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NUAL ATION EVALU FOLLO NiCd/NiMH Battery Fast-Charge Controllers


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19-0371; 5/97
NUAL ATION EVALU FOLLO
NiCd/NiMH Battery Fast-Charge Controllers
Stand-Alone NiCd NiMH Fast Chargers Pulsed Trickle-Charge Mode (MAX2003A only) Provide Switch-Mode, Gated, Linear Control Regulation Small, Narrow Package Available On-Chip Fast-Charge Termination Methods: Temperature Slope Maximum Voltage Negative Delta Voltage Maximum Time Maximum Temperature Automatically Switch from Fast-Charge Trickle-Charge Top-Off Charge Optional Discharge-Before-Charge Directly Drive Status LEDs Optional Top-Off Charge
General Description
MAX2003/MAX2003A fast-charge battery chargers (with conditioning) NiCd (nickel cadmium) NiMH (nickel-metal hydride) rechargeable batteries. MAX2003A same features MAX2003 with additional pulsed trickle-charge mode prevent dendrite formation NiMH batteries. Each configured switch-mode current regulator gating controller external current source. Switch-mode current regulation provides efficient energy transfer, reducing power dissipation associated heating. Gating control external current source requires minimal components, saving space cost. On-chip algorithms determine charge termination, MAX2003/MAX2003A used stand-alone chargers. Fast-charge termination accomplished five methods: temperature slope, negative voltage change, maximum temperature, maximum time, maximum voltage. safety feature, start fastcharge inhibited until battery voltage temperature within safe limits. selecting appropriate charge-termination method, single circuit built with MAX2003/MAX2003A fast-charge both NiMH NiCd batteries. MAX2003/MAX2003A provide switch-activated discharge-before-charge option that allows battery conditioning more accurate capacity measurement. Other features include optional top-off charging direct drivers status lights. MAX2003, wide packages, direct plug-in replacement bq2003. MAX2003/ MAX2003A also come space-saving narrow package. MAX2003A evaluation (MAX2003A EVKIT-SO) available assist designs.
MAX2003/MAX2003A
Ordering Information
PART MAX2003CPE MAX2003CSE MAX2003CWE MAX2003C/D MAX2003ACPE MAX2003ACSE MAX2003ACWE MAX2003AC/D TEMP. RANGE +70°C +70°C +70°C +70°C +70°C +70°C +70°C +70°C PIN-PACKAGE Plastic Narrow Wide Dice* Plastic Narrow Wide Dice*
Contact factory dice specifications.
_Pin Configuration
VIEW
CCMD DCMD DVEN
_Applications
Battery-Powered Equipment: Laptop, Notebook, Palmtop Computers Handy-Terminals Portable Consumer Products: Portable Stereos Cordless Phones Backup-Battery Applications: Memory Hold-Up Emergency Switchovers
MAX2003 MAX2003A
TEMP
DIP/SO
Maxim Integrated Products
free samples latest literature: http://www.maxim-ic.com, phone 1-800-998-8800. small orders, phone 1-800-835-8769.
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
ABSOLUTE MAXIMUM RATINGS
Pins .-0.3V, +6.0V Continuous Power Dissipation +70°C) Plastic (derate 10.53mW/°C above +70°C) .842mW Narrow (derate 8.70mW/°C above +70°C) .696mW Wide (derate 9.52mW/°C above +70°C).762mW Operating Temperature Range.0°C +70°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10sec) .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC 4.5V 5.5V, Figure measurements with respect VSS, TMIN TMAX, unless otherwise noted.) PARAMETER Supply Voltage Supply Current Cell Potential Battery Voltage Input Temperature Potential Temperature Sense Input Voltage End-of-Discharge Voltage Maximum Cell Voltage Low-Temperature Trip Threshold Temperature Cutoff Voltage High-Temperature Trip Threshold SYMBOL VCELL VBAT VTEMP VEDV VMCV VLTF VTCO VHTF VTCO 1.4V VSNS load VBAT VSNS 0.2VCC 30mV VEDV 0.4VCC 30mV VLTF 0.2VCC (VLTF/8) (7VTCO/8) 30mV 0.05VCC 25mV 0.044VCC 25mV (VLTF/8) 7VTCO/8 0.4VCC 0.2VCC CONDITIONS 0.75 0.2VCC 30mV VEDV 0.2VCC 0.4VCC 30mV VLTF (VLTF/8) (7VTCO/8) 30mV 0.05VCC 25mV 0.044VCC 25mV UNITS
Sense Trip Threshold High Sense Trip Threshold Delta Sense Voltage (Note Negative Delta Voltage (Note Thermistor Input Resolution (Note
VSNSHI VSNSLO VSNSHI VSNSLO VTHERM
0.05VCC 0.044VCC
NiCd/NiMH Battery Fast-Charge Controllers
ELECTRICAL CHARACTERISTICS (continued)
(VCC 4.5V 5.5V, Figure measurements with respect VSS, TMIN TMAX, unless otherwise noted.) PARAMETER Logic-High Threshold SYMBOL CONDITIONS DIS, TEMP CHG, ILOAD 5mA; MOD, ILOAD 10mA DIS, TEMP CHG, ILOAD 5mA; MOD, ILOAD 10mA CCMD, DCMD, DVEN TM1, CCMD, DCMD, DVEN TM1, CCMD, DCMD, DVEN TM1, TM1, TM1, tri-state BAT, MCV, TCO, SNS, -2.0 -1.0 -70.0 70.0 UNITS
MAX2003/MAX2003A
Logic-Low Threshold
Input Logic Voltage High Input Logic Voltage Input Logic Leakage Input Logic Current High Input Logic Current Input Logic Current High-Z Input Impedance
ILKG
Note sense trip levels determined internal resistor divider network that provides typical difference 30mV from SNSHI SNSLO. Slight variation this delta seen there resistor mismatch network. Note Typical variations Negative Delta Voltage Thermistor Input Resolution parameters less than ±4mV.
