AN146

AN146
H I G H - S PEED L I T H I U M I O N B ATTERY C HARGER
Introduction
•
On-chip comparator and PWM provides a
means to implement a high speed buck converter with a small external inductor.
On-chip temperature sensor provides an accurate and stable drive voltage for determining
battery temperature. An external RTD (resistive
temperature device) can also be accommodated.
A single C8051F300 provides full product
range for multi-chemistry chargers, expediting
time to market and reducing inventory.
Driven by the need for untethered mobility and
ease of use, many systems rely on rechargeable bat- •
teries as their primary power source. The battery
charger is typically implemented using a fixedfunction IC to control the charging current/voltage
profile.
•
The C8051F300 family provides a flexible alternative to fixed-function linear battery chargers. This
note discusses how to use the C8051F300 device in
Li-Ion battery charger applications. The Li-Ion
charging algorithms can be easily adapted to other Charging Basics
battery chemistries.
Batteries are exhaustively characterized to determine safe yet time-efficient charging profiles. The
The code accompanying this application note was optimum charging method for a battery is depenoriginally written for C8051F30x devices. The dent on the battery’s chemistry (Li-Ion, NiMH,
code can also be ported to other devices in the Sili- NiCd, SLA, etc.). However, most charging stratecon Labs microcontroller range.
gies implement a 3-phase scheme:
Key Points
1. Low-current conditioning phase
•
2. Constant-current phase
On-chip high-speed ADC provides superior
accuracy in monitoring charge voltage (critical
to prevent overcharging in Li-Ion applications),
maximizing charge effectiveness and battery
life.
3. Constant-voltage phase/charge termination
Figure 1. Lithium Ion Battery Charger Block Diagram.
V Pos (+)
LDO
8k FLASH, PWM,
Temp Sensor,
Precision Time Base
8051F300
LED
Cygnal
Integrated
Products
Buck
Converter
PWM Out
Rev. 1.3 7/13
Li-Ion
Cells
AIN1 - Voltage
AIN2 - Current
V Neg (-)
Resistor
Divider
Amplifier
Sense Resistor
Copyright © 2013 by Silicon Laboratories
Silicon Laboratories Confidential. Information contained herein is covered under non-disclosure agreement (NDA).
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All batteries are charged by transferring electrical
energy into them. The maximum charge current for
a battery is dependent on the battery’s rated capacity (C). For example, a battery with a cell capacity
of 1000mAh is referred to as being charged at 1C
(1 times the battery capacity) if the charge current
is 1000mA. A battery can be charged at 1/50C (20
mA) or lower if desired. However, this is a common trickle-charge rate and is not practical in fast
charge schemes where short charge-time is desired.
Most modern chargers utilize both trickle-charge
and rated charge (also referred to as bulk charge)
while charging a battery. The trickle-charge current
is usually used in the initial phases of charging to
minimize early self heating which can lead to premature charge termination. The bulk charge is usually used in the middle phase where the most of the
battery’s energy is restored.
During the final phase of battery charge, which
generally takes the majority of the charge time,
either the current or voltage or a combination of
both are monitored to determine when charging is
complete. Again, the termination scheme depends
on the battery’s chemistry. For instance, most Lithium Ion battery chargers hold the battery voltage
constant, and monitor for minimum current. NiCd
batteries use a rate of change in voltage or temperature to determine when to terminate.
Hardware Description
Li-Ion batteries are currently the battery chemistry
of choice for most applications due to their high
energy/space and energy/weight characteristics
when compared to other chemistries. Most modern
linear Li-Ion chargers use the tapered charge termination, minimum current (see Figure 2) method to
ensure the battery is fully charged, as does the
example code provided at the end of this application note.
Buck Converter
The most economical way to create a tapered termination linear charger is to use a buck converter.
A buck converter is a switching regulator that uses
an inductor and/or a transformer (if isolation is
desired), as an energy storage element to transfer
energy from the input to the output in discrete
packets. Feedback circuitry regulates the energy
transfer via the transistor, also referred to as the
pass switch, to maintain a constant voltage or constant current within the load limits of the circuit.
While charging, some of the electrical energy is
converted to thermal energy, until the battery
reaches full charge, at which time all the electrical
energy is converted to thermal energy. If charging
isn’t terminated, the battery can be damaged or
destroyed. Fast chargers (chargers that charge batteries fully in less than two hours) compound this
issue, as these chargers use a high charge current to
minimize charge time. Therefore, monitoring a battery’s temperature is critical especially for Li-Ion
batteries which may explode if overcharged. Temperature is monitored during all phases and charge
is terminated immediately if the temperature
exceeds a preset maximum limit.
2
Rev. 1.3
AN146
Figure 2. Lithium Ion Charge Profile.
Charge Voltage
Charge Current
Conditioning Current regulation
Phase
Voltage regulation
Time
Figure 3. Buck Converter.
Switch
+
VIN
Supply
Current
L
Switch
Path of current flow
from VIN
-
-
VIN
D
C
+
Battery
D
L
Inductor
Current
VBatt
+
Path of current flow
from L and C
C
Battery
- VBatt
+ VREF
VREF
Comparator
Comparator
Switch OFF when
VBatt > VREF
Switch ON when
VBatt < VREF
a) Switch ON
b) Switch OFF
Rev. 1.3
3
AN146
Buck Regulator Operation
The buck regulator operates by controlling the duty
cycle of a transistor switch. The duty cycle is automatically increased to dispense more current into
the battery. A comparator closes the switch when
VBATT < VREF. As shown in Figure 3a, current
flows into the battery and capacitor C. This current
is also stored in inductor L. VBATT rises until it
exceeds VREF at which time the comparator turns
the switch off (Figure 3b). The current stored in the
inductor rapidly decreases until diode D is forward
biased, causing inductor current to flow into the
battery at a decreasing rate. Capacitor C begins discharging after the inductor current has decayed and
eventually VBATT begins to fall. When VBATT falls
below VREF, the comparator again turns the switch
on and another cycle begins. On a larger scale, if
the duty cycle is decreased (shorter “on” time), the
average voltage decreases and vice versa. Therefore, controlling the duty cycle allows one to regulate the voltage or the current to within desired
limits.
Selecting the Buck Converter
Inductor
To size the inductor in the buck converter, one first
assumes a 50 percent duty cycle, as this is where
the converter operates most efficiently.
Duty cycle is given by Equation 1, where T is the
period of the PWM (in our example T = 10.5S).
ton
DutyCycle = --------T
Equation 1. Duty Cycle.
With this established, select a PWM switching frequency. As Equation 2 shows, the larger the PWM
switching frequency, the smaller (and more cost
effective) the inductor. Our example code config-
4
ures the ‘F300’s hardware to generate a 510kHz
switch rate.
 Vi – Vsat – Vo ton
L = ---------------------------------------------------2Iomax
Equation 2. Inductor Size.
Now we can calculate the inductor’s size. Assuming Vi, the charging voltage, is 15V, Vsat, the saturation voltage, is 0.5V, the desired output voltage,
Vo, is 4.2V, and I0MAX, the maximum output current, is 1500 mA, the inductor should be at least
4H.
Note that the capacitor in this circuit is simply a
ripple reducer. The larger it is the better as ripple is
inversely proportional to the size of the capacitor.
High Speed Charger
As AN037, Lithium Ion Battery Charger Using
C8051F300, illustrates, the F300’s 8-bit PWM can
be configured to generate a 96kHz PWM with no
external components. This PWM output can be
used to drive the pass switch in a buck converter
and charge a battery. However, a 96kHz frequency
requires a buck converter to utilize a relatively
large 18H inductor. For some applications, this is
too large and costs too much. To reduce the size
and cost of this inductor requires that the switch
rate of the buck converter increase. The beauty of
the F300 lies in its flexible feature set. As mentioned, included in the device is a PCA (Programmable Counter Array) that has three 16-bit capture/
compare modules with corresponding output drives
that can be configured to provide numerous functions. We can use two of the PCA’s modules, along
with two external single-pole low-pass filters, and
the on-chip comparator to generate an 8-bit,
510kHz PWM (refer to Figure 4 for details). By
setting the switch rate to 510kHz, the inductor
required to satisfy the buck converter equations is
reduced by a factor of five to approximately 4H.
Rev. 1.3
AN146
To create a 510kHz PWM with the F300, Module 0
of the PCA is configured to provide a 510kHz
square wave via the Frequency Output Mode. This
square wave is then filtered through a low-pass filter with a 500kHz corner frequency to provide
approximately a 2 Volt peak-to-peak pseudo triangle wave to the positive input of the on-chip comparator. For the minus input of the comparator,
Module 1 is configured as an 8-bit PWM at 96kHz
switch rate. This PWM output is then low pass filtered with a corner frequency of approximately
15Hz to create a simple DC digital-to-analog converter. By comparing the pseudo triangle wave to a
DC input, the output of the comparator’s output
becomes a 510kHz PWM.
