AN2361 USB-Powered Battery Charger for NiCd/NiMH Batteries.pdf

AN2361
USB-Powered Battery Charger for NiCd/NiMH Batteries
Author: Svyatoslav Paliy
Associated Project: Yes
Associated Part Family: CY8C24794
Software Version: PSoC Designer™ 5.4
Related Application Notes: For a complete list of the application notes, click here.
To get the latest version of this application note, or the associated project file, plea se visit
http://www.cypress.com/go/AN2361.
This application note describes a USB-powered battery charger for NiCd/NiMH batteries that permits rapid recharging.
Dedicated PC-based software has been developed to monitor and control the charging process in real time and to
display data in a graphical user interface. The charger can be embedded into consumer, office, and industrial
applications. It needs no drivers and starts working immediately when plugged into a USB port. A battery can be left in
the charger for any length of time without the risk of overcharge.
Contents
Introduction
Introduction ....................................................................... 1
Rapid Battery Charging ..................................................... 2
Charger Hardware ............................................................. 2
Charger Firmware ............................................................. 5
State Transition Descriptions........................................ 6
USB Connection ................................................................ 7
PC Utilities and Debugging ............................................... 7
Design Modifications ......................................................... 8
Summary ......................................................................... 10
Related Application Notes ............................................... 10
Appendix A. Charger Schematic ..................................... 11
Appendix B. Board Photo ................................................ 12
Worldwide Sales and Design Support ............................. 14
The growing popularity of wireless computer peripherals
such as the wireless mouse, keyboard, and similar devices
is likely to spur demand for a device that can be recharged
rapidly. Rechargeable batteries are also widely used in
peripheral and non-computer-related appliances.
The charger described in this application note can easily be
incorporated into computer peripherals. For example, one
battery can be located in a mouse or another wireless
device, and a second battery inserted into a combination
host/charger that is connected to the USB port of a
computer. When the battery in the peripheral device is
drained, you can simply swap the two batteries. Moreover,
this charger can charge or discharge user batteries under
manual charge control. You can control the charger from PC
software, immediately stopping or starting the charge
process. As an added option, it is possible to discharge the
battery before charging. This allows you to control the
charge level of batteries using a discharge-charge cycle.
This application note describes how the charger works, its
various aspects, and how it can be modified:





www.cypress.com
Rapid battery charging
Charger hardware
Charger firmware
USB connection
PC utilities and debugging
Document No. 001-17400 Rev. *E
1
USB-Powered Battery Charger for NiCd/NiMH Batteries


Figure 1. NiCd/NiMH Battery Pack Voltage in Time Graph
Design modifications
VBAT
Appendixes
Stop charge point
Battery is fully charged
Rapid Battery Charging
This charger uses the pulse method for nickel-based
batteries, which makes rapid battery charging possible and
preserves battery health. Table 1 lists the main charger
characteristics.
The battery is charged by constant current impulses of 5second duration, alternated with 0.5-second latent periods
during which no charge is applied. Then the charger
measures the battery voltage. When the battery voltage
stops increasing or starts decreasing, the battery is fully
charged. Figure 1 shows the charge termination criteria and
the battery voltage upon full charge.
Time
Charge Timeout
The charge stage should be limited by a timeout that
extends for approximately 120 to 150 percent of the
estimated time required to charge NiCd/NiMH batteries with
expected maximal capacity.
Table 1. Main Charger Characteristics
No.
Parameter Name
Two Cells
Three Cells
1
Voltage indicating battery presence, V
0.5
0.75
2
Recharge voltage level, V
1.8
2.7
3
Emergency charger stop voltage, V
3.5
5.25
4
Discharge stop voltage, V
1.0
1.5
INT – Switched capacitor–based integrator.
Charger Hardware
The charger system is shown in Figure 2. See Appendix
A. Charger Schematic for more details. The acronyms
used in Figure 2 are defined as follows:
USB – Full-speed Universal Serial Bus engine used to
receive control data from the PC and send data about
charger status and battery states to the PC.
