

Rev 1.0

25

Si4x55-C

TX = 19 mA

Tune = 100us@7.1 mA

Ready = 300 us@1.8 mA

Reg Inrush = 5 us@2 mA

Standby = 40 nA

Figure 15. Start-Up Timing and Current Consumption using Standby State

5.2.1. Shutdown State

The shutdown state is the lowest current consumption state of the device and is entered by driving SDN (Pin 2)

high. In this state, all register contents are lost and there is no SPI access. To exit this mode, drive SDN low. The

device will then initiate a power on reset (POR) along with internal calibrations. Once this POR period is complete,

the POWER_UP command is required to initialize the radio and the configuration can then be loaded into the

device. The SDN pin must be held high for at least 10 µs before driving it low again to insure the POR can be

executed correctly. The shutdown state can be used to fully reset the part. If POR timing and voltage requirements

cannot be met, it is highly recommended that SDN be controlled using the host processor rather than tying it to

GND on the board.

5.2.2. Standby State

The standby state has similar current consumption to the shutdown state but retains all register values, allowing for

a much faster response time. Because of these benefits, most applications will want to use standby mode rather

than shutdown. The standby state is entered by using the CHANGE_STATE API command. While in this state, the

SPI is accessible but any SPI event will automatically transition the chip to the SPI active state. After the SPI event,

the host will need to re-command the device to standby mode.

5.2.3. SPI Active State

The SPI active state enables the device to process any SPI events, such as API commands. In this state, the SPI

and boot up oscillator are enabled. The SPI active state is entered by using the CHANGE_STATE command or

automatically through an SPI event while in standby mode. If the SPI active state was entered automatically from

standby mode, a CHANGE_STATE command will be needed to return the device to standby mode.

5.2.4. Ready State

Ready state is designed to give a fast transition time to TX or RX state with minimized current consumption. In this

mode the crystal oscillator remains enabled to minimize the transition time. Ready state can be entered using the

CHANGE_STATE command.

26

Rev 1.0

Si4x55-C

5.2.5. Power on Reset

A Power On Reset (POR) sequence is used to boot the device up from a fully off or shutdown state. To execute this

process, VDD must ramp within 1 ms and must remain applied to the device for at least 10 ms. If VDD is removed,

then it must stay below 0.15 V for at least 10 ms before being applied again. Refer to Figure 16 and Table 13 for

details.

Figure 16. POR Timing Diagram

Table 13. POR Timing

Variable

Description

Min

Typ

Max Units

High time for VDD to fully settle POR circuit.

t

10

ms

V

PORH

Low time for VDD to enable POR.

Voltage for successful POR.

t

10

90%*Vdd

0

PORL

V

RRH

Starting Voltage for successful POR.

Slew rate of VDD for successful POR.

V

150

1

mV

ms

RRL

t

SR

Rev 1.0

27

Si4x55-C

5.2.6. TX State

The TX state is used whenever the device is required to transmit data. It is entered using either the START_TX or

CHANGE_STATE command. With the START_TX command, the next state can be defined to insure optimal

timing. When either command is sent to enter TX state, an internal sequencer automatically takes care of all

actions required to move between states with no additional user commands needed. Examples of the timing of this

transition can be seen in Figure 14 and Figure 15. The specific sequencer controlled events that take place during

this time can include enable internal LDOs, start up crystal oscillator, enable PLL, calibrate VCO/PLL, active power

amplifier, and transmit packet.

Figure 17 shows an example of the commands and timing for the START_TX command. CTS will go high as soon

as the sequencer puts the part into TX state. As the sequencer is stepping through the events listed above, CTS

will be low and no new commands or property changes are allowed. If the nIRQ is used to monitor the current

state, there will be a slight delay caused by the internal hardware from when the event actually occurs to when the

transition occurs on the nIRQ. The time from entering TX state to when the nIRQ will transition is 13 µs. If a GPIO

is programmed for TX state or used as control for a transmit/receive switch (TR switch), there is no delay.

CTS

nSEL

SDI

Current State

FRR

START_TX

Initial State

TX State

TXCOMPLETE_STATE

Initial State

TX State

TXCOMPLETE_STATE

nIRQ

GPIO-TX State

Figure 17. START_TX Commands and Timing

5.2.7. RX State

The RX state is used whenever the device is required to receive data. It is entered using either the START_RX or

CHANGE_STATE commands. With the START_RX command, the next state can be defined to insure optimal

timing. When either command is sent to enter RX state, an internal sequencer automatically takes care of all

actions required to move between states with no additional user commands needed. The sequencer controlled

events can include enable the digital and analog LDOs, start up the crystal oscillator, enable PLL, calibrate VCO,

enable receiver circuits, and enable receive mode. The device will also automatically set up all receiver features

such as packet handling based upon the initial configuration of the device.

28

Rev 1.0

Si4x55-C

5.3. Interrupts

The Si4x55 is capable of generating an interrupt signal when certain events occur. The chip notifies the

microcontroller that an interrupt event has occurred by setting the nIRQ output pin LOW = 0. This interrupt signal

will be generated when any one (or more) of the interrupt events occur. The nIRQ pin will remain low until the

microcontroller reads the Interrupt Status Registers. The nIRQ output signal will then be reset until the next change

in status is detected.

