19-2880; Rev 0; 6/03
MAX1908 Evaluation Kit
General Description
The MAX1908 evaluation kit (EV kit) is an accurate and
efficient multichemistry battery charger. It uses analog
inputs to control charge voltage and current. The EV kit
can charge 2 to 4 series lithium-ion (Li+) cells with a
current up to 3A. High efficiency is achieved by a buck
topology with synchronous rectification. The EV kit pro-
vides outputs that can be used to monitor the input cur-
rent, the battery-charging current, and the presence of
an AC adapter.
o
Input Current Limiting
o
±0.5% Battery-Voltage Set-Point Accuracy Using
Internal Reference
o
Analog Inputs Control Charge Current and
Battery-Voltage Set Point
o
Monitor Outputs for
Current Drawn from AC Input Source
Charging Current
AC Adapter Presence
o
Up to 17.6V Battery-Voltage Set Point
o
+8V to +25V Input Voltage
o
3A Battery Charge Current
o
Charges Any Battery Chemistry: Li+, NiCd, NiMH,
Lead Acid, etc.
o
Surface-Mount Construction
o
Fully Assembled and Tested
Features
Evaluates: MAX1908
Ordering Information
PART
MAX1908EVKIT
TEMP RANGE
0°C to +70°C
IC PACKAGE
28 QFN
Component List
DESIGNATION
C1, C4
C2, C3
C5, C6
C7, C9, C12,
C18, C19, C20
C8, C13, C14,
C15, C17
C10
QTY
2
0
0
DESCRIPTION
22µF
±20%,
25V X5R ceramic
capacitors (2220)
TDK C5750X5R1E226M
Not installed (2220)
Not installed, E size
0.1µF
±10%,
25V X7R ceramic
capacitors (0603)
Murata GRM188R71E104K
TDK C1608X7R1E104K
Not installed (0603)
D1
1
4.7µF
±10%,
6.3V X5R ceramic
capacitor (0603)
TDK C1608X5R0J475K
1µF
±10%,
6.3V X5R ceramic
capacitors (0603)
Murata GRM188R60J105K
Taiyo Yuden JMK107BJ105KA
TDK C1608X5R1A105K
D2, D3
2
1
C21, C22
2
DESIGNATION
QTY
DESCRIPTION
1µF
±10%,
25V X7R ceramic
capacitor (1206)
Murata GRM31MR71E105K
Taiyo Yuden TMK316BJ105KL
TDK C3216X7R1E105K
0.01µF
±10%,
50V X7R ceramic
capacitors (0603)
Murata GRM188R71H103K
Taiyo Yuden UMK107B103KZ
TDK C1608X7R1H103K
Schottky diode, 10A, D-Pak
Diodes Inc. MBRD1035CTL
ON Semiconductor MBRD1035CTL
Schottky diodes, 0.5A, 30V
SOD-123
Diodes Inc. B0530W
General Semiconductor MBR0530
ON Semiconductor MBR0530
Schottky diode, 1A, 40V, SMA
Central Semiconductor
CMSH1-40ML
Diodes Inc. B130L
C16
1
6
0
C11, C23
2
D4
1
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX1908 Evaluation Kit
Evaluates: MAX1908
Component List (continued)
DESIGNATION
J1
JU1
JU2, JU3, JU5,
JU6
JU4
L1
QTY
1
1
4
0
1
DESCRIPTION
Smart battery header assembly,
right angle, keyless, 5-position
Tyco Electronics 787441-1
2-pin header
3-pin headers
Not installed
10µH, 4.4A inductor
Sumida CDRH104R-100NC
TOKO 919AS-100M
Dual, N-channel, 8-pin SO, MOSFET
Fairchild FDS6912A
Not installed
0.01Ω
±1%,
0.5W sense resistor
(2010)
Vishay Dale WSL2010 0.010 1.0%
IRC LRC-LR2010-01-R010-F
0.015Ω
±1%,
0.5W sense resistor
(2010)
Vishay Dale WSL2010 0.015 1.0%
IRC LRC-LR2010-01-R015-F
Not installed (0603)
590kΩ
±1%
resistor (0603)
196kΩ
±1%
resistor (0603)
4.7kΩ
±5%
resistor (0603)
10kΩ
±5%
resistors (0603)
50kΩ potentiometers (multiturn)
33Ω
±5%
resistor (0603)
1MΩ
±5%
resistor (0603)
10Ω ±5% resistor (0603)
MAX1908ETI (28-pin QFN-EP)
• DC source capable of supplying a voltage between
+2.5V to +3.6V for REFIN.