The DC control path, Module1’s output in this
example, controls the duty cycle of the 510kHz
PWM output from the comparator. By varying the
duty cycle of the 8-bit 96kHz PWM, the minus
input to the comparator can be varied from 0 volts
to the supply, typically 3.3V. The accuracy of the
DC control path is limited by the settling time of
the external RC filter. For this example, components were selected to minimize errors contributed
from this path. For more details on component
selection for the DC path, refer to AN010, 16-Bit
PWM Using an On-Chip Timer.
The overall accuracy of the 510kHz PWM output
from the comparator is mostly limited by the
pseudo triangle path to the comparator. Assuming
the DC path is error free, to create a true 8-bit
510kHz PWM output from the comparator requires
that a perfectly linear full-scale triangle wave be
input to the positive input of the comparator. A true
full scale triangle wave refers to a triangle wave
that linearly ramps from 0 volts to the positive supply and then returns back the negative supply in a
similar fashion. However, the charge and discharge
profile of a capacitor in the low pass configuration
is not linear past a time constant. Moreover, it is
desirable not to allow this capacitor to fully charge
as the pseudo triangle wave becomes more nonlinear towards its peaks. Unfortunately, limiting the
overall charge time/voltage limits the overall accuracy of the 510kHz PWM. For example, if we compare a triangle wave with a peak-to-peak voltage of
1/4 the supply to the DC control path’s voltage, we
could generate a 2-bit 510kHz PWM output from
the comparator. In practical applications, a 2-bit
510kHz has very limited use. To improve the accuracy requires either one of two changes: 1) increase
the voltage of the pseudo triangle wave or 2)
increase the resolution of the DC path’s PWM control. As mentioned earlier, increasing the peak-topeak voltage of the pseudo triangle wave can be
easily accomplished by adjusting its low pass filter
components accordingly. Our example is designed
Figure 4. High Speed Charger.
C8051F300
VBAT
Module1
IBAT
TBAT
Module0
Comparator
CMP0
CEX1
DC
Control
CEX0
CMP+
CMPHigh Speed PWM
Rev. 1.3
Pseudo
Triangle
Wave
Buck
Converter
5
AN146
to provide approximately a 2 volt peak-to-peak
pseudo triangle wave. When compared to the 8-bit
PWM dc control path, we achieve approximately
7.5-bits of performance at 510kHz switch rate.
The overall resolution of the high speed PWM output can be increased very easily by configuring
Module 1 to a 16-bit PWM. On an aside, if a faster
PWM output, greater than 510kHz, is desired to
reduce the inductor size further, the user can reconfigure Module 0 to provide a faster square wave up
to ½ the internal oscillator frequency or approximately 12MHz. If this is desired, the external low
pass filter for the pseudo triangle wave path will
have to be modified to accommodate the faster
square wave. Other limitations, like comparator
speed and voltage induced across the inductor due
to the higher current transients will also have to be
considered.
Software Description
takes these two points, calculates a slope and an
offset for both the current and voltage channels,
and stores the results in FLASH. All future conversions are scaled relative to these slope and offset
calculations.
Temperature
To monitor the temperature, the algorithms use the
on-chip temperature sensor. The sensor is left
uncalibrated, but still provides a sufficiently accurate temperature measurement. For more accurate
temperature measurement, one or two-point temperature calibration is required.
An external temperature sensor can be used if
desired. The AMUX can be reconfigured to accommodate this additional input voltage.
Current
The current delivered to the battery cells is monitored by measuring the voltage across a sense resistor (typically tens of mohms; our example uses a
0.24 ohm resistor). To maximize current measurement accuracy, this reference design uses an external amplifier with a gain of 10. This provides about
11-bits of current measurement accuracy (8-bits
from the ADC and 3-bits from the external gain
amplifier). To further maximize current measurement accuracy, the raw current measurements are
scaled via the slope and offset calibration coefficients every time a measurement conversion is
taken.
The software example that follows demonstrates a
Li-Ion battery charger using the C8051F300. The
algorithms discussed are written entirely in “C”
making them easily portable. Refer to the F300’s
datasheet for a full description of the device. Note
that the software architecture for the low speed
(96kHz) charger discussed in AN037 and the high
speed charger (510kHz) are essentially the same
(i.e. the flow charts that follow can be used for
either hardware configuration). The main difference are the control mechanisms. For the slow
speed charger in AN037, Module 0 (CEX0) is used
to control the duty cycle. For the high speed char- To determine the minimum current resolution,
ger Module 1 (CEX1) is used to control the duty recall that the output code of a ADC is given by
cycle.
Equation 3
n
 Ain 2
Dout = -------------------Vref
Calibration
To ensure accurate voltage and current measurements, the algorithms use a two-point system calibration scheme. In this scheme, the user is expected
to apply two known voltages and two known currents, preferable, one point near ground and the
other point near full-scale. The algorithm then
6
Rev. 1.3
Equation 3. Digital Output Code.
AN146
Accounting for the external amplifier, Equation 4
Ain =  Iin  Rs  10 
The battery’s voltages are divided down and monitored via external resistors. Note that this example
uses the supply voltage as the ADC voltage reference. Any monitored voltage above the reference
voltage must be divided down for accurate monitoring. If a more accurate reference is required, an
external voltage reference can be used. Adjustment
to the divide resistors must be made accordingly.
Equation 4. Input Current with 10x Gain.
states that Ain is
Iin is then given by Equation 5
 Dout  Vref 
Iin = -----------------------------------n
2  10  Rs
Equation 5. Input Current.
Charging - Phase1
In Phase 1, (for description purposes, we assume
the battery is initially discharged), the ‘F30x regulates the battery’s current to ILOWCURRENT (typically 1/50 C) until the battery’s voltage reaches
VMINVOLTBULK. Note that the battery’s charge current is current limited to ILOWCURRENT to ensure
safe initial charge and to minimize battery selfheating. If at any time the temperature increases out
of limit, charging is halted.
Assuming
•
•
•
•
•
Voltage
Rs = 0.24 
VREF = 3.3 V
2N = 256, an 8-bit converter
External Gain = 10
No External Gain = 1
When Dout = 1, IMIN is given by Equation 6.
Charging - Phase 2
mA
Imin =  5.37  --------------Code
Once the battery reaches VMINVOLTBULK the charger enters Phase 2, where the battery’s algorithm
controls the PWM pass switch to ensure the output
voltage provides a constant charge-current IBULK
to the battery (rate or bulk current is usually 1C and
is definable in the header file as is ILOWCURRENT
and VMINVOLTBULK).
Equation 6. IMIN.
When Dout=256, Imax is given by Equation 7.
Imax =  1.37 Amps
Equation 7. Imax.
Charging - Phase 3
It is important to note that if one chooses to modify
the algorithm, the order of mathematical operations
is important. To minimize truncation error effects,
be sure to perform multiply operations first making
the numerator as large as possible, before performing divide operations. Further recall that a long
type variable, which is the limit for the F300’s
compiler, is limited to 232-1 or approximately 4 billion.
After the battery reaches VTop (typically 4.2 V in
single cell charger), the charger algorithm enters
Phase 3, where the PWM feeds back and regulates
the battery’s voltage. In Phase 3, the battery continues to charge until the battery’s charge current
reaches IMINIBULK, after which, the battery is
charged for an additional 30 minutes and then
charge terminates. Phase 3 typically takes the
majority of the charging time.
Rev. 1.3
7
AN146
Note that in most practical applications, such as a
portable PC, the batteries may be in any of the three
phases when charging is activated. This doesn’t
really affect the charger as it simply monitors the
battery’s current condition and starts charging from
that point.
To charge more than 1 battery cell, both the hardware and software will need to be modified. For
example, to charge two 4.2 V batteries simultaneously, resistors R11 and R12 will need to be
switched. Then, the header file will need these
modifications:
Getting Started
CELLs = 2
The reference design that accompanies this application note is designed to charge a single cell 4.2 V
lithium ion battery. To accommodate numerous
power supplies and batteries, it charges at 250mA
bulk current. To charge a battery, first connect
power to the board by applying an 8V to 15V supply to JP1. The power supply should be able to supply a minimum of 500mA. Once the appropriate
supply is connected, connect the battery to JP3.
Connect the positive lead of the battery to pin 1 and
connect the negative lead to pin 3. Terminal 2 of
JP3 can be left unconnected as no code has been
developed to monitor temperature via an external
temperature sensor at this time. Finally, press the
reset switch and the battery will begin charging.
The PWM charge control signal can be monitored
by probing pin 5 on the C8051F300.
RESB = 10
Recommended Operating Conditions
•
•
Supply: 8V to 15V
Battery: One cell, 4.2V,
with <1000mAh rating
Default Charging Parameters
Once the header file is modified, recompile the
software and down load the new source code to the
charger board. A similar scheme can be used to
modify the board for any number of cells.
Conclusion
The C8051F300’s high level of analog integration,
small form-factor, integrated FLASH memory, and
low power consumption make it ideal for flexible
next generation battery charging applications. This
note discussed how to use the C8051F300 in Lithium Ion battery charger applications at 510kHz
switch rate. Example code is provided as well.
