MAX1879EVKIT

19-2177; Rev 1; 9/05
MAX1879 Evaluation Kit
The MAX1879, in conjunction with a P-channel MOSFET
and a current-limited wall-mount adapter with an output
voltage between +4.7V to +20V, allows safe and quick
charging of a single lithium-ion (Li+) cell.
The MAX1879 evaluation kit (EV kit) is a complete, fully
assembled and tested Li+ battery charger. Jumpers on
the EV kit allow easy adjustment to a +4.1V or +4.2V
battery regulation voltage. A light-emitting diode (LED)
indicates the cell’s charging status.
Features
♦ Simple Stand-Alone Li+ Charger
♦ Low Power Dissipation
♦ Safely Precharges Over-Discharged Cells
♦ Top-Off Charging to Achieve Full Battery Capacity
♦ 8-Pin µMAX® Package
♦ Surface-Mount Construction
♦ Fully Assembled and Tested
Ordering Information
Component Suppliers
PHONE
FAX
PART
TEMP RANGE
Fairchild
408-822-2000
408-822-2102
MAX1879EVKIT
0°C to +70°C
Murata
814-237-1431
814-238-0490
SUPPLIER
Nihon
661-867-2555
661-867-2698
Taiyo Yuden
408-573-4150
408-573-4159
Toshiba
949-455-2000
949-859-3963
Note: Indicate that you are using the MAX1879 when contacting
these manufacturers.
IC PACKAGE
8 µMAX
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Component List
DESIGNATION
C1, C6
C2, C3
C4
C5
C7
D1
QTY
DESCRIPTION
0
Not installed (0805)
2
0.1µF ±10%, 50V ceramic
capacitors (0805)
Taiyo Yuden UMK212BJ104KG
0
Not installed (0603)
1
2.2µF ±20%, 10V ceramic
capacitor (0805)
Taiyo Yuden LMK212BJ225MG
1
1000pF ±10%, 50V ceramic
capacitor (0603)
Murata GRM188R71H102KA01
1
1A Schottky diode (SOT123)
Nihon EP10QY03 or
Toshiba CRS02
DESIGNATION
QTY
DESCRIPTION
LED1
1
LED (T-13/4)
J1
1
PC-mount power jack, 2.1mm
JU1
1
4-pin header
JU2, JU3
2
2-pin headers
P1
1
20V, 4.5A, p-channel MOSFET
(6-pin SuperSOT)
Fairchild FDC638P
R1
1
412kΩ ±1% resistor (0805)
R2
1
10kΩ ±5% resistor (0805)
U1
1
MAX1879EUA (8-pin µMAX)
—
3
Shunts (JU1, JU2, JU3)
—
1
MAX1879 PC board
________________________________________________________________ Maxim Integrated Products
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.
1
Evaluates: MAX1879
General Description
Evaluates: MAX1879
MAX1879 Evaluation Kit
Quick Start
The MAX1879 EV kit is a fully assembled and tested surface-mount board. Follow the steps below to verify board
operation. Do not plug the WALL CUBE in until indicated.
1) Install a shunt across pins 1 and 2 of jumper JU1 (TSEL)
for a minimum 34ms on-time top-off pulse width.
2) Install a shunt across jumper JU2 (THERM) to disable the temperature-monitoring function.
3) Verify that a shunt is not across jumper JU3 (ADJ) if
charging a +4.2V Li+ battery. Install a shunt across
jumper JU3 if charging a +4.1V Li+ battery.
4) Connect a 6V current-limiting (≤ 1A) power supply
across the EV kit’s WALL CUBE and GND terminals.
5) Place a voltmeter across the EV kit’s BATT+ and
BATT- terminals.
6) Observe correct Li+ cell polarity. Connect a single-cell Li+ battery across the EV kit’s BATT+ and
BATT- terminals. The LED turns on if the battery
voltage is below the predetermined voltage (4.1V or
4.2V) and greater than +2.5V. See Table 4 for additional LED status descriptions.
7) The LED turns off once the Li+ cell has been
charged to the predetermined voltage.
Detailed Description
The MAX1879 EV kit is a fully assembled and tested
single Li+ battery charger. The EV kit contains an external p-channel MOSFET for current switching and can
deliver up to 1A of current to an Li+ battery.
The EV kit contains a jumper that sets the battery (BATT)
regulation voltage to +4.1V or +4.2V. An external resistor can also adjust the regulation voltage from +4.0V to
+4.2V. An LED indicates the charging status of the battery. The maximum charging time is 6.25 hours.
The MAX1879 employs thermistor feedback to prequalify
the Li+ cell’s temperature for fast charging. The EV kit contains a jumper that allows the user to bypass this feature or
to connect an external thermistor to the EV kit board.
