CMOSTEK CMT2157A, CMT2157A-ESB, CMT2157A-ESR Manual
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CMT2157A
CMT2157A
240 – 960 MHz (G)FSK/OOK Stand-Alone Transmitter with Encoder
Features
Embedded EEPROM
Very Easy Development with RFPDK
All Features Programmable
Frequency Range: 240 to 960 MHz
FSK, GFSK and OOK Modulation
Symbol Rate:
0.5 to 100 ksps (FSK/GFSK)
0.5 to 40 ksps (OOK)
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
Up to 7 Configurable Data Pins for Push Buttons
LED Indicator for Low Battery Detection and Transmission
Sync ID Auto-Study with CMOSTEK Receiver
FCC / ETSI Compliant
RoHS Compliant
14-pin SOP Package
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 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 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 transmitter remotely by end customers. An embedded
EEPROM allows the RF and encoder parameters to be 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 NextGenRF
TM
family, together with CMT225x series receivers, they enable ultra low cost, low power consumption RF links.
Applications
Low-Cost Consumer Electronics Applications
Home and Building Automation
Remote Fan Controllers
Infrared Transmitter Replacements
Industrial Monitoring and Controls
Remote Lighting Control
Wireless Alarm and Security Systems
Remote Keyless Entry (RKE)
Ordering Information
Part Number
CMT2157A-ESR
CMT2157A-ESB
More Ordering Info: See Page 26
LED
VDD
GND
RFO
K7
K6
K5
1
2
3
4
5
6
7
Frequency Package
868.35 MHz
868.35 MHz
SOP14
14
13
12
11
10
CMT2157A
9
8
T&R
Tube
2,500 pcs
1,000 pcs
XTAL
CLK
DATA
K1
K2
K3
K4
MOQ
Copyright © By CMOSTEK Rev 0.8 | Page 1/31 www.cmostek.com
Typical Application
CMT2157A
ANT
C2
L2
C1
VDD
L1
SW7
SW6
SW5
C0
D1
1
LED
2
VDD
3
GND
4
RFO
5
K7
6
K6
7
K5
CMT2157A
U1
14
XTAL
13
CLK
DATA
12
11
K1
10
K2
9
K3
8
K4
CLK
DATA
X1
SW1
SW2
SW3
SW4
U1
X1
C0
C1
C2
L1
L2
D1
SW[7:1]
Designator
Figure 1. CMT2157A Typical Application Schematic
Table 1. BOM of 433.92/868.35 MHz Typical Application
Descriptions
Value
433.92 MHz 868.35 MHz
Unit
CMT2157A, 240 – 960 MHz (G)FSK/OOK stand-alone transmitter with encoder
±20 ppm, SMD32*25 mm crystal
±20%, 0402 X7R, 25 V
±5%, 0402 NP0, 50 V
±5%, 0402 NP0, 50 V
±5%, 0603 multi-layer chip inductor
±5%, 0603 multi-layer chip inductor
D0603, red LED
Push buttons
82
9.1
180
22
-
26
0.1
-
-
82
3.9
100
5.1
-
MHz uF pF pF nH nH
-
-
VDD
CLK
DATA
J1
1
2
3
4
Note: Connector J1 is for
EEPROM Programming
Manufacturer
CMOSTEK
EPSON
Murata GRM15
Murata GRM15
Murata GRM15
Murata LQG18
Murata LQG18
-
-
Rev 0.8 | Page 2/31 www.cmostek.com
Abbreviations
CMT2157A
ESD
ESR
FSK
GFSK
GUI
IC
LDO
Max
MCU
Min
MOQ
NP0
Abbreviations used in this data sheet are described below
AN
BOM
BSC
BW
DC
EEPROM
Application Notes
Bill of Materials
Basic Spacing between Centers
Bandwidth
Direct Current
Electrically Erasable Programmable Read-Only
Memory
Electro-Static Discharge
Equivalent Series Resistance
Frequency Shift Keying
Gauss Frequency Shift Keying
Graphical User Interface