Reference
Applications of Linear Integrated Circuits.
Eugene Hnatek, John Wiley and Sons, 1975.
• Trickle Current = 135mA
• Bulk Current = 250mA
• Regulation Voltage = 4.2V
• Termination Current = 125mA
Efficiency of Charger
•
•
•
Switching Efficiency > 80%
Voltage Accuracy > 1%
Current Accuracy > 2%
Charging 2 Cells or More
8
Rev. 1.3
AN146
Appendix A - Schematic
Figure 5. High Speed Charger Schematic.
Rev. 1.3
9
Value
Package
Notes
C8051F300 MLP-11
Cygnal Integrated Products C8051F300
LPV321M5 SOT-23-5
National (LPV321M5 or equivalent)
N-Channel SOT-23
Zetex, N-Channel 30-V (D-S) MOSFET, (2N7002CT or equivalent)
P-Channel SOT-23
Zetex, P-Channel 30-V (D-S) MOSFET, (ZXMP3A13FCT-ND or equivalent)
22uH
SMD
Coil Craft Inductor, 22uH, 1.5 A, (DO3316P-223 or equivalent)
Schottky
SMC
3A 40V Power Rectifier Diode (MBRS340CT or equivalent)
0.1uF
0805
Cap X7R 50V 5% (Kemet C0805C104J5RACTU or equivalent)
33pF
0805
Cap X7R, 50V 10% (Kemet C0805330J5GACTU or equivalent)
1 uF
0805
Cap X7R, 10V 10% (Kemet C0805105K8RACTU or equivalent)
22uF
EIA6032-28
Cap Tantalum, 16V, 10% (Kemet T491C226K016AS or equivalent)
100pF
0805
Cap X7R 50V 5% (Kemet C0805C101K5GACTU or equivalent)
100k
0805
Resistor 1/10W, 5% (Panasonic P100KCCT-ND or equivalent)
10k
0805
Resistor 1/10W, 5% (Panasonic P10.0KCCT-ND or equivalent)
1k
0805
Resistor 1/10W, 5% (Panasonic P1.0KCCT-ND or equivalent)
200
0805
Resistor 1/10W, 5% (Panasonic P200CCT-ND or equivalent)
20k
0805
Resistor 1/10W, 5% (Panasonic P20.0KCCT-ND or equivalent)
Switch
6MM, SQ
Momentary switch (Panasonic P8007S-ND or equivalent)
0.24 ohm
0805
Resistor 1/4W, 2% (Panasonic RL12T0.24GCT or equivalent)
BOM TOTAL
Included on Demo Board, but NOT Part of Battery Charger BOM
Item QTY
Part
Value
Package
Notes
1
1 U2
MIC5235
SOT-23-5
Micrel Semiconductor (MIC5235-3.3M5)
2
1 C1
1 uF
0805
Cap X7R, 10V 10% (Kemet C0805105K8RACTU or equivalent)
3
1 C2
2.2 uF
EIA3216-18
Cap Tantalum, 16V, 10% (Kemet T491A225K016AS or equivalent)
4
2 R1,R2
475 ohm
0805
Resistor 1/10W, 5% (Panasonic P475CCT-ND or equivalent)
5
2 R5,7
1k
0805
Resistor 1/10W, 5% (Panasonic P1.0KCCT-ND or equivalent)
6
1 R6
10k
0805
Resistor 1/10W, 5% (Panasonic P10.0KCCT-ND or equivalent)
7
1 D1
LED, Red
0.1" thru hole T-1 3/4 (Panasonic LN21RPHL or equivalent)
8
1 D2
LED, Green 0.1" thru hole T-1 3/4 (Panasonic LN31GPHL or equivalent)
9
1 Shunt
Shunt
0.1"
Shunt (929957-08 or equivalent)
10
2 JP1,JP2
1x2 Header 0.1" thru hole Sullins (S2105-02 or equivalent)
11
1 JP3
1x3 Header 0.1" thru hole Sullins (S2105-03 or equivalent)
12
1 JP4
2x5 Header 0.1" thru hole Protected with central polarizing key slot (3M 2510-6002UB or equiv.)
13
1 P1
RAPC722
2x5.5mm Jack Switchcraft (SC1153-ND or equivalent)
14
1 Board
2-Layer
2"x1.75"
PCBEXPRESS (board manufacturing services)
Item QTY
Part
1
1 U1
2
1 U3
3
1 Q1
4
1 Q2
5
1 L1
6
2 D3,4
7
6 C3,5,7,9,10,12
8
1 C4
9
1 C6
10
1 C8
11
1 C11
12
2 R3,15
13
5 R4,10,11,13,14
14
1 R9
15
2 R8,16
16
1 R12
17
1 S1
18
1 RSENSE
AN146
Appendix B - Bill Of Materials
Figure 6. High Speed Charger Bill of Materials.
10
Rev. 1.3
AN146
Appendix C - PCB Layout
Figure 7. High Speed Charger Layout (Silk Screen)
JP3: Battery Input
Terminal
3.3V LDO &
Power LED
JP1: 8V-15V Input Supply Terminal
(+)(-)
Battery(+)
Temp
Battery(-)
C2 Interface
Buck Regulator Sub-circuit
C8051F300
Reset Switch
Current and Voltage Feedback Monitoring Sub-circuits
Rev. 1.3
11
AN146
Figure 8. High Speed Charger Layout (Top Layer)
12
Rev. 1.3
AN146
Figure 9. High Speed Charger Layout (Bottom Layer)
Rev. 1.3
13
14
Value
C8051F300
LPV321M5
N-Channel
P-Channel
22uH
Schottky
0.1uF
33pF
1 uF
22uF
100pF
100k
10k
1k
200
20k
Switch
0.24 ohm
Package
MLP-11
SOT-23-5
SOT-23
SOT-23
SMD
SMC
0805
0805
0805
EIA6032-28
0805
0805
0805
0805
0805
0805
6MM, SQ
0805
p
( Notes
)
Cygnal Integrated Products C8051F300
National (LPV321M5 or equivalent)
Zetex, N-Channel 30-V (D-S) MOSFET, (2N7002CT or equivalent)
Zetex, P-Channel 30-V (D-S) MOSFET, (ZXMP3A13FCT-ND or equivalent)
Coil Craft Inductor, 22uH, 1.5 A, (DO3316P-223 or equivalent)
3A 40V Power Rectifier Diode (MBRS340CT or equivalent)
Cap X7R 50V 5% (Kemet C0805C104J5RACTU or equivalent)
Cap X7R, 50V 10% (Kemet C0805330J5GACTU or equivalent)
Cap X7R, 10V 10% (Kemet C0805105K8RACTU or equivalent)
Cap Tantalum, 16V, 10% (Kemet T491C226K016AS or equivalent)
Cap X7R 50V 5% (Kemet C0805C101K5GACTU or equivalent)
Resistor 1/10W, 5% (Panasonic P100KCCT-ND or equivalent)
Resistor 1/10W, 5% (Panasonic P10.0KCCT-ND or equivalent)
Resistor 1/10W, 5% (Panasonic P1.0KCCT-ND or equivalent)
Resistor 1/10W, 5% (Panasonic P200CCT-ND or equivalent)
Resistor 1/10W, 5% (Panasonic P20.0KCCT-ND or equivalent)
Momentary switch (Panasonic P8007S-ND or equivalent)
Resistor 1/4W, 2% (Panasonic RL12T0.24GCT or equivalent)
Included on Demo Board, but NOT Part of Battery Charger BOM
Item QTY
Part
Value
Package
p
( Notes
)
1
1 U2
MIC5235
SOT-23-5
Micrel Semiconductor (MIC5235-3.3M5)
2
1 C1
1 uF
0805
Cap X7R, 10V 10% (Kemet C0805105K8RACTU or equivalent)
3
1 C2
2.2 uF
EIA3216-18
Cap Tantalum, 16V, 10% (Kemet T491A225K016AS or equivalent)
4
2 R1,R2
475 ohm
0805
Resistor 1/10W, 5% (Panasonic P475CCT-ND or equivalent)
5
2 R5,7
1k
0805
Resistor 1/10W, 5% (Panasonic P1.0KCCT-ND or equivalent)
6
1 R6
10k
0805
Resistor 1/10W, 5% (Panasonic P10.0KCCT-ND or equivalent)
7
1 D1
LED, Red
0.1" thru hole T-1 3/4 (Panasonic LN21RPHL or equivalent)
8
1 D2
LED, Green 0.1" thru hole T-1 3/4 (Panasonic LN31GPHL or equivalent)
9
1 Shunt
Shunt
0.1"
Shunt (929957-08 or equivalent)
10
2 JP1,JP2
1x2 Header 0.1" thru hole Sullins (S2105-02 or equivalent)
11
1 JP3
1x3 Header 0.1" thru hole Sullins (S2105-03 or equivalent)
12
1 JP4
2x5 Header 0.1" thru hole Protected with central polarizing key slot (3M 2510-6002UB or equiv.)