Input Source
The input source for the MAX1879 EV kit must be a
current-limited supply capable of continuous short-circuit
operation. The supply should have a current limit of
≤ 1A and an output voltage between +4.7V and +20V.
Connect a current-limited wall cube to power jack J1
(center pin is the positive terminal); otherwise, connect a
current-limited power-supply across the WALL CUBE and
GND PC pads. Current-limited power sources with higher
charge currents can be used, but diode D1 and MOSFET
P1 must be rated accordingly.
2
Jumper Selection
The MAX1879 EV kit features jumpers (JU1, JU2, and
JU3) to configure the circuit for optimal charging performance and evaluation.
Jumper JU1 sets the minimum on-time pulse width. See
Table 1 for the JU1 shunt configuration to select the
appropriate top-off pulse width. Refer to the Selecting
Minimum On-Time section in the MAX1879 data sheet
for information on selecting the minimum on-time pulse
width in top-off mode.
Table 1. JU1 Shunt Positions
SHUNT
POSITION
TSEL PIN
MINIMUM ON-TIME
IN TOP-OFF (ms)
1-2
Connected to BATT
34
1-3
Connected to ADJ
69
1-4
Connected to GND
137
Jumper JU2 connects the MAX1879 thermistor input
(THERM) to a 10kΩ resistor, thus disabling temperature
qualification. To enable temperature qualification,
remove the shunt from JU2 and connect a thermistor
between the THERM and GND pads. The thermistor
should be 10kΩ at +25°C and have a negative temperature coefficient. See Table 2 for the JU2 configuration.
Refer to the Thermistor section in the MAX1879 data
sheet for other thermistor details.
Table 2. Using a Thermistor
JUMPER
JUMPER STATE
FUNCTION
Open
Open before connecting a
thermistor from THERM pad
to GND
JU2
Closed
Bypasses THERM with
10kΩ resistor
Jumper JU3 sets the battery regulation voltage. The EV
kit comes with two voltage options, 4.2V (JU3 open)
and 4.1V (JU3 closed). For other voltages (+4.0V to
+4.2V), replace resistor R1. Refer to the Adjusting the
Battery Regulation Voltage section in the MAX1879
data sheet to select resistor R1. See Table 3 for the JU3
configuration.
_______________________________________________________________________________________
MAX1879 Evaluation Kit
JUMPER
JU3
JUMPER STATE
Open
Closed
VOLTAGE REGULATION
4.2V
4.1V
Table 4. LED States
LED
CONDITION
CHG STATE
Off
No battery, no WALL CUBE,
cell voltage < 2.2V, top-off,
or battery charged
High impedance
On
Fast-charge in
progress
Low impedance
Precharging near-dead
cells (+2.2 to +2.5V) or
temperature fault during
fast-charge
High-low
impedance
(50% duty cycle)
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 a thermistor is installed, and the cell temperature is
unacceptable for fast charging, or the charger is in the
precharging state, the LED blinks at 2Hz. The EV kit
stops charging the cell during a temperature fault. See
Table 4 for LED and CHG states.
Blinking
(2Hz)
For driving logic circuits, remove the LED and install a
100kΩ pullup resistor from CHG to the logic supply of
the CHG monitoring circuit. A logic-low signal appears
at CHG when the charger is in fast-charge; otherwise, a
logic high signal is detected. During the precharging or
temperature fault state, the output logic signal alternates between low and high at a fixed frequency of
2Hz. See Table 4.
_______________________________________________________________________________________
3
Evaluates: MAX1879
Table 3. Fixed Voltage Regulation
Evaluates: MAX1879
MAX1879 Evaluation Kit
BATT-
GND
WALL CUBE
+
-
D1
1
3 J1
2
4 P1
LED1
3
1
2
BATT+
C5
2.2µF
5
6
C1
OPEN
VIN
1
IN
BATT
8
C2
0.1µF
GATE
2
GATE
THERM
C4
OPEN
U1
CHG
THERM
7
JU2
MAX1879
3
4
CHG
GND
TSEL
ADJ
R2
10kΩ
6
5
C7
1000pF
2
JU1 1
4
3
C3
0.1µF
JU3
R1
412kΩ
1%
Figure 1. MAX1879 EV Kit Schematic
4
_______________________________________________________________________________________
C6
OPEN
MAX1879 Evaluation Kit
Figure 3. MAX1879 EV Kit PC Board Layout—Component Side
Figure 4. MAX1879 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
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
Evaluates: MAX1879
Figure 2. MAX1879 EV Kit Component Placement Guide—
Component Side