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19-2354; Rev 0; 2/02
MAX1898 Evaluation Kit
General Description
The MAX1898 evaluation kit (EV kit) is a complete, fully assembled and tested single-cell lithium-ion (Li+) battery charger. The EV kit charges a single Li+ battery to 4.2V using a power supply with an output voltage of 4.7V to 12V. At input voltages greater than 6V, the allowed charging current may be limited by the powerdissipation rating of the external MOSFET. Jumpers on the EV kit allow simple adjustment to the total charging time and charger restart voltage levels. An LED indicates the cell's charging status. To charge a Li+ battery to 4.1V, replace the MAX1898 (U1) IC on the EV kit board with the MAX1898EUB41. o Simple Stand-Alone Li+ Charger o Safely Pre-Charges Deeply-Discharged Cells o Top-Off Charging to Achieve Full Battery Capacity o Fully Assembled and Tested
Features
Evaluates: MAX1898
Selector Guide
PART NUMBER MAX1898EUB42 MAX1898EUB41 CHARGING VOLTAGE 4.2V 4.1V PACKAGE 10-pin MAX 10-pin MAX PART MAX1898EVKIT
Ordering Information
TEMP RANGE 0C to +70C IC PACKAGE 10 MAX
Component List
DESIGNATION QTY C1 1 DESCRIPTION 10F, 10%, 16V tantalum capacitor (B) AVX TPSB106K016R0800 0.1F, 10%, 16V X7R ceramic capacitors (0603) TDK C1608X7R1C104KT or Taiyo Yuden EMK107BJ104KA Not installed, capacitor (1206) 1.0F, 10%, 10V X5R ceramic capacitor (0603) TDK C1608X5R1A105K 1A 30V Schottky diode (SOT123) Nihon EP10QY03 or Toshiba CRS02 Red light-emitting diode (LED) DESIGNATION QTY JU1, JU2, JU3 P1 R1 R2 U1 None None None None 3 DESCRIPTION 2-pin headers 30V 5.7A 3W P-channel power MOSFET (SOT-223) Fairchild NDT454P 1.74k 1% resistor (0603) Not Installed, resistor (0805) MAX1898EUB42 (10-pin MAX) Shunts (JU1, JU2, JU3) MAX1898 PC board MAX1898 data sheet MAX1898 EV kit data sheet
C2, C3
2
1 1 0 1 3 1 1 1
C4 C5
0 1
D1 D2
1 1
________________________________________________________________ Maxim Integrated Products
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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.
MAX1898 Evaluation Kit Evaluates: MAX1898
Component Suppliers
SUPPLIER AVX Fairchild Nihon Taiyo Yuden TDK Toshiba Zetex PHONE 843-946-0238 888-522-5372 81-33343-3411 800-348-2496 847-803-6100 949-455-2000 852-543-7100 FAX 843-626-3123 972-910-8036 81-33342-5407 847-925-0899 847-390-4498 949-859-3963 852-864-7630 WEBSITE www.avxcorp.com www.fairchildsemi.com www.niec.co.jp www.t-yuden.com www.component.tdk.com www.toshiba.com/taec/ www.zetex.com
Note: Please indicate you are using the MAX1898 when contacting these component suppliers.
Quick Start
The MAX1898 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 indicated. 1) Verify that a shunt is not installed on jumpers JU1 (charger enabled), and JU2 (timer enabled). 2) Verify that a shunt is installed on jumper JU3 (automatic restart enabled). 3) Place a voltmeter across the BATT+ and BATT- terminals. 4) Connect the positive terminal of the 4.7V to 6V power supply to the VIN pad. Connect the ground terminal of the power supply to the GND pad. 5) Turn on the power supply. 6) Verify that the no-load voltage across BATT+ and BATT- is 4.2V 0.75%. 7) Observe correct Li+ cell polarity. Connect a single-cell Li+ battery across the BATT+ and BATTterminals of the EV kit. The LED will turn on and charging will begin. 8) The LED will turn off once the charging current falls to approximately 160mA (20% of the fast charge current) indicating that the Li+ cell has been charged.
Replacing components on the EV kit board can reconfigure the charging current, total charge time, and Li+ charging voltage. The EV kit can charge a Li+ battery to 4.1V by replacing the MAX1898EUB42 (U1) IC, installed on the board, with the MAX1898EUB41 IC. A red LED indicates the cell's charging status.
Input Source
The MAX1898 EV kit requires a power supply that can supply at least 800mA with an output voltage of 4.7V to 6V. The input voltage can be increased up to 12V, however the EV kit maximum input voltage is limited by the power rating of the MOSFET P1 and the charging current. For higher input voltages, verify that the power dissipated by MOSFET P1 will not exceed the MOSFET's maximum ratings (3W for the NDT454P). Replace MOSFET P1 or reduce the charging current if necessary.