DSM – Delta-sigma modulator for current regulator control
output.
ADC – Incremental analog-to-digital converter used to
measure battery voltage.
AMUX – Analog multiplexer used to switch between two
analog signals for measurement.
CPU – Central processor core to implement charge
algorithms and perform charge control functions.
INA – Switched capacitor-based instrumentation amplifier.
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Document No. 001-17400 Rev. *E
2
USB-Powered Battery Charger for NiCd/NiMH Batteries
Figure 2. Charger System with Switching Regulator
Current Sense
Q1
Charge Current
D3
L1
R9
R10
R11,
R12,
R13
D4
PC
Discharge
Current
Q2
VCC
Battery Pack
P2[1]
P2[3]
R19
Charge +
Power
USB
Data
Vb+ Sense
Vref
USB
+
INA
+
INT
VINA
VINT
P0[3]
RS-Trigger
DSM
Charge GND
-
Reset
Power
Vb- Sense
D1
P5[0]
P4[4]
R4
Set
R5
Q
Red
P2[0]
P5[2]
D5
CPU
D2
P0[7]
Green
R3
P0[1]
AMUX
ADC
R5
P0[5]
R8
PSoC Internals
The main task of the charger is efficient use of the
maximum allowed current from the USB bus (0.5 A) to
minimize total charge time. The amount of the current
drawn from a USB is insufficient for a fast battery charge
with a fixed amount of the current. It is the current drawn
from the USB that is controlled rather than the charge
current. The battery charge current is determined by the
instantaneous battery voltage, keeping regulator input
power maintained at a constant level.
The current regulator uses a hardware control loop. The
hardware control loop consists of an instrumentation
amplifier (INA) to handle a current sense resistor (R9)
signal; a differential integrator (INT), which acts as an
integrating difference amplifier; and a delta-sigma
modulator (DSM) as a voltage-to-pulse-density converter.
This loop controls the MOSFET gate duty cycle to keep
the input current constant. This hardware control loop
method enables the greatest use of available USB power.
This implementation uses three configurable switched
capacitor blocks: one for the instrumentation amplifier, one
for the differential integrator, and one for the delta-sigma
modulator. The configuration of parameters of the
switched capacitor block is described in AN2041 –
Understanding Switched Capacitor Analog Blocks. The
following equations describe the operation of the regulator:
VINA 
VINA 
C AINA
C INA
V
 BINA VP 2[3] ;
INA P 2[1]
CF
CF
C
C
INA
A
INA
F
VINA is the output voltage of the instrumentation amplifier,
and C AINA , CBINA , CFINA , C AINT , CBINT , and CFINT are values of
the capacitors in the switched capacitor blocks. For correct
operation, C AINA must be equal to CBINA . VP2[1] and VP2[3] are
the voltage on the PSoC®1 pins P2[1] and P2[3],
respectively. Rsense is the current sense resistor value. Ibus
is the current drawn from the USB power source. VINT is
the differential integrator output. Vref is the bandgap
reference voltage. In steady state, the integrator’s
differential input voltage, Vref – VINA, is driven to zero.
Thus, the target value of the regulator charging current
can be calculated as follows:
I bus 
If
CFINA  C AINT Vref
CBINT  C AINA  Rsense
CFINA =16,
C AINT =2,
Equation (3)
;
Vref
=1.3V,
CBINT =14,
C AINA = CBINA =31, and Rsense = 0.2 Ω, the charging current is
equal to 0.479 A. The charging current can be adjusted by
changing the capacitor values. However, the USB
specification enforces a 0.5-A current limitation.
The regulator’s typical operating waveforms are shown in
Figure 3. As the battery charges up, the pulse density of
the delta-sigma modulator decreases, as expected.
