Page 1
Freescale Semiconductor
User’s Guide
Document Number: KT34676BUG
Rev. 1.0, 2/2009
Using the High Input Voltage Charger for Single Cell Li-Ion Batteries (KIT34676EPEVBE)
1Purpose
This User Guide helps the Lithium-Ion (Li-Ion) battery
charger designer understand the MC34676B and its
evaluation board. It illustrates the design procedure when
using the MC34676B to design a Li-Ion battery charger, and
the way to get the best performance from the MC34676B.
2Scope
The 34676 is a dual 28V input voltage and fully-integrated
single cell Li-Ion battery charger, targeting smart handheld
applications. One of the inputs is optimized for charging with
a USB port, and the second is optimized for an AC/DC
adapter power source. The charger has two 28V power
devices, to eliminate the need of any external power source
selection and input over-voltage protection circuitry. Each of
the power devices independently controls the charge
current from the input, and performs as an independent
charger. Only one of the two chargers operate at a time.
The AC charger current and the USB charger current are
programmable, up to 1.2A and 400mA, with an external
resistor respectively. The voltage across the two external
resistors is also used to monitor the actual charge current
through each charger respectively. The EOC current of both
chargers is the same, and programmable by an external
resistor. The 4.85V regulator can be used to power a
sub-system directly.
The 34676 has a 5% constant current accuracy for the AC
Charger over -40 to 85
accuracy over -40 to 85
foldback feature, limits the charge current when the IC
internal temperature rises to a preset threshold.
o
C, and a 1.0% constant voltage
o
C. A charge current thermal
Contents
1 Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3 Application Diagram . . . . . . . . . . . . . . . . . . . 2
4 Evaluation Board Specification . . . . . . . . . . 3
5 Component Selection . . . . . . . . . . . . . . . . . . 4
6 Layout Design . . . . . . . . . . . . . . . . . . . . . . . . 6
7 Evaluation Board Configuration . . . . . . . . . . 9
8 Test Setup with the Evaluation Board . . . . 11
9 Bill of Material. . . . . . . . . . . . . . . . . . . . . . . . 13
10 References . . . . . . . . . . . . . . . . . . . . . . . . . 13
© Freescale Semiconductor, Inc., 2009. All rights reserved.
Page 2
Application Diagram
3 Application Diagram
3.1 Dual-Input Standalone Charger
The MC34676B can be used as a dual-input standalone Li-Ion charger. Figure 1 is the typical application circuit. Two
LEDs indicate the charge status.
C1
C2
USBEN
ON
OFF
3.2 Embedded Charger
When the MC34676B is embedded in the system, the system MCU can control the charger through the USBEN pin and
get the charge status through
C1 C2
AC
USB
BAT
USBOUT
BATDET
GND
MC34676B
PPR
CHG
IMIN IUSB
R
IMIN
R
IUSB
ISET
R
ISET
Figure 1. The dual-input Li-Ion Charger
PPR and CHG pins. Figure 2 is the typical application circuit.
MC34676B
AC
USB
GND
BAT
BATDET
USBOUT
C
C
3
4
C4
C3
IMIN
IUSB ISET
R
IMIN
R
IUSB
R
ISET
USBEN
PPR
CHG
AC
VDDIO
MCU
USB
Figure 2. The Li-Ion Charger Embedded in the Hand Held System
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
2 Freescale Semiconductor
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4 Evaluation Board Specification
9
H
The evaluation board is designed to work as a standalone charger, or as an embedded charger in a handheld system.
