Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - battery management Charge management Li-Ion SSOP 28 Surface-mount

General Description

The MAX1757 is a switch-mode lithium-ion (Li+) battery

charger that charges one to three cells. It provides a

regulated charging current accurate to ±10% and a

regulated voltage with only a ±0.8% total voltage error

at the battery terminals. The internal high-side switch

delivers a programmable current of up to 1.5A to

charge the battery. The built-in safety timer automatical-

ly terminates charging once the adjustable time limit

has been reached.

The MAX1757 regulates the voltage set point and

charging current using two loops that work together to

transition smoothly between voltage and current regula-

tion. An additional control loop monitors the total cur-

rent drawn from the input source (charging + system)

and by automatically reducing battery-charging current

prevents overload of the input supply, allowing the use

of a low-cost wall adapter.

The per-cell battery regulation voltage is set between

4.0V and 4.4V using standard 1% resistors. The num-

ber of cells is set from 1 to 3 by pin strapping. Battery

temperature is monitored by an external thermistor to

prevent charging outside the acceptable temperature

range.

The MAX1757 is available in a space-saving 28-pin

SSOP package. Use the MAX1757EVKIT to help reduce

design time. For a stand-alone charger with a 28V

switch, refer to the MAX1758 data sheet. For a charger

controller capable of up to 4A charging current, refer to

the MAX1737 data sheet.