Equation (1)
Rsense I bus ; C AINA  CBINA ;
 C INT

C INT
VINT    AINT Vref  BINT VINA dt ;
C
C
 F
F

www.cypress.com
Equation (2)
Document No. 001-17400 Rev. *E
3
USB-Powered Battery Charger for NiCd/NiMH Batteries
Figure 3. Integrator Output (Upper Trace) and
Delta-Sigma Modulator Output (Lower Trace)
Figure 4. Regulator Efficiency
85
80
Effi, %
75
70
65
60
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
Uout, V
VP0[1] and VP0[5] are the voltages on pins P0[1] and P0[5],
respectively. The value ∆nV is the ADC value without the
amplifier and ADC offset voltages. The value nmax is the
maximum ADC code, with a value equal to 2047 for an
11-bit incremental ADC. The value Vbat is battery voltage,
and GV is the input amplifier gain, equal to 1. The value
Vref is the bandgap reference voltage (1.3 V), and βV is the
resistive divider coefficient, which is equal to 0.25 for
R3 = 150 kΩ, R5 = 100 kΩ, and R8 =150 kΩ divider
resistors:
a) When Battery Voltage is 3.9 V
V 
Equation (5)
The ADC and regulator share comparator bus 1. Because
the regulator and ADC never work simultaneously, the
comparator bus reconnects by firmware to the ADC to
provide measurement. The comparator bus reconnects to
the delta-sigma modulator for hardware control of the
charge state. See the Charger Firmware section.
b) When Battery Voltage is 1.3 V
The battery charge current is determined by input current,
battery voltage, and regulator efficiency. Regulator
efficiency based on real measurements is shown in
Figure 4.
Note that low efficiency at low voltage output is caused by
voltage drops on diodes D3 and D4.
The battery voltage is measured by an ADC using a
resistive divider to condition the signals to the allowed
level. Correlated double sampling is used to null AD offset
errors. The ADC first measures voltages on pin P0[1] and
offset errors on pin P0[5]. The battery voltage is calculated
as the difference between the voltages measured on P0[1]
and P0[5]. The derived voltage measurement is shown in
the following equation:
Equation (4)
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1
R3  R8
1
R5
The MOSFET Q4 allows the battery to be discharged
before a charge. If Q2 is activated, the current from the
battery flows though R11, R12, and R13, shown in
schematics in Figure 2 and Figure 7, which are connected
in parallel to provide greater thermal dissipation, See
Appendix A. Charger Schematic. This battery discharge
feature can be activated only from the PC software as an
option for battery training; it is not automatic.
The charger can be used in applications that require
leaving the battery in the charger after the charge cycle,
even if the PC power is turned off. Overcharging the
battery can cause permanent damage or decrease battery
capacity. To prevent battery overcharge, battery charging
is initiated only after PC start when the battery voltage falls
below a predefined limit. This limit is called the “charge
restart condition.” But if you insert the battery in the
charger, the charger starts immediately, without testing the
voltage.
Document No. 001-17400 Rev. *E
4
USB-Powered Battery Charger for NiCd/NiMH Batteries
To detect that a battery was changed when the charger
was not powered from a USB, a simple RS-trigger,
powered from the battery, is used. The RS-trigger
automatically enters the reset state after the power goes
on. Thus, changing the battery automatically resets the
trigger. If the battery is not replaced in the charger, the
recharge starts only if the battery voltage has fallen below
a predefined limit. When the battery is changed, a charge
is initiated regardless of battery voltage. The RS-trigger is
built from two bipolar transistors, Q3 and Q4. As a result of
nonsymmetrical resistances in bases (R4 versus R5) and
collector circuits (R1 versus R2), a reset state is always
triggered upon power up. Refer to Appendix A. Charger
Schematic.
Two LEDs, green and red, are used to indicate the
charger state. When the charger is connected to the USB,
both LEDs are switched on. After device enumeration, the
LEDs indicate the charger state. A green LED means a
charge is in process. When both LEDs are turned off,
everything is functioning properly but no charge is being
applied to the battery at this time, possibly because the
battery is fully charged or there is no battery in the
charger. A red light indicates an error condition. The
following section provides more information about the
charger state.
One digital block and interrupt-based firmware are used
for charge-time control. The PSoC Timer8 User Module
generates an interrupt with a frequency of 20 Hz and
clocks from VC3 (5,859 kHz).