Figure 3 shows its schematic circuit. The normal operation range of the evaluation board is:
For AC charger:
V
I
AC_MAX
For USB charger:
V
I
USB_MAX
AC_MIN
USB_MIN
TP1
AC
TP3
USB
TP7
/P PR
TP1 0
VLogic
TP1 1
/C HG
TP1 3
USBEN
= 4.3V, V
= 1200mA
= 4.3V, V
= 400mA
1
1
J3
HDR_1X2
J5
HD R _1X3
BAT
1
J8
HD R _1X2
2
1
1
1
1
AC_MAX
USB_MAX
1
2
J1
HDR_1X2
1
2
3
2
21
1
R4
470 O HM
R6
100K
TP2 7
USBEN
J4
HDR_1X3
123
D1
RED
1
2
J9
HDR_1X2
R7
100K
HDR_1X2
= 6.8V
= 5.85V
21
D2
GREEN
R5
470 O HM
J13
/CHG
TP22
BAT
2
1
TP 15
AC
TP 17
USB
TP2 1
/P PR
C1
1.0U F
C3
1.0U F
R11
200K
1
2
3
4
5
6
1
2
U1
MC34 676B
AC
USB
PPR
CHG
USBEN
IMIN
J12
H DR _1X2
R10
28.7K
E-PA D
BATDE T
USBOUT
ISET
GND
IUSB
Evaluation Board Specification
C2
TP 16
NC
BATDE T
BAT
1
2
C4
1.0U F
TP 18
VBAT
C5
TP 19
1.0U F
USBOUT
R1
26.1K
12
11
BAT
10
9
8
7
R9
13.3K
1
2
J11
HDR_1X2
1
2
R8
13.0 K
J10
HDR_1X2
J2
HDR_1X2
TP20
ISET
TP26
IUSB
R3
6.4
1
2
J
R2
13.0K
1
2
J6
HDR_1X2
TP2 3
GND
TP2 4
GND
TP2 5
GND
TP28
IMIN
Figure 3. The Schematic Circuit of the Evaluation Board
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
Freescale Semiconductor 3
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Component Selection
5 Component Selection
5.1 Input capacitors C1 and C3
The input capacitor is used to minimize the input voltage transient that may cause instability. A ceramic capacitor of
1.0μF or above is required for most applications. X5R and X7R dielectrics have better temperature stability. The
evaluation board uses 1.0μF X5R ceramic capacitors. Considering the maximum input voltage rating of the MC34676B
is 28V, the input capacitor must have 16V DC rated voltage.
5.2 Output capacitors C4 and C5
The charger output capacitor is used for stable operation. An X5R ceramic capacitor minimum of a 1.0μF is required for
the charger output. Depending on the load transient current, a larger capacitance may be required. Because the highest
output voltage of the MC34676B is 4.2V, a 6.3V DC rated voltage is high enough for the output capacitor.
The regulator output capacitor is used for stable operation, too. An X5R ceramic capacitor minimum of a 1.0μF is
required for the regulator output. A 6.3V DC rated voltage is high enough for the regulator output capacitor because the
highest output voltage of the output regulator is 5V.
5.3 AC CC-mode charge current setting resistors R1, R2, and R3
The resistor between the ISET pin and GND sets the AC CC-mode charge current by the following equation:
3950
--------------
I
=
AC
R
ISET
where R
temperature stability. As a result, the charge current will be accurate over the whole temperature range.
On the evaluation board, three resistors with two pin header jumpers are used for the user to conveniently configure
different charge current values.
is in units of Ω, IAC is in units of amps. A metal film with a 1% tolerance resistor should be used for
ISET
Table 1 shows the charge current with the different settings of pin headers J6 and J7.
Eqn. 1
Table 1. The AC CC-mode Charge Current Settings
J6 J7 Charge Current
Open Open 150mA
Short Open 450mA
Open Short 750mA
Short Short 1050mA
5.4 USB CC-mode charge current setting resistors R8 and R9
The resistor between the IUSB pin and GND sets the USB CC-mode charge current by the following equation:
1975
--------------
=
I
USB
where R
temperature stability. As a result, the charge current will be accurate over the whole temperature range.
On the evaluation board, two resistors with two pin header jumpers are used for the user to conveniently configure
different charge current values. Table 2 shows the charge current with the different settings of pin headers J10 and J11.
is in units of Ω, I
USB
is in units of amps. A metal film with a 1% tolerance resistor should be used for
USB
Table 2. The USB CC-mode Charge Current Settings
J10 J11 Charge Current
R
IUSB
Eqn. 2
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
4 Freescale Semiconductor
Page 5
Table 2. The USB CC-mode Charge Current Settings
Open Open 400mA
Short Open 150mA
Open Short 150mA
Short Short 300mA
5.5 End-of-charge current setting resistors R10 and R11
The end-of-charge (EOC) current for both the AC charger and the USB charger can be set by the resistors R10 and R11.
On the evaluation board, two resistors with one pin header jumper are used for the user to conveniently configure
different EOC current values.
Table 3 shows the EOC current with the different settings of pin header J12.
Table 3. The EOC Current Settings
J12 Charge Current
Open 10mA
Short 80mA
Component Selection
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
Freescale Semiconductor 5
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Layout Design
6 Layout Design
6.1 Layout
The KIT34676EPEVBE PCB board has two copper layers. The component side of the KIT34676EPEVBE is provided
to locate all components.
Figure 4 is an overview of the board, followed by the layout of each layer.
Figure 4. The Overview of the Evaluation Board
Figure 5. The Component Side Silkscreen Layer of the Evaluation Board
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
6 Freescale Semiconductor
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Layout Design
Figure 6. The Component Side Layer of the Evaluation Board
Figure 7. The Solder Side Layer of the Evaluation Board
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
Freescale Semiconductor 7
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Layout Design
6.2 Layout considerations
• Place decoupling capacitors C1, C3 and C4 as close as possible to the AC pin, USB pin and BAT pin respectively.
