Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - battery management Charge management Li-Ion TQFN 12 (4x4) Surface-mount

General Description

The MAX1925/MAX1926 single-cell lithium-ion (Li+)

switch-mode battery chargers use an external PMOS

pass element step-down configuration. Charge current

is programmable, and an external capacitor sets the

maximum charge time.

Additional features include automatic input power

detection (ACON output), logic-controlled enable, and

temperature monitoring with an external thermistor. The

MAX1925 disables charging for inputs greater than

6.1V, while the MAX1926 charges for inputs between

4.25V and 12V.

The MAX1925/MAX1926 feature two precondition levels

to restore near-dead cells. The devices source 4mA to

a cell that is below 2V while sourcing C/10 to a cell

between 2V and 3V. Full charge current is then applied

above 3V. A CHG output drives an LED to indicate

charging (LED on) and fault conditions (LED blinking).

The MAX1925/MAX1926 are available in a 12-pin

4mm ✕ 4mm thin QFN package and are specified over

the extended temperature range (-40°C to +85°C). An

evaluation kit is available to speed design.

Applications

Digital Cameras

Self-Charging Battery Packs

PDAs

Cradle Chargers

Features

♦ Small (4mm ✕ 4mm) Package

♦ 4.25V to 12V Input Range (MAX1926)

♦ Overvoltage Lockout at 6.1V (MAX1925)

♦ ±0.75% Battery Regulation Voltage

♦ Set Charge Current with One Resistor

♦ Automatic Input Power Sense

♦ LED (or Logic-Out) Charge Status and Fault

Indicator

♦ Programmable Safety Timer

♦ Autorestart at Cell = 4V

♦ Thermistor Monitor Input

MAX1925/MAX1926

Switch-Mode 1-Cell Li+ Chargers

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

MAX1925

MAX1926

INP EXT PGND

INPUT

4.5V TO 12V

LED

CHG

OFF

ACON

THRM

GND

BATT

1-CELL

Li+

BATTERY

Typical Operating Circuit

19-2556; Rev 1; 10/02

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.

EVALUATION KIT

AVAILABLE

PART

TEMP

RANGE

PIN-

PACKAGE

INPUT

CHARGING

RANGE

MAX1925ETC -40°C to +85°C

12 Thin QFN

4mm

x 4mm

4.5V to 6.1V

MAX1926ETC -40°C to +85°C

12 Thin QFN

4mm

x 4mm

4.25V to 12V

INP

EXT

2EN

7THRM

PGND

GND

BATT

MAX1925

MAX1926

CHG

ACON

THIN QFN

Pin Configuration

Summary of content (16 pages)

