Document Number: KT34676BUG
Rev. 1.0, 2/2009
Freescale Semiconductor
User’s Guide
Using the High Input Voltage Charger for
Single Cell Li-Ion Batteries
(KIT34676EPEVBE)
Contents
1
2
Purpose
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.
Scope
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
o
Charger over -40 to 85 C, and a 1.0% constant voltage
o
accuracy over -40 to 85 C. A charge current thermal
foldback feature, limits the charge current when the IC
internal temperature rises to a preset threshold.
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Evaluation Board Specification
4
Evaluation Board Specification
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
= 4.3V, V
= 6.8V
AC_MIN
AC_MAX
I
= 1200mA
AC_MAX
For USB charger:
V
= 4.3V, V
= 5.85V
USB_MAX
USB_MIN
USB_MAX
I
= 400mA
TP1
AC
1
1
C1
1. 0UF
C2
NC
J 1
TP 16
HDR_ 1X2
TP 15
AC
BA TDET
TP3
USB
BAT
C3
C4
J 2
J3
1. 0UF
1. 0UF
TP 18
HDR _1X2
HDR_ 1X2
J4
TP 17
USB
VB AT
HDR_1X3
J 5
HD R_1X3
3
C5
1. 0UF
TP 19
USB OUT
2
1
TP20
ISET
D2
GR EEN
D1
RED
BAT
R1
26. 1K
R2
1 3. 0K
R3
6. 49
R4
47 0 OHM
R5
U1
MC34 676 B
TP7
/P PR
47 0 OHM
1
1
1
1
2
3
12
11
10
2
2
AC
BA TDET
BAT
TP2 1
/P PR
USB
J6
J
H
HDR_ 1X2
PP R
USBOUT
I SET
4
5
9
8
CHG
J 8
HDR _1X2
USB EN
I MIN
GN
D
2
1
1
2
/CHG
TP22
6
7
IUSB
TP2 3
GND
J9
HDR_1 X2
TP2 4
GND
R6
R
7
1 00K
1 00K
TP1 0
VLo gic
TP2 5
GND
1
R8
R9
13 .0 K
1 3. 3K
1
TP1 1
/C HG
2
1
2
1
2
TP26
IUSB
1
1
R11
20 0K
B AT
2
J 12
DR_1X2
H
J10
HDR_1 X2
J1 1
HDR_ 1X2
R10
28. 7K
TP2 7
USBE N
J1 3
HDR_1 X2
1
TP28
IMIN
TP1 3
USBE N
Figure 3. The Schematic Circuit of the Evaluation Board
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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
5.3
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.
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
RISET
-------------
IAC
=
Eqn. 1
where R
is in units of Ω, I is in units of amps. A metal film with a 1% tolerance resistor should be used for
ISET
AC
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. Table 1 shows the charge current with the different settings of pin headers J6 and J7.
Table 1. The AC CC-mode Charge Current Settings
J6
J7
Charge Current
Open
Short
Open
Short
Open
Open
Short
Short
150mA
450mA
750mA
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
--------------
IUSB
=
Eqn. 2
RIUSB
is in units of amps. A metal film with a 1% tolerance resistor should be used for
where R
is in units of Ω, I
USB
USB
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.
Table 2. The USB CC-mode Charge Current Settings
J10
J11
Charge Current
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Component Selection
Table 2. The USB CC-mode Charge Current Settings
Open
Short
Open
Short
Open
Open
Short
Short
400mA
150mA
150mA
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
Short
10mA
80mA
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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
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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
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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.
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Evaluation Board Configuration
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
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.
Table 4. The Default Settings of the Pin Headers
Pin Header Jumpers
J1
Default Setting
Shorted
J2
J3
J4
J5
J6
J7
J8
J9
J10
Shorted
Open
2-3 shorted
2-3 shorted
Shorted
Shorted
Open
Open
Open
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Evaluation Board Configuration
Table 4. The Default Settings of the Pin Headers
J11
J12
J13
Open
Shorted
Open
7.2
7.3
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 PPR, CHG, USBEN, BATDET, USBOUT, ISET, IUSB and 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.