Integrated Circuit
Low Drop-Out
Maximum
Microcontroller Unit
Minimum
Minimum Order Quantity
Negative-Positive-Zero
OBW
OOK
PA
PC
PCB
PLL
PN
RBW
RCLK
RF
RFPDK
RoHS
Rx
SOT
TBD
Tx
Occupied Bandwidth
On-Off Keying
Power Amplifier
Personal Computer
Printed Circuit Board
Phase Lock Loop
Phase Noise
Resolution Bandwidth
Reference Clock
Radio Frequency
RF Product Development Kit
Restriction of Hazardous Substances
Receiving, Receiver
Small-Outline Transistor
To Be Determined
Transmission, Transmitter
Typ Typical
XO/XOSC Crystal Oscillator
XTAL Crystal
Rev 0.8 | Page 3/31 www.cmostek.com
Table of Contents
CMT2157A
Rev 0.8 | Page 4/31 www.cmostek.com
CMT2157A
1. Electrical Characteristics
V
DD
= 3.3 V, T
OP
= 25
℃
, F
RF
= 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
Operation Voltage Supply
Operation Temperature
Supply Voltage Slew Rate
Symbol
V
DD
T
OP
Conditions
1.2 Absolute Maximum Ratings
Table 3. Absolute Maximum Ratings
[1]
Min
1.8
-40
1
Typ Max
3.6
85
Unit
V
℃ mV/us
Parameter Symbol Conditions Min Max Unit
Supply Voltage
Interface Voltage
Junction Temperature
Storage Temperature
Soldering Temperature
ESD Rating
Latch-up Current
V
DD
V
IN
T
J
T
STG
T
SDR
Lasts at least 30 seconds
Human Body Model (HBM)
@ 85
℃
-0.3
-0.3
-40
-50
-2
-100
V
DD
3.6
+ 0.3
125
150
255
2
100
V
V
℃
℃
℃ kV 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 www.cmostek.com
1.3 Transmitter Specifications
Table 4. Transmitter Specifications
CMT2157A
Parameter
Frequency Range
[1]
Synthesizer Frequency
Resolution
Symbol Rate
Symbol
F
RF
F
RES
SR
F
RF
≤
480 MHz
F
RF
> 480 MHz
FSK/GFSK
OOK
Conditions Min
240
0.5
0.5
Typ
198
397
Max
960
100
40
Unit
MHz
Hz
Hz ksps ksps
(G)FSK Modulation
Deviation Range
Bandwidth-Time Product
Maximum Output Power
Minimum Output Power
Output Power Step Size
PA Ramping Time
[2]
Current Consumption
[3]
@ 433.92 MHz
Current Consumption
[3]
@ 868.35 MHz
Sleep Current
Frequency Tune Time
Phase Noise @ 433.92
MHz
F
DEV
BT
P
OUT(Max)
P
OUT(Min)
P
STEP t
RAMP
GFSK modulation
OOK, 0 dBm
OOK, +10 dBm
OOK, +13 dBm
I
DD-433.92
I
DD-868.35
I
SLEEP t
TUNE
PN
433.92
FSK, 0 dBm
FSK, +10 dBm
FSK, +13 dBm
OOK, 0 dBm
OOK, +10 dBm
OOK, +13 dBm
FSK, 0 dBm
FSK, +10 dBm
FSK, +13 dBm
100 kHz offset from F
RF
600 kHz offset from F
RF
1.2 MHz offset from F
RF
1
-
0
0.5
+13
-10
1
6
8.5
10.2
10.8
23.8
32
6.1
9.3
11.2
12.3
26.7
35.3
20
370
-80
-96
-108
200
-
1024 kHz
- dBm dBm dB us mA mA mA mA mA mA mA mA mA mA mA mA nA us dBc/Hz dBc/Hz dBc/Hz
Phase Noise @ 868.35
MHz
Harmonics Output for
433.92 MHz
[4]
Harmonics Output for
868.35 MHz
[4]
OOK Extinction Ration
PN
868.35
H2
433.92
H3
433.92
H2
868.35
H3
868.35
100 kHz offset from F
RF
600 kHz offset from F
RF
1.2 MHz offset from F
RF
2 nd harm @ 867.84 MHz, +13 dBm P
OUT
3 rd harm @ 1301.76 MHz, +13 dBm P
OUT
2 nd harm @ 1736.7 MHz, +13 dBm P
OUT
3 rd
harm @ 2605.05 MHz, +13 dBm P
OUT
-74
-90
-102
-52
-57
-68
-52
60 dBc/Hz dBc/Hz dBc/Hz dBm dBm dBm dBm dB
Notes:
[1]. The frequency range is continuous over the specified range.
