Garmin MC34676B User Manual
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.
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
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
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
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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