TIMING CHARACTERISTICS
(VCC 4.5V 5.5V, Figure measurements with respect VSS, TMIN TMAX, unless otherwise noted. Typical values 5.0V, +25°C.) PARAMETER Minimum Pulse Width Variation Fast-Charge Timeout Switching Frequency Battery Replacement Timeout (Note fMAX tBTO SYMBOL tMPW CCMD, DCMD (Note fast-charge mode, CONDITIONS 0.84 1.00 1.16 UNITS
Note Ratio actual versus expected timeout (see Table Tested with floating. Note recognize battery insert signal, VBAT must greater than VMCV least tBTO.
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
_Pin Description
NAME CCMD DCMD DVEN TM1, FUNCTION Charge-Enabled Mode Input-initiates fast-charge digital signal (see Detailed Description operating conditions). Discharge-Enable Mode Input-initiates discharge-before-charge digital signal (see Detailed Description operating conditions). Negative Delta Voltage (-V) Enable Input-enables charge-termination mode. DVEN high, controller uses negative-voltage change detection terminate charge. DVEN low, this mode disabled. These inputs used program fast-charge hold-off times, enable top-off charge mode. inputs high, low, floating. Table details. Temperature Sense-Voltage Input from external thermistor. thermistor temperature coefficient negative, higher temperature, lower voltage this (See Detailed Description conditions operation). Input Voltage Single Battery Cell. more than cell present, resistor divider needed divide voltage down single cell voltage. Ground Current-Sense Input-connected negative battery terminal. referenced this pin. voltage directly proportional current through battery used determine when switches. Temperature Cutoff-Voltage Input. voltage from less than voltage TCO, thermistor (negative coefficient) detected fast top-off charging terminated. Maximum Cell Voltage Input. voltage from exceeds voltage MCV, fast top-off charging terminated. Temperature Status Output. This push/pull driver indicates that temperature outside acceptable limits, fast-charge top-off inhibited (see Maximum Temperature Termination section Detailed Description). Charge Status Output. This push/pull driver indicates charge status (see Detailed Description). Modulation Output. This push/pull output switches enable disable charging current. high, current enabled. low, current disabled. supply, voltage less than 220mV, high. voltage above 250mV, low. Discharge-Switch Control Output. This push/pull output turns that discharges battery. Power-Supply Voltage Input (+5V nominal). Bypass with 0.1µF capacitor placed close device.
TEMP
13V/2A SOURCE
(*150 (2W)) *TRICKLE-CHARGE RATE C/40
LM317 0.1µF 22µF 1N5819 ZENER 1N5822 CHARGE RATE
MMDF3P03HD 100µH 1N5822
22µF 0.1µF
22µF
0.1µF 74HC04 100k 0.1µF 100k TEMP 60.4k 3.48k 33.2k 0.1µF MMSF5NO3HD PUSH DISCHARGE RDIS (20W)
100k
DISCHARGE RATE DURACELL DR17 1700mAh NiMH
Figure Switched-Mode Operation NiMH Batteries with Termination
DCMD CCMD DVEN 100k
MAX2003 MAX2003A
RSNS 0.14 (1W)
MAX2003/MAX2003A
COMPONENT USED MAX2003.