The firmware is constructed as a state machine. Figure 5
shows the state diagram, in which active charge states are
highlighted in green and error states are highlighted in red.
Charger Firmware
Figure 5. Charger State Diagram
Stop
i
Discharge
g
m
Power On
Initialization
k
h
j
a
Wait
After
Discharge
l
Charge
p
b
f
o
No Battery
Wait
After
Charge
m
Voltage
Error
c
e
Timeout
Error
Charge
Complete
d
n
In Figure 5, state transitions are indicated by lines and
squares labeled with letters. See State Transition
Descriptions for explanations of the transitions. The states
in circles in Figure 5 are defined as follows:
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Initialization – Both LEDs are off. Test for battery
presence and state based on battery voltage.
Charge – Green LED is on. Charge for 5 seconds.
Document No. 001-17400 Rev. *E
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USB-Powered Battery Charger for NiCd/NiMH Batteries
Wait After Charge – Green LED is on. No charge, for 0.5
seconds.
Charge Complete – Both LEDs are off. No charge.
Battery is fully charged.
THEN Charge
If the battery voltage has fallen below the recharge voltage
level (possibly because the battery is self-discharging), the
battery charge is resumed.
Stop – Both LEDs are off. No charge. This state occurs
when the device gets a stop command from the PC. Wait
for the next command.
f)
Discharge – Green LED is on. Discharge is in progress
for 5 seconds.
If a battery is detected and is fully charged, transition to
the Charge Complete state occurs.
Wait After Discharge – Green LED is on. No charge, no
discharge, wait 0.5 seconds.
g)
No Battery – Both LEDs are off. Charger is turned off.
Wait for battery to be inserted.
If a stop command has been received from the PC, then
stop charging immediately, regardless of the current state.
Voltage Error – Red LED is on. Stop charging. Battery
voltage has reached the maximum permitted safe level.
The battery or charger may be damaged. Wait for battery
to be removed.
h)
Timeout Error – Red LED is on. Charging is stopped.
Charger has attempted to charge the battery for a
predefined period but detects that the battery has failed to
take a full charge. The battery may be damaged. Wait for
the battery to be removed.
State Transition Descriptions
The state transitions shown in Figure 5 are described as
follows:
a)
IF VNO-BATT < VBATT ≤ VRE-CH
THEN Charge Complete
THEN Stop
IF Charge command received
THEN Charge
If a charge command has been received from the PC, then
charging starts immediately, regardless of the battery
voltage.
i)
IF Discharge command received
THEN Discharge
If the discharge command is received from the PC, then
discharging starts immediately. This is the only way to
discharge the battery.
j)
IF TBATT ≤ TCOLD_STOP
Permits discharge of the battery for 5 seconds.
THEN Charge
k)
If a battery is detected and the battery is not already
charged, then the green LED is turned on, and transition
to the Charge state occurs.
IF VBATT > VDISCH
THEN Discharge
IF 5 seconds have elapsed
If batteries are not discharged, then discharge resumes
after 0.5 second.
THEN Wait After Charge
l)
IF VBATT ≤ VDISCH
THEN Charge
Charge the battery for 5 seconds.
c)
IF Stop command received
THEN Wait After Discharge
or BatteryChanged flag is set
b)
IF VRE-CH < VBATT
If the battery is fully discharged, transition to the Charge
state occurs.
IF battery voltage increasing
THEN Charge Complete
The charge termination criteria are that the voltage is
decreasing during a charge, or that the voltage remains
constant (no longer increasing) during a charge. If either
criterion is not met, then the battery charge continues.
d)
IF VBATT > VERR
THEN Voltage Error
IF battery voltage not increasing
If battery voltage exceeds the VERR level, transition to the
Voltage Error state occurs regardless of the present state.
THEN Charge Complete
n)
If termination criteria are met, the green LED is turned off
and the charge is stopped. Transition to the Charge
Complete state occurs.
e)
m)
IF VNO-BATT < VBATT ≤ VRE-CH
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IF duration of charge exceeds predefined limit
THEN Timeout Error
If the battery time charge exceeds a predefined limit, then
charging stops. The battery may be damaged.