13
1 P1
RAPC722
2x5.5mm Jack Switchcraft (SC1153-ND or equivalent)
14
1 Board
2-Layer
2"x1.75"
PCBEXPRESS (board manufacturing services)
Item QTY
Part
1
1 U1
2
1 U3
3
1 Q1
4
1 Q2
5
1 L1
6
2 D3,4
7
6 C3,5,7,9,10,12
8
1 C4
9
1 C6
10
1 C8
11
1 C11
12
2 R3,15
13
5 R4,10,11,13,14
14
1 R9
15
2 R8,16
16
1 R12
17
1 S1
18
1 RSENSE
AN146
Figure 10. High Speed Charger Bill of Materials
Rev. 1.3
AN146
Figure 11. main() Flow Chart
main()
Config_F300()
CalibrateADCfor
Measurement()
Enable Interrupts
Infinite
Loop
Yes/No
Clear Termination Flags
Clear Charge Status Flags
Yes
Error
Detected
?
No
Error
Detected
?
No
Status = BULK
?
Yes
Turn on LED0
Turn off LED0, Error
BULK_charge()
Infinite Loop
No
Yes/No
Status =
LOWCURRENT
?
Yes
LOWCURRENT_charge()
Rev. 1.3
15
AN146
Figure 12. CalibrateADCforMeasurement() Flow Chart
CalibrateADCforMearurement()
Setup ADC0's AMUX,
Throughput, Gain, for near
zero-scale voltage cal point
Acquire 16-bit
Measurement
Setup ADC0's AMUX,
Throughput, Gain, for near
zero-scale Current cal point
Setup ADC0's AMUX,
Throughput, Gain, for near
full-scale voltage cal point
Acquire 16-bit
Measurement
Acquire16-bit
Measurement
Setup ADC0's AMUX,
Throughput, Gain, for near
full-scale Current cal point
Calculate Voltage Slope
Coefficient
Acquire16-bit
Measurement
Calculate Voltage Offset
Coefficient
Calculate Current Slope
Coefficient
Erase Memory Page
0x1A00
Calculate Current Offset
Coefficient
Store Voltage Offset and
Slope Coefficients in
FLASH Memory
Store Current Offset and
Slope Coefficients in
FLASH Memory
END
16
Rev. 1.3
AN146
Appendix D - Software Flow Charts
Figure 13. Monitor_Battery() Flow Chart
Monitor_Battery()
Measurement
Type
?
Current
AMUX = Current
Charge Voltage
Temperature
Battery Voltage
AMUX = Volt
Stop PWM
Stop PWM
AMUX = Temperature
AMUX = Volt
AV = 0
I=0
No
I?
Voltage w/ or w/out PWM
Calculate Voltage w/
Calibration Coefficients
Yes
Current
Calculate Current w/
Calibration Coefficients
Temperature
Calculate Temperature w/
Calibration Coefficients
Start ADC0
No
ADC0 Done?
Yes
AV = AV + ADC0
Turn PWM on
Return Desired Parameter
AV = AV/10
END
Rev. 1.3
17
AN146
Figure 14. Bulk_Charge() Flow Chart (Part 1)
Bulk_Charge()
Start PWM w/ Zero Output
Status = const_C
T
Within Limits
?
No
Yes
V
<max_V &
> min_Bulk
?
No
Yes
Set Appropriate Flags
Calculate bulk_finish_time
Green LED On
Status =
BULK & No
Error?
No
Yes
Status =
const_c
?
No
Yes
Regulate Battery Current
Read Charge Voltage
Yes
Change Status from
const_C to const_V
B
18
C
Charge
Voltage Within
Limits
?
No
A
Rev. 1.3
D
AN146
Figure 15. BULKCurrent() Flow Chart (Part 2)
B
C
A
No
D
Status =
const_V &
Current
within Limits
?
Reset Flags for Low
Current Constant
Current Mode
Yes
Regulate Voltage()
Yes
Time
Overflow
?
Stop PWM
& Flag Error
No
Yes
Stop PWM
& Flag Error
Temp.
Overflow
?
No
No
60 Sec.
Over
?
Yes
No
const_V,
NOT Delay & Current
Below Threshold
?
Yes
Calculate bulk_finish_time
Status = Delay
Delay
Time
Over
?
Yes
No
Stop PWM
Status = const_C
Status = LOWCURRENT
Green LED Off
END
Rev. 1.3
19
AN146
Figure 16. LowCurrent_Charge() Flow Chart
LOWCURRENT_charge()
No
ResetTimeBase()
V
<BulkThreshold
?
Yes
Prepare Flags to enter
Bulk Mode
Calculate Finish_time
No
No ERROR &
LOWCURRENT =1
?
Yes
Change Status
from const_C to
const_V
Yes
No
Temp
within Limits
?
Charge
Voltage
Within Limits
?
No
Regulate Current
Yes
No
No
V
<max_V
?
Yes
Yes
Status = Delay
Green LED Blinking
Regulate Voltage
Yes
Green LED Off
Stop PWM
and flag error
END
20
Status = const_V
Rev. 1.3
Lowcurrent
Finish Time
reached?
No
AN146
Figure 17. Turn_PWM_Off() Flow Chart
Turn_PWM_Off()
No
CEX1
Counter
<0xF0?
Yes
Increment CEX1
Counter
CEX1
Counter
<0xF0?
Yes
No
Disable PWM Mode
END
Rev. 1.3
21
AN146
Figure 18. Measure() Flow Chart
measure()
Set accumulator and
counter i variables to zero
Clear End of Conversion
Flag
Start New Conversion
Conversion
Complete
?
No
Yes
accumulator =
accumulator + ADC0
Increment i
No
i=0
?
Yes
Return 16-bit
Measurement
END
22
Rev. 1.3
AN146
Figure 19. Regulate_Voltage() Flow Chart
Regulate_Voltage()
Measure Battery's
voltage
Voltage <
VOLT_BULK &
PCA not max
?
No
Yes
No
Make Duty Cycle Larger
Voltage >
VOLT_BULK &
PCA not 0
Yes
Make Duty Cycle Smaller
Voltage
< VOLT_BULK + Tolerence
& > VOLT_BULK
?
No
Yes
END
Rev. 1.3
23
AN146
Figure 20. Regulate_Current() Flow Chart
Regulate_Current()
Measure Current
Current <
passed current &
PCA not max
?
No
Yes
No
Make Duty Cycle Larger
Current >
passed current &
PCA not 0
Yes
Make Duty Cycle Smaller
Current =
passed value
?
No
Yes
Monitor Voltage
w/ PWM off
Voltage <
VOLT_LOWCURRENT
± Tolerence
?
No
Yes
CHARGE_STATUS =
const_V
END
24
Rev. 1.3
AN146
Figure 21. PCA_OVERFLOW_ISR() Flow Chart
PCA_OVERFLOW_ISR()
Reset PCA Counter and
PCA Interrupts
Decrement time.count
0 = time.count
No
Yes
Reset time.count to
overflow value
Increment time.sec
No
60 = time.sec
?
Yes
Reset time.sec
Increment time.min
No
LOW
CURRENT
charge &
no errors
?
No
60 = time.min
?
Yes
Increment time.hour
Yes
No
odd
second
?
Reset time.min
Yes
Turn on LED
No
24 = time.hour
Yes
Turn Off LED
Reset time.hour
END
Rev. 1.3
25
AN146
Appendix E - Firmware (Header File)
//----------------------------------------------------------------------------//
// Copyright 2003 Cygnal Integrated Products, Inc.
//
// Filename:
F300_HighSpeed_BC.h
// Target Device: 8051F300
// Created:
1 MAR 2003
// Created By:
DKC
// Tool chain: KEIL Eval C51
//
// This header file is used to define all preprocessor directives, prototypes,
// and global variable for F300_HighSpeed_BC.c.
//
// The user should modify this header file before proceeding as key
//
battery parameter limits are set here.