NiCd/NiMH Battery Fast-Charge Controllers
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
Detailed Description
MAX2003/MAX2003A fast-charge battery charger that uses several methods charge termination. device constantly monitors your choice following conditions determine termination fast-charge: Negative Delta Voltage (-V) Rate-of-Change Temperature (T/t) Maximum Voltage Maximum Time Maximum Temperature Figure shows block diagram MAX2003/ MAX2003A. first step creating fast-charge battery-charger circuit determine what type battery will used what conditions battery manufacturer recommends termination fast-charge. type battery (NiCd NiMH) charge rate determine which method(s) termination should used. charging characteristics NiMH batteries similar those NiCd batteries, there some differences that affect choice charge-termination method. Since type charge termination different NiCd NiMH batteries, always possible same circuit both battery types. comparison voltage profiles NiCd NiMH batteries (shown Figure reveals that NiCd batteries display larger negative drop voltage charge than NiMH batteries. Therefore, negative delta voltage detection (-V) method terminating fast-charge should only used NiCd batteries. This termination method cause errors NiMH batteries, since drop voltage full capacity great, lead overcharged battery. Figure shows temperature profiles types batteries. During first charge cycle, NiCd battery temperature slowly rises. NiMH battery temperature rises more rapidly during this period. cells approach capacity, temperature NiCd cells rises more rapidly. When cells approach full capacity, rates-of-rise temperature comparable both battery types. rate temperature change (T/t) therefore used terminate fast-charge both NiCd NiMH batteries; fast-charge terminated when rate temperature rise exceeds preset rate. Table provides some guidelines help selection proper fast-charge termination method, manufacturer's recommendations take priority case conflict.
Table Fast-Charge Termination Methods NiMH Batteries
Charge Rate >C/2 Negative Voltage Time Temp.
Table Fast-Charge Termination Methods NiCd Batteries
Charge Rate Negative Voltage Time Temp.
both these termination methods.
Figure shows standard application circuit switched-mode battery charger that charges NiMH batteries rate Though this circuit shown NiMH batteries, used NiCd batteries (see Table 1b). description below will this standard application explain, detail, functionality MAX2003/MAX2003A.
Battery Sense Voltage
measures per-cell voltage battery pack; this voltage used determine fast-charge initiation termination. voltage determined resistor-divider combination RB2, shown Figure where: Total Number Cells (RB1 RB2) Since extremely high input impedance (50M minimum), reasonable values selected resistors RB2. These values, however, must enough drain battery high enough unduly lengthen time constant signal going pin. total resistance value from positive negative terminal battery (RB1 RB2) should between 100k 500k prevent these problems. simple lowpass filter (RB, needed give more accurate reading removing noise that present. Remember that time delay from cell must exceed 200ms battery detection logic might function properly 200ms).
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
TIMING CONTROL
CHECK
CHECK
MAX2003 MAX2003A
TEMP
DISPLAY CONTROL (VTS VSNS)
CCMD DCMD DVEN
CHARGE CONTROL STATE MACHINE
(VBAT VSNS)
DISCHARGE CONTROL
CONTROL
CHECK
CHECK
Figure Block Diagram
MAX2003-03
NiCd VOLTAGE/CELL NiMH
NiMH TEMPERATURE (°C) NiCd
CHARGE CAPACITY MAXIMUM)
CHARGE CAPACITY MAXIMUM)
Figure Voltage-Charge Characteristics NiCd NiMH Batteries
Figure Temperature-Charge Characteristics NiCd NiMH Batteries
MAX2003-04
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
Temperature Measurement
MAX2003/MAX2003A employs negative temperature-coefficient (NTC) thermistor measure battery's temperature. This temperature value used determine start termination fast-charge. temperature conditions that used fastcharge termination are: Maximum Temperature Rate-of-Change Temperature (T/t) Figure shows various temperature cutoff points typical voltages that device will pin. VLTF (low-temperature fault voltage) refers voltage when battery temperature low, VHTF (high-temperature fault voltage) refers hightemperature cutoff. voltage outside these limits, MAX2003/MAX2003A will enter fast-charge mode. After fast-charge initiated, termination point high-temperature termination VTCO (temperature cutoff voltage), rather than VHTF. Figure TEMP status. VLTF internally 0.4VCC, (with supply) VLTF VTCO using external resistors determine high-temperature cutoff after fast-charge begins. VHTF internally (VLTF VTCO) above VTCO. Thermistors inherently nonlinear with respect temperature. This nonlinearity especially noticed when measurements made determine charge termination. simplest around this place resistor-divider network parallel with thermistor (Figure reduce effects nonlinearity. lowpass filter (RT, placed attenuates high-frequency noise signal seen
TEMP STATUS
Charge Pending
Before fast-charge initiated, cell voltage temperature battery pack must within assigned limits. voltage temperature outside these limits, device said "charge-pending" state. During this mode, will cycle (LED 0.125sec high (LED off) 1.375sec. Fast-charge normally initiated cell voltage greater than VEDV (end-of-discharge voltage). cell voltage (below VEDV), device waits until trickle current brings voltage before fastcharge initiated. VEDV internally 0.2VCC, (for supply) VEDV temperature cell between VLTF VHTF device also charge-pending state (see Temperature Measurement section).