The interrupt sources are grouped into three categories: packet handler, chip status, and modem. The individual

interrupts in these groups can be enabled/disabled in the interrupt property registers, 0x0101, 0x0102, and 0x0103.

An interrupt must be enabled for it to trigger an event on the nIRQ pin. The interrupt group must be enabled as well

as the individual interrupts in API property 0x0100.

When an interrupt event occurs and the nIRQ pin is low, the interrupts are read and cleared using the

GET_INT_STATUS command. By default all interrupts will be cleared once read. The instantaneous status of a

specific function may be read if the specific interrupt is enabled or disabled. The status results are provided after

the interrupts and can be read with the same commands as the interrupts. The status bits will give the current state

of the function whether the interrupt is enabled or not. The following is a list of possible interrupts:

Chip status

Modem status

Packet handler status

Packet sent

Packet received

CRC error

Invalid preamble detected

Invalid sync detected

Preamble detected

Sync detected

State change

Command error

Chip ready

TX FIFO almost empty

RX FIFO almost full

RSSI interrupt

Rev 1.0

29

Si4x55-C

5.4. GPIO

Four General Purpose IO (GPIO) pins are available for use in the application. The GPIOs are configured using the

GPIO_PIN_CFG command. GPIO pins 0 and 1 should be used for active signals such as data or clock. GPIO pins

2 and 3 have more susceptibility to generating spurious components in the synthesizer than pins 0 and 1. The drive

strength of the GPIO's can be adjusted with the GEN_CONFIG parameter in the GPIO_PIN_CFG command. By

default, the drive strength is set to the minimum. The default configuration and the state of the GPIO during

shutdown are shown in Table 14. For a complete list of the GPIO options, please refer to the EZRadio API

documentation zip file available from www.silabs.com.

Table 14. GPIOs

SDN State

POR Default

POR

GPIO0

GPIO1

GPIO2

GPIO3

nIRQ

0

CTS

POR

Resistive V pull-up

nIRQ

DD

SDO

Resistive V pull-up

SDO

DD

SDI

High Z

SDI

SCLK

NSEL

SCLK

NSEL

30

Rev 1.0

Si4x55-C

6. Data Handling and Packet Handler

6.1. RX and TX FIFOs

Two 64-byte FIFOs are integrated into the chip, one for RX and one for TX. Writing to command register 66h loads

data into the TX FIFO and reading from command register 77h reads data from the RX FIFO. For packet lengths

greater than 64 bytes, RX_FIFO_ALMOST_FULL and TX_FIFO_ALMOST_EMPTY status bits and interrupts can

be used to manage the FIFO. The threshold value for these can be configured via the WDS radio configuration

application GUI. The maximum payload length supported in packet handler mode is 255 bytes.

6.2. Packet Handler

The Si4x55 includes integrated packet handler features such as preamble and sync word detection as well as CRC

calculation. This allows the chip to qualify and synchronize with legitimate transmissions independent of the

microcontroller. These features can be enabled using the RCA. In this setup, the preamble and sync word length

can be modified and the sync word pattern can be selected. If the preamble is greater than or equal to 4 bytes, the

device uses the preamble detection circuit with a 2-byte detection threshold. If the preamble is less than 32 bits,

then at least two bytes of sync word are required plus at least one byte of 0101 pattern (3 bytes total). In this case,

preamble detection is skipped, and only sync word detection is used. For any combination of preamble and sync

word less than three bytes, the device will use direct mode. The general packet structure is shown in Figure 18.

The EZConfig setup also provides the option to select a variable packet length. With this setting, the receiver is not

required to know the packet length ahead of time. The transmitter sends the length of the packet immediately after

the sync word. The packet structure for variable length packets is shown in Figure 19.

Preamble

0 – 255 Bytes

Sync Word

1 – 4 Bytes

Data

1 – 255 Bytes

CRC

2 Bytes

Figure 18. Packet Structure for Fixed Packet Length

Preamble

0 – 255 Bytes

Sync Word

1 – 4 Bytes

Length

1 Byte

Data

1 – 255 Bytes

CRC

2 Bytes

Figure 19. Packet Structure for Variable Packet Length

6.3. Direct Mode

In direct mode, the packet handler (including FIFO) is bypassed, and the host MCU must feed the data stream to

the device in TX mode and read out the data stream in RX mode via GPIOs. The host MCU will process the data

and perform packet handler functions. This is commonly used to support legacy implementations where host MCU

software exists or to support non-standard packet structures. Some examples are packets with non 1010 preamble

pattern, no preamble or sync word, or sync word with no edge transitions. WDS provides example projects to

support both packet handler and direct modes.

