9-2805; Rev 2; 9/04 ILABLE N KIT AVA EVALUATIO Multichemistry Battery Chargers with Automatic System Power Selector The MAX1909/MAX8725 highly integrated control ICs simplify construction of accurate and efficient multichemistry battery chargers. The MAX1909/MAX8725 use analog inputs to control charge current and voltage, and can be programmed by a host microcontroller (µC) or hardwired. High efficiency is achieved through use of buck topology with synchronous rectification.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector ABSOLUTE MAXIMUM RATINGS DCIN, CSSP, CSSN, SRC, ACOK to GND..............-0.3V to +30V DHIV ........................................................…SRC + 0.3, SRC - 6V DHI, PDL, PDS to GND ...............................-0.3V to (VSRC + 0.3) BATT, CSIP, CSIN to GND .....................................-0.3V to +20V CSIP to CSIN or CSSP to CSSN or PGND to GND ...-0.3V to +0.3V CCI, CCS, CCV, DLO, IINP, REF, ACIN to GND ...
Multichemistry Battery Chargers with Automatic System Power Selector (Circuit of Figure 1, VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, GND = PGND = 0, PKPRES = GND, LDO = DLOV, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Charge-Current Accuracy VICTL Default Threshold SYMBOL CONDITIONS MAX1909: VICTL = 3.6V x 0.5, MAX8725: VICTL = 3.2V x 0.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, GND = PGND = 0, PKPRES = GND, LDO = DLOV, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 28 V SUPPLY AND LINEAR REGULATOR DCIN Input Voltage Range VDCIN 8.
Multichemistry Battery Chargers with Automatic System Power Selector (Circuit of Figure 1, VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, GND = PGND = 0, PKPRES = GND, LDO = DLOV, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, GND = PGND = 0, PKPRES = GND, LDO = DLOV, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
Multichemistry Battery Chargers with Automatic System Power Selector (Circuit of Figure 1, VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, GND = PGND = 0, PKPRES = GND, LDO = DLOV, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MAX1909: VICTL = 3.6V x 0.5, MAX8725: VICTL = 3.2V x 0.5 (including ICTL resistor tolerances of 1%) Charge-Current Accuracy VICTL Default Threshold MIN TYP MAX -7.0 +7.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, GND = PGND = 0, PKPRES = GND, LDO = DLOV, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL LDO Undervoltage-Lockout Trip Point CONDITIONS MAX UNITS 3.20 5.15 V 4.1960 4.2520 V 3.9 V 50 150 mV 100 300 mV 2.007 2.
Multichemistry Battery Chargers with Automatic System Power Selector (Circuit of Figure 1, VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, GND = PGND = 0, PKPRES = GND, LDO = DLOV, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN MODE Input High Voltage TYP MAX 2.8 UNITS V ACOK AND PKPRES ACOK Input Voltage Range 0 ACOK Sink Current VACOK = 0.4V, ACIN = 1.
Multichemistry Battery Chargers with Automatic System Power Selector LINE-TRANSIENT RESPONSE LDO LOAD REGULATION INDUCTOR CURRENT 200mA/div 3A VBATT AC-COUPLED 200mV/div MAX1909/MAX8725 toc04 0 30V VDCIN 20V -0.2 LDO OUTPUT ERROR (%) MAX1909/MAX8725 toc03 -0.4 -0.6 -0.8 -1.0 -1.2 1.8V VCCV 1.6V -1.4 500μs/div 0 1 2 3 4 5 6 7 8 10 9 LDO CURRENT (mA) LDO LINE REGULATION REF LOAD REGULATION 0 -0.05 MAX1909/MAX8725 toc06 0.05 0 -0.
Multichemistry Battery Chargers with Automatic System Power Selector SWITCHING FREQUENCY vs. VIN - VBATT 400 350 3.5 250 200 2.5 2.0 1.5 150 1.0 100 0.5 50 0 0 2 4 6 10 8 0 0.5 1.0 2.5 3.0 IINP ACCURACY vs. INPUT CURRENT INPUT CURRENT-LIMIT ACCURACY vs. SYSTEM LOAD 4 2 0 -2 -4 -6 4 INPUT CURRENT-LIMIT ACCURACY (%) MAX1909/MAX8725 toc11 6 -8 VBATT = 13V 3 VBATT = 10V 2 0 VBATT = 16V VBATT = 12V ICHARGE = 3A -1 -2 MAX1909 ONLY 0.5 1.0 INPUT CURRENT (A) 1.5 2.0 2.5 3.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector Typical Operating Characteristics (continued) (Circuit of Figure 2, VDCIN = 20V, charge current = 3A, 4 Li+ series cells, TA = +25°C, unless otherwise noted.
