CMT2157A
CMT2157A
240 – 960 MHz (G)FSK/OOK Stand-Alone Transmitter with Encoder
Features
Applications
Low-Cost Consumer Electronics Applications
Very Easy Development with RFPDK
Home and Building Automation
All Features Programmable
Remote Fan Controllers
Embedded EEPROM
Frequency Range: 240 to 960 MHz
Infrared Transmitter Replacements
FSK, GFSK and OOK Modulation
Industrial Monitoring and Controls
Symbol Rate:
Remote Lighting Control
0.5 to 100 ksps (FSK/GFSK)
Wireless Alarm and Security Systems
0.5 to 40 ksps (OOK)
Remote Keyless Entry (RKE)
Deviation: 1.0 to 200 kHz
Output Power: -10 to +13 dBm
Sleep Current: < 20 nA
Stand-Alone, No External MCU Control Required
Embedded 1920, 1527 and 2262 Data Encoder
Part Number
Frequency
Package
MOQ
Up to 7 Configurable Data Pins for Push Buttons
CMT2157A-ESR
868.35 MHz
T&R
2,500 pcs
LED Indicator for Low Battery Detection and Transmission
CMT2157A-ESB
868.35 MHz
Tube
1,000 pcs
Sync ID Auto-Study with CMOSTEK Receiver
FCC / ETSI Compliant
RoHS Compliant
14-pin SOP Package
Ordering Information
More Ordering Info: See Page 26
Descriptions
The CMT2157A is a true single-chip, highly flexible, high
performance, (G)FSK/OOK RF transmitter with embedded
data encoder ideally for 240 to 960 MHz wireless
applications. The device integrates a data encoder that is
not only compatible with the most common used encoding
SOP14
format of 1527 and 2262, but also a more efficient, flexible
and powerful format of 1920 designed by CMOSTEK. Up
to 7 configurable push buttons are supported in multiple
button modes. When pairing the device to CMOSTEK
LED
1
14
XTAL
VDD
2
13
CLK
GND
3
12
DATA
transmitter remotely by end customers. An embedded
RFO
4
11
K1
EEPROM allows the RF and encoder parameters to be
K7
5
10
K2
K6
6
9
K3
K5
7
8
K4
receiver, the synchronization ID can be programmed into
both
of
the
transmitter
and
receiver
during
the
manufacturing phase, or studied by the receiver from the
programmed into the chip using the CMOSTEK USB
Programmer and the RFPDK. Alternatively, in stock
product of 868.35 MHz is available for immediate demands
without
the
need
of
EEPROM
programming.
The
CMT2157A is part of the CMOSTEK NextGenRFTM family,
CMT2157A
together with CMT225x series receivers, they enable ultra
low cost, low power consumption RF links.
Copyright © By CMOSTEK
Rev 0.8 | Page 1/31
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CMT2157A
Typical Application
CMT2157A
X1
D1
VDD
1
ANT
XTAL
LED
2
L1
L2
C2
C0
C1
3
4
SW7
5
SW6
6
SW5
7
VDD
CLK
GND
DATA
RFO
U1
K1
K7
K2
K6
K3
K5
K4
14
J1
1
VDD
13
CLK
12
DATA
CLK
2
DATA
11
SW1
3
10
SW2
4
9
SW3
8
SW4
Note: Connector J1 is for
EEPROM Programming
Figure 1. CMT2157A Typical Application Schematic
Table 1. BOM of 433.92/868.35 MHz Typical Application
Value
Designator
Unit
Manufacturer
-
-
CMOSTEK
26
MHz
EPSON
Descriptions
433.92 MHz
U1
CMT2157A, 240 – 960 MHz (G)FSK/OOK
stand-alone transmitter with encoder
868.35 MHz
X1
±20 ppm, SMD32*25 mm crystal
C0
±20%, 0402 X7R, 25 V
uF
Murata GRM15
C1
±5%, 0402 NP0, 50 V
82
82
pF
Murata GRM15
C2
±5%, 0402 NP0, 50 V
9.1
3.9
pF
Murata GRM15
L1
±5%, 0603 multi-layer chip inductor
180
100
nH
Murata LQG18
L2
±5%, 0603 multi-layer chip inductor
22
5.1
nH
Murata LQG18
D1
D0603, red LED
-
-
-
Push buttons
-
-
-
SW[7:1]
0.1
Rev 0.8 | Page 2/31
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CMT2157A
Abbreviations
Abbreviations used in this data sheet are described below
AN
Application Notes
OBW
Occupied Bandwidth
BOM
Bill of Materials
OOK
On-Off Keying
BSC
Basic Spacing between Centers
PA
Power Amplifier
BW
Bandwidth
PC
Personal Computer
DC
Direct Current
PCB
Printed Circuit Board
EEPROM
Electrically Erasable Programmable Read-Only
PLL
Phase Lock Loop
Memory
PN
Phase Noise
ESD
Electro-Static Discharge
RBW
Resolution Bandwidth
ESR
Equivalent Series Resistance
RCLK
Reference Clock
FSK
Frequency Shift Keying
RF
Radio Frequency
GFSK
Gauss Frequency Shift Keying
RFPDK
RF Product Development Kit
GUI
Graphical User Interface
RoHS
Restriction of Hazardous Substances
IC
Integrated Circuit
Rx
Receiving, Receiver
LDO
Low Drop-Out
SOT
Small-Outline Transistor
Max
Maximum
TBD
To Be Determined
MCU
Microcontroller Unit
Tx
Transmission, Transmitter
Min
Minimum
Typ
Typical
MOQ
Minimum Order Quantity
XO/XOSC
Crystal Oscillator
NP0
Negative-Positive-Zero
XTAL
Crystal
Rev 0.8 | Page 3/31
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CMT2157A
Table of Contents
1. Electrical Characteristics ............................................................................................................................................ 5
1.1 Recommended Operating Conditions ................................................................................................................... 5
1.2 Absolute Maximum Ratings................................................................................................................................... 5
1.3 Transmitter Specifications ..................................................................................................................................... 6
1.4 Crystal Oscillator ................................................................................................................................................... 7
2. Pin Descriptions .......................................................................................................................................................... 8
3. Typical Performance Characteristics ......................................................................................................................... 9
4. Typical Application Schematics ............................................................................................................................... 10
4.1 Low-Cost Application Schematic ......................................................................................................................... 10
4.2 FCC/ETSI Compliant Application Schematic....................................................................................................... 11
5. Functional Descriptions ............................................................................................................................................ 12
5.1 Overview ............................................................................................................................................................. 12
5.2 Modulation, Frequency, Deviation and Symbol Rate .......................................................................................... 12
5.3 Embedded EEPROM and RFPDK ...................................................................................................................... 13
5.4 Power Amplifier ................................................................................................................................................... 15
5.5 PA Ramping ........................................................................................................................................................ 15
5.6 Working States .................................................................................................................................................... 16
5.7 The Encoder........................................................................................................................................................ 17
5.7.1 1920 Packet Structure............................................................................................................................................17
5.7.2 1527 Packet Structure............................................................................................................................................18
5.7.3 2262 Packet Structure............................................................................................................................................19
5.8 ID Study .............................................................................................................................................................. 20
5.9 Button Modes ...................................................................................................................................................... 21
5.9.1 Normal ......................................................................................................................................................................21
5.9.2 Matrix ........................................................................................................................................................................22
5.9.3 Toggle .......................................................................................................................................................................23
5.9.4 PWM .........................................................................................................................................................................23
5.10 LED Driving Capability ........................................................................................................................................ 24
5.11 Low Battery Detection (LBD) ............................................................................................................................... 24
5.12 Crystal Oscillator and RCLK................................................................................................................................ 24
6. Ordering Information ................................................................................................................................................. 26
7. Package Outline......................................................................................................................................................... 27
8. Top Marking ............................................................................................................................................................... 28
8.1 CMT2157A Top Marking ..................................................................................................................................... 28
9. Other Documentations .............................................................................................................................................. 29
10. Document Change List.............................................................................................................................................. 30
11. Contact Information .................................................................................................................................................. 31
Rev 0.8 | Page 4/31
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CMT2157A
1.