• Voltmeter.
• Battery pack or load.
Procedure
The MAX1908 EV kit is a fully assembled and tested
surface-mount board. Follow the steps below to verify
board operation.
Do not turn on the power supply
until all connections are completed. Observe all pre-
cautions on the battery manufacturer’s data sheet:
1) Install a shunt on JU1 to set the battery-voltage set
point to 4.2V per cell. If a different battery-voltage
set point is required, see the
Battery-Voltage Set
Point
section.
2) Place a shunt across pins 1-2 on JU2 to enable 3A
charging-current limit. If the battery is not rated for
3A charge current, then select a charge current and
set as explained in the
Charging-Current Limit
(Potentiometer R12)
section.
3) Set jumper JU5 to indicate the number of cells in
the battery pack (Table 1).
4) Place a shunt across pins 2-3 on JU6.
5) Place a shunt across pins 2-3 on JU3 to disable the
MAX1908.
6) Connect the input-current supply across the
ADAPTER_IN and PGND pads.
7) Connect the +2.5VDC to +3.6VDC power supply to
REFIN and GND.
8) Connect a battery pack between the BATT+ and
BATT- pads.
9) Turn on the power supplies.
10) Enable the MAX1908 by moving the shunt on JU3 to
the 1-2 position.
11) Verify current is being delivered to the battery.
N1
P1
1
0
R1
1
R2
1
R3–R6, R14,
R15, R17–R20,
R22, R23, R24
R7
R8
R9
R10, R11
R12, R13
R16
R21
R25
U1
0
1
1
1
2
2
1
1
1
1
Detailed Description
The MAX1908 includes all the functions necessary to
charge Li+ batteries. The EV kit is shipped with a charg-
ing-current limit of 3A and a battery-voltage set point of
4.2V times the number of cells in the battery pack.
The MAX1908 safely conditions overdischarged cells
by charging the battery pack at 300mA (1/10 of the
charging-current limit) until the battery-pack voltage
exceeds 3.1V times the number of cells. Once condi-
tioning is complete, the MAX1908 charges the battery
pack at a constant current of 3A (the charging-current
limit) until the battery pack voltage reaches 4.2V times
the number of cells (the battery-voltage set point). At
Quick Start
Required Equipment
Before beginning, the following equipment is required:
• DC source to supply the input current to the charg-
er. This source must be capable of supplying a volt-
age greater than the battery-voltage set point and
have a sufficient current rating.
2
_______________________________________________________________________________________
MAX1908 Evaluation Kit
this time, the MAX1908 charges the battery pack with a
constant voltage equal to the battery-voltage set point.
Note:
During charging, if the source-current limit is
reached, the charge current decreases.
For more information on the operation of the MAX1908,
refer to the
Detailed Description
section of the
MAX1908 data sheet.
Battery-Voltage Set Point
The default battery-voltage set point on the MAX1908
EV kit is 4.2V times the number of cells. To set it to a
value between 4.0V and 4.4V (times the number of
cells), remove the shunt on JU1 and install resistors at
R5 and R6. Use the following equation to calculate the
resistor values:
0.4
R5
=
R6
−
1
V
BATT
−
4
CELLS
V
BATT
is the desired battery-voltage set point and
CELLS is the number of cells selected by jumper JU5.
Choose 1% resistors with a total resistance less than
250kΩ to minimize error caused by bias current.
For V
BATT
/ CELLS = 4, use 100kΩ for R6 and leave R5
uninstalled.
Evaluates: MAX1908
Jumper JU1
Jumper JU1 connects VCTL to LDO. This sets the bat-
tery-voltage set point to 4.2V x the number of cells.