________________________Applications

Features

♦ Stand-Alone Charger for Up to 3 Li+ Batteries

♦ ±0.8% Battery Regulation Voltage Accuracy

♦ Low-Dropout 98% Duty Cycle

♦ Safely Precharges Near-Dead Cells

♦ Continuous Voltage and Temperature Monitoring

♦ 0.1µA Shutdown Battery Current

♦ Input Voltage Up to 14V

♦ Up to 1.5A Programmable Charge Current

♦ Input Current Limiting

♦ Space-Saving 28-Pin SSOP

♦ 300kHz PWM Oscillator Reduces Noise

Stand-Alone, Switch-Mode

Li+ Battery Charger with Internal 14V Switch

MAX1757

For pricing, delivery, and ordering information, please contact Maxim Direct at

1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

EVALUATION KIT AVAILABLE

DCIN

CSSP

CSSN

CCV

CCI

CCS

FASTCHG

BST

PGND

SHDN

FULLCHG

FAULT

TIMER2

TIMER1

CELL

HSD

BATT

VADJ

GND

REF

THM

ISETOUT

ISETTIN

SSOP

TOP VIEW

MAX1757

Pin Configuration

19-1754; Rev 1; 4/13

Ordering Information

28 SSOP

PIN-PACKAGETEMP. RANGE

-40°C to +85°CMAX1757EAI

PART

GND

DCIN

6V to 14V

CSSP

CSSN

BST

PGND

BATT

THM

THERM

FASTCHG

FULLCHG

FAULT

HSD

SYSTEM

LOAD

Li+ BATTERY

1 TO 3 CELLS

MAX1757

ISETOUT

ISETIN

VADJ

CCS

CCI

CCV

REF

TIMER1

TIMER2

SHDN

OFF

CELL

Li+ Battery Packs

Notebook Computers

Hand-Held Instruments

PDAs

Desktop Cradle Chargers

Typical Operating Circuit

Summary of content (17 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch General Description The MAX1757 is a switch-mode lithium-ion (Li+) battery charger that charges one to three cells. It provides a regulated charging current accurate to ±10% and a regulated voltage with only a ±0.8% total voltage error at the battery terminals. The internal high-side switch delivers a programmable current of up to 1.5A to charge the battery.
PAGE 2
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch ABSOLUTE MAXIMUM RATINGS BATT, CS, DCIN, CSSP, CSSN, HSD to GND ........-0.3V to +15V CSSP to CSSN.......................................................-0.6V to +0.6V BST to GND ............................................................-0.3V to +21V BST to LX..................................................................-0.3V to +6V LX to PGND ..............................................-0.6V to (VHSD + 0.
PAGE 3
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VHSD = VCSSP = VCSSN = 12V, V SHDN = VVL, VCELL = GND, VBATT = VCS = 4.2V, VVADJ = VREF/2, VISETIN = VISETOUT = VREF, RTHM = 10kΩ, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 2.4 2.7 3.0 A 14 V 4.
PAGE 4
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VHSD = VCSSP = VCSSN = 12V, V SHDN = VVL, VCELL = GND, VBATT = VCS = 4.2V, VVADJ = VREF/2, VISETIN = VISETOUT = VREF, RTHM = 10kΩ, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS BATT Undervoltage Threshold (Note 3) 2.4 2.5 2.6 V/cell BATT Overvoltage Threshold (Note 4) 4.
PAGE 5
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VHSD = VCSSP = VCSSN = 12V, V SHDN = VVL, VCELL = GND, VBATT = VCS = 4.2V, VVADJ = VREF/2, VISETIN = VISETOUT = VREF, RTHM = 10kΩ, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.
PAGE 6
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VHSD = VCSSP = VCSSN = 12V, V SHDN = VVL, VCELL = GND, VBATT = VCS = 4.2V, VVADJ = VREF/2, VISETIN = VISETOUT = VREF, RTHM = 10kΩ, TA = -40°C to +85°C, unless otherwise noted.) (Note 7) PARAMETER FULLCHG BATT Current Termination Threshold (Note 5) Temperature Measurement Frequency SYMBOL CONDITIONS MIN TYP MAX UNITS 250 400 mA 0.93 1.
PAGE 7
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch Typical Operating Characteristics (Circuit of Figure 1, VDCIN = 12V, V SHDN = VVL, VCELL = GND, VVADJ = VREF/2, VISETIN = VISETOUT = VREF, see Figure 1, TA = +25°C, unless otherwise noted.) 2.5 2.0 1.5 1.0 1.0 0.8 0.6 0.4 0.2 0.5 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0 CHARGING CURRENT (A) ISETOUT VOLTAGE (V) VOLTAGE LIMIT vs. VADJ VOLTAGE REFERENCE VOLTAGE vs. TEMPERATURE 4.40 4.30 4.25 4.20 4.15 4.10 4.05 4.205 4.200 4.
PAGE 8
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch Pin Description 8 PIN NAME FUNCTION 1 VL Chip Power Supply. Output of the 5.4V linear regulator from DCIN. Bypass VL to GND with 2.2µF or larger ceramic capacitor. 2 ISETIN Input Current Limit Adjust. Use a voltage divider to set the voltage between 0 and VREF. See Input Current Regulator section. 3 ISETOUT 4 THM Thermistor Input. Connect a thermistor from THM to GND to set qualification temperature range.
PAGE 9
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch MBR5340 INPUT SUPPLY D1 D2 28 DCIN CSSP 27 C7 0.1μF C8 0.1μF R1 0.05Ω MAX1757 CSSN 26 C9 0.1μF 17 TO VL 5 2 R4 3 C3 1μF 7 11 R5 VL ISETIN ISETOUT VADJ CELL R6 10k 25 CCV C1 0.1μF 24 CCI BST HSD HSD 12 FAULT 9 20 C14 0.1μF L1 22μH 19 D4 MBR5340 PGND CS CCS BATT 18 21 TIMER1 THM 8 C18 0.1μF C5 1nF FULL CHARGE 10 C16 0.1μF 23 FAST CHARGE C11 22μF TO SYSTEM LOAD 22 LX C2 0.
PAGE 10
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch Table 1.
PAGE 11
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch The MAX1757 includes a state machine that controls the charging algorithm. Figure 4 shows the state diagram. Table 1 is the charging state table. When power is applied, or SHDN input is driven high, the part goes into the reset state where the timers are reset to zero to prepare for charging. From the reset state, it enters the prequalification state.
PAGE 12
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch DCIN CSS LEVEL SHIFT AND GAIN OF 10 CSSP CSSN ENABLE TO BATT VL 5.
PAGE 13
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch SHUTDOWN SHUTDOWN IS ENTERED FROM ALL STATES WHEN SHDN IS LOW. FASTCHG = HIGH FULLCHG = HIGH FAULT = HIGH VDCIN < BATT SHDN HIGH VBATT < UNDERVOLTAGE THRESHOLD VDCIN > VBATT RESET FASTCHG = HIGH FULLCHG = HIGH FAULT = HIGH PREQUAL FAULT PREQUAL TIMEOUT FASTCHG = LOW FULLCHG = HIGH FAULT = HIGH FASTCHG = HIGH FULLCHG = HIGH FAULT = LOW VBATT > 2.
PAGE 14
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch cient voltage to fully drive the MOSFET gate even when its source is near the input voltage. Timers The MAX1757 includes safety timers to terminate charging and to ensure that faulty batteries are not charged indefinitely. TIMER1 and TIMER2 set the timeout periods. TIMER1 controls the maximum prequalification time, maximum full-charge time, and the top-off time. TIMER2 controls the maximum fast-charge time.
PAGE 15
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch CELL is the programming input for selecting cell count N. Table 2 shows how CELL is connected to charge 1, 2, or 3 cells. Setting the Charging Current Limit A resistor-divider from REF to GND sets the voltage at ISETOUT (VISETOUT). This determines the charging current during the current-regulation (fast-charge) mode. The full-scale charging current is 1.5A. The charging current (ICHG) is, therefore: ⎛ VISETOUT ⎞ ICHG = 1.
PAGE 16
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch capacitance and ESR rating of the capacitor are important for its effectiveness as a filter and to ensure stability of the PWM circuit. The minimum output capacitance for stability is: ⎛ VBATT ⎞ VREF ⎜1 + ⎟ ⎜ VDCIN(MIN) ⎟⎠ ⎝ COUT > VBATT x fOSC x RCS where: COUT is the total output capacitance. VREF is the reference voltage (4.2V). VBATT is the maximum battery regulation voltage (typically 4.2V per cell).
PAGE 17
MAX1757 Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch Revision History REVISION NUMBER REVISION DATE 0 6/00 Initial release 1 4/13 Corrected labels in Figure 1 and removed Chip Information section DESCRIPTION PAGES CHANGED — 9, 16 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied.