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CMT21xx Handheld Device Design Guide
Overview
When the CMT21xx series chips provided by CMOSTEK are used under the conditions of direct human body contact, especially
in handheld devices, the ESD differs according to different places and seasons. This document aims for providing guidelines for
users to improve chip anti-ESD capabilities mainly from the aspects of handheld device structure design and PCB design hence
to improve the product anti-ESD capability.
The product models covered in this document are shown in the table below.
Product
Frequency
Model
(MHz)
CMT2150A
240-480 MHz
CMT2157A
240-960 MHz
CMT2180A
240-480 MHz
CMT2189A
240-960 MHz
CMT2110A
240-480 MHz
CMT2119A
240-960 MHz
This document will discuss the ESD protection per CMT21xx chips used in handheld devices from the following perspectives.
causes and harms
©
Copyright
By CMOSTEK
Table 1. Product Models Covered in This Document
Modulation
Method
OOK
7- key transmitter with encoder
(G)FSK/OOK
7- key transmitter with encoder
Transmitter Soc
OOK
(G)FSK/OOK
Transmitter Soc
OOK
Single-wire, direct mode, transmitter-only
(G)FSK/OOK
Single-wire, direct mode, transmitter-only
anti-ESD design
Chip Function
Rev 0.6 | 1/12
AN121
AN121
Configuration
Package
Method
EEPROM
SOP14
EEPROM
SOP14
SOP14
EEPROM / Flash
SOP14
EEPROM / Flash
SOT23-6
EEPROM
SOT23-6
EEPROM/Registers
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Summary of Contents for CMOSTEK CMT21 Series
- Page 1 CMT21xx Handheld Device Design Guide Overview When the CMT21xx series chips provided by CMOSTEK are used under the conditions of direct human body contact, especially in handheld devices, the ESD differs according to different places and seasons. This document aims for providing guidelines for users to improve chip anti-ESD capabilities mainly from the aspects of handheld device structure design and PCB design hence to improve the product anti-ESD capability.
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Page 2: Table Of Contents
2 ESD Transmission Route ......................... 4 3 ESD Protection & Anti-interference Design ................... 5 3.1 Improve Anti-ESD Capability in Structure Design....................5 3.2 PCB Anti-ESD Design ............................7 4 Revise History ..........................11 5 Contacts ............................12 Rev 0.6 | 2/12 www.cmostek.com... -
Page 3: Esd Causes And Harms
Fingers feel very severe pain and the back of wrist feels strong electric-shock. 10,000 The whole wrist feels strong pain and the body feels current passing through. 12,000 Due to strong electric shock, the entire hand has a sense of heavy blow Rev 0.6 | 3/12 www.cmostek.com... -
Page 4: Esd Transmission Route
ESD will catch the weak points of handheld devices through a variety of coupling paths. To avoid interference and damage from ESD events, users should isolate these coupling paths or strengthen the anti-ESD capability accordingly. Rev 0.6 | 4/12 www.cmostek.com... -
Page 5: Esd Protection & Anti-Interference Design
ESD Protection & Anti-interference Design 3.1 Improve Anti-ESD Capability in Structure Design CMOSTEK's NextGenRF series products are high-performance, highly integrated CMOS devices, which are relatively subject to ESD impact like device breakdown, which may result in malfunction or direct damage to the devices. - Page 6 It is recommended to add a 0 Ω resistor or a low-resistance magnetic bead at the connection end, and add sawtooth discharge and copper plane between the two ground traces to reduce direct ESD damage as shown in the below figure. Rev 0.6 | 6/12 www.cmostek.com...
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Page 7: Pcb Anti-Esd Design
Place power trace close to ground trace. Make signal traces as short as possible and place them close to ground to reduce the loop area. Try to avoid place sensitive signals such as /RESET close to the edge of the board. Try to wrap all traces within ground traces. Rev 0.6 | 7/12 www.cmostek.com... - Page 8 Users should take careful consideration in where to place anti-ESD component. The anti-ESD components should be placed as close as possible to electrostatic induction ports but away from the protected components. Rev 0.6 | 8/12 www.cmostek.com...
- Page 9 . Place Large Ground Trace Figure 12 Try to use round traces overall to improve anti-ESD capability. Try to arrange round traces overall . Try to Arrange Round Traces Overall Figure 13 Rev 0.6 | 9/12 www.cmostek.com...
- Page 10 Add a TVS tube between power supply and ground to discharge ESD (it depends on users' outer casing design and the ESD rating requirements). If a 49US crystal is used, better connect it to ground. Note that the 3225 crystal has better anti-ESD performance than that of the 49US crystal . Rev 0.6 | 10/12 www.cmostek.com...
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Page 11: Revise History
AN121 Revise History Table 4. Revise History Records Version No. Chapter Description Date Initial version 2016-2-17 Rev 0.6 | 11/12 www.cmostek.com... -
Page 12: Contacts
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.
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