PAGE 1
9-2556; Rev 1; 10/02 KIT ATION EVALU E L B A AVAIL Switch-Mode 1-Cell Li+ Chargers Features ♦ Small (4mm ✕ 4mm) Package The MAX1925/MAX1926 feature two precondition levels to restore near-dead cells. The devices source 4mA to a cell that is below 2V while sourcing C/10 to a cell between 2V and 3V. Full charge current is then applied above 3V. A CHG output drives an LED to indicate charging (LED on) and fault conditions (LED blinking).
PAGE 2
MAX1925/MAX1926 Switch-Mode 1-Cell Li+ Chargers ABSOLUTE MAXIMUM RATINGS IN, INP, ACON to GND...........................................-0.3V to +14V CHG, EXT to PGND ...................................-0.3V to (VINP + 0.3V) CS, BATT, EN, THRM to GND ..................................-0.3V to +6V CT to GND ................................................................-0.3V to +4V EN, THRM, CT to IN................................................-14V to +0.3V INP to IN ....................................
PAGE 3
Switch-Mode 1-Cell Li+ Chargers (VPGND = VGND = 0, VINP = VIN = V CHG = 5V, VBATT = VCS = VEN = 4V, THRM = 10kΩ to GND, CCT = 100nF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) MIN TYP MAX UNITS Restart Threshold PARAMETER Charging restarts when BATT falls to this point CONDITIONS 3.92 4.00 4.08 V BATT Voltage Fault Threshold If BATT exceeds this threshold, EXT is high (external MOSFET is off) and CHG blinks 4.275 4.350 4.
PAGE 4
MAX1925/MAX1926 Switch-Mode 1-Cell Li+ Chargers ELECTRICAL CHARACTERISTICS (VPGND = VGND = 0, VINP = VIN = V CHG = 5V, VBATT = VCS = VEN = 4V, THRM = 10kΩ to GND, CCT = 100nF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 4) PARAMETER Supply Voltage Range CONDITIONS VINP, VIN (MAX1925 does not charge above 6.1V) VINP, VIN rising ACON Trip point VINP, VIN falling MIN MAX UNITS 4.5 TYP 12.0 V 4.78 MAX1925 4.30 MAX1926 4.0 4.5 MAX1925 4.17 4.
PAGE 5
Switch-Mode 1-Cell Li+ Chargers (VPGND = VGND = 0, VINP = VIN = V CHG = 5V, VBATT = VCS = VEN = 4V, THRM = 10kΩ to GND, CCT = 100nF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 4) PARAMETER CONDITIONS CHG Output High Leakage Current V CHG = 12V ACON High Leakage V ACON = 12V ACON Sink Current V ACON = 0.
PAGE 6
Typical Operating Characteristics (Circuit of Figure 1, VSUPPLY = 5V, VBATT = 4V, TA = +25°C, unless otherwise noted.) CHARGE-CURRENT ACCURACY vs. SUPPLY VOLTAGE 1.0 5 0 -5 VIN = 10V 0.8 SEE THE DROPOUT BEHAVIOR SECTION 0.4 4.208 0.2 6 7 8 9 10 11 4.204 4.202 4.200 4.198 4.194 3.0 12 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4 5 6 7 BATTERY VOLTAGE (V) VSUPPLY (V) SHUTDOWN BATTERY CURRENT vs. BATTERY VOLTAGE 95 VBATT = 4V EFFICIENCY (%) 3.0 2.5 2.0 1.
PAGE 7
Switch-Mode 1-Cell Li+ Chargers FREQUENCY vs. BATTERY VOLTAGE 300 250 VIN = 5V 200 tPREQUAL2 10 1 150 100 tPREQUAL1 0.1 MAX1925/26 toc12 1.0 CHARGE CURRENT (A) 350 tFULLCHG 100 TIMER (MINUTES) VIN = 8V 0.8 0.6 0.4 0.2 50 0 0 0.01 3.0 4.0 3.5 10 100 BATTERY VOLTAGE (V) 1000 0 0.5 BATTERY VOLTAGE vs. TIME 1.0 1.5 2.0 2.5 3.0 TIME (h) CT CAPACITANCE (nF) SWITCHING WAVEFORM MAX1925/26 toc14 4.5 MAX1925/26 toc13 2.5 4.
PAGE 8
Switch-Mode 1-Cell Li+ Chargers MAX1925/MAX1926 Pin Description PIN 8 NAME FUNCTION 1 CHG Charge Status LED Driver. Open-drain LED driver sinks 10mA when the MAX1925/MAX1926 are charging. CHG also blinks at a 0.5Hz rate during fault states (see the Timing section). High impedance when charger is in shutdown. See Tables 1 and 2. 2 EN Enable. Drive EN high to enable charger. Logic level input for normal ON/OFF control. In the MAX1926 EN is internally pulled up to 3V with a 300kΩ resistor.