Initiate Fast-Charge
MAX2003/MAX2003A charge-pending state, fast-charge initiated upon following conditions: Battery Replacement Applying Power MAX2003/MAX2003A (battery already present) Digital Control Signal During fast-charge, will continuously (LED on). initial period fast-charge (the hold-off time), voltage charge-termination methods disabled. hold-off time function charge rate selected (see Table
FILTER 100k
MAX2003 MAX2003A
VLTF 0.4VCC (VLTF VTCO) VHTF (VLTF VTCO) VTCO VLTF VTCO
0.1µF
Figure Temperature Measurement Scale
Figure Thermistor Configuration Temperature Measurement
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
Table Device Status Power-Up Battery Already Present
CCMD DCMD MAX2003/MAX2003A Status when Power Applied Fast-charge initiated power-up. device does enter fast-charge immediately. Fast-charge initiated falling edge pulse CCMD. device does enter fast-charge immediately. Fast-charge initiated rising edge pulse CCMD. Fast-charge initiated power-up. High Fast-charge initiated rising edge CCMD. Fast-charge initiated falling edge CCMD.
Table Digital Control Fast-Charge (VCC battery present)
CCMD DCMD CCMD Status Initiate Fast-Charge
High
High
Discharge-Before-Charge (optional)
discharge-before-charge function optional used condition batteries. especially useful NiCd batteries, since alleviates voltage depression problems associated with partially discharged NiCd cells. discharge-before-charge function initiated rising edge into DCMD. When digital signal applied, will pulled high, turning attached circuit discharging battery. discharge process continues until single cell voltage drops below 0.2VCC. During discharge phase, will (LED 1.375sec high (LED off) 0.125sec. MAX2003/MAX2003A does control current during discharge-before-charge. discharge rate great, battery could overheat damaged. battery manufacturer will able specify safe discharge rate, rate slower typically acceptable. also important choose components (Q2, that rated that particular discharge rate. Since gate-source drive 4.5V, logic-level MOSFET.
High
High
Battery Replacement Before battery inserted, pulled higher than maximum cell voltage (MCV) resistor (RTR) divider network (RB1/RB2) (Figure When battery inserted, voltage cell falls from default voltage battery voltage. Fast-charge initiated falling edge when voltage crosses voltage MCV. Applying Power MAX2003/MAX2003A (battery already present) There some cases where battery connected before power applied MAX2003/ MAX2003A. When power applied, device goes into reset mode approximately 1.5sec then samples CCMD DCMD pins. charge status determined voltage both CCMD DCMD pins. Table summarizes various conditions MAX2003/MAX2003A might power-up. Table shows that MAX2003/MAX2003A set-up fast-charge power-up making sure CCMD DCMD same potential. fastcharge power-up desired, make sure CCMD DCMD different logic levels during powerup, digital signal control fast-charge (see Digital Control section). Digital Control CCMD used initiate fast-charge. This useful when neither power supply battery removed from charger. CCMD signal needed initiate fast-charge depends potential DCMD. DCMD low, rising edge CCMD initiates fastcharge. DCMD high, falling edge CCMD provides fast-charge signal. Table summarizes conditions used start fast-charge.
Fast-Charge Current
fast-charge current generated using categories circuits: Circuits with sense resistor (RSNS) Circuits without sense resistor (SNS tied VSS)
Circuits with Resistor standard application circuit Figure uses inductor switched mode operation supply current. charge current determined sense resistor placed between negative terminal battery (SNS) ground (VSS). input comparator with hysteresis. voltage drops below 0.044VCC, turned voltage above 0.050VCC, turned off. switched mode
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
operation, voltage ramps between 0.044VCC 0.050VCC, which 220mV 250mV when (Figure average voltage SNS, therefore, 235mV, used calculate charge current follows: ICHARGE 0.235V RSNS where RSNS sense resistor ICHARGE charge current required.
Circuits without Resistor some applications (shown later), tied directly ground. these cases, remains until charge-termination condition exceeded (Figure reasonable external current limit (such current-limited source) must provided these applications, prevent battery damage excessive charge currents.
