Si4438
H
I G H
- P
ERFORMANCE
, L
O W
-C
U R R E N T
T
RANSCEIVER
Features
Frequency
Excellent selectivity performance
range = 425–525 MHz
58 dB adjacent channel
75 dB blocking at 1 MHz
Receive sensitivity = –124 dBm
Antenna diversity and T/R switch
Modulation
control
(G)FSK
Highly configurable packet handler
OOK
Max output power
TX and RX 64 byte FIFOs
+20 dBm
Auto frequency control (AFC)
Low active power consumption
Automatic gain control (AGC)
14 mA RX
Low BOM
Ultra low current powerdown
Low battery detector
modes
Temperature sensor
30 nA shutdown, 50 nA standby
20-Pin QFN package
Data rate = 100 bps to 500 kbps
IEEE 802.15.4g ready
Fast wake and hop times
China regulatory
Power supply = 1.8 to 3.6 V
Pin Assignments
GPIO3
GPIO2
XOUT
15 nSEL
14 SDI
13 SDO
12 SCLK
7
TXRamp
8
VDD
9
GPIO0
10 11 nIRQ
GPIO1
GND
XIN
SDN
1
20 19 18 17 16
RXp 2
RXn 3
TX 4
NC 5
Applications
China smart meters
GND
PAD
Description
Silicon Laboratories' Si4438 is a high-performance, low-current
transceivers covering the sub-GHz frequency bands from 425 to
525 MHz. The Si4438 is targeted at the Chinese smart meter market and
is especially suited for electric meters. This device is footprint- and
pin-compatible with the Si446x radios, which provide industry-leading
performance for worldwide sub-GHz applications. The radios are part of
the EZRadioPRO
®
family, which includes a complete line of transmitters,
receivers, and transceivers covering a wide range of applications. All
parts offer outstanding sensitivity of –124 dBm while achieving extremely
low active and standby current consumption. The 58 dB adjacent channel
selectivity with 12.5 kHz channel spacing ensures robust receive
operation in harsh RF conditions. The Si4438 offers exceptional output
power of up to +20 dBm with outstanding TX efficiency. The high output
power and sensitivity results in an industry-leading link budget of 144 dB
allowing extended ranges and highly robust communication links.
6
VDD
Patents pending
Rev 1.0 6/14
Copyright © 2014 by Silicon Laboratories
Si4438
Si4438
Functional Block Diagram
GPIO3 GPIO2
Loop
Filter
VCO
FBDIV
TX DIV
SDN
RF
PKDET
LNA
PGA
LO
Gen
IF
PKDET
MODEM
FIFO
Packet
Handler
nSEL
SDI
SDO
SCLK
nIRQ
SPI Interface
Controller
Frac-N Div
30 MHz XO
Bootup
OSC
PFD / CP
XIN XOUT
RXP
RXN
ADC
TX
PA
PowerRamp
Cntl
PA
LDO
LDOs
POR
LBD
32K LP
OSC
VDD
Digital
Logic
VDD
TXRAMP
GPIO0 GPIO1
Product
Si4438
Freq. Range
425–525 MHz
Max Output
Power
+20 dBm
TX Current
75 mA
RX Current
14 mA
2
Rev 1.0
Si4438
T
ABLE
Section
OF
C
ONTENTS
Page
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3. Controller Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1. Serial Peripheral Interface (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2. Fast Response Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
3.3. Operating Modes and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.4. Application Programming Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.5. Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.6. GPIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4. Modulation and Hardware Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.1. Modulation Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2. Hardware Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3. Preamble Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5. Internal Functional Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.1. RX Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2. RX Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.3. Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
5.4. Transmitter (TX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
5.5. Crystal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
6. Data Handling and Packet Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
6.1. RX and TX FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.2. Packet Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
7. RX Modem Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8. Auxiliary Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.1. Wake-up Timer and 32 kHz Clock Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.2. Low Duty Cycle Mode (Auto RX Wake-Up) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
8.3. Temperature, Battery Voltage, and Auxiliary ADC . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.4. Low Battery Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
8.5. Antenna Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9. Pin Descriptions: Si4438 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
10. Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
11. Package Outline: Si4438 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
12. PCB Land Pattern: Si4438 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
13. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
13.1. Si4438 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
13.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Rev 1.0
3
Si4438
1. Electrical Specifications
Table 1. DC Characteristics
*
Parameter
Supply Voltage
Range
Symbol
V
DD
RC Oscillator, Main Digital Regulator,
and Low Power Digital Regulator OFF
Register values maintained and RC
oscillator/WUT OFF
RC Oscillator/WUT ON and all register values main-
tained, and all other blocks OFF
Sleep current using an external 32 kHz crystal.
Low battery detector ON, register values maintained,
and all other blocks OFF
Crystal Oscillator and Main Digital Regulator ON,
all other blocks OFF
RX Tune
TX Tune
+20 dBm output power, class-E match, 490 MHz,
3.3 V
Test Condition
Min
1.8
—
—
—
—
—
—
—
—
—
—
Typ
3.3
30
50
900
1.7
1
1.8
7.2
8
14
75
Max
3.6
—
—
—
—
—
—
—
—
—
—
Unit
V
nA
nA
nA
µA
µA
mA
mA
mA
mA
mA
Power Saving Modes I
Shutdown
I
Standby
I
SleepRC
I
SleepXO
I
Sensor
-LBD
I
Ready
TUNE Mode Current
RX Mode Current
TX Mode Current
(Si4438)
I
Tune_RX
I
Tune_TX
I
RXH
I
TX_+20
*Note:
All minimum and maximum values are guaranteed by production test unless otherwise stated. All typical values apply at
VDD = 3.3 V and 25 °C unless otherwise stated.
4
Rev 1.0
Si4438
Table 2. Synthesizer AC Electrical Characteristics
1
Parameter
Synthesizer Frequency
Range (Si4438)
Synthesizer Frequency
Resolution
2
Synthesizer Settling Time
Symbol
F
SYN
F
RES-525
t
LOCK
425–525 MHz
Measured from exiting Ready mode with
XOSC running to any frequency.
Including VCO Calibration.
F
= 10 kHz, 460 MHz
F
= 100 kHz, 460 MHz
F
= 1 MHz, 460 MHz
F
= 10 MHz, 460 MHz
Test Condition
Min
425
—
—
Typ
—
14.3
50
Max
525
—
—
Unit
MHz
Hz
µs
Phase Noise
L(f
M
)
—
—
—
—
–106
–110
–123
–130
—
—
—
—
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
Notes:
1.
All minimum and maximum values are guaranteed by production test unless otherwise stated. All typical values apply
at VDD = 3.3 V and 25 °C unless otherwise stated.
2.
Default API setting for modulation deviation resolution is double the typical value specified.
Rev 1.0
5
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