[2]. 0 and 2 n 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 www.cmostek.com
1.4 Crystal Oscillator
CMT2157A
Table 5. Crystal Oscillator Specifications
Parameter
Crystal Frequency
[1]
Crystal Tolerance
[2]
Load Capacitance
[3]
Crystal ESR
XTAL Startup Time [4]
Symbol
F
XTAL
C
LOAD
Rm t
XTAL
Conditions Min
26
12
Typ
26
±20
400
Max
26
20
60
Unit
MHz ppm pF
Ω 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 www.cmostek.com
2. Pin Descriptions
Pin Number
1
2
3
4
5 - 11
12
13
14
Name
LED
VDD
GND
RFO
K[7:1]
DATA
CLK
XTAL
CMT2157A
LED 1
2
3
4
5
6
7
14
13
12
11
10
9
8
XTAL
CLK VDD
GND DATA
K1 RFO
K7 K2
K3 K6
K5 K4
I/O
I
IO
I
O
I
I
O
I
Figure 2. CMT2157A Pin Assignments
Table 6. CMT2157A Pin Descriptions
Descriptions
LED driver, active low
Power supply input
Ground
Power amplifier output
Push button 7 to 1
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 www.cmostek.com
3. Typical Performance Characteristics
CMT2157A
20
Phase Noise @ 433.92 MHz
15
Phase Noise @ 868.35 MHz
13.0 dBm
@ 868.35 MHz
13.4dBm
@ 433.92 MHz
5
10
0
-5
-15
-10
OOK Spectrum
-25
-20
-30 -35
-40 -45
-55.9 dBm
@ 869.55 MHz
-50
-56.8 dBm
@ 435.12 MHz
-55
-60
432.42 432.72 433.02 433.32 433.62 433.92 434.22 434.52 434.82 435.12 435.42
Frequency (MHz)
Figure 4. Phase Noise, F
RF
= 433.92 MHz,
P
OUT
= +13 dBm, RBW = 10 kHz, Un-encoded
-65
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)
Figure 3. Phase Noise, F
RF
= 868.35 MHz,
P
OUT
= +13 dBm, RBW = 10 kHz, Un-encoded
FSK vs. GFSK
20 20
10
0
-10
-20
-30
-40
-50
-60
432.92 433.12 433.32 433.52 433.72 433.92 434.12 434.32 434.52 434.72 434.92
Frequency (MHz)
Figure 5. OOK Spectrum,
P
OUT
= +10 dBm, t
RAMP
= 32 us
10
0
-10
-20
-30
-40
-50
433.62
433.72
433.82
433.92
Frequency (MHz)
434.02
FSK
GFSK
434.12
Figure 6. FSK/GFSK Spectrum,
SR = 9.6 ksps, F
DEV
= 15 kHz
434.22
Spectrum of Various PA Ramping Options P
OUT vs. V
DD
10
0
-10
-20
-30
-40
1024 us
512 us
256 us
128 us
64 us
32 us
SR = 1.2 ksps
16
14
12
10
8
6
4
2
0
-2
1.6
1.8
13 dBm
10 dBm
0 dBm
-50
433.17
433.37
433.57
433.77
433.97
Frequency (MHz)
434.17
434.37
434.57
2 2.2
2.4
2.6
2.8
3
Supply Voltage (V)
3.2
3.4
3.6
3.8
Figure 7. Spectrum of PA Ramping,
SR = 1.2 ksps, P
OUT
= +10 dBm
Rev 0.8 | Page 9/31
Figure 8. Output Power vs. Supply
Voltages, F
RF
= 433.92 MHz
www.cmostek.com
4. Typical Application Schematics
4.1 Low-Cost Application Schematic
CMT2157A
CMT2157A
ANT
C2
L2
C1
VDD
L1
SW7
SW6
SW5
C0
D1
1
LED
2
VDD
3
GND
4
RFO
5
K7
6
K6
7
K5
U1
14
XTAL
13
CLK
DATA
12
11
K1
10
K2
9
K3
8
K4
CLK
DATA
X1
SW1
SW2
SW3
SW4
VDD
CLK
DATA
J1
1
2
3
4
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.