Charge Termination
MAX2003 several charge-termination methods. termination method selected depends type battery charge rate used. Table summarizes conditions used terminate fast-charge with different battery types charge rates.
Temperature Rate Termination Temperature Rate Termination (T/t) method terminates fast-charge when particular rate-of-change temperature exceeded. battery begins fastcharge, temperature increases slow rate. When battery nears full capacity, this rate temperature change increases. When rate temperature change exceeds preset number, fast-charge terminated. This method fast-charge termination used both NiCd NiMH batteries. MAX2003 samples voltage every seconds compares with value taken seconds earlier. Since thermistor used temperature measurements, gradual rise temperature will result successively lower voltage readings. reading more than 0.0032VCC (16mV below reading, fast-charge terminated. MAX2003A varies sampling interval function charge rate (Table charge rate increases, sampling interval decreases, thereby allowing more accurate termination fast charge. Note: This method charge termination valid only when battery's temperature between VLTF VTCO (Figure
FAST CHARGE FAST-CHARGE TERMINATE
FAST CHARGE
FAST-CHARGE TERMINATE
0.050 0.044 IBAT
TIME
0.050 0.044
TIME
TIME
IBAT
TIME
ILOAD
ILOAD
TIME
TIME
Figure Current Regulation with Resistor
Figure Current Regulation without Resistor
NiCd/NiMH Battery Fast-Charge Controllers
Negative Delta Voltage Termination Negative Delta Voltage Termination (-V) method measures negative delta voltage determine termination fast-charge. After maximum charge reached, terminal voltage NiCd batteries declines significantly, whereas terminal voltage NiMH batteries does not. Hence, method fast-charge termination suitable NiCd batteries, NiMH batteries. MAX2003/MAX2003A sample every seconds compare with previous values. value less than previous values more than 12mV, negative delta voltage been detected fast-charge terminated. Note: This method charge termination valid only when voltage between VMCV VMCV 0.2VCC. method inhibited during hold-off time prevent false termination fast-charge. hold-off time depends charge rate used, selected inputs shown Table After hold-off time expired, device begins monitor voltage drop. Maximum Temperature Termination Maximum Temperature Termination method used safety prevent problems, should never needed under normal operation charger. maximum temperature that battery reach during fast-charge corresponding voltage-the temperature cutoff voltage (VTCO), seen Figure This voltage externally using resistor divider from Although rarely experienced, excessively temperature will also terminate fastcharge. minimum temperature temperature fault (VLTF). This value internally 0.4VCC. When thermistor exceeds these temperature limits, fast-charge terminated. thermistor configuration shown Figure used measure battery's temperature scale operate from VTCO. Resistors calculated provide required cutoff VTCO. Design Guide section detailed design example. Maximum Voltage Termination Maximum Voltage Termination method another safety feature designed work something drastically wrong. Under normal operation charger, this condition should only reached when battery removed. maximum cell voltage expected applied using resistor-divider network. cell voltage measured exceeds that MCV, fastcharge terminated. most applications using both NiCd NiMH batteries, this voltage (VMCV) 1.9V. MAX2003/MAX2003A terminate fast-charge maximum voltage reached before hold-off time expired. cell voltage greater than during hold-off time, device will continue fast-charge until hold-off time expired, then will terminate fast-charge. hold-off time determined inputs TM2, shown Table
MAX2003/MAX2003A
Maximum Timeout Termination final method Maximum Timeout Termination, which (like maximum voltage maximum temperature methods) another backup safety feature. timeout time depends charge rate selected control signals TM2. Table shows list different timeout periods available different control-signal inputs. timeout reached before other termination method seen, fastcharge terminated protect charger battery.
Top-Off Charge
Top-off charge used provide last charge needed reach full capacity after fast-charge terminated. Top-off charging puts slightly more energy into battery than simple trickle charging, used both NiCd NiMH batteries. Select choosing appropriate control signals (Table
Table Programmable Inputs Pulse Trickle (VCC
Fast- Hold-Off MAX2003A MAX2003A FastCharge Time Top-Off Trickle Sampling Charge Timeout V/MCV Charge Charge Interval Rate (min) (sec) On/Off (sec) Disable Disable Disable Disable Disable *Enable *Enable *Enable *Enable Disable
Open
Open Open Open Open Open
MAX2003 4sec 30sec. MAX2003A 0.5sec 3.5sec.
