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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 provides outputs that can be used to monitor the input current, 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 0C to +70C 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 22F 20%, 25V X5R ceramic capacitors (2220) TDK C5750X5R1E226M Not installed (2220) Not installed, E size 0.1F 10%, 25V X7R ceramic capacitors (0603) Murata GRM188R71E104K TDK C1608X7R1E104K Not installed (0603) D1 1 4.7F 10%, 6.3V X5R ceramic capacitor (0603) TDK C1608X5R0J475K 1F 10%, 6.3V X5R ceramic capacitors (0603) Murata GRM188R60J105K Taiyo Yuden JMK107BJ105KA TDK C1608X5R1A105K D2, D3 2 1 C21, C22 2 DESIGNATION QTY DESCRIPTION 1F 10%, 25V X7R ceramic capacitor (1206) Murata GRM31MR71E105K Taiyo Yuden TMK316BJ105KL TDK C3216X7R1E105K 0.01F 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
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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 10H, 4.4A inductor Sumida CDRH104R-100NC TOKO 919AS-100M Dual, N-channel, 8-pin SO, MOSFET Fairchild FDS6912A Not installed 0.01 1%, 0.5W sense resistor (2010) Vishay Dale WSL2010 0.010 1.0% IRC LRC-LR2010-01-R010-F 0.015 1%, 0.5W sense resistor (2010) Vishay Dale WSL2010 0.015 1.0% IRC LRC-LR2010-01-R015-F Not installed (0603) 590k 1% resistor (0603) 196k 1% resistor (0603) 4.7k 5% resistor (0603) 10k 5% resistors (0603) 50k potentiometers (multiturn) 33 5% resistor (0603) 1M 5% resistor (0603) 10 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 precautions 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 charging-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 conditioning 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 charger. This source must be capable of supplying a voltage greater than the battery-voltage set point and have a sufficient current rating.
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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 VBATT -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 250k to minimize error caused by bias current. For VBATT / CELLS = 4, use 100k for R6 and leave R5 uninstalled.
Evaluates: MAX1908
Jumper JU1
Jumper JU1 connects VCTL to LDO. This sets the battery-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 potentiometer R12. Connecting ICTL to LDO sets the charging-current limit to 3A. Connecting ICTL to potentiometer 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 temperature 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 sourcecurrent-limit input. Adjusting R13 allows the input-current 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 1M pullup resistor or to an optional MOSFET circuit (P1, R22, and R23). Using a MOSFET provides a lower dropout voltage than Schottky diode D1. Use a P-channel MOSFET such as Fairchild FDS6675 for P1. Choose resistor values for R22 and R23 that ensure VGS 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.
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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 (VICTL = REFIN/32) and 5A (VICTL = REFIN). Note: VICTL < 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 1M 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.
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ADPPWR_S D1 R1 0.01 REVBLK_S JU4 CUT HERE LOAD C9 0.1F REFIN BATTCELLS 2 3 2 C10 4.7F U1 15 LDO JU1 R6 OPEN 13 ICTL TP2 DHI C12 0.1F TP3 BST LX 23 SHDN 7 2 8 D4 N1-A 1 L1 10H 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 10k CSIN 18 7 C20 0.1F R9 4.7k 6 C21 0.01F 5 CCS REF 4 CLS 3 CLS C23 1F 3 2 R13 50k 1 CCI BATT 16 C3 OPEN GND 14 C4 22F BATTCCV C15 OPEN R20 SHORT (PC TRACE) BATT+ C19 0.1F C13 OPEN 19 C14 OPEN R19 SHORT (PC TRACE) R2 0.015 20 R10 10k IINP C18 0.1F 21 8 3 ICHG TP1 10 C11 1F DLOV 22 BST SCL 1 2 JU2 3 R3 OPEN VCTL BST 24 R25 10 D3 SDA LDO R16 33 THM 17 1 JU5 CELLS J1-1 J1-6 C2 OPEN C1 22F 6 5 1
ADPPWR_D
REVBLK_D
ADAPTER_IN 7 8 3 2 4 R22 OPEN
C5 OPEN LDO P1 OPEN ACOK 321 27 D2 1 DCIN C16 1F 12 R12 50k LDO R5 OPEN C17 OPEN REFIN LDO CSSP CSSN JU6 R23 OPEN 26
C6 OPEN
ACIN
R21 1M
R14 SHORT (PC TRACE) C7 0.1F R15 SHORT (PC TRACE) C8 OPEN
Figure 1. MAX1908 EV Kit Schematic
J1-2 J1-7 J1-3 J1-8
R8 196k 1%
R7 590k 1%
REFIN
MAX1908
J1-4 J1-9
PGND SHDN
GND
Evaluates: MAX1908
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R24 SHORT (PC TRACE) C22 0.01F
MAX1908 Evaluation Kit
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MAX1908 Evaluation Kit Evaluates: MAX1908
Figure 2. MAX1908 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX1908 EV Kit PC Board Layout--Component Side
Figure 4. MAX1908 EV Kit PC Board Layout--Signal and Ground Layer
Figure 5. MAX1908 EV Kit PC Board Layout--Ground Layer
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MAX1908 Evaluation Kit Evaluates: MAX1908
Figure 6. MAX1908 EV Kit PC Board Layout--Solder Side
Figure 7. MAX1908 EV Kit PC Board Layout--Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 7 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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