Wavecom GX64 Installation and operating instructions

GX64
A
PPLICATION NOTE
Charging Interface
Reference:
W
I_DEV_Gx64_APN_002
Version: 001
Date: 2007/01/30

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Charging Interface
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Trademarks
®, WAVECOM®, WISMO®, Open AT®, Wireless CPU®, Wireless Microprocessor®and certain
other trademarks and logos appearing on this document, are filed or registered trademarks
of Wavecom S.A. in France or in other countries. All other company and/or product names
mentioned may be filed or registered trademarks of their respective owners.
Copyright
This manual is copyrighted by WAVECOM with all rights reserved. No part of this manual may
be reproduced in any form without the prior written permission of WAVECOM.
No patent liability is assumed with respect to the use of the information contained herein.
No Warranty
WAVECOM publishes this manual without making any warranty as to the content contained
herein. Further Wavecom Inc reserves the right to make modifications, additions and
deletions to this manual due to typographical errors, inaccurate information, or
improvements to programs and/or equipment at any time and without notice. Such changes
will, nevertheless be incorporated into new editions of this manual.

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Table of Contents
1General ................................................................................................... 5
1.1 SCOPE ...................................................................................................................... 5
1.2 ABBREVIATIONS ........................................................................................................ 5
1.3 NOTATION ............................................................................................................... 6
2Built-in Charge Circuitry ......................................................................... 7
2.1 OVERVIEW ................................................................................................................ 7
2.1.1 GR/GS64 CHARGING BLOCK DIAGRAM................................................................ 7
2.1.2 APPLICATION CHARGING BLOCK DIAGRAM ......................................................... 8
2.2 IMPLEMENTATION..................................................................................................... 8
2.2.1 HARDWARE ........................................................................................................ 8
2.2.2 SOFTWARE IMPLEMENTATION........................................................................... 10
2.2.3 CHARGING VIA USB .......................................................................................... 11
2.3 OPERATION ............................................................................................................ 12
3Charger Power Supply (CPS) Reference Designs ..................................... 14
3.1 DISCLAIMER............................................................................................................ 14
3.1 DC/DC VERSION ..................................................................................................... 14
3.2 AC/DC VERSION ..................................................................................................... 15
4Using Custom Charge Circuitry ............................................................. 16
4.1 LM3658 SINGLE CHIP CHARGER SOLUTION.............................................................. 16
4.1.1 OVERVIEW ........................................................................................................ 16
4.1.2 CHARGING FROM AC/DC OR DC/DC-ADAPTER................................................. 17
Appendix A: AC/DC 5V supply ................................................................... 18
Appendix B: DC/DC 5V supply ................................................................... 19

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Table of Figures
Figure 1. GR/GS64 Charge Circuitry Block Diagram........................................................... 7
Figure 2. Application Charging Block Diagram .................................................................. 8
Figure 3. USB Charger Block Diagram.............................................................................. 11
Figure 4. Charger State Diagram ..................................................................................... 13
Figure 5. LM3658 Implementation Block Diagram ........................................................... 17

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1General
1.1 Scope
This document is meant to be used in addition to the Integrators Manual of the
intended GR/GS64 Wireless CPU. Basic information such as electrical requirements,
safety concerns, etc. can be found in the Integrators Manual, while this document
focuses more on the different aspects of application implementations.
GR/GS64 Wireless CPUs are designed with the capability to be integrated into an
application which supplies it with power from a Li-Ion battery and provides the
capability to charge this battery through an internal charging algorithm.
Application requirements are:
•A charger voltage and current limited to ~5.5V and 500mA respectively with a
reverse current protection diode (CPS).
•A Li-Ion battery pack, with a built-in Thermistor that shares a common
ground with the battery pack.
•Thermistor bias resistor from VREF to ADIN1.
1.2 Abbreviations
Abbreviation Description
ADC Analogue to Digital Conversion
ADIN1 Designated ADC-input for battery thermistor.
Application Customer hardware and software that contain and control
the GR/GS64 Wireless CPU.
CPS
Charger Power Supply. Refers to the 500mA current limited
supply that should be connected to the CHG_IN-signal of the
GR/GS64.
DRX GSM Discontinuous Receive mode.
FRC AT-command Final Result Code
NTC Negative Temperature Coefficient Thermistor
NVM Non Volatile Memory
PTC Positive Temperature Coefficient Thermistor
RTH nom Nominal Thermistor resistance value at 25°C.
VREF
Reference voltage used by the interface logic. This signal is
either an output from the Wireless CPU (GS64, GR64001), or
an input to the Wireless CPU (GR64002).