//
//----------------------------------------------------------------------------// Function Prototypes
//----------------------------------------------------------------------------void Config_F300(void);
void Reset_Time_Base(void);
void CalibrateADCforMeasurement(void);
void Regulate_Current(int);
void Regulate_Voltage(void);
void Turn_PWM_Off(void);
int Monitor_Battery(unsigned char);
void Bulk_Charge(void);
void Lowcurrent_Charge(void);
unsigned int Measure(void);
//----------------------------------------------------------------------------// UNIONs, STRUCTUREs, and ENUMs
//----------------------------------------------------------------------------typedef union LONG {
// byte-addressable LONG
long l;
unsigned char b[4];
} LONG;
typedef union INT {
int i;
unsigned char b[2];
} INT;
typedef struct
{
unsigned long int t_count;
int sec;
int min;
int hour;
}time_struct;
// byte-addressable INT
// global seconds
// global minutes
// global hour
//----------------------------------------------------------------------------// Global Variable Definitions
//----------------------------------------------------------------------------time_struct TIME;
// Global Struct to Track Time
26
Rev. 1.3
AN146
char bdata TERMINATION;
char bdata CHARGE_STATUS;
INT code CHECK_BYTE
_at_
LONG code VOLT_SLOPE
_at_
LONG code VOLT_OFFSET
_at_
LONG code I_NOAMP_SLOPE _at_
LONG code I_NOAMP_OFFSET _at_
LONG temp_LONG_1,temp_LONG_2;
INT temp_INT_1,temp_INT_2;
int Current = 0;
int Voltage = 0;
0x1A00;
0x1A60;
0x1A64;
0x1A70;
0x1A74;
//
//
//
//
//
//
//
//
//
//
//
//
Global Variable to Track Termination
Global Variable to Track Charging
0x0A0A Default value, for later use
Volt Slope Register
Volt Offset Register
Current Slope Register,ext. amp off
Current Offset Register,ext. amp.off
Temporary Storage Variables
Temporary Storage Variables
Most recent Current Measurement
used to account for voltage drop
across sense resistor
//----------------------------------------------------------------------------// Bit maskable CHARGE STATUS Register Definition
//----------------------------------------------------------------------------sbit BULK
= CHARGE_STATUS^0;
// bit 0 : BULK charge status bit
sbit LOWCURRENT = CHARGE_STATUS^1;
// bit 1 : LOWCURRENT charge status bit
sbit ERROR
= CHARGE_STATUS^2;
// bit 2 : ERROR before/during charging
sbit CONST_V
= CHARGE_STATUS^3;
// bit 3 : charged w/ constant VOLTAGE
sbit CONST_C
= CHARGE_STATUS^4;
// bit 4 : charged w/ constant CURRENT
sbit DELAY
= CHARGE_STATUS^5;
// bit 5 : BULK charge DELAY for LiIon
//
after CURRENT threshold detection
sbit READY
= CHARGE_STATUS^6;
// bit 6 : Lowcurrent charge is
//
terminated; battery is charged
sbit FREE1
= CHARGE_STATUS^7;
// bit 7 : Not Currently used
//----------------------------------------------------------------------------// Bit Maskable TERMINATION Register Definition
//----------------------------------------------------------------------------sbit TEMP_MIN = TERMINATION^0;
// bit 0 : minimum TEMPERATURE overflow
sbit TEMP_MAX = TERMINATION^1;
// bit 1 : maximum TEMPERATURE overflow
sbit I_MIN
= TERMINATION^2;
// bit 2 : minimum CURRENT overflow
sbit I_MAX
= TERMINATION^3;
// bit 3 : maximum CURRENT overflow
sbit TIME_MAX = TERMINATION^4;
// bit 4 : maximum time overflow
sbit VOLT_MAX = TERMINATION^5;
// bit 5 : maximum VOLTAGE overflow
sbit VOLT_MIN = TERMINATION^6;
// bit 6 : minimum VOLTAGE overflow
sbit FREE2
= TERMINATION^7;
// bit 7 : Not Currently used
//----------------------------------------------------------------------------// Bit maskable PORT Definitions
//----------------------------------------------------------------------------sbit LED0
= P0 ^ 2;
// bit 2 : LED0, Pin P0.2
sbit CMPOUT
= P0 ^ 3;
// bit 3 : Comparator Output
sbit CMPIN1
= P0 ^ 4;
// bit 4 : Comparator + Input
sbit CMPIN2
= P0 ^ 5;
// bit 5 : Comparator - Input
sbit CEX0
= P0 ^ 6;
// bit 6 : Frequency Output Mode.
sbit CEX1
= P0 ^ 7;
// bit 7 : 8-bit PWM
// AMUX Selections; Analog Inputs
#define VBAT
0xF0;
// bit 0 : Voltage Ch.; Analog In
#define IBAT
0xF1;
// bit 1 : Current Ch.; Analog In
#define TBAT
0xF8;
// bit 2 : Temp.
Ch.; Analog In
//----------------------------------------------------------------------------// 8051F300 PARAMETERS
//----------------------------------------------------------------------------#define SYSCLK
24500000
// System clock frequency
#define TEMP_SENSOR_GAIN
3300
// Temp Sensor Gain in (uV / degC)
#define TEMP_GAIN
2
// PGA gain setting
Rev. 1.3
27
AN146
#define
#define
#define
#define
#define
INT_CURRENT_GAIN
EXT_CURRENT_GAIN
VREF
SCRATCH_PAGE
PWM_CLOCK
1
10
3300
0x1C00
SYSCLK/255
//
//
//
//
//
PGA gain setting
External gain setting
ADC Voltage Reference (mV)
FLASH page used for temp storage
PWM frequency is 96 kHz
//----------------------------------------------------------------------------// Calibration/Calculation PARAMETERS
//----------------------------------------------------------------------------#define V1_CAL
67
// 1st cal point for 2 point cal.
#define V2_CAL
2800
// 2nd cal point for 2 point cal.
#define I1_CAL
33
// 1st cal point for 2 point cal.
#define I2_CAL
2800
// 2nd cal point for 2 point cal.
#define RSENSE
24
// RSENSE is default to 240mohm
#define RESB
20
// 20k Ohms,Voltage Divide Resistor
#define RESAB
30
// 30k Ohms,Sum of Divide Resistor
#define TEMP_SLOPE ((long) TEMP_GAIN * TEMP_SENSOR_GAIN * 65536 / 100 / VREF)
// An estimate of the Temperature<SLOPE>
// in [tenth codes / K]
// The temperature measurement is
// within 3 degrees of accuracy.
//----------------------------------------------------------------------------// Monitor_Battery Switch PARAMETERS
//----------------------------------------------------------------------------#define TEMPERATURE
7
// Value for Switch Statement
#define VOLTAGE
5
// Value for Switch Statement
#define VOLTAGE_PWM_OFF
3
// Value for Switch Statement
#define CURRENT
1
// Value for Switch Statement
//----------------------------------------------------------------------------// Battery/Pack Parameters
//----------------------------------------------------------------------------#define CELLS
1
// Number of cells in the battery pack
#define CAPACITY
250
// mAh, Battery Capacity (LiIon)
#define LiIon_CELL_VOLT
4200
// mV, Nominal Charge Voltage
#define I_BULK
(unsigned int)(CAPACITY)
#define I_LOWCURRENT
(unsigned int)(135)
#define VOLT_BULK
(unsigned int)(CELLS*LiIon_CELL_VOLT)
#define VOLT_LOWCURRENT
(unsigned int)(CELLS*LiIon_CELL_VOLT)
#define
#define
#define
#define
(unsigned int)(CELLS*LiIon_CELL_VOLT/100)// 1 Percent Acc
(unsigned int)(CAPACITY/10)
// 10 Percent Acc
100
// Minium Battery Charging is 100 mA
1350
// Maximum Allowed Current to Protect Hardware
VOLT_TOLERANCE
CURRENT_TOLERENCE
IMIN
IMAX
//----------------------------------------------------------------------------// Battery Characteristics: Charge TERMINATION Limits
//----------------------------------------------------------------------------#define MIN_TEMP_ABS
26300
// Abs. min. TEMPERATURE = -10 C, 263K
#define MAX_TEMP_ABS
35300
// Abs. max. TEMPERATURE = 70C, 323K:
#define MIN_VOLT_BULK
(unsigned int)(CELLS*LiIon_CELL_VOLT*2/3) // Minimum BULK Voltage
#define MAX_VOLT_ABS
(unsigned int)(CELLS * LiIon_CELL_VOLT)
#define MIN_I_BULK
(unsigned int)(125)
#define MAX_TIME_LOWCURRENT 30
// Max Lowcurrent Charge Time = 90min
#define MAX_TIME_BULK
90
// Maximum BULK Charge Time = 90 min
28
Rev. 1.3
AN146
#define BULK_TIME_DELAY
END OF FILE
30
//
at 1C CURRENT
// DELAY = 30min after “MIN_I_BULK”
Rev. 1.3
29
AN146
Appendix F - Firmware (Source File)
//----------------------------------------------------------------------------//
// Copyright 2003 Cygnal Integrated Products, Inc.
//
// Filename:
F300_HighSpeed_BC.c
// Target Device: 8051F300
// Created:
1 March 2003
// Created By:
DKC
// Tool chain:
KEIL Eval C51
//
// This is a stand alone battery charger for a Lithium ION battery.
// It utilizes a buck converter, controlled by the on-chip 8-bit PWM,
// to provide constant current followed by constant voltage battery charge.
// The High Frequency Output Mode is used to generate the switch rate.
// The default rate is 510 kHz.
//
//----------------------------------------------------------------------------// Includes
//----------------------------------------------------------------------------#include <c8051f300.h>
#include “F300_HighSpeed_BC.h”
// Battery Hearder File
//----------------------------------------------------------------------------// Functions
//----------------------------------------------------------------------------void Config_F300(void)
{ RSTSRC
= 0x02;
XBR0
= 0x37;
XBR1
= 0x90;
XBR2
= 0x40;
//
//
//
//
//
//
Enable VDD Monitor
Skip P0.0,1,2,4,5; they’re analog In
Enable P0.6, P0.7, as CEX0 and CEX1
Make CEX0 an 8-Bit PWM
and CEX1 Frequency Output Mode
Also, Enable crossbar and weak pull-ups
CMPIN2
CMPIN1
= 1;
= 0;
// Make Comparator Output Initially low
// to minimize current spikes on start-up
P0MDOUT
P0MDIN
= 0xC8;
= 0xC8;
// Set P0.3,6,7 output to push-pull
// Configure P0.0,1,2,4,5 as Analog Inputs
OSCICN
= 0x07;
// Set SYSCLK to 24.5MHz, internal osc.