Rev 1.0

31

Si4x55-C

7. Pin Descriptions

GND

SDN

RXp

RXn

TX

1

2

3

4

5

6

20 19 18 17 16 nSEL

15 SDI

14 SDO

Si4x55

13 SCLK

12 nIRQ

GND

7

8

9

10 11 GPIO1

Pin Name

I/O

GND Ground

Description

1

GND

Shutdown (0 – V V) – SDN=1, part will be in shutdown mode and contents of all

DD

2

SDN

I

registers are lost. SDN=0, all other modes

Si4455: Differential RF receiver input

Si4055: No Connect

3

RXp

I

Si4355: Differential RF receiver input

Si4455: Differential RF receiver input

Si4055: No Connect

Si4355: Differential RF receiver input

Si4455: Transmit RF output

4

5

RXn

I

TX

O

Si4055: Transmit RF output

Si4355: No Connect

6

7

GND

GND Ground

V

Supply voltage

DD

8

DD

9

GND

GND Ground

10

11

GPIO0

GPIO1

I/O

General Purpose Digital I/O

Interrupt Status Output – nIRQ = 0, interrupt event has occurred. Read interrupt

status for event details

12

13

14

15

16

nIRQ

SCLK

SDO

SDI

O

I

Serial Clock Input (0 – V V): Provides serial data clock for 4-line serial data bus

DD

Serial Data Output (0 – V V): Provides serial data readback function of internal

DD

O

I

control registers

Serial Data Input (0 – V V): Serial data stream input for 4-line serial data bus

DD

Serial Interface Select Input (0 – V V): Provides select/enable function for 4-line

DD

nSEL

I

serial data bus

32

Rev 1.0

Si4x55-C

Pin Name

I/O

Description

17

XOUT

O

Crystal Oscillator Output

Crystal Oscillator Input: No dc bias required, but if used, should be set to 0.7 V.

Also used for external TCXO input.

18

XIN

I

19

20

GPIO2

GPIO3

I/O

General Purpose Digital I/O

The exposed metal paddle on the bottom of the package supplies the RF and cir-

cuit ground(s) for the entire chip. It is very important that a good solder connection

is made between this exposed metal paddle and the ground plane of the underly-

ing PCB.

PKG PADDLE_GND GND

Rev 1.0

33

Si4x55-C

8. Ordering Information

*

Description

Package Type

Operating

Temperature

Part Number

Si4455-C2A-GM

Si4355-C2A-GM

Si4055-C2A-GM

EZRadio Transceiver

EZRadio Receiver

EZRadio Transmitter

3x3 QFN-20

Pb-free

–40 to 85 °C

3x3 QFN-20

Pb-free

3x3 QFN-20

Pb-free

*Note: Add an “R” at the end of the device part number to denote tape and reel option.

34

Rev 1.0

Si4x55-C

9. Package Outline

Figure 20. 20-pin QFN Package

Rev 1.0

35

Si4x55-C

Table 15. Package Diagram Dimensions

Dimension

Min

0.80

0.00

—

Nom

0.85

Max

0.90

0.05

—

A

A1

A2

A3

b

0.035

0.65

0.203 REF

0.25

0.20

0.25

0.30

0.35

b1

D

0.30

3.00 BSC.

0.50 BSC.

0.515 BSC.

1.70

E

e

e1

J

1.60

0.35

0.25

1.80

0.45

0.35

K

1.70

L

0.40

L1

aaa

bbb

ccc

ddd

eee

0.30

0.10

0.08

0.10

Notes:

1. All dimensions shown are in millimeters (mm) unless otherwise noted.

2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.

3. The drawing complies with JEDEC MO-220.

4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification

for Small Body Components.

36

Rev 1.0

Si4x55-C

10. PCB Land Pattern

Figure 21. 20-pin QFN PCB Land Pattern

Table 16. PCB Land Pattern Dimensions

Dimension

C1

MIN

MAX

3.00

C2

E

0.50 REF

X1

X2

Y1

Y2

Y3

f

0.25

1.65

0.85

1.65

0.37

0.35

1.75

0.95

1.75

0.47

2.40 REF

c

0.25

0.35

Note: All dimensions shown are in millimeters (mm) unless otherwise noted.

Rev 1.0

37

Si4x55-C

11. Top Marking

11.1. Si4x55 Top Marking

Figure 22. Si4x55 Top Marking

11.2. Top Marking Explanation

Mark Method:

Laser

Line 1 Marking:

Part Number

455A = Si4455-C2A

055A = Si4055-C2A

355A = Si4355-C2A

Firmware Revision

TTTT = Trace Code

A = C2A

Line 2 Marking:

Line 3 Marking:

Internal tracking number

Circle = 0.5 mm Diameter

(Bottom-Left Justified)

Y = Year

WW = Workweek

Assigned by the Assembly House. Corresponds to the last

significant digit of the year and work week of the mold date.

38

Rev 1.0

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code libraries & more. Available

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Disclaimer

Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers

using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific

device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories

reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy

or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply

or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific

written consent of Silicon Laboratories. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected

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thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZMac®, EZRadio®, EZRadioPRO®, DSPLL®, ISOmodem ®, Precision32®, ProSLIC®, SiPHY®,

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型号：	Si4455-C2A-GM
厂家：	SILICON
描述：	EASY-TO-USE, LOW-CURRENT OOK/(G)FSK SUB-GHZ TRANSCEIVER, TRANSMITTER, AND RECEIVER 电信电信集成电路
文件：	总39页 (文件大小：1244K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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