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.
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Test Setup with the Evaluation Board
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.
BATDET
A
V
A
DC
Power
Source
Li+
Battery
Figure 8. The AC Charger Set Up for the Evaluation Board
A
V
A
Li+
Battery
USB
Power
Port
Figure 9. The USB Charger Set Up for the Evaluation Board
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Bill of Material
9
Bill of Material
Part
Reference
Item Qty
Value
DESCRIPTION
Footprint
Mfr
PN
1
2
C1,C3
1.0UF
CAP CER 1.0UF 16V 10% X5R 0603 CC0603
MURATA
GRM188R61C105KA93
C1608X5R1C105K
TDK
2
3
1
2
C2
NC
No Connection CC0603
N/A
N/A
C4,C5
1.0UF
CAP CER 1.0UF 10V 10% X5R 0603 CC0603
CAP CER 1.0UF 6.3V 10% X5R 0603
MURATA
TDK
GRM188R61C105KA61
C1608X5R0J105K
4
5
6
1
1
D1
D2
RED
LED ULTA BRIGHT RED 30MA 5V
SMT 0603
LED_0603_ LITE ON
C1
LTST-C190KRKT
LTST-C190KGKT
826629-2
GREEN
LED ULTRA-BRIGHT GREEN SMT
0603
LED_0603_ LITE ON
C1
11
J1,J2,J3,J6, HDR_1X2
J7,J8,J9,J10
HDR 1X2 TH 100MIL SP 375H AU
HDR102
TYCO ELEC-
TRONICS
,J11,J12,J13
7
2
J4,J5
HDR_1X3
HDR 1X3 TH 100MIL SP 374.01H AU HDR103
TYCO ELEC-
TRONICS
826629-3
8
1
2
1
2
2
1
1
1
R1
26.1K
13.0K
6.49K
470 OHM
100K
RES MF 26.1K 1/10W 1% 0603
RES MF 13.0K 1/10W 1% 0603
RES MF 6.49K 1/10W 1% 0603
RES TF 470 1/10W 5% RC0603
RES MF 100K 1/10W 5% 0603
RES MF 13.3K 1/10W 1% 0603
RES MF 28.7K 1/10W 1% 0603
RES MF 200K 1/10W 1% 0603
RC0603
RC0603
RC0603
RC0603
RC0603
RC0603
RC0603
RC0603
KOA SPEER
KOA SPEER
KOA SPEER
BOURNS
RK73H1JTTD2612F
RK73H1JTTD1302F
RK73H1JTTD6491F
CR0603JW471E
CR0603-JW-104ELF
RK73H1JTTD1332F
RK73H1JTTD2872F
RK73H1JTTD2003F
N/A
9
R2,R8
R3
10
11
12
13
14
15
16
R4,R5
R6,R7
R9
BOURNS
13.3K
28.7K
200K
KOA SPEER
KOA SPEER
KOA SPEER
R10
R11
14 TP1,TP2,TP TEST PAD
3,TP4,TP5,T
PCB PAD OVAL DOUBLE SIDE WITH 200x1000ov N/A
THRU HOLE
P6,TP7,TP8,
TP9,TP10,T
P11,TP12,T
P13,TP14
17
18
14 TP15,TP16, TEST
TP17,TP18, POINT
TP19,TP20,
TEST POINT PIN .109 X .087 TH YEL- TEST_LOO COMPONENTS TP-105-01-00
LOW
P
CORPORATION
TP21,TP22,
TP23,TP24,
TP25,TP26,
TP27,TP28
1
U1
MC34676B
3x3
Freescale
UDFN-12
* 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.
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References
10 References
Following are URLs where you can obtain information on other Freescale products and application
solutions:
Products
Links
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KT34676BUG
Rev. 1.0
2/2009
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