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1.3 Notation
The following symbols and admonition notation are used to draw the reader’s
attention to notable or crucially-important information.
Note
Draws the readers attention to pertinent, useful or interesting
information
Tip
Provides advice, suggestions, guidance or recommendations which
augment the formal text
Caution
Cautionary information must be heeded, it draws the readers attention
to the need for understanding, care or watchfulness in relation to the
information provided
Warning
Notes marked warning must be heeded, they alert readers to
precautionary measures, risks, hazards or safety information which
directly effects equipment function, warranty or personnel safety
Danger
This information must be heeded, it identifies information and
cautionary behaviour that otherwise ignored could result in
catastrophic equipment failure, bodily injury or death
TIP
CAUTION
!
WARNING
DANGE
R
NOTE

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2Built-in Charge Circuitry
2.1 Overview
The charging algorithm and its support circuitry that is built into the GR/GS64 family
of products require a DC-voltage on the CHG_IN signal. It also requires a Li-Ion
battery connected between VCC and GND of the system connector. The Li-Ion battery
must include a thermistor with one side connected to GND and the other connected to
ADIN1 of the system connector, so that the battery cell temperature can be
monitored. The thermistor temperature curve can be calibrated by the customer,
making the application very flexible.
The CPS for the charger must be a 500mA current limited 4.5V to 6.0V supply with
reversed current protection.
2.1.1 GR/GS64 Charging Block Diagram
All circuitry required to charge a Li-Ion battery is included in the Wireless CPU. Below
is a block diagram that gives a basic view of how it is implemented inside the Wireless
CPU.
Figure 1. GR/GS64 Charge Circuitry Block Diagram

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2.1.2 Application Charging Block Diagram
The figure below shows a typical implementation of a battery solution with a
capability to charge using the built-in charger of the GR/GS64 Wireless CPU.
Figure 2. Application Charging Block Diagram
2.2 Implementation
2.2.1 Hardware
The following subsections define the Charging Power Supply and Battery Thermistor,
software implementation, and general hardware usage.
2.2.1.1 Charging Power Supply (CPS)
To charge a single cell Li-Ion battery a voltage and current limited power supply is
required between the CHG_IN-input of the Wireless CPU and ground. Reference
designs for an AC/DC and a DC/DC charger are provided in Appendix A and B at the
end of this document.
The CPS must have a reverse current protection diode on its output and a capacitor of
at least 10uF value must be provided as close to the CHG_IN signal as possible.
A single Li-Ion battery should be applied between all six VCC and GND pins. The
routing length should be kept to a minimum and be designed to handle a minimum of
3A current. This leaves approximately 50% margin.
A bias resistor for the battery built-in thermistor is required. This resistor should be
connected between VREF and ADIN1 (see Battery Thermistor section below).

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2.2.1.2 Battery Thermistor
The battery thermistor can be of either PTC or NTC type. The resistor value of both
the thermistor and the bias resistor shall be selected so that the most optimal ADC-
range is available. The slope of the Thermistor curve is not important.
Wireless
CPU type VREF level Description
GS64 1.8V RBIAS, RTH nom values should be the same.
GR64001 2.8V RBIAS, RTH nom values should be the same.
GR64002 1.8V to 2.8V RBIAS, RTH nom values should be the same.
GR64002 >2.8V to 5.0V
The value of RBIAS should be selected so that the
voltage level on ADIN1 does not exceed 2.5V at
any extreme temperature.
There are four temperatures that must be calibrated (low, resume_low, resume_high,
high).
Temp mode Temp
(°C) Description
low 0
Low temperature limit. Charging will be suspended if
temperature goes below this limit.
resume_low +4
Charging resume level. After the low limit has been
reached, charging will not resume until temperature
exceeds this level.
resume_high +36
Charging resume level. After the high limit has been
reached, charging will not resume until temperature
is below this level.
high +40
High temperature limit. Charging will be suspended
if temperature goes above this limit.