Electrical Characteristics
VDD = 3.3 V, TOP = 25 ℃, FRF = 433.92 MHz, output power is +10 dBm terminated in a matched 50 Ω impedance, unless
otherwise noted.
1.1 Recommended Operating Conditions
Table 2. Recommended Operation Conditions
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Operation Voltage Supply
VDD
1.8
3.6
V
Operation Temperature
TOP
-40
85
℃
Supply Voltage Slew Rate
1
mV/us
1.2 Absolute Maximum Ratings
Table 3. Absolute Maximum Ratings
Parameter
Symbol
Conditions
[1]
Min
Max
Unit
Supply Voltage
VDD
-0.3
3.6
V
Interface Voltage
VIN
-0.3
VDD + 0.3
V
Junction Temperature
TJ
-40
125
℃
Storage Temperature
TSTG
-50
150
℃
Soldering Temperature
TSDR
255
℃
Lasts at least 30 seconds
ESD Rating
Human Body Model (HBM)
Latch-up Current
@ 85 ℃
-2
2
kV
-100
100
mA
Note:
[1]. Stresses above those listed as “absolute maximum ratings” may cause permanent damage to the device. This is a stress
rating only and functional operation of the device under these conditions is not implied. Exposure to maximum rating
conditions for extended periods may affect device reliability.
Caution! ESD sensitive device. Precaution should be used when handling the device in order
to prevent permanent damage.
Rev 0.8 | Page 5/31
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CMT2157A
1.3 Transmitter Specifications
Table 4. Transmitter Specifications
Parameter
Symbol
[1]
Frequency Range
Conditions
FRF
Synthesizer Frequency
Resolution
Symbol Rate
FRES
SR
(G)FSK Modulation
Typ
240
Max
Unit
960
MHz
FRF ≤ 480 MHz
198
Hz
FRF > 480 MHz
397
Hz
FSK/GFSK
0.5
100
ksps
OOK
0.5
40
ksps
1
200
kHz
FDEV
Deviation Range
Min
Bandwidth-Time Product
BT
Maximum Output Power
POUT(Max)
GFSK modulation
+13
dBm
Minimum Output Power
POUT(Min)
-10
dBm
Output Power Step Size
PSTEP
PA Ramping Time[2]
tRAMP
Current Consumption
@ 433.92 MHz
Current Consumption[3]
@ 868.35 MHz
IDD-433.92
IDD-868.35
Sleep Current
ISLEEP
Frequency Tune Time
tTUNE
Phase Noise @ 433.92
MHz
Phase Noise @ 868.35
MHz
Harmonics Output for
[4]
433.92 MHz
PN433.92
PN868.35
H2433.92
H3433.92
0.5
-
1
0
OOK, 0 dBm
[3]
-
-
dB
1024
us
6
mA
OOK, +10 dBm
8.5
mA
OOK, +13 dBm
10.2
mA
FSK, 0 dBm
10.8
mA
FSK, +10 dBm
23.8
mA
FSK, +13 dBm
32
mA
OOK, 0 dBm
6.1
mA
OOK, +10 dBm
9.3
mA
OOK, +13 dBm
11.2
mA
FSK, 0 dBm
12.3
mA
FSK, +10 dBm
26.7
mA
FSK, +13 dBm
35.3
mA
20
nA
370
us
100 kHz offset from FRF
-80
dBc/Hz
600 kHz offset from FRF
-96
dBc/Hz
1.2 MHz offset from FRF
-108
dBc/Hz
100 kHz offset from FRF
-74
dBc/Hz
600 kHz offset from FRF
-90
dBc/Hz
1.2 MHz offset from FRF
-102
dBc/Hz
2nd harm @ 867.84 MHz, +13 dBm POUT
-52
dBm
-57
dBm
-68
dBm
-52
dBm
60
dB
rd
3 harm @ 1301.76 MHz, +13 dBm POUT
nd
Harmonics Output for
H2868.35
2
868.35 MHz [4]
H3868.35
3rd harm @ 2605.05 MHz, +13 dBm POUT
harm @ 1736.7 MHz, +13 dBm POUT
OOK Extinction Ration
Notes:
[1]. The frequency range is continuous over the specified range.
[2]. 0 and 2n us, n = 0 to 10, when set to “0”, the PA output power will ramp to its configured value in the shortest possible
time.
[3]. The working currents are tested with: 1527 packet format/Normal button mode/ 4 push buttons/Sync ID = 0/No LED.
[4]. The harmonics output is measured with the application shown as Figure 10.
Rev 0.8 | Page 6/31
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CMT2157A
1.4 Crystal Oscillator
Table 5. Crystal Oscillator Specifications
Parameter
[1]
Crystal Frequency
Symbol
Conditions
FXTAL
Min
26
Crystal Tolerance[2]
[3]
Load Capacitance
Crystal ESR
Typ
Max
Unit
26
26
MHz
±20
CLOAD
12
Rm
[4]
XTAL Startup Time
tXTAL
ppm
20
pF
60
Ω
400
us
Notes:
[1]. The CMT2157A can directly work with external 26 MHz reference clock input to XTAL pin (a coupling capacitor is
required) with amplitude 0.3 to 0.7 Vpp.
[2]. This is the total tolerance including (1) initial tolerance, (2) crystal loading, (3) aging, and (4) temperature dependence.
The acceptable crystal tolerance depends on RF frequency and channel spacing/bandwidth.
[3]. The required crystal load capacitance is integrated on-chip to minimize the number of external components.
[4]. This parameter is to a large degree crystal dependent.