• Place the charge current setting resistor as close as possible to the current setting pin to minimize the parasitic
capacitance between the current setting pin and ground.
• Use wide traces to connect input power source to the AC pin and USB pin, and BAT pin to the battery.
• To get better thermal performance, put the EPAD pin of the MC34676B on a large ground plane on the component
side, and use a via array to connect the EPAD pin to the ground layer, or the large ground plane on the other layer.
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
8 Freescale Semiconductor
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7 Evaluation Board Configuration
7.1 Pin Headers
The J1 and J3 pin headers link the external power source to the AC pin or USB pin of the MC34676B respectively. It
allows the user to measure the current from the power source to the evaluation board when using a current meter
between pin 1 and pin 2 of J1 or J3. The default setting of the two pin headers is to short pins 1 and 2 of J1, and open
pins 1 and 2 of J3.
The J2 pin header links the BAT pin and the external battery connector. It allows the user to measure the charging
current from the MC34676B into the battery with a current meter between pin 1 and pin 2. The default setting is to short
pins 1 and 2.
The J4 and J5 pin headers select the voltage to supply the D1 and D2 LED indicator. Shorting pins 2 and 3 of J4 and
pins 2 and 3 of J5 select AC to power the LEDs. Shorting pins 1 and 2 of J4 and pins 2 and 3 of J5 select USB to power
the LEDs. Shorting pins 1 and 2 of J5 and let all pins of J4 open select BAT to power the LEDs. The default settings of
J4 and J5 are to short pins 2 and 3 of J4 and pins 2 and 3 of J5.
IMPORTANT: DO NOT APPLY HIGHER THAN A 12V DC INPUT VOLTAGE TO AC OR USB WHEN AC OR USB IS
SELECTED TO POWER THE LEDS.
The absolute maximum voltage at the PPR pin and CHG pin is 12V. When applying higher than a 12V input voltage,
select BAT to power the LEDs.
J6 and J7 set the AC CC-mode charge current. The current values related to J6 and J7 settings are shown in Table 1.
J8 and J9 are used to let the user supply an I/O logic voltage to the PPR pin and the CHG pin, so the system can
interface the PPR and CHG signals with the same voltage level. When using LEDs to indicate the charging status, leave
J8 and J9 open. When interfacing the PPR and CHG signals to the system, short pins 1 and 2 of J8 and J9 and leave
J5 open.
J10 and J11 set the USB CC-mode charge current. The current values related to J10 and J11 settings are shown in
Table 2.
J12 sets the end-of-charge (EOC) current. The current values related to J12 settings are shown in Table 3.
The J13 pin header allows the user to choose the AC charger when leaving it open, the USB charger is chosen when
shorting pins 1 and 2.
The default settings of the evaluation board are shown in Table 4, which selects the AC charger of MC34676B.
Evaluation Board Configuration
Tab le 4. The Default Settings of the Pin Headers
Pin Header Jumpers Default Setting
J1 Shorted
J2 Shorted
J3 Open
J4 2-3 shorted
J5 2-3 shorted
J6 Shorted
J7 Shorted
J8 Open
J9 Open
J10 Open
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
Freescale Semiconductor 9
Page 10
Evaluation Board Configuration
7.2 Connector Pads
There are 14 connecting pads (TP1 to TP14 with corresponding names) on the evaluation board to let the user simply
connect the board to their system. The GND pads link power ground of the MC34676B. The AC pad or USB pad connect
an external power source to the evaluation board. The
IMIN pads link to the corresponding pins of the MC34676B. The VL pad is for the user to supply a logic I/O voltage to
the evaluation board, if that application system needs a logic voltage level to interface to the PPR and CHG pins of the
MC34676B. The VBAT pad connects the positive pole of the Li+ battery being charged.
7.3 Test Points
The KIT34676EPEVBE evaluation board provides 11 signal test points and 3 ground test points for users to conveniently
hook up multi-meters and oscilloscope probes to evaluate the MC34676B. The test points connect the pins of the
MC34676B with the same names directly.
Table 4. The Default Settings of the Pin Headers
J11 Open
J12 Shorted
J13 Open
PPR, CHG, USBEN, BATDET, USBOUT, ISET, IUSB and the
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
10 Freescale Semiconductor
Page 11
8 Test Setup with the Evaluation Board
The test setup is shown in Figure 8 and Figure 9. Connect a DC power source with a larger than 2.0A current limit to
the AC pad or a USB power port to the USB pad on the evaluation board. Connect the positive and negative polarities
of the Li+ battery to the VBAT pad and the GND pad on the evaluation board respectively. Use a current meter and a
voltage meter to measure the charge current and the voltage respectively. Turn on the power supply and let the V
is less than 1.75V to enable the MC34676B, then the evaluation board starts charging the battery.