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.
3. 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
Designator Descriptions
Value
433.92 MHz 868.35 MHz
Unit Manufacturer
U1
X1
C0
C1
C2
L1
L2
D1
SW[7:1]
CMT2157A, 240 – 960 MHz (G)FSK/OOK stand-alone transmitter with encoder
±20 ppm, SMD32*25 mm crystal
±20%, 0402 X7R, 25 V
±5%, 0402 NP0, 50 V
±5%, 0402 NP0, 50 V
±5%, 0603 multi-layer chip inductor
±5%, 0603 multi-layer chip inductor
D0603, red LED
Push buttons
82
9.1
180
22
-
26
0.1
-
-
82
3.9
100
5.1
-
MHz uF pF pF nH nH
-
-
CMOSTEK
EPSON
Murata GRM15
Murata GRM15
Murata GRM15
Murata LQG18
Murata LQG18
-
-
Rev 0.8 | Page 10/31 www.cmostek.com
4.2 FCC/ETSI Compliant Application Schematic
CMT2157A
CMT2157A
ANT
C3
L3
C2
L2
C1
VDD
L1
SW7
SW6
SW5
C0
D1
1
LED
2
VDD
3
GND
4
RFO
5
K7
6
K6
7
K5
U1
14
XTAL
13
CLK
12
DATA
11
K1
10
K2
9
K3
K4
8
CLK
DATA
X1
SW1
SW2
SW3
SW4
VDD
CLK
DATA
J1
1
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.
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.
3. 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
Designator
U1
C3
L1
L2
L3
D1
X1
C0
C1
C2
SW[7:0]
Descriptions
CMT2157A, 240 – 960 MHz (G)FSK/OOK stand-alone transmitter with encoder
±20 ppm, SMD32*25 mm crystal
±20%, 0402 X7R, 25 V
±5%, 0402 NP0, 50 V
±5%, 0402 NP0, 50 V
±5%, 0402 NP0, 50 V
±5%, 0603 multi-layer chip inductor
±5%, 0603 multi-layer chip inductor
±5%, 0603 multi-layer chip inductor
D0603, red LED
Push buttons
Value
433.92 MHz 868.35 MHz
Unit Manufacturer
- CMOSTEK
68
15
15
180
36
18
-
-
26
0.1
68
10
6.8
100
5.6
6.8
-
-
MHz uF pF pF pF nH nH nH
-
-
EPSON
Murata GRM15
Murata GRM15
Murata GRM15
Murata GRM15
Murata LQG18
Murata LQG18
Murata LQG18
Rev 0.8 | Page 11/31 www.cmostek.com
5. Functional Descriptions
CMT2157A
VDD
GND
XOSC
LDOs POR Bandgap
VCO
LED Driver LED
XTAL
PFD/CP
Loop
Filter
Frac-N DIV
PA RFO
K[7:1] Encoder 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 NextGenRF
TM
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
Rev 0.8 | Page 12/31 www.cmostek.com
Table 9. Modulation, Frequency, Deviation and Symbol Rate
Parameter
Modulation
Frequency
Deviation
Frequency Resolution (F
RF
≤
480 MHz)
Frequency Resolution (F
RF
> 480 MHz)
Symbol Rate (FSK/GFSK)
Symbol Rate (OOK)
Value
(G)FSK/OOK
240 to 960
1 to 200
198
397
0.5 to 100
0.5 to 40
Unit
-
MHz kHz
Hz
Hz ksps ksps
5.3 Embedded EEPROM and RFPDK
CMT2157A
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
CMT2157A on the RFPDK.