Rev 0.8 | Page 7/31
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CMT2157A
2. Pin Descriptions
LED
1
14
XTAL
VDD
2
13
CLK
GND
3
12
DATA
RFO
4
11
K1
K7
5
10
K2
K6
6
9
K3
K5
7
8
K4
Figure 2. CMT2157A Pin Assignments
Table 6. CMT2157A Pin Descriptions
Pin Number
Name
I/O
Descriptions
1
LED
O
LED driver, active low
2
VDD
I
Power supply input
3
GND
I
Ground
4
RFO
O
Power amplifier output
5 - 11
K[7:1]
I
Push button 7 to 1
12
DATA
IO
13
CLK
I
14
XTAL
I
Data pin to access the embedded EEPROM, internally pulled up to VDD
Clock pin to access the embedded EEPROM, internally pulled up to VDD
26 MHz single-ended crystal oscillator input or
External 26 MHz reference clock input
Rev 0.8 | Page 8/31
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CMT2157A
3. Typical Performance Characteristics
Phase Noise @ 868.35 MHz
Phase Noise @ 433.92 MHz
15
20
13.4dBm
@ 433.92 MHz
10
-5
Power (dBm)
0
Power (dBm)
13.0 dBm
@ 868.35 MHz
5
-10
-20
-30
-15
-25
-35
-55.9 dBm
@ 869.55 MHz
-45
-40
-56.8 dBm
@ 435.12 MHz
-50
-55
-60
-65
432.42 432.72 433.02 433.32 433.62 433.92 434.22 434.52 434.82 435.12 435.42
866.85 867.1 867.35 867.6 867.85 868.1 868.35 868.6 868.85 869.1 869.35 869.6 869.85
Frequency (MHz)
Frequency (MHz)
Figure 4. Phase Noise, FRF = 433.92 MHz,
Figure 3. Phase Noise, FRF = 868.35 MHz,
POUT = +13 dBm, RBW = 10 kHz, Un-encoded
POUT = +13 dBm, RBW = 10 kHz, Un-encoded
FSK vs. GFSK
OOK Spectrum
20
20
10
10
0
0
Power (dBm)
Power (dBm)
FSK
-10
-20
-10
GFSK
-20
-30
-30
-40
-40
-50
-50
-60
433.62
433.72
433.82
432.92 433.12 433.32 433.52 433.72 433.92 434.12 434.32 434.52 434.72 434.92
433.92
434.02
434.12
434.22
Frequency (MHz)
Frequency (MHz)
Figure 5. OOK Spectrum,
Figure 6. FSK/GFSK Spectrum,
POUT = +10 dBm, tRAMP = 32 us
SR = 9.6 ksps, FDEV = 15 kHz
Spectrum of Various PA Ramping Options
POUT vs. VDD
10
16
Power (dBm)
-10
14
12
SR = 1.2 ksps
Power (dBm)
1024 us
512 us
256 us
128 us
64 us
32 us
0
-20
10
8
13 dBm
6
10 dBm
4
-30
0 dBm
2
-40
0
-2
-50
433.17
433.37
433.57
433.77
433.97
434.17
Frequency (MHz)
434.37
434.57
1.6
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
Supply Voltage (V)
Figure 7. Spectrum of PA Ramping,
Figure 8. Output Power vs. Supply
SR = 1.2 ksps, POUT = +10 dBm
Voltages, FRF = 433.92 MHz
Rev 0.8 | Page 9/31
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CMT2157A
4. Typical Application Schematics
4.1 Low-Cost Application Schematic
CMT2157A
X1
D1
VDD
1
ANT
2
L1
L2
C2
C0
C1
3
4
SW7
5
SW6
6
SW5
7
VDD
CLK
GND
DATA
RFO
14
XTAL
LED
U1
K1
K7
K2
K6
K3
K5
K4
J1
1
VDD
13
CLK
12
DATA
CLK
2
DATA
11
SW1
3
10
SW2
4
9
SW3
8
SW4
Note: Connector J1 is for
EEPROM Programming
Figure 9. Low-Cost Application Schematic
Notes:
1.
Connector J1 is a must for the CMT2157A EEPROM access during development or manufacture phase.
2.
The general layout guidelines are listed below. For more design details, please refer to “AN111 CMT215x Schematic and
PCB Layout Design Guideline”
Use as much continuous ground plane metallization as possible.
Use as many grounding vias (especially near to the GND pins) as possible to minimize series parasitic inductance
between the ground pour and the GND pins.
3.
Avoid using long and/or thin transmission lines to connect the components.
Avoid placing the nearby inductors in the same orientation to reduce the coupling between them.
Place C0 as close to the CMT2157A as possible for better filtering.
The table below shows the BOM of 433.92/868.35 MHz Low-Cost Application. For the BOM of more applications, please
refer to “AN111 CMT215x Schematic and PCB Layout Design Guideline”.
Table 7. BOM of 433.92/868.35 MHz Low-Cost Application
Value
Designator
Unit
Manufacturer
-
-
CMOSTEK
26
MHz
EPSON
Descriptions
433.92 MHz
U1
CMT2157A, 240 – 960 MHz (G)FSK/OOK
stand-alone transmitter with encoder
868.35 MHz
X1
±20 ppm, SMD32*25 mm crystal
C0
±20%, 0402 X7R, 25 V
uF
Murata GRM15
C1
±5%, 0402 NP0, 50 V
82
82
pF
Murata GRM15
C2
±5%, 0402 NP0, 50 V
9.1
3.9
pF
Murata GRM15
L1
±5%, 0603 multi-layer chip inductor
180
100
nH
Murata LQG18
L2
±5%, 0603 multi-layer chip inductor
22
5.1
nH
Murata LQG18
D1
D0603, red LED
-
-
-
Push buttons
-
-
-
SW[7:1]
0.1
Rev 0.8 | Page 10/31
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CMT2157A
4.2 FCC/ETSI Compliant Application Schematic
CMT2157A
X1
D1
VDD
1
ANT
2
L1
L2
L3
C3
C0
C1
3
4
C2
SW7
5
SW6
6
SW5
7
LED
XTAL
VDD
CLK
DATA
GND
RFO
U1
K1
K7
K2
K6
K3
K4
K5
J1
1
VDD
14
13
CLK
CLK
12
DATA
DATA
11
SW1
10
SW2
9
SW3
8
SW4
2
3
4
Note: Connector J1 is for
EEPROM Programming
Figure 10. FCC/ETSI Compliant Application Schematic
Notes:
1.
Connector J1 is a must for the CMT2157A EEPROM access during development or manufacture phase.
2.
The general layout guidelines are listed below. For more design details, please refer to “AN111 CMT215x Schematic and
PCB Layout Design Guideline”.
Use as much continuous ground plane metallization as possible.
Use as many grounding vias (especially near to the GND pins) as possible to minimize series parasitic inductance
between the ground pour and the GND pins.
3.
Avoid using long and/or thin transmission lines to connect the components.
Avoid placing the nearby inductors in the same orientation to reduce the coupling between them.
Place C0 as close to the CMT2157A as possible for better filtering.
The table below shows the BOM of 433.92/868.35 MHz FCC/ETSI Compliant Application. For the BOM of more
application, please refer to “AN111 CMT215x Schematic and PCB Layout Design Guideline”.
Table 8. BOM of 433.92/868.35 MHz FCC/ETSI Compliant Application
Value
Designator
Descriptions
Unit
433.92 MHz
U1
CMT2157A, 240 – 960 MHz (G)FSK/OOK
stand-alone transmitter with encoder
Manufacturer
868.35 MHz
-
-
CMOSTEK
26
MHz
EPSON
X1
±20 ppm, SMD32*25 mm crystal
C0
±20%, 0402 X7R, 25 V
uF
Murata GRM15
C1
±5%, 0402 NP0, 50 V
68
68
pF
Murata GRM15
C2
±5%, 0402 NP0, 50 V
15
10
pF
Murata GRM15
C3
±5%, 0402 NP0, 50 V
15
6.8
pF
Murata GRM15
L1
±5%, 0603 multi-layer chip inductor
180
100
nH
Murata LQG18
L2
±5%, 0603 multi-layer chip inductor
36
5.6
nH
Murata LQG18
L3
±5%, 0603 multi-layer chip inductor
18
6.8
nH
Murata LQG18
D1
D0603, red LED
-
-
-
Push buttons
-
-
-
SW[7:0]
0.1
Rev 0.8 | Page 11/31
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CMT2157A
5. Functional Descriptions
VDD
LDOs
GND
POR
Bandgap
XOSC
XTAL
LED Driver
LED
PA
RFO
VCO
PFD/CP
Loop
Filter
Frac-N DIV
Encoder
K[7:1]
Modulator
EEPROM
Ramp-control
K0
K0/DATA
CLK
Interface & Control Logics
Figure 11. CMT2157A Functional Block Diagram
5.1 Overview
The CMT2157A is a true single-chip, highly flexible, high performance, OOK RF transmitter with embedded data encoder ideal
for 240 to 960 MHz wireless applications. It is part of the CMOSTEK NextGenRFTM family, which includes a complete line of
transmitters, receivers and transceivers. The device integrates a data encoder that is not only compatible with the most
common used encoding format of 1527 and 2262, but also a more efficient, flexible and powerful format of 1920 designed by
CMOSTEK. Up to 7 configurable push buttons are supported in multiple button modes. The device is optimized for the low
system cost, low power consumption, battery powered application with its highly integrated and low power design.