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
Table Charge Status
Charge State Battery Absent Charge Pending Discharge-Before-Charge Fast-Charge Charge Complete TopOff Status 0.125sec, 1.375sec 1.375sec, 0.125sec 0.125sec, 0.125sec
top-off charge done fast-charge rate. MAX2003, activated every second period supply current battery seconds (MOD oscillates seconds stays seconds) (Figure external regulation used (SNS tied ground), stays high seconds seconds (Figure This top-off process continues until fast-charge timeout (Table exceeded, maximum temperature maximum voltage condition detected. MAX2003A slightly modified turn 0.5sec every second period. This shorter on-time reduces battery heat increases charge acceptance. During topoff charge, will cycle (LED 0.125sec high (LED off) 0.125sec.
would C/16, NiMH batteries could rate C/40. resistor value used depends maximum voltage typical battery voltage. example, six-cell 800mAh NiCd pack with nominal voltage 1.2V cell would have total voltage 1.2V 7.2V. supply voltage used 14V, voltage across trickle resistor would 14.0V 7.2V 6.8V. trickle current needed would C/16 50mA. trickle resistor would therefore 6.8V 50mA 150. Similar calculations should made NiMH batteries using C/40 trickle-charge rate. trickle-charge needed, higher value trickle resistor (like 100k) selected sense battery insertion.
Charge Status
connected that indicates operating mode. Table summarizes different charge conditions.
_Design Guide
Using circuit Figure example, following nine steps show design 1.7A switch-mode fast-charger that charge Duracell DR17 (NiMH six-cell battery pack with 1700mAh capacity). Select Power Supply. first step select power supply (such wall cube). minimum supply voltage should have supply equal about cell, plus headroom external circuitry ((2V/cell) 1V). minimum supply voltage must greater than example, there cells, minimum supply about needed cells 1V). Determine Charge Rate. charge rate, fastcharge current (IFAST), determined factors: capacity battery, time which user wants battery charged. battery manufacturer recommends maximum fast-charge rate, which must exceeded. Capacity Battery (mAh) IFAST (mA) Charge Time example, 1700mAh battery needs charged hours (C/2), fast-charge current least 850mA needed. charge rate will ideally charge battery hours but, because inefficiencies battery's chemical processes, time could more. example circuit (Figure charges Duracell battery pack rate 1.7A, which should fully charge discharged battery approximately minutes.
Trickle-Charge
trickle-charge applied battery after fastcharge top-off charge have terminated compensate self discharge. There methods trickle charge: constant pulsed.
Pulsed Trickle-Charge (MAX2003A)
MAX2003A provides pulsed trickle-charge battery turning briefly during fixed period time. duty cycle pulse function programmable inputs (Table MAX2003A does trickle resistor provide trickle charge. However, trickle resistor cannot entirely omitted because also used batterydetect circuitry.
Constant Trickle-Charge (MAX2003)
MAX2003 provides steady trickle-charge battery connecting resistor from supply positive battery terminal. This resistor dual purpose, that provides trickle-charge pulls above when battery absent. trickle-charge rate depends type battery used. NiCd batteries, nominal trickle-charge rate
NiCd/NiMH Battery Fast-Charge Controllers
Select Sense Resistor. sense resistor determines rate which battery fast-charged. sense pin, SNS, average voltage 235mV (see Detailed Description) and, since charge current (IFAST) known from above, resistor calculated RSNS VSNS IFAST 0.235 IFAST this example, fast-charge current 1.7A requires sense resistor about 0.14 watt). Select TM2. Once charge rate determined, Table used select inputs. safety timeout, holdoff time, top-off enable (see Fast-Charge Termination section Detailed Description). Figure fast-charge rate with top-off would require VCC. Select RB2. MAX2003A requires user select indicate number cells battery. total resistance value (RB1 RB2) should between 100k 500k prevent problems with noise. Figure (with cells) selected 100k and, from following equation: (Number Cells 100k calculated 20k. Select Temperature-Control Components. Most sealed rechargeable battery packs have built-in thermistor prevent currents from corrupting accurate temperature measurements. thermistor size temperature characteristics obtained from battery-pack manufacturer, help designing rest circuit. Three-terminal battery packs that incorporate thermistor generally share common connection thermistor battery negative terminal. Large charging currents produce voltage drops across common negative connector, causing errors thermistor readings. Using separate contacts thermistor ground sense battery ground sense negative battery terminal will reduce these errors. external thermistor used, take care ensure that placed direct contact with battery, that battery/thermistor set-up placed sealed container. Neither NiCd NiMH batteries should fastcharged outside maximum minimum temperature limits. However, some applications also require termination using criterion. resistors (Figure will determine temperature cutoff (VTCO) rate-of-change temperature (T/t). Though NiCd batteries always require termination using feature, possible isolate disable this mode. therefore recommended that NiCd NiMH batteries same termination parameters. Duracell DR17 battery pack used example circuit recommended fault temperature (VLTF) +10°C maximum temperature cutoff TCO) +50°C. These maximum temperature values will never reached most cases, used safety prevent battery damage. According Duracell, thermistor inside pack varies from 17.96k +10°C 4.16k +50°C. circuit Figure will designed that battery temperature change 1°C/min will result fast-charge termination. 