Charge Current
The maximum cell-charging current is programmed by resistor R1, which is connected between the ISET pin and GND. The EV kit's maximum charging current is set to 800mA with the 1.74k resistor installed at R1. For other charging currents, refer to the Current-Limit Mode section in the MAX1898 data sheet. An output voltage proportional to the charging current is available at the ISET PC board pad.
Detailed Description
The MAX1898 EV kit is a fully assembled and tested single-cell Li+ battery charger. The EV kit charges a single Li+ battery using a power supply with an output voltage between 4.7V and 12V. The EV kit is set to charge a Li+ battery to 4.2V at a maximum charging time of 3 hours with a charging current of 800mA. Jumpers on the EV kit allow simple adjustments to the total charging time and charger restart voltage levels.
Transistors
The MAX1898 EV kit circuit utilizes a P-channel MOSFET (P1). However, the circuit can also utilize PNP transistors in place of the MOSFET. To evaluate a PNP transistor as the pass element, replace P1 with a Zetex FZT968 PNP transistor, which is pin-for-pin compatible with the installed MOSFET. Change capacitor C2 to 220nF if a FZT968 is utilized. Refer to the MAX1898 data sheet for details.
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MAX1898 Evaluation Kit
Jumper Settings
The MAX1898 EV kit features several jumpers to reconfigure the circuit's charging settings. See Table 1 for jumper JU1, JU2, and JU3 configurations. A shunt on jumper 1 (JU1) disables the charger by connecting the enable pin (EN) to GND. Remove the shunt on JU1 to enable the charger. A shunt on jumper 2 (JU2) bypasses capacitor C3 and disables the timer function by connecting the timer control pin (CT) to GND. Removing the shunt from JU2 enables the timer. The 0.1F capacitor on C3 sets the safety timeout interval to 3 hours. Refer to the Selecting Maximum Charge Time section in the MAX1898 data sheet to modify the timeout interval. A shunt on jumper 3 (JU3) enables the preset restart battery threshold of 4V by connecting the automatic restart control pin (RSTRT) to GND. Removing the shunt from JU2 floats the RSTRT pin and disables the restart function. To adjust the restart voltage threshold, remove the shunt from JU2 and install a resistor on R2. Refer to the Controlling Automatic Restart section in the MAX1898 data sheet to select R2 values.
Output Signal
The LED on the EV kit is driven by the CHG pin. Depending on the Li+ cell's charging status, the pin is low or high impedance, thus turning the LED ON or OFF. If the Li+ cell cannot be charged to 2.5V in less than 1/4 of the total programmed charge time, the charger will go into fault mode. During the fault mode the CHG pin alternates between low and high impedance at an average frequency of 1.5Hz causing the LED to blink. The LED turns OFF when charging is complete or total charge time has elapsed. To drive logic circuits, remove the red LED and install a 100k resistor across the D2 connection, and connect the external logic circuit to the CHG pin. A logic LOW signal is output during charging; otherwise CHG is HIGH. In fault mode, the output logic signal will alternate between LOW and HIGH at an average frequency of 1.5Hz. See Table 2 for LED and CHG states. Also refer to the CHG Status Output section in the MAX1898 data sheet condition details.
Evaluates: MAX1898
Table 1. Jumper Selection
JUMPER JU1 JU2 SHUNT STATE None Installed None Installed None JU3 Installed FUNCTION Charger is enabled Charger is disabled Charger times out after 3hrs Timer function is disabled Automatic Restart Control is disabled New charging cycle reinitiates automatically if the Li+ cell drops below 4V
Table 2. Table 2. LED States
LED CONDITION No Li+ Battery, No Input Power, Charge Cycle Complete, or Safety Timer Expires Battery Charging Fault Mode CHG STATE
OFF
High Impedance
ON BLINKING (1.5Hz)
Low Impedance High-Low Impedance (50% duty cycle)
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MAX1898 Evaluation Kit Evaluates: MAX1898
VIN VIN C5 1F GND D2 2 CHG 1 IN
CS
10
DRV
9 VIN
1
3 P1 2 4 D1
U1 EN 3 JU1 EN/OK
C2 0.1F
MAX1898
BATT 7 C4 OPEN C1 10F 16V GND BATT+
ISET R1 1.74k 1% C3 0.1F JU2
4
ISET
GND
8
BATT-
5
CT
RSTRT
6 R2 OPEN
JU3
Figure 1. MAX1898 EV Kit Schematic
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MAX1898 Evaluation Kit Evaluates: MAX1898
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Figure 2. MAX1898 EV Kit Component Placement Guide-- Component Side
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Figure 3. MAX1898 EV Kit PC Board Layout--Component Side
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Figure 4. MAX1898 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 _____________________ 5 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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