A AV
DC
Power
Source
Test Setup with the Evaluation Board
BATDET
Li+
Battery
Figure 8. The AC Charger Set Up for the Evaluation Board
A AV
USB
Power
Port
Figure 9. The USB Charger Set Up for the Evaluation Board
Li+
Battery
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
Freescale Semiconductor 11
Page 12
Bill of Material
9 Bill of Material
Item Qty
1 2 C1,C3 1.0UF CAP CER 1.0UF 16V 10% X5R 0603 CC0603 MURATA
2 1 C2 NC No Connection CC0603 N/A N/A
3 2 C4,C5 1.0UF CAP CER 1.0UF 10V 10% X5R 0603
4 1 D1 RED LED ULTA BRIGHT RED 30MA 5V
5 1 D2 GREEN LED ULTRA-BRIGHT GREEN SMT
6 11 J1,J2,J3,J6,
7 2 J4,J5 HDR_1X3 HDR 1X3 TH 100MIL SP 374.01H AU HDR103 TYCO ELEC-
8 1 R1 26.1K RES MF 26.1K 1/10W 1% 0603 RC0603 KOA SPEER RK73H1JTTD2612F
9 2 R2,R8 13.0K RES MF 13.0K 1/10W 1% 0603 RC0603 KOA SPEER RK73H1JTTD1302F
10 1 R3 6.49K RES MF 6.49K 1/10W 1% 0603 RC0603 KOA SPEER RK73H1JTTD6491F
11 2 R4,R5 470 OHM RES TF 470 1/10W 5% RC0603 RC0603 BOURNS CR0603JW471E
12 2 R6,R7 100K RES MF 100K 1/10W 5% 0603 RC0603 BOURNS CR0603-JW-104ELF
13 1 R9 13.3K RES MF 13.3K 1/10W 1% 0603 RC0603 KOA SPEER RK73H1JTTD1332F
14 1 R10 28.7K RES MF 28.7K 1/10W 1% 0603 RC0603 KOA SPEER RK73H1JTTD2872F
15 1 R11 200K RES MF 200K 1/10W 1% 0603 RC0603 KOA SPEER RK73H1JTTD2003F
16 14 TP1,TP2,TP
17 14 TP15,TP16,
18 1 U1 MC34676B 3x3
Part
Reference
J7,J8,J9,J10
,J11,J12,J13
3,TP4,TP5,T
P6,TP7,TP8,
TP9,TP10,T
P11,TP12,T
P13,TP14
TP17,TP18,
TP19,TP20,
TP21,TP22,
TP23,TP24,
TP25,TP26,
TP27,TP28
Value DESCRIPTION Footprint Mfr PN
GRM188R61C105KA93
TDK
CC0603 MURATA
CAP CER 1.0UF 6.3V 10% X5R 0603
LED_0603_C1LITE ON LTST-C190KRKT
SMT 0603
LED_0603_C1LITE ON LTST-C190KGKT
0603
HDR_1X2 HDR 1X2 TH 100MIL SP 375H AU HDR102 TYCO ELEC-
TEST PAD PCB PAD OVAL DOUBLE SIDE WITH
THRU HOLE
TEST
POINT
TEST POINT PIN .109 X .087 TH YELLOW
200x1000ov N/A N/A
TEST_LOOPCOMPONENTS
UDFN-12
TDK
TRONICS
TRONICS
CORPORATION
Freescale
C1608X5R1C105K
GRM188R61C105KA61
C1608X5R0J105K
826629-2
826629-3
TP-105-01-00
* These are pads only. No component is populated
Freescale does not assume liability, endorse, or warrant components from external manufacturers that are referenced
in circuit drawings or tables. While Freescale offers component recommendations in this configuration, it is the
customer’s responsibility to validate their application.
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
12 Freescale Semiconductor
Page 13
10 References
Following are URLs where you can obtain information on other Freescale products and application
solutions:
Products Links
Data Sheet MC34676 www.freescale.com/files/analog/doc/data_sheet/MC34676.pdf
Freescale’s Web Site www.freescale.com
Freescale’s Analog Web Site www.freescale.com/analog
Freescale’s Power Management www.freescale.com/powermanagement
References
Using the Dual 28V Input Voltage Charger with Linear Regulator, Rev. 1.0
Freescale Semiconductor 13
Page 14
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© Freescale Semiconductor, Inc., 2009. All rights reserved.
KT34676BUG
Rev. 1.0
2/2009
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