1°C/min, battery will take minutes change 40°C (10°C 50°C). Since charge rate used this example, Table shows that MAX2003A samples every seconds compares with value taken seconds earlier. device will terminate fast-charge voltage changes more than 0.0032VCC (16mV 5V). charge rate 16mV every seconds, will charge 280mV minutes (40min 60sec/min 16mV/136sec). fault temperature (VLTF) internally 0.4VCC, which 2.0V supply temperature cutoff voltage (VTCO) will 280mV below VLTF, VTCO (2.00V 0.28V) 1.72V Figure shows that, given temperature: (RT2 RNTC) [(RT2 RNTC) RT1] When battery temperature +10°C, voltage VTS10 (RT2 RNTC10) [(RT2 RNTC10) RT1] +50°C: VTS50 (RT2 RNTC50) [(RT2 RNTC50) RT1]
MAX2003/MAX2003A
Figure Resistor Configuration
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
From solving these simultaneous equations: [(X) (RNTC10) (RNTC50)] [(RT2) (RNTC10) (VCC VTS10)] [VTS10 (RT2 RNTC10)]. [(RNTC50)(VTS10)(VCC VTS50)] where [(RNTC10) (VTS50) (VCC VTS10)] Using RNTC50 4.16k, RNTC10 17.96k, VTS50 1.72V, VTS10 2.00V, calculated that 1.599k 2.303k. Select preferred resistor values (2.21k) (1.62k). actual voltages verified follows: VTS10 Select Trickle Resistor (MAX2003 only). trickle resistor (RTR) selected allow trickle-charge rate C/16 C/40. resistor value given (VDC VBAT) where required trickle current, supply voltage, VBAT number cells times cell voltage after fast-charge. example, 1700mAh NiMH battery needs trickle current C/40; i.e., 42mA (1700mAh/40h). Therefore, minimum voltage (from formula above) follows: [13.0V 1.2V)] 42mA maximum power dissipated resistor calculated Power (VDC VBAT(MIN))2 where VBAT(MIN) minimum cell voltage, supply voltage, trickle resistor value. Since shorted battery could have this must minimum cell voltage possible. Therefore power dissipated trickle resistor would Power 1.2W resistor should sufficient tricklecharge resistor. MAX2003A, refer TrickleCharge section. Select Inductor. inductor value calculated using formula: where maximum voltage across inductor, minimum inductor value, change induci current, minimum on-time switch.
RNTC10
1.62k 17.96k
RNTC10
1.62k 17.96k 2.21k RNTC50
2.01V VTS50
RNTC50
1.62k 4.16k
1.62k 4.16k 2.21k
1.72V
Select Maximum Cell Voltage (MCV) Temperature Cutoff (TCO). selected with resistor-divider combination (Figure example, been +10°C, which corresponds voltage 1.72V pin. most fast-charge batteries about 1.9V. minimize current load VCC, choose range 200k. this example, choose 60.4k, then calculate follows: (VTCO (VCC VMCV) 33.5k (1%) (VMCV (VCC VMCV) 3.51k (1%) Select preferred resistor values (3.48k) (33.2k). actual voltages verified follows VTCO (R3) 1.71V VMCV 1.89V.
INDUCTOR CURRENT
IMAX IMIN
IMAX 1.9A ILOAD IMIN 1.5A
tOFF
TIME
Figure Inductor-Current Waveform ContinuousConduction Mode
NiCd/NiMH Battery Fast-Charge Controllers
order provide high currents with minimum ripple, device must function continuous-conduction mode. Figure shows current waveform inductor continuous-conduction mode (where coil current never falls zero). average load current (ILOAD) through inductor must 1.7A, peak current (IMAX) 1.9A should give fairly ripple while keeping inductor size minimal. This means that total current change (Figure across inductor (1.9 1.7) 0.4A. maximum voltage across inductor present when battery voltage minimum. minimum cell voltage start fast-charge will cell, giving battery voltage cells. maximum voltage (VL) across inductor therefore: (input voltage minimum battery voltage) input voltage this application 13V, maximum voltage (13V minimum on-time switch given (VOUT PERIOD where VOUT minimum battery voltage, maximum input voltage, PERIOD period switching signal. maximum input voltage this application will 14V, maximum allowed switching frequency 100kHz gives period 10µs. minimum on-time will therefore (VOUT PERIOD 13V) 10µs 4.62µs inductor value calculated from: 4.62µs) 0.4A 81µH. this inductor value used, actual switching frequency will lower than 100kHz expected, comparator delays variations duty cycle. inductor value selected application will 100µH-a preferred value just above calculated value. important choose saturation current rating inductor little higher than peak currents, prevent inductor from saturating during operation. inductor must selected ensure that switching frequency will exceed 100kHz maximum.