The battery-voltage set point can be set between 4.0V
and 4.4V (times the number of cells) by removing the
shunt on JU1 and installing resistors at R5 and R6. See
the
Battery-Voltage Set Point
section for more information.
Jumper JU2
Jumper JU2 connects ICTL to either LDO or poten-
tiometer R12. Connecting ICTL to LDO sets the charg-
ing-current limit to 3A. Connecting ICTL to potentiome-
ter R12 provides adjustment of the charging-current
limit to between 0.156A and 5A. Refer to the
Setting the
Charging-Current Limit
section of the MAX1908 data
sheet for more information.
Note:
Applying a voltage less than REFIN/32 to ICTL
places the MAX1908 in shutdown mode; 5A charging
current requires a different inductor. The 8-pin SO dual
MOSFET (N1) is capable of handling 5A at room tem-
perature only. For a higher ambient temperature,
replace it with two single 8-pin SO MOSFETs.
Charging-Current Limit
(Potentiometer R12)
The default charging-current limit on the MAX1908 EV
kit is 3A. To set it to a value between 0.156A and 5A,
move the shunt on jumper JU2 to the 2-3 position and
adjust potentiometer R12. Refer to the
Setting the
Charging-Current Limit
section of the MAX1908 data
sheet for more information.
Note:
Five-amp charging current requires a different
inductor. The 8-pin SO dual MOSFET (N1) is capable of
handling 5A at room temperature only. For a higher
ambient temperature, replace it with two single 8-pin
SO MOSFETs.
Jumper JU3
Jumper JU3 either enables the MAX1908 or places it
into shutdown. See Table 1 for jumper settings.
Jumper JU4
Jumper JU4 is factory reserved.
Source-Current Limit (Potentiometer R13)
Potentiometer R13 is connected to CLS, the source-
current-limit input. Adjusting R13 allows the input-cur-
rent limit to be set between 3.75A and 7.5A. Refer to
the
Setting the Input-Current Limit
section of the
MAX1908 data sheet for more information.
Jumper JU5
Jumper JU5 selects the number of series cells to be
charged. See Table 1 for jumper settings.
Jumper JU6
Jumper JU6 connects
ACOK
to either a 1MΩ pullup
resistor or to an optional MOSFET circuit (P1, R22, and
R23). Using a MOSFET provides a lower dropout volt-
age than Schottky diode D1.
Use a P-channel MOSFET such as Fairchild FDS6675
for P1. Choose resistor values for R22 and R23 that
ensure V
GS
is not exceeded on the MOSFET.
Evaluating the MAX1908 Above 25V
To evaluate the MAX1908 with an input voltage greater
than 25V (up to 28V), capacitors C1, C7, C9, and C16
must be replaced with higher voltage rating parts. Any
capacitors that were installed in locations C2, C5, and
C6 must also meet the higher voltage rating.
_______________________________________________________________________________________
3
MAX1908 Evaluation Kit
Evaluates: MAX1908
Table 1. Jumper Selection
JUMPER
JUMPER
POSITION
Open
Closed*
1-2*
JU2
2-3
1-2*
JU3
2-3
Open
Open
JU4
Closed* (shorted
by PC board
trace)
1-2
JU5
2-3*
Open
JU6
1-2
2-3*
FUNCTION
Battery-voltage set point can be set between 4.0V and 4.4V times the number of cells.
Resistors R5 and R6 must be installed.
VCTL = LDO. Battery-voltage set point set to 4.2V times the number of cells.
ICTL = LDO. Charging-current limit set to 3A.
ICTL connected to potentiometer R12. Charging-current limit can be adjusted between 0.156A
(V
ICTL
= REFIN/32) and 5A (V
ICTL
= REFIN).
Note:
V
ICTL
< REFIN/32 places the MAX1908 in shutdown.
SHDN
= high. MAX1908 enabled.
SHDN
= low. MAX1908 disabled.
Drive pad
SHDN
with an external signal.
Factory reserved.
Normal operation.
CELL = REFIN, cell count = 4.
CELL = GND, cell count = 2.