CMT2157A
RFPDK
EEPROM
Interface
CLK
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 Mode
RF Settings
Parameters
Frequency
Descriptions
To input a desired transmitting radio frequency in the range from 240 to 960 MHz. The step size is
0.001 MHz.
Modulation The option is FSK or GFSK and OOK.
Tx Power
Xtal Cload
Symbol Rate
To select a proper transmitting output power from
-10 dBm to +14 dBm, 1 dBm margin is given above +13 dBm.
On-chip XOSC load capacitance options: from 10 to 22 pF.
To determines the symbol rate of the transmitted data: from 0.5 to 100 ksps in (G)FSK mode and
0.5 to 40 ksps in OOK mode.
Default
868.35 MHz
FSK
2.4
+13 dBm
15.00 pF
Basic
Advanced
Basic
Advanced
Basic
Advanced
Basic
Advanced
Basic
Advanced
Rev 0.8 | Page 13/31 www.cmostek.com
Category
Encoder
Settings
Push Button
Settings
Parameters Descriptions
Deviation
PA Ramping
LED Driving
Capability
LBD Threshold
Data
Representation
Encoder
Bit Format
Number of
Packets
Packet Interval
Button Mode
On/Off
Button(s)
Number of
Button(s)
Data Inversion
Periodic
Transmission
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 2 n
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.
This defines the Low Battery Detection 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” represent data 0 or 1. The options are:
0: F-high 1: F-low, or
0: F-low 1: F-high.
Select the packet encoding format, the options
are: 1920, 1527 and 2262. See Table 13, Table
14 and Table 15 for the configurable parameters
in each packet.
This tells the device how many symbols are used to construct a single bit in the 1920 mode. The options are: 3, 4, 5 or 6 sym/bit. The Bit Format is fixed at 4 sym/bit in 1527 mode and 8 sym/bit in
2262 mode. It is only available in 1920 mode.
This defines the minimum number of packet(s) being transmitted during each button pressing action. It also defines the number of packet(s) being transmitted during each periodic transmission. The range is from 1 to 256.
This defines the time interval amount two consecutive transmitted packets. The unit is in symbol, the range is from 0 to 255 symbols of zero.
Select the button encoding mode, the options are: Normal, Matrix, Toggle and PWM. For 1920 and 1527 format, all these button modes are supported; For 2262 format, only Normal button mode is supported.
Select the numbers of on/off button for Toggle and PWM button modes, the options are: Single or Separated.
This option is only available in Normal Button
Mode, and Encoder is set to 1920 and 1527. It defines the number of activated button(s) to be used in the application. The range is from 1 to 7.
Allow the user to select whether or not to inverse the transmitted data bits values in the Normal and
Toggle Button Mode. The options are: No or Yes.
Turn on/off the periodic transmission mode of the device. The options are: On or Off.
Default
35 kHz
0 us
5 mA
2.4 V
0: F-low
1: F-high
1527
3
1
Single
4
No
Off
0 symbols of zero
Normal
CMT2157A
Mode
Basic
Advanced
Advanced
Advanced
Advanced
Advanced
Basic
Advanced
Basic
Advanced
Advanced
Basic
Advanced
Basic
Advanced
Basic
Advanced
Basic
Advanced
Advanced
Advanced
Rev 0.8 | Page 14/31 www.cmostek.com
Category
Study Settings
Parameters
Periodic Time
ID Study
Study Trigger
Time
Study Button
Study Power
Descriptions
This parameter is only available when Periodic
Transmission is turned on. It defines the periodic 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 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 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).
This parameter is only available when ID Study is turned on. It defines which button is used to 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 turned on. It defines the PA power when the device is transmitting the study packets. The range is from –10 to +14 dBm.