The functional block diagram of the CMT2157A is shown in figure above. The CMT2157A is based on direct synthesis of the
RF frequency by means of a fully integrated low-noise fractional-N frequency synthesizer. It uses a 1-pin crystal oscillator
circuit with the required crystal load capacitance integrated on-chip to minimize the number of external components. Every
analog block is calibrated on each Power-on Reset (POR) to an internal reference voltage source. The calibration can help the
chip to finely work under different temperatures and supply voltages. The transmission is triggered by pressing the push
button(s). The data is modulated and sent out by a highly efficient PA which output power can be configured from -10 to +13
dBm in 1 dB step size. RF Frequency, PA output power and other product features can be programmed into the embedded
EEPROM by the RFPDK and USB Programmer. This saves the cost and simplifies the product development and
manufacturing effort. Alternatively, in stock product of 868.35 MHz is available for immediate demands with no need of
EEPROM programming. The CMT2157A operates from 1.8 to 3.6 V so that it can finely work with most batteries to their useful
power limits. It only consumes 26.7 mA when transmitting +10 dBm FSK signal at 868.35 MHz under 3.3 V supply voltage.
5.2 Modulation, Frequency, Deviation and Symbol Rate
The CMT2157A supports GFSK/FSK modulation with the symbol rate up to 100 ksps, as well as OOK modulation with the
symbol rate up to 40 ksps. The supported deviation of the (G)FSK modulation ranges from 1 to 200 kHz. It continuously covers
the frequency range from 240 to 960 MHz, including the license free ISM frequency band around 315 MHz, 433.92 MHz,
868.35 MHz and 915 MHz. The device contains a high spectrum purity low power fractional-N frequency synthesizer with
output frequency resolution better than 198 Hz when the frequency is less than 480 MHz, and is about 397 Hz when the
frequency is larger than 480 MHz. See Table 9 for the modulation, frequency, deviation and symbol rate specifications.
Rev 0.8 | Page 12/31
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CMT2157A
Table 9. Modulation, Frequency, Deviation and Symbol Rate
Parameter
Value
Unit
Modulation
(G)FSK/OOK
-
Frequency
240 to 960
MHz
Deviation
1 to 200
kHz
198
Hz
Frequency Resolution (FRF ≤ 480 MHz)
Frequency Resolution (FRF > 480 MHz)
397
Hz
Symbol Rate (FSK/GFSK)
0.5 to 100
ksps
Symbol Rate (OOK)
0.5 to 40
ksps
5.3 Embedded EEPROM and RFPDK
The RFPDK (RF Products Development Kit) is a very user-friendly software tool delivered for the user configuring the
CMT2157A in the most intuitional way. The user only needs to fill in/select the proper value of each parameter and click the
“Burn” button to complete the chip configuration. No register access and control is required in the application program. See
figure below for the accessing of the EEPROM and Table 10 for the summary of all the configurable parameters of the
CMT2157A on the RFPDK.
CMT2157A
RFPDK
EEPROM
CLK
Interface
DATA
CMOSTEK USB
Programmer
Figure 12. Accessing Embedded EEPROM
For more details of the CMOSTEK USB Programmer and the RFPDK, please refer to “AN113 CMT2150A/2250(1)A One-Way
RF Link Development Kits User’s Guide”. For the detail of CMT2157A configurations with the RFPDK, please refer to “AN142
CMT2157A Configuration Guideline”.
Table 10. Configurable Parameters in RFPDK
Category
Parameters
Descriptions
Default
To input a desired transmitting radio frequency in
Frequency
the range from 240 to 960 MHz. The step size is
868.35 MHz
0.001 MHz.
Modulation
The option is FSK or GFSK and OOK.
FSK
To select a proper transmitting output power from
RF Settings
Tx Power
-10 dBm to +14 dBm, 1 dBm margin is given
+13 dBm
above +13 dBm.
Xtal Cload
On-chip XOSC load capacitance options: from 10
to 22 pF.
15.00 pF
To determines the symbol rate of the transmitted
Symbol Rate
data: from 0.5 to 100 ksps in (G)FSK mode and
0.5 to 40 ksps in OOK mode.
Rev 0.8 | Page 13/31
2.4
Mode
Basic
Advanced
Basic
Advanced
Basic
Advanced
Basic
Advanced
Basic
Advanced
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CMT2157A
Category
Parameters
Deviation
PA Ramping
LED Driving
Capability
Descriptions
The FSK frequency deviation. The range is from
1 to 200 kHz.
To control PA output power ramp up/down time,
options are 0 and 2n us (n from 0 to 10).
This defines the driving current of the LED pin.
The options are: Disable, 5, 10, 15 or 20 mA.
Default
35 kHz
Mode
Basic
Advanced
0 us
Advanced
5 mA
Advanced
2.4 V
Advanced
This defines the Low Battery Detection threshold.
LBD Threshold
The options are: Disable, 1.7, 1.8, 1.9, 2.0, 2.1,
2.2, 2.3, 2.4, 2.5, 2.6, 2.7 or 2.8 V.
To select whether the frequency “Fo + Fdev”
Data
Representation
represent data 0 or 1. The options are:
0: F-low
0: F-high 1: F-low, or
1: F-high
Advanced
0: F-low 1: F-high.
Select the packet encoding format, the options
Encoder
are: 1920, 1527 and 2262. See Table 13, Table
14 and Table 15 for the configurable parameters
1527
Basic
Advanced
in each packet.
This tells the device how many symbols are used
to construct a single bit in the 1920 mode. The
Bit Format
options are: 3, 4, 5 or 6 sym/bit. The Bit Format is
3
fixed at 4 sym/bit in 1527 mode and 8 sym/bit in
Encoder
2262 mode. It is only available in 1920 mode.
Settings
This defines the minimum number of packet(s)
Number of
Packets
Basic
Advanced
being transmitted during each button pressing
action. It also defines the number of packet(s)
1
Advanced
consecutive transmitted packets. The unit is in
0 symbols of
Basic
symbol, the range is from 0 to 255 symbols of
zero
Advanced
being transmitted during each periodic
transmission. The range is from 1 to 256.
This defines the time interval amount two
Packet Interval
zero.
Select the button encoding mode, the options
are: Normal, Matrix, Toggle and PWM. For 1920
Button Mode
and 1527 format, all these button modes are
Normal
supported; For 2262 format, only Normal button
Basic
Advanced
mode is supported.
On/Off
Button(s)
Push Button
Settings
Select the numbers of on/off button for Toggle
and PWM button modes, the options are: Single
Single
or Separated.
Basic
Advanced
This option is only available in Normal Button
Number of
Mode, and Encoder is set to 1920 and 1527. It
Button(s)
defines the number of activated button(s) to be
4
Basic
Advanced
used in the application. The range is from 1 to 7.
Allow the user to select whether or not to inverse
Data Inversion
the transmitted data bits values in the Normal and
No
Advanced
Off
Advanced
Toggle Button Mode. The options are: No or Yes.
Periodic
Transmission
Turn on/off the periodic transmission mode of the
device. The options are: On or Off.