CELL = float, cell count = 3.
ACOK
connected to optional MOSFET circuit (P1, R22, and R23).
ACOK
connected to 1MΩ pullup resistor.
JU1
*Default position.
Component Suppliers
SUPPLIER
Central Semiconductor
Diodes Inc.
Fairchild Semiconductor
General Semiconductor
International Resistive Co. (IRC)
Murata
ON Semiconductor
Sumida
Taiyo Yuden
TDK
TOKO
Vishay Dale
PHONE
631-435-1110
805-446-4800
888-522-5372
760-804-9258
361-992-7900
770-436-1300
602-244-6600
847-545-6700
800-348-2496
847-803-6100
847-297-0070
402-564-3131
FAX
631-435-1824
805-381-3899
—
760-804-9259
361-992-3377
770-436-3030
602-244-4545
847-545-6720
847-925-0899
847-390-4405
847-699-1194
402-563-6296
WEBSITE
www.centralsemi.com
www.diodes.com
www.fairchildsemi.com
www.gensemi.com
www.irctt.com
www.murata.com
www.onsemi.com
www.sumida.com
www.t-yuden.com
www.component.tdk.com
www.tokoam.com
www.vishay.com
Note:
Please indicate you are using the MAX1908 when contacting these manufacturers.
4
_______________________________________________________________________________________
ADPPWR_S
D1
R1
0.01Ω
REVBLK_S
JU4
CUT HERE
LOAD
C9
0.1µF
REFIN
BATT-
CELLS
2
3
2
C10
4.7µF
U1
15
LDO
JU1
R6
OPEN
13
ICTL
TP2
DHI
C12
0.1µF
TP3
BST
LX 23
SHDN
7
2
8
D4
N1–A
1
L1
10µH
R18
SHORT TP4
(PC TRACE)
SMART BATTERY
CONNECTOR
25
4
5
6
N1–B
3
BATT+
J1–5
J1–10
R17
SHORT
(PC TRACE)
ACIN
R4
OPEN
ACOK
ACIN
ACOK
ACOK
11
REFIN
1
2
JU3
9
ICHG
DLO
PGND
28
IINP
CSIP
R11
10kΩ
CSIN 18
7
C20
0.1µF
R9
4.7kΩ
6
C21
0.01µF
5
CCS
REF
4
CLS
3
CLS
C23
1µF
3
2
R13
50kΩ
1
CCI
BATT
16
C3
OPEN
GND
14
C4
22µF
BATT-
CCV
C15
OPEN
R20
SHORT
(PC TRACE)
BATT+
C19
0.1µF
C13
OPEN
19
C14
OPEN
R19
SHORT
(PC TRACE)
R2
0.015Ω
20
R10
10kΩ
IINP
C18
0.1µF
21
8
3
ICHG
TP1
10
C11
1µF
DLOV
22
BST
SCL
1
2
JU2
3
R3
OPEN
VCTL
BST
24
R25
10Ω
D3
SDA
LDO R16
33Ω
THM
17
1
JU5
CELLS
J1–1
J1–6
C2
OPEN
C1
22µF
6
5
1
ADPPWR_D
REVBLK_D
ADAPTER_IN
7
8
3
2
4
R22
OPEN
C5
OPEN
LDO
P1
OPEN
ACOK
3 2 1
27
D2
1
DCIN
C16
1µF
12
R12
50kΩ
LDO
R5
OPEN
C17
OPEN
REFIN
LDO
CSSP
CSSN
JU6
R23
OPEN
26
C6
OPEN
ACIN
R21
1MΩ
R14
SHORT
(PC TRACE)
C7
0.1µF
R15
SHORT
(PC TRACE)
C8
OPEN
Figure 1. MAX1908 EV Kit Schematic
J1–2
J1–7
J1–3
J1–8
R8
196kΩ
1%
R7
590kΩ
1%
REFIN
MAX1908
J1–4
J1–9
PGND
SHDN
GND
Evaluates: MAX1908
_______________________________________________________________________________________
R24
SHORT
(PC TRACE)
C22
0.01µF
MAX1908 Evaluation Kit
5
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