Document No. 001-17400 Rev. *E
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USB-Powered Battery Charger for NiCd/NiMH Batteries
o)
IF VBATT ≤ VNO-BATT
THEN No Battery
Exit from the current state and transition to No Battery
state if the battery has been removed.
p)
IF VBATT > VNO-BATT
The supporting documents (see supporting files in the
project .zip) contain tables of the USB descriptors and HID
report descriptors. Both descriptors are represented in
PSoC style, corresponding to the USB Setup Wizard
tables.
PC Utilities and Debugging
THEN Charge
If a newly inserted battery is detected, a charge starts. A
charge always starts after a battery is inserted.
Note that if a battery is removed, then the charger goes to
the No Battery state from any other state except the Stop
state.
A time-based interrupt handler is used to implement sleep
mode (Suspend state of the USB). The interrupt handler
checks the bus activity bit. If the bus enters USB Suspend
mode, the charger goes into CPU sleep mode. The CPU
stays in sleep mode until it receives a wake-up event from
the USB. Sleep mode support is required for full
compliance with USB standards.
USB Connection
The charger uses USB for two purposes:

To receive and manually control data that relates to
the charge process.

As a power source for the charger
Logically, the charger is represented as a Human Interface
Device (HID). The charger requires only a low data rate.
An HID is very useful in this case. The advantage of an
HID is that no special driver is needed and software
support is simplified.
Dedicated charger control software has been developed to
monitor the charge process. The user interface (UI) is very
simple, as shown in Figure 6.
The UI consists of a chart that displays battery voltage,
labels indicating the present charger state (Stopped, in
Figure 6), battery voltage (2.79 V), and four buttons to
manually control the charge process.
The software is optional and not required for charger
operation.
Table 2 shows the data packets that are sent from the
charger to the PC and from the PC to the charger. The
data packet from the charger to the PC contains the
charger state and battery voltage. This package has a
length of 3 bytes, as specified in Table 2. Using this data,
the software builds a chart and prints the actual battery
voltage. The battery voltage is calculated in Equation (6)
from the returned ADC code by the inverse function of
Equation (4):
VBATT 
nV BATT
Vref nV BATT
GV V nmax
;
Equation (6)
is the battery voltage in ADC code from the data
packet.
The data packet from the PC to the charger contains a
single 1-byte command.
www.cypress.com
Document No. 001-17400 Rev. *E
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USB-Powered Battery Charger for NiCd/NiMH Batteries
Figure 6. Charger Monitoring Software
Charger
State
Battery
voltage
Chart with
Charge
Control
Buttons
Battery Voltage
Table 2. Data Packets
Item No.
Length in Bytes
Reference
Description
a) Data Packet from Charger to PC
1
2
1
2
State
nVBATT
Charger State
• INITIALIZATION = 0
• CHARGE = 1
• WAIT AFTER CHARGE = 2
• CHARGER COMPLETE = 3
• NO BATTERY = 4
• DISCHARGE = 5
• WAIT AFTER DISCHARGE = 6
• STOP = 7
• VOLTAGE ERROR = 8
• TIMEOUT ERROR = 9
Battery voltage in ADC code
b) Data Packet from PC to Charger
1
1
Cmd
Command to Charger
• STOP = 1
• CHARGE = 2
• RECHARGE = 3
• DISCHARGE = 4
• SET TIMEOUT = 5
Design Modifications
It is possible to decrease the cost of the charger by
eliminating the coil and Schottky diode and substituting a
pulse regulator with a linear current source. However, this
alternative increases the charge time because if a linear
regulator is used, the charge current is not greater than
0.5 A. The constant current source consists of an
instrumentation amplifier to sense the current and a
differential
integrator.
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Figure 7 shows the structure of a charger with a linear
current source. The DSM is eliminated, and the differential
integrator directly drives the MOSFET gate. The
differential amplifier inputs are swapped to obtain an
inverted signal on the output. The inverted signal is
required to form negative feedback in order to drive a
P-channel MOSFET. In contrast to a switching regulator,
the MOSFET in a linear regulator operates in linear mode.