ADC0CN
= 0xC0;
// Turn on the ADC Module;
// enable low power mode for settling
REF0CN
= 0x0C;
// Configure ADC’s to use VDD for
// Voltage Reference,
// Enable On-chip Temperature Sensor
//---------------------------------------------------------------// Comparator Register Configuration
//---------------------------------------------------------------CPT0MX = 0x22;
30
// Comparator 0 MUX Selection Register
// P0.4,5 Input to Comparator
Rev. 1.3
AN146
CPT0MD = 0x00;
CPT0CN = 0x80;
// P0.3 Output of Comparator
// Comparator 0 Mode Selection Register
// Comparator 0 Control Register, Turn on
//----------------------------------------------------------------------------// PCA Configuration
//----------------------------------------------------------------------------PCA0MD
= 0x00;
// Disable WDT
PCA0MD
= 0x08;
// Set PWM Time base = SYSCLK
PCA0L
PCA0H
= 0x00;
= 0x00;
// Initialize PCA Counter to Zero
PCA0CN
= 0x40;
//Module
PCA0CPM0
PCA0CPL0
PCA0CPH0
0
= 0x00;
= 0x28;
= 0x28;
// Enable PCA Counter
// Clear PCA Counter Overflow flag
//Module
PCA0CPM1
PCA0CPL1
PCA0CPH1
1
= 0x42;
= 0xE0;
= 0xE0;
//Module 2
PCA0CPM2 = 0x49;
PCA0CPL2 = 0xFF;
PCA0CPH2 = 0x00;
}
EIE1
= 0x08;
//
//
//
//
Configure CCM0 to Frequency
Initialize PCA PWM to small
0x18 makes output frequency
0x28 makes output frequency
Output Mode
duty cycle
~510kHz
~306kHz
// Configure CCM0 to 8-bit PWM mode
// Initialize PCA PWM to small duty cycle
// 0xB9 Ensures a Soft Initial Charge
//
//
//
//
//
//
Configure Module 1 as software timer
Initialize to 255 so that Interrupt
is generated when PCA ends
8-bit PWM Cycle
PCA0CPH is the high byte of the
Output Compare Module
// Enable PCA Overflow Interrupt
//----------------------------------------------------------------------------// Reset_Time_Base - Resets all Time Counting Values
//----------------------------------------------------------------------------void Reset_Time_Base()
{
TIME.sec
= 0x00;
TIME.min
= 0x00;
TIME.hour
= 0x00;
TIME.t_count = PWM_CLOCK;
}
//----------------------------------------------------------------------------// Initialize CalibrateADCforVoltageMeasurement
//----------------------------------------------------------------------------// This function calibrates the voltage channel and stores the calibration
// coefficients in the parameters volt_slope and volt_offset.
//
void CalibrateADCforMeasurement()
// This calibration routine uses a 2 point cal.
{ unsigned char xdata *pwrite;
// FLASH write pointer
long i=0;
Rev. 1.3
31
AN146
EA = 0;
// Disable All Interrupts
// Wait until 1st calibration voltage is ready for cal
//while (SW0 == 1);
// Wait until SW0 pushed
for (i=0;i<100000;i++);
// Wait for Switch Bounce
// Once ready, Get the first calibration voltage
AMX0SL = VBAT;
// Select appropriate input for AMUX
ADC0CF = (SYSCLK/5000000) << 3;
// ADC conversion clock = 5.0MHz
ADC0CF &=0xF8;
// Clear any Previous Gain Settings
ADC0CF |= 0x01;
// PGA gain = 1
temp_INT_1.i = Measure();
// Wait until 2nd calibration voltage is ready for cal
//while (SW0 == 1);
// Wait until SW0 pushed
//for (i=0;i<100000;i++);
// Wait for Switch Bounce
// Once ready, Get the 2nd calibration voltage
AMX0SL = VBAT;
//Change Mux for second point
temp_INT_2.i = Measure();
// Calculate the SLOPE
// V1 and V2 are in tenth of a degree
temp_LONG_1.l = (unsigned)(temp_INT_2.i-temp_INT_1.i);
temp_LONG_1.l *= (unsigned)100;
// Account for Math Truncation Error
temp_LONG_1.l /= (unsigned)(V2_CAL - V1_CAL);
// Calculate the OFFSET
temp_LONG_2.l = (unsigned)temp_INT_1.i;
temp_LONG_2.l -= (signed)(temp_LONG_1.l * V1_CAL/100);
temp_LONG_1.l = 2050;
temp_LONG_2.l = 0;
// If no cal. use these
// as default values
// Erased memory at page 0x1A00
pwrite = (char xdata *)&(CHECK_BYTE.b[0]);
PSCTL = 0x03;
// MOVX writes target FLASH memory;
// FLASH erase operations enabled
FLKEY = 0xA5;
FLKEY = 0xF1;
*pwrite = 0x00;
// FLASH key sequence #1
// FLASH key sequence #2
// initiate PAGE erase
// Write the Volt SLOPE and OFFSET to Flash
PSCTL = 1;
// MOVX writes to Flash
pwrite = (char xdata *)&(VOLT_SLOPE.b[0]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable flash write
*pwrite = temp_LONG_1.b[0];
pwrite = (char xdata *)&(VOLT_SLOPE.b[1]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable flash write
*pwrite = temp_LONG_1.b[1];
pwrite = (char xdata *)&(VOLT_SLOPE.b[2]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable flash write
*pwrite = temp_LONG_1.b[2];
32
Rev. 1.3
AN146
pwrite = (char xdata *)&(VOLT_SLOPE.b[3]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable flash write
*pwrite = temp_LONG_1.b[3];
pwrite = (char xdata *)&(VOLT_OFFSET.b[0]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[0];
pwrite = (char xdata *)&(VOLT_OFFSET.b[1]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[1];
pwrite = (char xdata *)&(VOLT_OFFSET.b[2]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[2];
pwrite = (char xdata *)&(VOLT_OFFSET.b[3]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[3];
PSCTL = 0;
flash write
flash write
flash write
flash write
// MOVX writes target XRAM
//----------------------------------------------------------------------------// Initialize CalibrateADCforCurrentMeasurement_NOAMP
//----------------------------------------------------------------------------// This function calibrates the current channel with no external amp
// and stores the calibration coefficients in the
// parameters i_noamp_slope and i_noamp__offset.
//
// This calibration routine uses a 2 point cal.
// Wait until calibration voltage is ready for cal
//while (SW0 == 1);
// Wait until SW0 pushed
//for (i=0;i<100000;i++);
// Wait for Switch Bounce
// Once ready, Get the first calibration voltage
AMX0SL = IBAT;
// Select appropriate input for AMUX
ADC0CF = (SYSCLK/5000000) << 3;
// ADC conversion clock = 5.0MHz
ADC0CF &=0xF8;
// Clear any Previous Gain Settings
ADC0CF |= 0x03;
// Set PGA gain = 4
temp_INT_1.i = Measure();
// Acquire 16-bit Conversion
temp_INT_1.i *= 2;
// Account for Differential Mode
// Wait until 2nd calibration voltage is ready for cal
//while (SW0 == 1);
// Wait until SW0 pushed
//for (i=0;i<100000;i++);
// Wait for Switch Bounce
// Once ready, Get the 2nd calibration voltage
temp_INT_2.i = Measure();
// Acquire 16-bit Conversion
temp_INT_2.i *=2;
// Account for Differential Mode
// Calculate the
temp_LONG_1.l =
temp_LONG_1.l *=
temp_LONG_1.l /=
temp_LONG_1.l /=
SLOPE
(unsigned)(temp_INT_2.i - temp_INT_1.i);
(unsigned)100;
// Account for Math Truncation Error
(unsigned)(I2_CAL - I1_CAL);
(unsigned)INT_CURRENT_GAIN;// Account for Gain
// Calculate the OFFSET
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temp_LONG_2.l = (signed)(temp_INT_1.i/INT_CURRENT_GAIN);
temp_LONG_2.l -= (signed)(temp_LONG_1.l * V1_CAL/100);
temp_LONG_1.l = 2050;
temp_LONG_2.l = 0;
// If no cal. use these
// as default values
// Memory at 0x1A00 is already erased
// Write the Volt SLOPE and OFFSET to Flash
PSCTL = 1;
// MOVX writes to Flash
pwrite = (char xdata *)&(I_NOAMP_SLOPE.b[0]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_1.b[0];
pwrite = (char xdata *)&(I_NOAMP_SLOPE.b[1]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_1.b[1];
pwrite = (char xdata *)&(I_NOAMP_SLOPE.b[2]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_1.b[2];
pwrite = (char xdata *)&(I_NOAMP_SLOPE.b[3]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_1.b[3];
pwrite = (char xdata *)&(I_NOAMP_OFFSET.b[0]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[0];
pwrite = (char xdata *)&(I_NOAMP_OFFSET.b[1]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[1];
pwrite = (char xdata *)&(I_NOAMP_OFFSET.b[2]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[2];
pwrite = (char xdata *)&(I_NOAMP_OFFSET.b[3]);
FLKEY = 0xA5;
FLKEY = 0xF1;
// enable
*pwrite = temp_LONG_2.b[3];
}
PSCTL = 0;
flash write
flash write
flash write
flash write
flash write
flash write
flash write
flash write
// MOVX writes target XRAM
//----------------------------------------------------------------------------// Measure
//----------------------------------------------------------------------------//
// This routine averages 65536 ADC samples and returns a 16-bit unsigned
// result.
//
unsigned int Measure (void)
{
unsigned i;
// sample counter
unsigned long accumulator=0L;
// here’s where we integrate the
// ADC samples
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// read the ADC value and add to running total
i = 0;
do {
AD0INT = 0;
// clear end-of-conversion indicator
AD0BUSY = 1;
// initiate conversion
while(!AD0INT);
// wait for conversion to complete
accumulator += ADC0;
// read adc value and accumulate
i++;
// update counter
} while (i != 0x0000);
}
// the accumulator now contains 16 added bits of which 8 are usable
return (unsigned int) (accumulator >> 8);
//----------------------------------------------------------------------------// Regulate_Current
//----------------------------------------------------------------------------// This routine monitors the battery’s current and adjusts
// the PWM (i.e. duty cycle) to keep the current at a known value
//
void Regulate_Current(int passed_current)
{ unsigned int temp = 0,delay_count = 0;
do{
temp = Monitor_Battery(CURRENT);
// Measure Current
if (temp < passed_current)
{
PCA0CPH1--;
for(delay_count = 0;delay_count<2500;delay_count++);
}
if (temp > passed_current)
{ PCA0CPH1++;
for(delay_count = 0;delay_count<2500;delay_count++);
}
}while ((temp < (passed_current - CURRENT_TOLERENCE)) ||
(temp > (passed_current + CURRENT_TOLERENCE)));
// I_BULK or I_LOWCURRENT is set now
temp = Monitor_Battery(VOLTAGE_PWM_OFF);
// If VOLTAGE within range,
// change from constant CURRENT charge
// mode to constant VOLTAGE charge mode
if ((temp >= (VOLT_LOWCURRENT - VOLT_TOLERANCE*2)) &&
(temp <= (VOLT_LOWCURRENT + VOLT_TOLERANCE*2)))
{
CONST_C = 0;
CONST_V = 1;
}
}
//----------------------------------------------------------------------------// Regulate_Voltage
//----------------------------------------------------------------------------// This routine monitors the battery’s voltage and adjusts
// the PWM (i.e. duty cycle) to keep the voltage at a known value
//
void Regulate_Voltage(void)
{ unsigned int temp = 0,delay_count = 0;
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do{
temp = Monitor_Battery(VOLTAGE);
// set VOLT_BULK (with “soft start”)
if (temp < VOLT_BULK)
{
PCA0CPH1--;
for(delay_count = 0;delay_count<2500;delay_count++);
}
if (temp > VOLT_BULK)
{ PCA0CPH1++;
for(delay_count = 0;delay_count<2500;delay_count++);
}
}
}while ((temp < (VOLT_BULK - VOLT_TOLERANCE)) ||
(temp > (VOLT_BULK + VOLT_TOLERANCE)));
// VOLTAGE is set now
//----------------------------------------------------------------------------// Turn_PWM_Off
//----------------------------------------------------------------------------// This routine peforms a soft charge turn off by taking the PWM’s
// duty cycle slowly to zero.
//
void Turn_PWM_Off(void)
{
do{
if (PCA0CPH1 < 0xF0)
PCA0CPH1++;
}while (PCA0CPH1 < 0xF0);
// Duty Cycle is now small and safe to turn off.
}
PCA0CPM0 = 0x00;
// Disable PWM
//----------------------------------------------------------------------------// Monitor_Battery
//----------------------------------------------------------------------------// This routine acts as a switch when gathering different conversion types.
// It adjusts the throughput, adjust the AMUX and returns the current in mA,
// voltage in mV, and temperature in C, 2% accurate.
//
int Monitor_Battery(unsigned char value)
{
char i;
unsigned long av =0,delay_count=0;
long signed result;
ADC0CF = (SYSCLK/5000000) << 3;
ADC0CF &= 0xF8;
switch (value)
{
case TEMPERATURE:
//Turn_PWM_Off();
AMX0SL = TBAT;
ADC0CF |= 0x02;
break;
36
// ADC conversion clock = 5.0MHz
// Clear any Previous Gain Settings
// Turn PWM Off
// Select appropriate input for AMUX
// Set PGA gain = 2
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case VOLTAGE:
AMX0SL = VBAT;
ADC0CF |= 0x01;
break;
// Select appropriate input for AMUX
// Set PGA gain = 1
case VOLTAGE_PWM_OFF:
//Turn_PWM_Off();
AMX0SL = VBAT;
ADC0CF |= 0x01;
break;
// Turn PWM Off
// Select appropriate input for AMUX
// Set PGA gain = 1
case CURRENT:
AMX0SL = IBAT;
ADC0CF |= 0x01;
break;
// Select appropriate input for AMUX
// Set PGA gain = 1
}
//Compute average of next 10 A/D conversions
for(delay_count = 0;delay_count<2500;delay_count++);// Allow Settling Time
for(av=0,i=10;i;--i){
AD0INT = 0;
// clear end-of-conversion indicator
AD0BUSY = 1;
// initiate conversion
while(!AD0INT);
// wait for conversion to complete
av = av+ADC0;
}
av = av/10;
av = av<<8;
// Compute the average
// Convert to 16-bit conversion
// ...to account for 16-bit cal.
//
coefficients
PCA0CPM0 = 0x46;
// Turn on PWM
switch (value)
{ case TEMPERATURE:
result = (long) av * 1000/TEMP_SLOPE;
break;
}
case VOLTAGE:
case VOLTAGE_PWM_OFF:
result = (av - VOLT_OFFSET.l);
// Account for System Errors
result *= 100;
// Account for Math Truncation Error
result *= RESAB;
// Account for Divide Resistors
result /= VOLT_SLOPE.l;
// Convert to Voltage in Millivolts
result /= RESB;
result -= ((RSENSE*Current)/100); // Account for Sense Resistor Voltage Drop
break;
case CURRENT:
result = (av - I_NOAMP_OFFSET.l); // Account for System Errors
result *= 100;
// Account for Math Truncation Error
result *= 100;
// Account for Sense Resistor
result /= I_NOAMP_SLOPE.l;
// Convert to Milliamps
result /= RSENSE;
// Account for Sense Resistor
result /= EXT_CURRENT_GAIN;
// Account for external Amplifier
Current = (int) result;
break;
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}
return (int) result;
//----------------------------------------------------------------------------// Bulk_Charge Function
//----------------------------------------------------------------------------void Bulk_Charge(void)
{
unsigned int temp = 0;
unsigned int bulk_finish_hour = 0;
unsigned int bulk_finish_min = 0;
unsigned int delay_hour = 0;
unsigned int delay_min = 0;
unsigned int last_min = 0;
Reset_Time_Base();
// Reset Time Base to zero
// Calculate BULK charge finish time
bulk_finish_min = (TIME.min + MAX_TIME_BULK);
bulk_finish_hour = TIME.hour;
while (bulk_finish_min > 60)
{
bulk_finish_min = bulk_finish_min - 60;
bulk_finish_hour++;
}
CONST_C = 1;
DELAY
= 0;
// Start in constant current charge mode
// Reset timer DELAY
temp = Monitor_Battery(TEMPERATURE);
// Monitor Temperature
// Is temperature within range?
if ((temp > MIN_TEMP_ABS) && (temp < MAX_TEMP_ABS))
{
temp = Monitor_Battery(VOLTAGE);
// Monitor Voltage
// Is Voltage within range?