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CMT2157A
Category
Parameters
Descriptions
Default
Mode
1.000 s
Advanced
Off
Advanced
5s
Advanced
Pin 11 (K1)
Advanced
This parameter is only available when Periodic
Transmission is turned on. It defines the periodic
Periodic Time
time for transmitting a fixed set of data. The
range is from 2 to 7683.512 s, accurate to 3
decimal points. It is only available when Periodic
Transmission is on.
Turn on/off the Sync ID study function, the
ID Study
options are: On or Off. The ID Study is only
supported in 1920 and 1527 mode.
This parameter is only available when ID Study is
Study Trigger
Time
turned on. It defines the time from the instance of
pressing the study button to the instance at which
the device starts to transmit the study packets.
The range is from 1 to 15 second(s).
Study Settings
This parameter is only available when ID Study is
turned on. It defines which button is used to
Study Button
trigger the transmission of the study packets. The
options are the current buttons used in the Push
Button Settings.
This parameter is only available when ID Study is
Study Power
turned on. It defines the PA power when the
device is transmitting the study packets. The
-6 dBm
Basic
Advanced
range is from –10 to +14 dBm.
5.4 Power Amplifier
A highly efficient single-ended Power Amplifier (PA) is integrated in the CMT2157A to transmit the modulated signal out.
Depending on the application, the user can design a matching network for the PA to exhibit optimum efficiency at the desired
output power for a wide range of antennas, such as loop or monopole antenna. Typical application schematics and the
required BOM are shown in “Chapter 4 Typical Application Schematic”. For the schematic, layout guideline and the other
detailed information please refer to “AN111 CMT215x Schematic and PCB Layout Design Guideline”.
The output power of the PA can be configured by the user within the range from -10 dBm to +13 dBm in 1 dB step size using
the CMOSTEK USB Programmer and RFPDK.
5.5 PA Ramping
When the PA is switched on or off quickly, its changing input impedance momentarily disturbs the VCO output frequency. This
phenomenon is called VCO pulling, and it manifests as spectral splatter or spurs in the output spectrum around the desired
carrier frequency. By gradually ramping the PA on and off, PA transient spurs are minimized. The CMT2157A has built-in PA
ramping configurability with options of 0, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 and 1024 us, as shown in Figure 13. When the
option is set to “0”, the PA output power will ramp up to its configured value in the shortest possible time. The ramp down time
is identical to the ramp up time in the same configuration.
CMOSTEK recommends that the maximum symbol rate should be no higher than 1/2 of the PA ramping “rate”, as shown in the
formula below:
SRMax ≤ 0.5 * (
1
tRAMP
Rev 0.8 | Page 15/31
)
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CMT2157A
In which the PA ramping “rate” is given by (1/tRAMP). In other words, by knowing the maximum symbol rate in the application,
the PA ramping time can be calculated by:
tRAMP ≤ 0.5 * (
1
)
SRMAX
The user can select one of the values of the tRAMP in the available options that meet the above requirement. If somehow the
tRAMP is set to be longer than “0.5 * (1/SRMax)”, it will possibly bring additional challenges to the OOK demodulation of the Rx
RFO Amplitude
device. For more detail of calculating tRAMP, please refer to “AN142 CMT2157A Configuration Guideline”.
0 us
1 us
2 us
4 us
8 us
512 us
1024 us
Data
Time
Logic 1
Logic 0
Time
Figure 13. PA Ramping Time
5.6 Working States
The CMT2157A has following 4 different working states: SLEEP, XO-STARTUP, TUNE and TRANSMIT. The device stays in
the SLEEP state when no transmission is performed. Once the button(s) is/are pressed, the device goes through the sequence
of SLEEP XO-STARTUP TUNE TRANSMIT to transmit the data. After the transmission the device goes back to the
SLEEP state. When the device works in the periodic transmission mode, the device periodically wakes up from the SLEEP
state, goes the same sequence, performs the transmission and goes back to the SLEEP state. All the details of push button(s)
function and periodic transmission can be referred to “AN142 CMT2157A Configuration Guideline”.
SLEEP
When the CMT2157A is in the SLEEP state, all the internal blocks are turned off and the current consumption is minimized to
20 nA typically.
XO-STARTUP
Once the CMT2157A received the valid control signal, it will go into the XO-STARTUP state, and the internal XO starts to work.
The user has to wait for the tXTAL to allow the XO to get stable. The tXTAL is to a large degree crystal dependent. A typical value
of tXTAL is provided in the Table 11.
TUNE
The frequency synthesizer will tune the CMT2157A to the desired frequency in the time tTUNE. The PA can be turned on to
transmit the data generated by the embedded encoder only after the TUNE state is done.
TRANSMIT
The CMT2157A starts to modulate and transmit the data. The data packets being transmitted are generated by the embedded
encoder, and they are determined by the encoder selected, the button mode and the button being pressed.
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CMT2157A
Table 11. Main Timing Spec in Different Working States
Parameter
XTAL Startup Time
Symbol
[1]
Time to Tune to Desired Frequency[2]
Min
Typ
Max
Unit
tXTAL
400
us
tTUNE
370
us
Notes:
[1]. This parameter is to a large degree crystal dependent.
[2]. From XO stable to ready to transmit.
5.7 The Encoder
The device supports 3 types of encoding formats: 1920, 1527 and 2262. The packets of these 3 modes have different
structures which will be introduced in the below sub-sections. The table below summarizes the major features of the 3
encoding formats.
Table 12. Feature Summary of the 3 Encoding Formats
Bit Format
Sync ID Length
Data Length
(sym/bit)
(bits)
(bits)
1920
3/4/5/6
1 – 32
1–7
Support
Support
All
1527
4
20
1–7
NA
Support
All
2262
8
6 – 11
1–6
NA
Not Support
Normal Mode
Format
CRC
ID Study
Button Modes[1]
Note:
[1]. Button Modes include Normal Mode, Matrix Mode, Toggle Mode and PWM Mode.
All the details of these 3 types of encoding formats are given in the document “AN142 CMT2157A Configuration Guideline”. The
following sections only give the abstracts of these formats. In the below explanations, some elements in the packet are measured
in the unit of “symbol”, while some of them are measured in the unit of “bit”. For those which have the unit of “bit”, one “bit” is
constructed (encoded) by several “symbols”. In the figures, “SYM” represents the word “symbol”.
5.7.1 1920 Packet Structure
Two types of packet structures are supported for 1920 format: Normal Packet and Study Packet. The following configurable
parameters are shared by the two structures.
Table 13. Configurable Parameters in 1920 Packet
Parameter
Preamble
Address (Sync ID)
Length
Address (Sync ID)
Value
Descriptions
The size of the valid preamble, the options are: None or
16-symbol.
The range of the Sync ID Length is from 1 to 32 bits.
The value of the Sync ID has the range from 0 to 2Length-1.
Default
None
32-bit
0
Mode
Basic
Advanced
Basic
Advanced
Basic
Advanced
Normal Packet
The normal packet is used to control the data pins of the CMOSTEK receiver CMT2250A or PWM output of the CMT2251A. It
contains a 16-symbol Preamble, a 32-symbol Head_N (which indicates that the current packet is a normal packet rather than a
study packet), a Sync ID, a Configurable Data Field and an 8-symbol CRC.