As a result, the power dissipation on the MOSFET is
higher, so a small heat sink may be necessary. A PCB
plane is suitable for this role.
Document No. 001-17400 Rev. *E
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USB-Powered Battery Charger for NiCd/NiMH Batteries
Figure 7. Charger Structure with Linear Regulator
Current Sense
Charge Current
D3
Q1
R9
R11,
R12,
R13
R10
PC
Discharge
Current
Q4
VCC
Battery Pack
P2[1]
P2[3]
R20
R19
+
Power
USB
Data
INA
USB
VINA
Vb+ Sense
+
-
INT
Vref
D1
Red
Charge +
VINT
P0[1]
RS-Trigger
Charge GND
-
Reset
P5[0]
P4[4]
R4
Set
P2[0]
P5[2]
Power
R5
Vb- Sense
Q
D5
CPU
D2
P0[7]
Green
R3
P0[3]
AMUX
ADC
R5
P0[5]
R8
PSoC Internals
Figure 8 shows the charge current versus battery voltage
for the switching regulator.
Figure 9. Switching and Linear Regulator Output Power
Versus Battery Voltage
Figure 8. Charge Current Versus Battery Voltage
(mA)
2,2
1100
2,0
1000
1,8
900
1,6
Power, W
Iout
1200
800
700
Switching reg
Linear reg.
1,4
1,2
1,0
600
0,8
500
0,6
400
1,0
1,0
1,5
2,0
2,5
3,0
3,5
4,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
Uout,V
4,5
Uout (V)
For the linear regulator, the current is constant and does
not exceed 0.5 A. So when a switching regulator is used to
charge two batteries (2.6 V in a charged state), the charge
current is significantly greater than the charge current
when a linear current source is used. For three batteries
with 3.9 V in a charged state, the charge current is about
the same for both kinds of regulators. For deeply
discharged batteries (2.4 V), the charge current is greater.
However, the overall benefit is not great when a switching
regulator is used to charge three NiCd/NiMH batteries. So
in this case, a linear regulator can be used with a very
small loss of efficiency. Figure 9 shows switching and
linear regulator efficiencies against battery voltage.
www.cypress.com
Table 3 lists the time required to charge different batteries
when the two regulator types are used.
Table 3. Charge Time Examples
No.
Case
Time
1
Two cells by 1400 mAh using switching
regulator
189 min
2
Two cells by 1400 mAh using linear
regulator
323 min
3
Three cells by 1800 mAh using switching
regulator
384 min
4
Three cells by 1800 mAh using linear
regulator
426 min
Document No. 001-17400 Rev. *E
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USB-Powered Battery Charger for NiCd/NiMH Batteries
The USB charger is designed to be part of a more
complex system. Additional resources can be allocated to
the unused digital blocks. For example, the SPIM User
Module can be added for communication with the WUSB
User Module. The size of the firmware code is small,
about 4.5 KB (less than 30 percent of flash). A total of 104
bytes of SRAM is used for variables—13 percent using the
large memory model (LMM), 40 percent without.
Resources are thus available to combine this charger onto
one PSoC device with the user’s own design.
Summary
Related Application Notes
AN2041 – Understanding
Capacitor Analog Blocks
PSoC
1
Switched
About the Author
Name:
Svyatoslav Paliy.
Title:
Sys Desgn/Arch Engrg Mgr Sr
This application note demonstrated the USB-powered
NiCd/NiMH battery charger using the PSoC CY8C24794
device. It described both switching and linear regulator
methods, which you can select depending on cost and
efficiency requirements.