5.4 Power Amplifier
Default
1.000 s
Off
5 s
Pin 11 (K1)
-6 dBm
CMT2157A
Mode
Advanced
Advanced
Advanced
Advanced
Basic
Advanced
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
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
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:
SR
Max
≤
0.5 * (
1 t
RAMP
)
Rev 0.8 | Page 15/31 www.cmostek.com
CMT2157A
In which the PA ramping “rate” is given by (1/t
RAMP
). In other words, by knowing the maximum symbol rate in the application, the PA ramping time can be calculated by: t
RAMP
≤
0.5 * (
1
SR
MAX
)
The user can select one of the values of the t
RAMP
in the available options that meet the above requirement. If somehow the t
RAMP
is set to be longer than “0.5 * (1/SR
Max
)”, it will possibly bring additional challenges to the OOK demodulation of the Rx device. For more detail of calculating t
RAMP
, please refer to “AN142 CMT2157A Configuration Guideline”.
0 us
1 us
2 us
4 us
8 us
512 us
1024 us
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 t
XTAL
to allow the XO to get stable. The t
XTAL
is to a large degree crystal dependent. A typical value of t
XTAL
TUNE
The frequency synthesizer will tune the CMT2157A to the desired frequency in the time t
TUNE
. 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
[1]
Time to Tune to Desired Frequency
[2]
Notes:
[1]. This parameter is to a large degree crystal dependent.
[2]. From XO stable to ready to transmit.
5.7 The Encoder
Symbol t
XTAL t
TUNE
Min Typ
400
370
Max Unit us us
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
Format
1920
1527
2262
Bit Format
(sym/bit)
3/4/5/6
4
8
Sync ID Length
(bits)
1 – 32
20
6 – 11
Data Length
(bits)
1 – 7
1 – 7
1 – 6
CRC
Support
NA
NA
ID Study
Support
Support
Not Support
Button Modes
[1]
All
All
Normal Mode
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 Descriptions Default Mode
Preamble
Address (Sync ID)
Length
Address (Sync ID)
Value
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 2 Length -1.
None
32-bit
0
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.
Rev 0.8 | Page 17/31 www.cmostek.com
CMT2157A
Preamble
16 symbols
Head_N
32 symbols
Address (Sync ID) configurable 1-32 bits
D0
1 bit
D1
1 bit
D2
1 bit
D3
1 bit
CRC
8 symbols
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
4 Symbols/Bit
5 Symbols/Bit
3 SYM
Bit 1
1 SYM
2 SYM
Bit 1
3 SYM
1 SYM 3 SYM
Bit 0
3 SYM
Bit 0
2 SYM
6 Symbols/Bit
1 SYM 1 SYM 2 SYM
Bit 1
2 SYM 1 SYM 1 SYM 1 SYM
Bit 0
Figure 16. 1920 Bit Format Options
5.7.2 1527 Packet Structure
3 SYM
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
The range of the Sync ID value is from 0 to 2
20
-1. This is because the Sync ID Length is fixed at 20 for 1527.
Default
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”.
Sync
32 symbols
Address (Sync ID) configurable 20 bits
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 1 Bit 0
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
Address (Sync ID)
Length
This is the range of the Sync ID Length. The range is from
6 to 11 bits. This parameter also defines the number of data bits, because the total number of Sync ID and Data bits is fixed at 12.