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CMT2157A
Head_N
32 symbols
Preamble
16 symbols
D1
1 bit
D0
1 bit
Address (Sync ID)
configurable 1-32 bits
CRC
8 symbols
D3
1 bit
D2
1 bit
Figure 14. 1920 Normal Packet Structure
Study Packet
The study packet is used for the receiver to learn the Sync ID from the CMT2157A in order to pair the two devices. It contains
an optional Preamble, a 32-symbol Head_S, a Sync ID and an 8-symbol CRC.
Preamble
(Optional)
16-symbol
Head_S
32-symbol
Address (Sync ID)
configurable 1-32 bits
CRC
8-symbol
Figure 15. 1920 Study Packet Structure
Bit Format
In 1920 packet, a single bit can be constructed (encoded) by 3, 4, 5 or 6 symbols. The user can select the desired value of the
“Bit Format” parameter on the RFPDK. Please note that only the Sync ID field and the D0, D1, D2, D3, D4, D5, D6 have the
unit of “bit”.
1 SYM
2 SYM
2 SYM
1 SYM
3 Symbols/Bit
Bit 1
Bit 0
3 SYM
1 SYM
1 SYM
3 SYM
4 Symbols/Bit
Bit 1
Bit 0
2 SYM
3 SYM
3 SYM
2 SYM
5 Symbols/Bit
Bit 1
1 SYM 1 SYM
Bit 0
2 SYM
2 SYM
1 SYM 1 SYM 1 SYM
3 SYM
6 Symbols/Bit
Bit 1
Bit 0
Figure 16. 1920 Bit Format Options
5.7.2 1527 Packet Structure
Two types of packet structures are supported for 1527 format: Normal Packet and Study Packet. The following configurable
parameter is shared by the two structures.
Table 14. Configurable Parameters in 1527 Packet
Parameter
Address (Sync ID)
Value
Descriptions
Default
20
The range of the Sync ID value is from 0 to 2 -1. This is
because the Sync ID Length is fixed at 20 for 1527.
0
Mode
Basic
Advanced
In the traditional 1527 format, 8 OSC clocks are equal to 1 LCK, 4 LCK are equal to 1 symbol. By using the CMT2250A pairing
with CMT2157A, the user does not need to adjust the OSC to determine the symbol rate, because the symbol rate is directly
programmed. The Bit Format is fixed at 4 symbols (16 LCK) per bit.
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CMT2157A
Normal Packet
The traditional 1527 packet contains a 32-symbol Sync, a 20-bit Address (Sync ID) and 4-bit Data. CMOSTEK has defined a
1527 Study Packet to support the ID study in 1527 mode. The traditional packet introduced here is called the “Normal Packet”.
Address (Sync ID)
configurable 20 bits
Sync
32 symbols
D0
1 bit
D1
1 bit
D2
1 bit
D3
1 bit
Figure 17. 1527 Normal Packet Structure
Study Packet
The 1527 Study packet contains a 32-symbol Head_S and a 20-bit Address (Sync ID), as shown below.
Head_S
32-symbol
Address (Sync ID)
20 bits
Figure 18. 1527 Study Packet Structure
Bit Format
In 1527 packet, a single bit is constructed by 4 symbols, as shown below. The user can select the desired value of the “Bit
Format” parameter on the RFPDK. Please note that only the Sync ID field and the D0, D1, D2, D3, D4, D5, D6 field have the
unit of “bit”.
3 SYM
1 SYM
1 SYM
3 SYM
Bit 0
Bit 1
Figure 19. 1527 Bit Format Options
5.7.3 2262 Packet Structure
ID Study is not supported in 2262 mode. Only one packet structure is supported.
Table 15. Configurable Parameters in 2262 Packet
Parameter
Descriptions
Default
Mode
This is the range of the Sync ID Length. The range is from
Address (Sync ID)
6 to 11 bits. This parameter also defines the number of
Length
data bits, because the total number of Sync ID and Data
8-bit
Basic
Advanced
bits is fixed at 12.
Address (Sync ID)
Value
The value of each bit of the Sync ID can only be
represented by 0, 1 or f.
00000000
Basic
Advanced
In the traditional 2262 format, 4 OSC clocks (1 OSC clock cycle is notated as 1 α) are equal to 1 symbol. By using the
CMOSTEK products, the user does not need to adjust the OSC to define the symbol rate, because the symbol rate is directly
programmed. The Bit Format is fixed at 8 symbols per bit.
Normal Packet
The traditional 2262 packet contains an Address (Sync ID), a Data, and a 32-symbol Sync.
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CMT2157A
Address (Sync ID)
configurable 8-11 bits
Data
4-1 bit(s)
Sync
32 symbols
Figure 20. 2262 Packet Structure
Bit Format
In 2262 packet, a single bit is constructed by 8 symbols, as shown below. Please note that only the Address (Sync ID) field and
the Data field have the unit of “bit”. In the below diagram, 1 OSC clock cycle is notated as 1 α referring to the original 2262
timing descriptions.
3 SYM
(12 α)
1 SYM
(4 α)
3 SYM
(12 α)
1 SYM
(4 α)
1 SYM
(4 α)
3 SYM
(12 α)
3 SYM
(12 α)
3 SYM
(12 α)
Bit 0
Bit 1
1 SYM
(4 α)
1 SYM
(4 α)
3 SYM
(12 α)
1 SYM
(4 α)
Bit f
Figure 21. 2262 Bit Format Options
5.8 ID Study
The ID Study function, which is supported in 1920 and 1527 modes, allows the receiver to study the Sync ID sent by the
CMT2157A. Since then, the receivers Sync ID is identical to that of the CMT2157A and therefore two devices are paired. The
lengths of the Sync ID are different in the different packet formats. In 1920 format, it is from 1 to 32 bits. In 1527 format, it is
fixed at 20 bits.
The ID Study is initialized by the CMT2157A. It is done by executing the following steps. An example of CMT2157A paring with
CMT2250/51A is given below.
1.
Press the Study Button on the CMT2157A and hold it over the time defined by the “Study Trigger Time”.
2.
CMT2157A starts to transmit the Study Packets, wait 1-2 seconds then release the Study Button.
3.
Try to press a certain button on the CMT2157A to check if the CMT2250/51A react correctly.
The figure below shows the timing characteristic after pressing down a study button. The Study Power is always independently
configure from the TX Power. In this example, the Study Power is set smaller than the TX Power.
One Normal
Packet
Packet
Interval
TX Power = 0 dBm
One Study
Packet
Packet
Interval
Study Power = -6 dBm
time
Study Time
(Default is 5 s)
Study Button
Pressed
Study Button
Released
Figure 22. Timing of Study Button Pressing Event
More information about the ID Study can be found in the document “AN142 CMT2157A Configuration Guideline”.
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CMT2157A
5.9 Button Modes
The button modes define the functions of the input pins K1 – K7. The CMT2157A supports 4 different button modes: Normal,
Matrix, Toggle and PWM, which are configured on the RFPDK. The following sections give the abstract of each button mode.
All the details of the button modes are given in the document “AN142 CMT2157A Configuration Guideline”.
5.9.1 Normal
The Normal Button Mode is supported in 1920, 1527 and 2262 format. In this mode, the buttons are directly mapped to the
data field of the packet. Multiple buttons can be pressed at the same time. For 1920 and 1527, the largest number of buttons is
7 which are defined by the parameter “Number of Button(s)”. For 2262, the largest number of buttons is 6, which is determined
by the Sync ID Length. The figure below gives an example which 4 push button keys are selected.
LED
1
14
XTAL √ XTAL
VDD √ VDD
2
13
CLK
√ CLK
GND √ GND
3
12
K0
× NC
RFO √ RFO
4
11
K1
√ D0
LED √
NC ×
K7
5
10
K2
√ D1
NC ×
K6
6
9
K3
√ D2
NC ×
K5
7
8
K4
√ D3
Figure 23. Normal Button Mode
In normal button mode, the number of button(s) is used to determines the number of data bits in a packet. The table below
shows when 4 buttons are used and the pins K1 – K4 are mapped to the data D0 – D3, “1” in the Push Buttons section means
the corresponding button(s) is/are pressed, while the “1” in the Data Bits section means logic “1” to be transmitted.
Table 16. Mapping from K1-K4 to D0-D3 in Normal Button Mode
Push Buttons
The Data Bits
K1
K2
K3
K4
D0
D1
D2
D3
1
0
0
0
1
0
0
0
0
1
0
0
0
1
0
0
1
1
0
0
1
1
0
0
0
0
1
0
0
0
1
0
1
0
1
0
1
0
1
0
0
1
1
0
0
1
1
0
1
1
1
0
1
1
1
0
0
0
0
1
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
1
1
0
1
1
1
0
1
0
0
1
1
0
0
1
1
1
0
1
1
1
0
1
1
0
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
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CMT2157A
5.9.2 Matrix
The Matrix Button Mode is supported in 1920 and 1527 format. In the Matrix Button Mode, the number of buttons is fixed at 5.
On the RFPDK, it can be seen that the 5 buttons are assigned to pin 11 (K1) – pin 7 (K5). In this mode, at most two buttons can
be pressed at the same time. The figure below gives an example of Matrix mode push button arrangement.
LED
1
14
XTAL √ XTAL
VDD √ VDD
2
13
CLK
√ CLK
GND √ GND
3
12
K0
× NC
RFO √ RFO
4
11
K1
√ B0
LED √
NC ×
K7
5
10
K2
√ B1
NC ×
K6
6
9
K3
√ B2
B4 √
K5
7
8
K4
√ B3
Figure 24. Matrix Button Mode
The user is able to use the 5 buttons K1(B0) – K5(B4) to generate different combinations of the data D0 – D3 to be transmitted.
The number of data bits to be transmitted is fixed at 4. The table below shows the matrix. For the K1 – K5 buttons, “1” in the
Push Buttons section means the corresponding button(s) is/are pressed down, while the “1” in the Data Bits section means a
logic “1” to be transmitted..
Table 17. Mapping from K1-K5 to D0-D3 in Matrix Button Mode
Push Buttons
K1
K2
K3
The Data Bits
K4
K5
D0
D1
D2
D3
1
0
0
0
0
1
0
0
0
0
1
0
0
0
0
1
0
0
0
0
1
0
0
1
1
0
0
0
0
0
1
0
0
0
1
0
0
0
0
0
1
1
0
1
0
1
1
0
0
0
0
1
1
0
1
0
1
0
0
1
1
1
0
1
0
0
1
0
0
0
0
1
1
0
0
0
1
1
0
0
1
0
1
1
0
0
0
1
0
1
0
1
0
1
0
1
1
0
1
0
1
0
0
1
0
0
1
1
0
0
1
1
0
1
0
1
1
0
0
1
0
1
0
1
1
1
0
0
0
1
1
1
1
1
1
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CMT2157A
5.9.3 Toggle
The Toggle Button Mode is supported in 1920 and 1527. In this mode, 5 or 6 buttons are used. Four buttons directly mapped to
the data D0 – D3 are used to control the data. Besides, a single button or two separated buttons used to turn on/off the data
can be chosen by the parameter “On/Off Button(s)”. In this mode, only one button can be pressed at the same time. Pin 12 (K0)
and Pin 5 (K7) are never used in this mode. The figure below gives examples of the pin functions in Toggle mode.
LED
1
14
XTAL √ XTAL
VDD √ VDD
2
13
CLK
GND √ GND
3
12
RFO √ RFO
4
LED √
LED
1
14
XTAL √ XTAL
√ CLK
VDD √ VDD
2
13
CLK
√ CLK
K0
× NC
GND √ GND
3
12
K0
× NC
11
K1
√ ON/OFF
RFO √ RFO
4
11
K1
√ ON
LED √
NC ×
K7
5
10
K2
× NC
NC ×
K7
5
10
K2
√ OFF
D3 √
K6
6
9
K3
√ D0
D3 √
K6
6
9
K3
√ D0
D2 √
K5
7
8
K4
√ D1
D2 √
K5
7
8
K4
√ D1
Figure 25. Toggle Button Mode with Single (left) and Separated (right) ON/OFF Button(s)
For the 4 data buttons mapped to D0 – D3, every time a button is pressed, the generated data bit toggles. For example, if the
default value of D1 is 0, press K4 down, the D1 is set to 1 in the current transmission, release the K4 and press it down again,
the D1 is set to 0 in the current transmission, and so on. This is what it means by “Toggle”. See the table below for the
examples of toggle button mode
Table 18. Examples of the Toggle Button Mode
On/Off Button(s)
Pressed Button (Times)
D0
D1
D2
D3
Press K4 (D1) – 1 Time
0
1
0
0
Press K4 (D1) – 2nd Time
0
0
0
0
0
1
0
0
Press K1 – 1 Time (On)
1
1
1
1
Press K1 – 2nd Time (Off)
0
0
0
0
Press K1 – 3rd Time (On)
1
1
1
1
Press K4 (D1) – 1 Time
0
1
0
0
Press K4 (D1) – 2nd Time
0
0
0
0
Press K4 (D1) – 3 Time
0
1
0
0
Press K1 (On)
1
1
1
1
Press K2 (Off)
0
0
0
0
Press K1 (On)
1
1
1
1
st
Single
(K1 is On/Off)
rd
Press K4 (D1) – 3 Time
st
st
Separated
(K1 is On
K2 is Off)
rd
5.9.4 PWM
The PWM Button Mode is only supported for 1920 and 1527 encoding format. In this mode, 2 buttons are used to send out
commands to increase or decrease the duty ratio of the PWM output of the CMT2251A. A single on/off button, or two
separated on/off buttons can be chosen by the parameter “On/Off Button(s)”. The “On” command sets the PWM output of the
CMT2251A to 100% of duty ratio, while the “Off” command sets the PWM output to 0% of duty ratio. In this mode, only one
button can be pressed at the same time. Pin 12 (K0), Pin 9 (K3), Pin 6 (K6) and Pin 5 (K7) are never used in this mode. The
commands of On, Off, Increase and Decrease are represented by D0 – D3. The figure below gives examples of the pin
Rev 0.8 | Page 23/31
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CMT2157A
functions in PWM mode.
LED
1
14
XTAL √ XTAL
√ CLK
VDD √ VDD
2
13
CLK
√ CLK
K0
× NC
GND √ GND
3
12
K0
× NC
11
K1
√ ON/OFF
RFO √ RFO
4
11
K1
√ ON/OFF
LED
1
14
XTAL √ XTAL
VDD √ VDD
2
13
CLK
GND √ GND
3
12
RFO √ RFO
4
LED √
LED √
NC ×
K7
5
10
K2
× NC
NC ×
K7
5
10
K2
√ OFF
NC ×
K6
6
9
K3
× NC
NC ×
K6
6
9
K3
× NC
DEC √
K5
7
8
K4
√ INC
DEC √
K5
7
8
K4
√ INC
Figure 26. PWM Button Mode with Single (left) and Separated (right) ON/OFF Button(s)
If K1 is used as the On/Off Button, press it down once, the “On” command is transmitted, release and press it down again, the
“Off” command is transmitted, and so on. In this case, K1 is a “Toggle” button. If the K1 is used as the On Button and K2 is
used as the Off Button, pressing K1, the “On” command is transmitted; pressing K2, the “Off” command is transmitted.