Multichemistry Battery Chargers with Automatic System Power Selector PIN NAME 1 DCIN DC Supply Voltage Input. Bypass DCIN with a 1μF capacitor to power ground. 2 LDO Device Power Supply. Output of the 5.4V linear regulator supplied from DCIN. Bypass with a 1μF capacitor. 3 ACIN AC Detect Input. This uncommitted comparator input can be used to detect the presence of the charger’s power source. The comparator’s open-drain output is the ACOK signal. 4 5 FUNCTION REF 4.2235V Voltage Reference.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector P3 RS1 0.01Ω AC ADAPTER TO SYSTEM LOAD 0.1μF 0.1μF OUTPUT VOLTAGE: 12.6V C22 1μF CHARGE I LIMIT: 3.0A CSSP SRC CSSN PDS D4 R6 590kΩ 1% C1 22μF C17 0.1μF SRC R7 196kΩ 1% DCIN C5 1μF VCTL R4 100kΩ LDO DHIV MAX1909 MAX8725 PDL LDO ICTL OUTPUT DLOV ACIN LDO P2 C13 1μF R13 33Ω C16 1μF MODE P1 (INPUT I LIMIT: 7.
Multichemistry Battery Chargers with Automatic System Power Selector P4 RS1 0.01Ω TO SYSTEM LOAD 0.1μF 0.1μF OUTPUT VOLTAGE: 16.8V C15 1μF CSSP SRC CSSN C17 0.1μF SRC R7 196kΩ 1% C1 22μF PDS D4 R6 590kΩ 1% DHIV DCIN C5 1μF LDO D/A OUTPUT VCTL MAX1909 MAX8725 PDL LDO P2 C13 1μF ICTL OPEN-DRAIN DLOV OUTPUTS MODE ACIN R13 33Ω C16 1μF LDO P1 R8 1MΩ DHI ACOK INPUT PKPRES (MAX8725 ONLY) OUTPUT DLO A/D INPUT C14 0.1μF R9 10kΩ (INPUT I LIMIT: 7.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector DCIN MAX8725 ONLY PKPRES LDO PACK_ON RDY 5.4V LINEAR REGULATOR 0.9 * LDO 4.2235V REFERENCE ICTLOK GND ACIN ACOK CHG LOGIC 0.8V REF BATT 2.048V SRDY DRIVER DCIN GND SRC PDS CHG CCS SRC-10V DRIVER PDL CLS MODE 100kΩ GMS CSSP SWITCH LOGIC LEVEL SHIFTER CSSN CSIP LEVEL SHIFTER CSIN Gm IINP SRC GMI DRIVER ICTL DHI CCI BATT DHIV MAX1909 ONLY LVC BATT_UV 3.
Multichemistry Battery Chargers with Automatic System Power Selector The MAX1909/MAX8725 include all of the functions necessary to charge Li+, NiMH, and NiCd batteries. A high-efficiency, synchronous-rectified step-down DCDC converter is used to implement a precision constant-current, constant-voltage charger with input current limiting.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector The input range for ICTL is 0 to 3.6V on the MAX1909, and 0 to 3.2V on the MAX8725. The charger shuts down if ICTL is forced below 0.75V for the MAX1909 and 0.06V for the MAX8725. When choosing current-sense resistor RS2, note that it must have a sufficient power rating to handle the full-load current. The sense resistor’s I2R power loss reduces charger efficiency.
Multichemistry Battery Chargers with Automatic System Power Selector Charging can also be inhibited by driving ICTL below 0.035V, which suspends switching and pulls CCI, CCS, and CCV to ground. The PDS and PDL drivers, LDO, input current monitor, and control logic (ACOK) all remain active in this state. Approximately 3mA of supply current is drawn from the AC adapter and 3µA (max) is drawn from the battery to support these functions.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector AC ADAPTER CSSP CSSN MAX1909 MAX8725 DHI CSS 20X DHI IMAX 1.94V R Q S Q COMP DLO DLO IMIN 0.15V TOFF ZCMP 0.1V LVC CLS GMS ICTL CSIP LVC GMI CSI 20X CSIN VCTL GMV CCV CCI CCS BATT COUT RCCV CCV CCI CCS Figure 4.