8-bit
Basic
Advanced
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
)
Bit 1
3 SYM
(12
α
)
1 SYM
(4
α
)
1 SYM
(4
α
)
3 SYM
(12
α
)
1 SYM
(4
α
)
Bit 0
3 SYM
(12
α
)
1 SYM
(4
α
)
3 SYM
(12
α
)
Bit f
3 SYM
(12
α
)
1 SYM
(4
α
)
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
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”. time
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5.9 Button Modes
CMT2157A
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
√
LED
VDD
√
VDD
GND
√
GND
RFO
√
RFO
NC
×
K7
NC
×
NC
×
K6
K5
3
4
1
2
5
6
7
14
13
12
11
10
9
8
XTAL
√
XTAL
CLK
K0
K1
K2
√
CLK
×
NC
√
D0
√
D1
K3
K4
√
D2
√
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
K1
0
1
0
1
0
1
1
0
1
0
1
0
1
0
1
Push Buttons
K3
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
K2
0
0
1
0
1
1
0
1
1
0
1
0
0
1
1
K4
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
D0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
The Data Bits
D2
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
D1
0
0
1
0
1
1
0
1
1
0
1
0
0
1
1
D3
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
Rev 0.8 | Page 21/31 www.cmostek.com
5.9.2 Matrix
CMT2157A
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
√
LED
VDD
√
VDD
GND
√
GND
RFO
√
RFO
NC
×
NC
×
B4
√
K7
K6
K5
3
4
5
6
7
1
2
12
11
10
9
8
14
13
XTAL
√
XTAL
CLK
√
CLK
K0
K1
×
NC
√
B0
K2
K3
K4
√
B1
√
B2
√
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
K1
0
0
0
1
0
0
0
0
0
1
1
0
0
1
1
K2
1
0
0
0
1
1
0
0
0
1
0
1
0
0
0
Push Buttons
K3
0
1
1
0
1
0
0
0
0
0
0
0
1
1
0
K4
0
1
0
0
0
1
1
1
0
0
0
0
0
0
1
D0
0
1
0
1
0
1
1
0
1
0
1
0
1
1
0
K5
1
0
1
1
0
0
1
0
1
0
0
0
0
0
0
The Data Bits
D1
0
0
1
0
1
1
1
0
0
1
0
1
1
1
0
D2
1
1
1
0
0
0
1
1
1
1
0
0
0
1
0
D3
1
1
1
1
1
1
1
0
0
0
0
0
0
0
1
Rev 0.8 | Page 22/31 www.cmostek.com
5.9.3 Toggle
CMT2157A
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
√
LED
VDD √ VDD
GND √ GND
RFO
√
RFO
NC ×
D3 √
D2
√
K7
K6
K5
4
5
6
7
1
2
3
11
10
9
8
14
13
12
XTAL
√
XTAL
CLK
K0
K1
√ CLK
× NC
√
ON/OFF
K2
K3
K4
× NC
√ D0
√
D1
LED
√
LED
VDD √ VDD
GND √ GND
RFO
√
RFO
NC ×
D3 √
D2
√
K7
K6
K5
4
5
6
7
1
2
3
11
10
9
8
14
13
12
XTAL
√
XTAL
CLK
K0
K1
√ CLK
× NC
√
ON
K2
K3
K4
√ OFF
√ D0
√
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)
Single
(K1 is On/Off)
Separated
(K1 is On
K2 is Off)
Pressed Button (Times)
Press K4 (D1) – 1 st Time
Press K4 (D1) – 2 nd
Time
Press K4 (D1) – 3 rd
Time
Press K1 – 1 st
Time (On)
Press K1 – 2 nd
Time (Off)
Press K1 – 3 rd
Time (On)
Press K4 (D1) – 1 st
Time
Press K4 (D1) – 2 nd
Time
Press K4 (D1) – 3 rd
Time
Press K1 (On)
Press K2 (Off)
Press K1 (On)
D0
0
1
0
0
0
0
0
1
0
1
0
1
D1
0
1
1
0
1
0
1
1
1
1
0
1
D2
0
1
0
0
0
0
0
1
0
1
0
1
D3
0
1
0
0
0
0
0
1
0
1
0
1
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 www.cmostek.com
functions in PWM mode.
CMT2157A
LED √ LED
VDD
√
VDD
GND
√
GND
RFO √ RFO
NC
×
K7
NC ×
DEC √
K6
K5
1
2
3
4
5
6
7
14
13
12
11
10
9
8
XTAL √ XTAL
CLK
√
CLK
K0
×
NC
K1
K2
K3
K4
√ ON/OFF
×
NC
× NC
√ INC
LED √ LED
VDD
√
VDD
GND
√
GND
RFO √ RFO
NC
×
K7
NC ×
DEC √
K6
K5
1
2
3
4
5
6
7
14
13
12
11
10
9
8
XTAL √ XTAL
CLK
√
CLK
K0
K1
K2
K3
K4
×
NC
√ ON/OFF
√
OFF
× NC
√ 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
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 C
LOAD
ranging from 12 to 20 pF. To save the external load capacitors, a set of variable load capacitors C
L 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 C
LOAD
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 C
L
.