5.10 LED Driving Capability
This defines the maximum current driving capacity on the LED pin. Once the LED pin is enabled, it will light up or flash to
indicate two events:
When the chip is transmitting data, the LED will light up until the transmission is finished to notify the user the chip is
working, when the LBD is disabled, or LBD is enabled but there is no low battery detected.
When the LBD is enabled and there is valid low battery detection on the button(s) pressing, the LED will flash at least
5 times at the frequency of 6 Hz to notify the user the battery is running out.
5.11 Low Battery Detection (LBD)
This defines the Low Battery Detection threshold. Once the LBD is enabled, the chip will automatically check the battery status
before each transmission. Once the chip finds that the battery output is less than the detection threshold, the LED will flash at
least 5 times at the frequency of 6 Hz to notify the user. Once the LED flashes, the performance of the transmission is not
guaranteed. The user should change the batteries to new ones.
5.12 Crystal Oscillator and RCLK
The CMT2157A uses a 1-pin crystal oscillator circuit with the required crystal load capacitance integrated on-chip. Figure 27
shows the configuration of the XTAL circuitry and the crystal model. The recommended specification for the crystal is 26 MHz
with ±20 ppm, ESR (Rm) < 60 Ω, load capacitance CLOAD ranging from 12 to 20 pF. To save the external load capacitors, a set
of variable load capacitors CL is built inside the CMT2157A to support the oscillation of the crystal.
The value of load capacitors is configurable with the CMOSTEK USB Programmer and RFPDK. To achieve the best
performance, the user only needs to input the desired value of the XTAL load capacitance CLOAD of the crystal (can be found in
the datasheet of the crystal) to the RFPDK, then finely tune the required XO load capacitance according to the actual XO
frequency. Please refer to “AN113 CMT2157A/2250(1)A One-Way RF Link Development Kits User’s Guide” for the method of
choosing the right value of CL.
Rev 0.8 | Page 24/31
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CMT2157A
Crystal Model
CMT2157A
CMT2157A
Cc
XTAL
RCLK
26 MHz
0. 3 – 0. 7 Vpp
Rm
Cm
XTAL
C0
CL
CL
Lm
Figure 27. XTAL Circuitry and Crystal Model
Figure 28. RCLK Circuitry
If a 26 MHz RCLK (reference clock) is available in the system, the user can directly use it to drive the CMT2157A by feeding
the clock into the chip via the XTAL pin. This further saves the system cost due to the removal of the crystal. A coupling
capacitor is required if the RCLK is used. The recommended amplitude of the RCLK is 0.3 to 0.7 Vpp on the XTAL pin. Also,
the user should set the internal load capacitor CL to its minimum value. See Figure 28 for the RCLK circuitry.
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CMT2157A
6. Ordering Information
Table 19. CMT2157A Ordering Information
Part Number
Descriptions
Package
Package
Operating
MOQ /
Type
Option
Condition
Multiple
SOP14
Tape & Reel
SOP14
Tube
240 – 960 MHz
CMT2157A-ESR[1]
(G)FSK/OOK Stand-Alone
Transmitter with Encoder
240 – 960 MHz
[1]
CMT2157A-ESB
(G)FSK/OOK Stand-Alone
Transmitter with Encoder
1.8 to 3.6 V,
2,500
-40 to 85 ℃
1.8 to 3.6 V,
1,000
-40 to 85 ℃
Note:
[1]. “E” stands for extended industrial product grade, which supports the temperature range from -40 to +85 ℃.
“S” stands for the package type of SOP14.
“R” stands for the tape and reel package option, the minimum order quantity (MOQ) for this option is 2,500 pcs. “B”
stands for the tube package option, with the MOQ of 1,000 pcs.
The default frequency for CMT2157A is 868.35 MHz, for the other settings, please refer to the Table 10 of Page 13.
Visit www.cmostek.com/products to know more about the product and product line.
Contact sales@cmostek.com or your local sales representatives for more information.
Rev 0.8 | Page 26/31
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CMT2157A
7. Package Outline
D
A3
h
A2 A
0.25
c
θ
A1
L
L1
E1
b
E
e
Figure 29. 14-Pin SOP Package
Table 20. 14-Pin SOP Package Dimensions
Size (millimeters)
Symbol
Min
Typ
Max
A
-
-
1.75
A1
0.05
-
0.225
A2
1.30
1.40
1.50
A3
0.60
0.65
0.70
b
0.39
-
0.48
C
0.21
-
0.26
D
8.45
8.65
8.85
E
5.80
6.00
6.20
E1
3.70
3.90
4.10
e
1.27 BSC
h
0.25
-
0.50
L
0.30
-
0.60
L1
θ
1.05 BSC
0
-
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8°
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CMT2157A
8. Top Marking
8.1 CMT2157A Top Marking
CMT 2 1 5 7 A
Y Y W W ①②③④⑤⑥
Figure 30. CMT2157A Top Marking
Table 21. CMT2157A Top Marking Explanation
Mark Method :
Laser
Pin 1 Mark :
Circle’s diameter = 1 mm
Font Size :
0.35 mm, right-justified
Line 1 Marking :
CMT2157A, represents part number CMT2157A
YYWW is the Date code assigned by the assembly house. YY represents the last two digits of
Line 2 Marking :
the mold year and WW represents the workweek
①②③④⑤⑥ is the internal tracking number
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CMT2157A
9. Other Documentations
Table 22. Other Documentations for CMT2157A
Brief
AN111
AN142
AN113
AN115
Name
Descriptions
CMT215x Schematic and PCB Layout
Design Guideline
CMT2157A/2250(1)A One-Way RF Link
Pairing CMT215x and CMT225x
rules, RF matching network and other application layout
design related issues.
CMT2157A Configuration Guideline
Development Kits User’s Guide
Details of CMT2150/57A PCB schematic and layout design
Details of configuring CMT2157A features on the RFPDK.
User’s Guides for CMT2157A/2250(1)A Development Kits,
including Evaluation Board and Evaluation Module,
CMOSTEK USB Programmer and RFPDK.
Provide quick guideline in how to pair the CMT2150/57A with
CMT2250/51A.
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CMT2157A
10. Document Change List
Table 23. Document Change List
Rev. No.
Chapter
0.8
All
Description of Changes
Initial released version
Rev 0.8 | Page 30/31
Date
2015-02-11
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CMT2157A
11. Contact Information
Hope Microelectronics Co., Ltd
Address: 2/F,Building3,Pingshan Private Enterprise science and Technology Park,Xili Town,Nanshan District,Shenzhen,China
Tel: +86-755-82973805
Fax: +86-755-82973550
Email: sales@hoperf.com
hoperf@gmail.com
Website: http://www.hoperf.com
http://www.hoperf.cn
Copyright. CMOSTEK Microelectronics Co., Ltd. All rights are reserved.
The information furnished by CMOSTEK is believed to be accurate and reliable. However, no responsibility is assumed for
inaccuracies and specifications within this document are subject to change without notice. The material contained herein is
the exclusive property of CMOSTEK and shall not be distributed, reproduced, or disclosed in whole or in part without prior
written permission of CMOSTEK. CMOSTEK products are not authorized for use as critical components in life support
devices or systems without express written approval of CMOSTEK. The CMOSTEK logo is a registered trademark of
CMOSTEK Microelectronics Co., Ltd. All other names are the property of their respective owners.
Rev 0.8 | Page 31/31
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