Multichemistry Battery Chargers with Automatic System Power Selector • IMAX: Compares the charge current (CSI) to the internally fixed cycle-by-cycle current limit. The current-sense voltage limit is 97mV. With RS2 = 0.015Ω, this corresponds to 6A. The high-side MOSFET on-time is terminated if the IMAX output is high and a new cycle cannot begin until IMAX goes low. IMAX protects against sudden overcurrent faults.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector In discontinuous mode, a new cycle is not started until the LVC voltage rises above 0.15V. Discontinuousmode operation can occur during conditioning charge of overdischarged battery packs, when the charge current has been reduced sufficiently by the CCS control loop, or when the charger is in constant voltage mode with a nearly full battery pack.
Multichemistry Battery Chargers with Automatic System Power Selector ROGMV × (1 + sCCV × RCV ) (1+ sCCV × ROGMV ) ≅ RCV COUT also has a much lower impedance than RL near crossover, so the parallel impedance is mostly capacitive and: RL (1+ sCOUT × RL ) ≅ sCOUT RCV GMV sCOUT 80 -45 20 -90 -20 MAG PHASE -40 0.1 1 10 100 1k FREQUENCY (Hz) 10k 100k -135 1M PHASE (DEGREES) MAGNITUDE (dB) 60 0 For stability, choose a crossover frequency lower than 1/10th of the switching frequency.
100 CSIP CSIN RS2 CSI 0 MAG PHASE 80 GMOUT MAGNITUDE (dB) MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector 60 40 -45 20 0 CCI -20 GMI CCI -40 ROGMI -90 0.1 10 1k 100k FREQUENCY (Hz) ICTL Figure 7. CCI Loop Diagram Figure 8. CCI Loop Response This describes a single-pole system.
Multichemistry Battery Chargers with Automatic System Power Selector 0 MAGNITUDE (dB) 60 40 -45 20 PHASE (DEGREES) MAG PHASE 80 0 -20 -40 0.1 10 1k 100k -90 10M FREQUENCY (Hz) Figure 10.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector Table 2. Recommended Components REFERENCE QTY C1, C4 C5, C15 C9, C10 C11, C14, C17 C12, C13, C16 DESCRIPTION 2 22µF ±20%, 35V E-size low-ESR tantalum capacitors AVX TPSE226M035R0300 Kemet T495X226M035AS 2 1µF ±10%, 25V, X7R ceramic capacitors (1206) Murata GRM31MR71E105K Taiyo Yuden TMK316BJ105KL TDK C3216X7R1E105K 2 0.01µF ±10%, 25V, X7R ceramic capacitors (0402) Murata GRP155R71E103K TDK C1005X7R1E103K 3 0.
Multichemistry Battery Chargers with Automatic System Power Selector MOSFET Power Dissipation Worst-case conduction losses occur at the duty factor extremes. For the high-side MOSFET, the worst-case power dissipation (PD) due to resistance occurs at the minimum supply voltage: ⎛V ⎞⎛ I ⎞2 PD(P1) = ⎜ BATT ⎟ ⎜ LOAD ⎟ × RDS(ON) ⎝ VDCIN ⎠ ⎝ 2 ⎠ Generally, a small high-side MOSFET is desired to reduce switching losses at high input voltages.
MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector The ripple current is determined by: ΔIL = VBATT tOFF / L where: tOFF = 2.5µs (VDCIN - VBATT) / VDCIN for VBATT < 0.88 VDCIN or: tOFF = 0.3µs for VBATT > 0.88 VDCIN Figure 11 illustrates the variation of the ripple current vs. battery voltage when the circuit is charging at 3A with a fixed input voltage of 19V. Higher inductor values decrease the ripple current.
Multichemistry Battery Chargers with Automatic System Power Selector f) Minimize the LX node (MOSFETs, rectifier cathode, inductor (15mm max length)). PGND POWER PATH Ideally, surface-mount power components are flush against one another with their ground terminals almost touching. These high-current grounds are then connected to each other with a wide, filled zone of top-layer copper, so they do not go through vias.
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.) QFN THIN.EPS MAX1909/MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