Rev 0.8 | Page 24/31 www.cmostek.com
CMT2157A
Crystal Model
Rm
Cm
Lm
C0
XTAL
CMT2157A
C
L
Cc
XTAL
RCLK
26 MHz
0. 3 – 0. 7 Vpp
CMT2157A
C
L
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 C
L
to its minimum value. See Figure 28 for the RCLK circuitry.
Rev 0.8 | Page 25/31 www.cmostek.com
6. Ordering Information
CMT2157A
Table 19. CMT2157A Ordering Information
Part Number Descriptions
Package
Type
Package
Option
Operating
Condition
MOQ /
Multiple
CMT2157A-ESR
[1]
CMT2157A-ESB
[1]
240 – 960 MHz
(G)FSK/OOK Stand-Alone
Transmitter with Encoder
240 – 960 MHz
(G)FSK/OOK Stand-Alone
Transmitter with Encoder
SOP14
SOP14
Tape & Reel
Tube
1.8 to 3.6 V,
-40 to 85 ℃
1.8 to 3.6 V,
-40 to 85 ℃
2,500
1,000
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.
Visit www.cmostek.com/products to know more about the product and product line.
Contact [email protected]
or your local sales representatives for more information.
Rev 0.8 | Page 26/31 www.cmostek.com
7. Package Outline
D
CMT2157A
A3
A2 A
A1 c
θ
E1 E
Symbol b
C
D
E
A
A1
A2
A3
E1 e h
L
L1
θ b e
Figure 29. 14-Pin SOP Package
Table 20. 14-Pin SOP Package Dimensions
Min
-
0.05
1.30
0.60
0.39
0.21
8.45
5.80
3.70
0.25
0.30
0
Size (millimeters)
Typ
-
-
1.40
0.65
-
-
8.65
6.00
3.90
1.27 BSC
-
-
1.05 BSC
- h
0.25
L
L1
Max
1.75
0.225
1.50
0.70
0.48
0.26
8.85
6.20
4.10
0.50
0.60
8°
Rev 0.8 | Page 27/31 www.cmostek.com
8. Top Marking
8.1 CMT2157A Top Marking
Mark Method :
Pin 1 Mark :
Font Size :
Line 1 Marking :
Line 2 Marking :
CMT2157A
C M T 2 1 5 7 A
Y Y W W ① ② ③ ④ ⑤ ⑥
Figure 30. CMT2157A Top Marking
Table 21. CMT2157A Top Marking Explanation
Laser
Circle’s diameter = 1 mm
0.35 mm, right-justified
CMT2157A, represents part number CMT2157A
YYWW is the Date code assigned by the assembly house. YY represents the last two digits of the mold year and WW represents the workweek
①②③④⑤⑥ is the internal tracking number
Rev 0.8 | Page 28/31 www.cmostek.com
9. Other Documentations
Brief
AN111
AN142
AN113
AN115
CMT2157A
Table 22. Other Documentations for CMT2157A
Name
CMT215x Schematic and PCB Layout
Design Guideline
CMT2157A Configuration Guideline
CMT2157A/2250(1)A One-Way RF Link
Development Kits User’s Guide
Pairing CMT215x and CMT225x
Descriptions
Details of CMT2150/57A PCB schematic and layout design rules, RF matching network and other application layout design related issues.
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.
Rev 0.8 | Page 29/31 www.cmostek.com
10. Document Change List
Rev. No.
0.8
Chapter
All
Table 23. Document Change List
Description of Changes
Initial released version
CMT2157A
Date
2015-02-11
Rev 0.8 | Page 30/31 www.cmostek.com
11. Contact Information
CMT2157A
CMOSTEK Microelectronics Co., Ltd.
Room 202, Honghai Building, Qianhai Road. Nanshan District
Shenzhen, Guangdong, China PRC
Zip Code: 518000
Tel: 0755 - 83235017
Fax: 0755 - 82761326
Sales: [email protected]
Technical support: [email protected]
www.cmostek.com
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 www.cmostek.com
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