PAGE 9
Switch-Mode 1-Cell Li+ Chargers MAX1925/MAX1926 D1 POWER SOURCE C3 10µF D3 LED Q1 D2 L1 10µH CHG ACON IN INP EXT 4.5V FOR MAX1926 4.25V FOR MAX1925 10mA ACON PREQUAL1 4mA CS RSET 0.14Ω BATT > 2V 6.1V MAX1925 ONLY BATT MAX1925 MAX1926 INP C2 10µF HV DRIVER REF/8 OSC C2 0.1µF PGND REF/10 I > 12% REF ACON REF BATT > 2V REF STATE MACHINE AND TIMERS EN BATT > 3V REF 353µA TEMP FAULT 49µA REF BATT > 4.35V REF 3V_ANA 3V_DIG ACON THRM 10kΩ IN REGULATOR REF GND PGND Figure 1.
PAGE 10
MAX1925/MAX1926 Switch-Mode 1-Cell Li+ Chargers mode, the charger regulates the peak and valley of the output ripple. Detailed Description The MAX1925/MAX1926 switch-mode battery chargers form a complete solution for a single-cell Li+ battery. The devices include battery undervoltage/overvoltage fault protection. The MAX1925/MAX1926 use EN and THRM for shutdown, battery detection, and temperature monitoring. The devices provide outputs to indicate charge status (CHG) and presence of input power (ACON).
PAGE 11
Switch-Mode 1-Cell Li+ Chargers MAX1925/MAX1926 CHG LED OFF FULL TOPOFF CVM 4V CCM FASTCHG PREQUAL1 3V PREQUAL2 CELL VOLTAGE 2V 1V 4mA C/10 C/8 C CHARGE CURRENT CVM NORMAL VOLTAGE PROFILE 4V 4.2V CCM C FAULT FASTCHG 2V NORMAL CURRENT PROFILE FAULT CHARGE CURRENT CELL VOLTAGE CHG LED OFF 3V C/8 1V C/10 2mA t tPREQUAL2 = t/16 tPREQUAL1 = t/1024 CHARGE TIME (tFULLCHG = 3 HOURS WITH CCT = 100nF) Figure 3.
PAGE 12
MAX1925/MAX1926 Switch-Mode 1-Cell Li+ Chargers and a new battery is connected during either fast-charge or full topoff modes, the charger begins with full charge current without prequalification unless the part is reset. Detect battery insertion by connecting THRM to a thermistor on the battery, if a thermistor is used, or to a 10kΩ resistor linked to a battery door mechanism. Constant-Current Mode (CCM) When the battery voltage is below 4.
PAGE 13
Switch-Mode 1-Cell Li+ Chargers ACON CHARGING CHG LED LOW YES ON (until charge complete) VIN > VACON threshold and VIN < VBATT (Note: This state should never occur) High Z NO OFF VIN < VACON threshold High Z NO OFF LOW YES ON (until charge complete) VIN > VACON threshold and VIN < VBATT (Note: This state should never occur) High Z NO OFF VIN < VACON Threshold High Z NO OFF PART VIN VIN > VACON threshold (4.5V nom) and < 6.1V, and VIN > VBATT MAX1925 VIN > VACON threshold (4.
PAGE 14
MAX1925/MAX1926 Switch-Mode 1-Cell Li+ Chargers mode. To ensure stable transition from CCM to CVM choose a capacitor with the following ESR: V RESR > VHIST × RSET VIHIST where VVHIST is the voltage hysteresis (15mV typ) and VIHIST is the current-sense threshold hysteresis (typically 30mV). Tantalum capacitors are recommended. However a ceramic capacitor (typically 10µF) with a series resistor can also be used. MOSFET Selection The MAX1925/MAX1926 drive an external P-channel MOSFET’s gate from IN to GND.
PAGE 15
Switch-Mode 1-Cell Li+ Chargers PACKAGE OUTLINE 12,16,20,24L QFN THIN, 4x4x0.8 mm 21-0139 A ______________________________________________________________________________________ 15 MAX1925/MAX1926 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.
PAGE 16
MAX1925/MAX1926 Switch-Mode 1-Cell Li+ Chargers Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) PACKAGE OUTLINE 12,16,20,24L QFN THIN, 4x4x0.8 mm 21-0139 A Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.