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2.2.2 Software Implementation
A charging algorithm for Li-Ion batteries is implemented in the GR/GS64 software.
When a CPS is detected, the charging algorithm becomes enabled. The battery
temperature is then measured continuously on ADIN1 with a sampling duty cycle rate
of approximately 450ms.
If the CPS is removed, the CPS-availability polling is aligned with the paging channel
(DRX-mode) to minimise current consumption. This will affect the time it takes to
detect a CPS, since in worst case it will only be sampled once every 2.1s (2118 ms).
2.2.2.1 How to calibrate the Thermistor ADC-values
The application will have to set the ADC-values for 0°C, +4°C, +36°C and +40°C. To
permanently program these four levels into the Wireless CPU the following sequence
should be performed for each temperature:
•Place the whole application (or only the battery with the included Thermistor)
into a temperature chamber. Power on the application and the Wireless CPU.
•Set the temperature of the chamber to the desired level. After the set
temperature has been reached, let the device soak until the temperature of the
whole device is stable.
•Read the ADC-value of ADIN1 by sending AT*E2IO=0,”AD1”. Record the
received value when it is stable.
When the ADC-value for all four temperatures have been recorded they need to be
stored in NVM by sending “AT*EBATTCNF=1,<0°C value>,<+4°C value>,<+36°C
value>,<+40°C value>”. The values are permanently stored to NVM when
AT*EBATTCNF is issued, but a Wireless CPU restart is required to begin utilising the
newly stored parameters.
If the application has implemented its own temperature protection
circuitry the built-in thermistor table can be disabled by setting the
values to extreme levels (AT*EBATTCNF=1,0,0,1023,1023). It should
be noted that any battery safety circuitry indicated by battery vendor
must be implemented.
DANGE
R

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2.2.2.2 Test of charge temperature operation
To test that the circuitry works properly, place the application with a Wireless CPU in a
temperature chamber with a charger attached.
Take the temperature below 0°C. Ensure that charging is suspended by sending
“AT+CBC” to the Wireless CPU. You should receive “+CBC: 0,<% capacity>”. The
important parameter is the “0” following “+CBC:”.
Take the temperature above +4°C. Ensure that charging resumes by sending
“AT+CBC?” to the Wireless CPU. You should receive “+CBC: 1,<% capacity >”. The
important parameter is the “1” following “+CBC:”. It is also possible to use the
“AT*ECHGSTAT?”-command (see AT-command manual for more information).
Repeat the same scenario for the high temperature and ensure that the behaviour is
comparable.
2.2.3 Charging via USB
It is possible to charge via USB by connecting VUSB to CHG_IN through a current
limiter.
Figure 3. USB Charger Block Diagram
It should be noted that there are two types of USB hub versions:
•Low power, with a supply current of maximum 100mA.
•High power, with a supply current of maximum 500mA.

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The GR/GS64’s internal current limit is set to 1.3A. This means that an external
current limiter has to be implemented. This current limiter must be set to 100mA,
but can have the option of a 500mA setting. The default must always be 100mA, but
it can be switched to 500mA if connected to a high power hub.
The current limiter used in the example above is a Maxim MAX890L. The current is
set by a resistance to ground on pin 5. GPIOx should be default low, causing the
resistance to ground to be 15.0k (~100mA) after a high-power hub is detected GPIOx
can be set high causing the resistance to ground to be 15.0k//4.42k (3.41k) which
corresponds to ~400mA.
2.3 Operation
The GR/GS64 power supply implementation using a battery-charger solution is
dependent on the battery being attached to VCC and GND at all times. The GR/GS64
cannot be powered through CHG_IN without a Li-Ion battery available.
The “charge only”-mode feature mentioned below is a SW upgrade that
might not be available in all SW-versions. Let your Wavecom FAE know
if this feature does not work as expected, since that might mean that a
newer SW is required.
If a CPS is applied to a GR/GS64 that is currently powered down, the Wireless CPU will
enter a “charge only”-mode. This mode is from a SW point of view part of “+CFUN: 0”
(power down). In this mode it is not possible to run embedded scripts, send and
receive AT-commands, etc. The only three events that can power up the GR/GS64
are:
•a low pulse on ON/OFF
•a high level on PON_H
•an ALARM generated by the RTC
NOTE