Voltage = temp;
// for Debug
if ((temp <= (MAX_VOLT_ABS + VOLT_TOLERANCE)) && (temp > MIN_VOLT_BULK))
{
PCA0CPM0 = 0x46;
// Turn on PWM
// Enter main loop in Bulk_Charge()
while ((BULK == 1) && (ERROR == 0))
{
if (CONST_C == 1)
Regulate_Current(I_BULK);
else if (CONST_V == 1)
{ Current = Monitor_Battery(CURRENT);
// Measure Current
if((Current < IMIN)||(Current > IMAX))
{ CONST_V = 0;
// Exit CONST_V
CONST_C = 1;
// Prepare to enter CONST_C
BULK = 0;
// Prepare to exit BULK mode
LOWCURRENT = 1;
// Prepare to enter LOWCURRENT Mode
if (Current < IMIN)
I_MIN = 1;
// Indicate Specific Error for Debug
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else
I_MAX = 1;
// Indicate Specific Error for Debug
}
else if ((Current < IMAX) && (Current > IMIN))
{ I_MAX = 0;
// Reset Error Flag
I_MIN = 0;
// Reset Error Flag
Regulate_Voltage();
// Charge with Constant Voltage
}
}
// Now, Check for error and charge termination conditions
// If above max charge time, flag error
// Test for BULK Charge Time Out
// Monitor Time
if ((TIME.hour == bulk_finish_hour) && (TIME.min == bulk_finish_min)
&& (DELAY == 0))
{
Turn_PWM_Off();
// Turn Off PWM
TIME_MAX = 1;
// Set Time max error flag
ERROR
= 1;
// Set general error flag
}
{
// Monitor Temperature
temp = Monitor_Battery(TEMPERATURE);
if ((temp < MIN_TEMP_ABS) && (temp > MAX_TEMP_ABS))
Turn_PWM_Off();
if (temp < MIN_TEMP_ABS)
TEMP_MIN = 1;
else
TEMP_MAX = 1;
}
ERROR
= 1;
// Turn Off PWM
// Set Temperature below minimum flag
// Set Temperature exceeds maximum flag
// Set general error flag
// Minute elapsed?
// Check for minimum current
// if reached, enter last DELAY charge
if (TIME.min != last_min)
{
last_min = TIME.min;
if ((CONST_V == 1) && (DELAY == 0) && (Monitor_Battery(CURRENT)
<= MIN_I_BULK))
{
// Calculate TOP OFF Battery Time finish time
delay_min = (TIME.min + BULK_TIME_DELAY);
delay_hour = TIME.hour;
while (delay_min > 60)
{
delay_min = delay_min - 60;
delay_hour++;
}
DELAY = 1;
// Set Delay Flag
}
// Monitor Delay time, time up?
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}
}
}
}
if ((TIME.hour == delay_hour)&&(TIME.min == delay_min) &&
(DELAY == 1))
{
Turn_PWM_Off();
// Turn Off PWM
CONST_V = 0;
// Exit CONST_V
CONST_C = 1;
// Prepare to enter CONST_C
BULK = 0;
// Prepare to exit BULK mode
LOWCURRENT = 1;
// Prepare to enter LOWCURRENT Mode
}
else if(ERROR == 0)
{
if (temp > (MAX_VOLT_ABS + VOLT_TOLERANCE))
{ VOLT_MAX = 1;
// Set Max Voltage error flag
ERROR
= 1;
// Set general error flag
}
else if(temp < MIN_VOLT_BULK)
{ VOLT_MIN = 1;
// Set Minimum bulk voltage error flag
LOWCURRENT = 1;
// Switch to LOWCURRENT mode
BULK = 0;
// Exit Bulk Charge mode
}
// battery’s voltage very low
}
else if(ERROR == 0)
{
if (temp < MIN_TEMP_ABS)
TEMP_MIN = 1;
else
TEMP_MAX = 1;
}
}
// End Main While loop
ERROR = 1;
// Absolute temperature out of range?
// Set Temperature below minimum flag
// Set Temperature exceeds maximum flag
// Set general error flag
//----------------------------------------------------------------------------// Lowcurrent_Charge
//----------------------------------------------------------------------------void Lowcurrent_Charge(void)
{
unsigned int temp = 0;
unsigned int lowcurrent_finish_min = 0;
unsigned int lowcurrent_finish_hour = 0;
Reset_Time_Base();
// Reset Time base to zero
// Calculate LOWCURRENT finish time
lowcurrent_finish_min = (TIME.min + MAX_TIME_LOWCURRENT);
lowcurrent_finish_hour = TIME.hour;
while (lowcurrent_finish_min > 60)
{
lowcurrent_finish_min = lowcurrent_finish_min - 60;
lowcurrent_finish_hour++;
}
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// Enter Main Lowcurrent Loop.
// Only exits are upon error and full charge
while ((LOWCURRENT == 1) && (ERROR == 0))
{
temp = Monitor_Battery(TEMPERATURE);// Get Temperature Reading
// Is TEMPERATURE within limits
if ((temp > MIN_TEMP_ABS) && (temp < MAX_TEMP_ABS))
{
// Is Battery’s Charge Voltage below max charge voltage
temp = Monitor_Battery(VOLTAGE); // Get Voltage Reading
if (temp <= (VOLT_LOWCURRENT + VOLT_TOLERANCE))
{
if (CONST_C == 1)
// CONST_C ?, charge w/ constant current
Regulate_Current(I_LOWCURRENT);
if (CONST_V == 1)
Regulate_Voltage();
// CONST_V?, charge w/ constant voltage
if ((temp >= MIN_VOLT_BULK) && (DELAY == 0))// Bulk Threshold voltage met?
{ LOWCURRENT = 0;
// Exit LOWCURRENT mode
BULK = 1;
// Switch to Bulk Charge mode
}
// Check elapsed time
if ((TIME.hour == lowcurrent_finish_hour) &&
( TIME.min == lowcurrent_finish_min))
{
TIME_MAX = 1;
// Set Time MAX error flag
ERROR
= 1;
// Set general error flag
}
}
else if(ERROR == 0)
{
VOLT_MAX = 1;
ERROR
= 1;
}
}
else if(ERROR == 0)
{
if (temp < MIN_TEMP_ABS)
TEMP_MIN = 1;
else
TEMP_MAX = 1;
}
}
}
ERROR = 1;
// Voltage to high?
// Set Max voltage error flag
// Set general error flag
// Absolute temperature out of range?
// Set Temperature below minimum flag
// Set Temperature exceeds maximum flag
// Set general error flag
//----------------------------------------------------------------------------// Main Function
//----------------------------------------------------------------------------void main(void)
{
EA = 0;
// Disable All Interrupts
Reset_Time_Base();
Config_F300();
// Config F300
//Turn_PWM_Off();
// Turn PWM off before Calibration
//CalibrateADCforMeasurement();
// Calibrate F300
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EA = 1;
// Enable All Active Interrupts
while(1)
{
LED0 = 0;
// Turn LED0 off
TERMINATION = 0x00;
CHARGE_STATUS = 0x00;
LOWCURRENT = 0;
BULK = 1;
CONST_C = 1;
while (ERROR == 0)
{
if (BULK == 1)
{
Bulk_Charge();
}
if (LOWCURRENT == 1)
Lowcurrent_Charge();
}
if (ERROR == 1)
{
Turn_PWM_Off();;
EA = 0;
while (1);
}
}
}
// Reset Termination Flags
// Reset Charge Status Flags
// Start in LOWCURRENT Charge Mode
// Enter Bulk Charge Mode
// Enter Lowcurrent_Charge function
// Toggle LED0 at 1 Hz rate via ISR
//
//
//
//
Turn PWM Off
Disable All Interrupts
Enter a eternal loop
No recovery except “reset-button”
//----------------------------------------------------------------------------// Interrupt Service Routines
//----------------------------------------------------------------------------//----------------------------------------------------------------------------// PCA_ISR
//----------------------------------------------------------------------------// This routine counts the elapsed time in seconds, minutes, hours.
// It also toggles LED0 every second when in Lowcurrent Charge Mode.
// This routine interrupts every time the PCA counter overflows, every 256
// SYSCLK cycles. After SYSCLK/256 interrupts, one second has elapsed.
//
void PCA_OVERFLOW_ISR (void) interrupt 9
{ int time_sec;
PCA0CN = 0x40;
// Reset all PCA Interrupt Flags
PCA0H = 0x00;
if (0x0000 == --TIME.t_count)
{
TIME.t_count = PWM_CLOCK;
if ( 60 == ++TIME.sec )
{
TIME.sec = 0x00;
if ( 60 == ++TIME.min )
42
// Reset High Byte of PCA Counter
//
of 8-bit PWM we are using Module1
// Reset 1 Second Clock
// Account for elapsed seconds
// Reset second counter every minute
// Account for elapsed minutes
Rev. 1.3
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{
TIME.min = 0x00;
if ( 24 == ++TIME.hour )
TIME.hour = 0x00;
}
}
time_sec = TIME.sec;
}
}
// Reset minute counter every hour
// Account for elapsed hours
// Reset hour counter every day
if ((LOWCURRENT == 1) && (ERROR == 0))
{
// Blink LED0 at 1 Hz if in Lowcurrent
//if (TIME.sec % 2)
// LED0 = 0;
// Turn on LED every odd second
//else
// LED0 = 1;
// Turn on LED every even second
}
END OF FILE
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CONTACT INFORMATION
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Patent Notice
Silicon Labs invests in research and development to help our customers differentiate in the market with innovative low-power, small size, analogintensive mixed-signal solutions. Silicon Labs' extensive patent portfolio is a testament to our unique approach and world-class engineering team.
The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice.
Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences resulting from
the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Laboratories assume any
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