www.cypress.com
Document No. 001-17400 Rev. *E
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USB-Powered Battery Charger for NiCd/NiMH Batteries
Appendix A. Charger Schematic
DISCH
VN
VP
VDD
P2[3]
P2[1]
P4[7]
P4[5]
P4[3]
P4[1]
P3[7]
P3[5]
P3[3]
P3[1]
P5[7]
P5[5]
P5[3]
P5[1]
P0[6]
P0[4]
P0[2]
P0[0]
P2[6]
P2[4]
Vss
D+
DVdd
19
20
21
22
15
16
17
18
1
2
3
4
5
42
41
40
39
38
37
36
35
34
33
32
31
30
29
R1
330
R2
330
D1
RED
T_read
T_Set
D2
GREEN
Vbat
P7[7]
P7[0]
P1[0]
P1[2]
P1[4]
P1[6]
CY 8C24794
P1[7]
P1[5]
P1[3]
P1[1]
+5V
J1
P2[2]
P2[0]
P4[6]
P4[4]
P4[2]
P4[0]
P3[6]
P3[4]
P3[2]
P3[0]
P5[6]
P5[4]
P5[2]
P5[0]
23
24
25
26
27
28
1
2
3
4
5
6
7
8
9
10
11
12
13
14
IN
IP
48
47
46
45
44
43
50
49
Vss
Vdd
P2[5]
P2[7]
P0[1]
P0[3]
P0[5]
P0[7]
U1
56
55
54
53
52
51
DRIVE
R3
150K
R4
VDD
+5V
VP
10R
ISSP/DEBUG
R6
24R
+5V
C1
1u
R7
24R
+
R5
100K
C2
100u
VN
J2
Vdd
-D
+D
Gnd
1
2
3
4
R8
150K
USB-B
Switch-mode Regulator
IP
IN
Q1
IRLML6402
+5V
Vbat
D3
L1
R9 0.2R 1%
J3
47uH*
1
2
+
C3
100u
+
C5
0.1u
C4
100u
MBR320
R10
1M
D4
MBR320*
C6
1u
BATTERY
DRIVE
Linear Regulator
IP
IN
Q1
MMSF3P03HD
+5V
Vbat
D3
J3
R9 0.2R 1%
1
2
+
C3
100u
C5
0.1u
MBR320
C6
0.1u
R10
100K
R20 1.5K
BATTERY
DRIVE
Discharge Switch
RS-trigger
Vbat
R11
30R
Vbat
R12
30R
R14
47k
R13
30R
R15
330k
T_read
R16 1M
Q2
IRML2502
DISCH
R17
1M
Q3
BC817
R19
1M
R18
180k
Q4
BC817
D5
T_Set
LL4148
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Document No. 001-17400 Rev. *E
11
USB-Powered Battery Charger for NiCd/NiMH Batteries
Appendix B. Board Photo
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Document No. 001-17400 Rev. *E
12
USB-Powered Battery Charger for NiCd/NiMH Batteries
Document History
Document Title: USB-Powered Battery Charger for NiCd/NiMH Batteries - AN2361
Document Number: 001-17400
Revision
ECN
Orig. of
Change
Submission
Date
Description of Change
**
1352143
HMT
See ECN
New application note.
*A
1629363
HMT
See ECN
Updated to new template.
*B
2816409
SYVP
11/27/09
Updated PSoC Designer version and author email id.
Ported accompanying projects from PD 4.2 to PD 5.0.
*C
3113712
YARA
12/17/2010
Updated software version from PSoC Designer 5.0 to 5.1.
Updated the associated project files.
*D
4268216
RJVB
01/31/2014
Added Summary.
Updated Related Application Notes (Removed obsolete specs).
Updated to new template.
Completing Sunset Review.
*E
4568981
ASRI
11/14/2014
Updated Introduction:
Updated description.
Updated Rapid Battery Charging:
Updated description.
Updated Charger Hardware:
Updated description.
Updated Charger Firmware:
Updated description.
Updated State Transition Descriptions:
Updated description.
Updated USB Connection:
Updated description.
Updated PC Utilities and Debugging:
Updated description.
Updated Figure 6.
Updated Design Modifications:
Updated description.
Updated Figure 8.
Updated Summary:
Updated description.
Updated Related Application Notes:
Removed references of AN2203 and AN2260.
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Document No. 001-17400 Rev. *E
13
USB-Powered Battery Charger for NiCd/NiMH Batteries
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Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any
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Document No. 001-17400 Rev. *E
14