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Figure 4. Charger State Diagram
The numbers in the circles in Error! Reference source not found. refer to the
AT+CFUN-mode. The state diagram shows how different HW signals affect the
Wireless CPU. These states can also be changed using AT+CFUN=<fun> command.
If the CPS is connected or enabled while the battery voltage is too low to power up the
GR/GS64 (VCC <3.2), the GR/GS64 trickle charges the battery through its 50mA
constant current source. The battery will then slowly charge until the voltage reaches
~3.2V, at which time the GR/GS64 powers up in “charge only”-mode enabling the
rapid charger.
It is possible for the application to read the battery voltage level on VCC by using the
“AT*EADCREAD=1”-command (see AT-command manual for more information).

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3Charger Power Supply (CPS) Reference Designs
3.1 Disclaimer
Wavecom Inc is not responsible for the charger power supplies reference design. The
integrator should refer technical questions regarding the charger power supplies
listed below directly to National Semiconductors.
3.1 DC/DC version
The implementation shown in Appendix B is the reference design of a 5V DC/DC buck
regulator from National Semiconductors. The input voltage can be between 6VDC to
20VDC. For more information on the design please contact National Semiconductors.
This DC/DC power supply does not include a current limiter. The application is
required to implement a 500mA current limiter, such as the Maxim MAX890L, before
applying this voltage to CHG_IN. It should be noted that if the Maxim MAX890L is
used as current limiter, the supply voltage must be limited to 5V ±10% since the
upper limit operating voltage for the Maxim part is 5.5V.
Bill Of Material:

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3.2 AC/DC version
The implementation shown in Appendix A is the reference design of a 5V AC/DC
flyback regulator from National Semiconductors. The input voltage can be between
85VAC to 265VAC. For more information on the design please contact National
Semiconductors.
Bill Of Material:

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4Using Custom Charge Circuitry
The integrators can choose to use their own charge solution. This is necessary if a
battery other than Li-Ion is used. This is also an option for a Li-ion battery, in case
the charging algorithm built into GR/GS64 does not meet customer requirements.
In the case of a customer using their own charging circuitry they should leave CHG_IN
signal to the GR/GS64 open, not connected. It should furthermore be noted that the
integrator will have to implement enabling of the charger, charge indicators, etc. into
their embedded script or their stand alone processor.
4.1 LM3658 Single Chip Charger solution
The following subsections describe the LM3658 single chip charger and its usage.
4.1.1 Overview
The LM3658 is a single chip charger IC from National Semiconductor designed for
handheld applications. LM3658 can safely charge and maintain a single Li-
Ion/Polymer battery operating off an AC wall adapter or the USB power (VUSB). Input
power source selection of USB/AC is automatic. With both power sources present, the
AC power source has priority. Charge current is programmed through an external
resistor when operating from a wall AC adapter allowing charge currents from 50mA
to 1000mA. When the battery is charged using USB power, charge currents of 100mA
or 500mA are pin selectable. The termination voltage is controlled to within 1% of
4.2V. The LM3658 requires few external components and integrates internal power
FET’s, reverse current protection and current sensing. The internal power FET’s are
thermally regulated to obtain the most efficient charging rate for a given ambient
temperature.
The LM3658 operates in five phases:
•Pre-qualification
•Constant current
•Constant voltage
•Top-off
•Maintenance
Additionally, the LM3658-B charger IC operates as a linear regulator or in “LDO-
mode” when the AC wall adapter is connected and no battery is present. Optimal
battery management is obtained through the integration of thermal protection,
battery temperature measurement and a multi-mode safety timer. The LM3658
provides two open-drain output signals for LED status indication or connection to
GPIO’s. For more information, please refer to the LM3658 datasheet.

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Figure 5. LM3658 Implementation Block Diagram
4.1.2 Charging from AC/DC or DC/DC-Adapter
When the LM3658 is accepting charge from the AC/DC or DC/DC-adapter, the “Iset”
pin is used to program the full-rate charge current. The charge current can be
calculated using this equation:
ISET
ISET
CHG R
K
I=, where KISET = 2500
The same AC/DC and DC/DC-adapters as described in 3 Charger Power Supply (CPS)
Reference Designs can be used for this custom charger.

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T
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APPENDIX A: AC/DC 5V SUPPLY

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APPENDIX B: DC/DC 5V SUPPLY

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