MAX2003/MAX2003A
Additional Applications _Information
MAX2003/MAX2003A several other circuits charge batteries. Figure shows circuit that uses Darlington transistor regulate current six-cell NiCd battery pack receives. Figure shows gated current-limited supply being used charge Duracell NiMH battery pack. Table lists external components used these application configurations.
Linear Regulation Charge Current
circuit Figure uses inexpensive transistor provide charge current. Since input MAX667 tolerate 16V, this circuit charge cells. MAX667 replaced with different regulator more cells need charged. source must supply voltage equal number cells, plus overhead accommodate drop across external components. When fast-charge initiated, voltage sampled compared trip levels (220mV 250mV high). voltage below 220mV, will switch high, 10k/1µF lowpass filter will pull high, turning transistor. This will pull base Darlington TIP115 low, turning allowing current flow into battery. When current through battery resistor high enough, voltage will exceed 250mV will turn off. amount current battery receives depends resistor between VSS. example circuit, average current through resistor will ISNS(AVG) VSNS(AVG) RSNS 0.235 0.28 0.84A maximum current resistor will receive ISNS(MAX) VSNS(MAX) RSNS 0.25 0.28 0.90A Darlington transistor must biased ensure that minimum 0.90A will supplied. This minimum
Table External Component Sources
Device Power Supply Thermistor Power MOSFET Darlington Transistor Manufacturer Phone Number Advanced Power Solutions Alpha Thermistor (510) 734-3060 (800) 235-5445 Number (510) 460-5498 (619) 549-4791
Motorola
(602) 303-5454
(602) 994-6430
Battery
Duracell Energizer Power Systems
(800) 431-2658 (904) 462-3911
(203) 791-3273 (904) 462-4726
MAX2003/MAX2003A
NiCd/NiMH Battery Fast-Charge Controllers
Figure Linear Mode Charge NiCD Batteries with Termination
14V/2A SOURCE 47µF TIP115 HEATSINK 0.1µF 47µF CHARGE RATE 1N5822 (*150 (2W)) *TRICKLE-CHARGE RATE C/16
0.1µF
MAX667
6.8k
0.1µF DVEN DCMD CCMD 100k 0.1µF 1.62k 2.21k MMSF5NO3HD RDIS (10W) 2N2222 PUSH DISCHARGE
DISCHARGE RATE
100k
100k
800mAh NiCd
ALPHA CURVE THERMISTOR
TEMP 3.48k 33.2k
MAX2003 MAX2003A
60.4k
0.1µF 100k RSNS 0.294 (1W) *COMPONENT USED MAX2003.
ILIMITED VSOURCE MMDF3P03HD 1N5822 ZENER 0.1µF 22µF CHARGE RATE *TRICKLE-CHARGE RATE C/40
*180 (2W)
2.6A LM317
22µF
0.1µF
22µF
0.1µF 2N2222 RDIS (20W) 2.21k DCMD CCMD DVEN 100k 0.1µF MMSF3N03HD DISCHARGE RATE PUSH DISCHARGE 100k
80.6k
Figure Current-Limited Mode NiMH Batteries with Termination
DURACELL DR35 2600mAh NiMH 1.62k TEMP 3.48k 33.2k *COMPONENT USED MAX2003. 0.1µF 100k 60.4k
MAX2003/MAX2003A
MAX2003 MAX2003A
NiCd/NiMH Battery Fast-Charge Controllers
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
current value must sufficiently guardbanded ensure limiting factor resistor, transistor. example, maximum current supplied Darlington will guardbanded 1.8A. Since beta Darlington typically 1000, base current needed will BETA 1.8A 1000 1.8mA emitter TIP115 will 14V, base will about 12.6V. When high, 2N2222 transistor base resistor will 12.6V 1.8mA 6.8k This 1.8A current will never reached because will when voltage reaches 0.25V (0.9A).
Current-Limited Supply
circuit Figure charge Duracell DR35 battery pack (nine cells, 2.6Ah) using 19V, 2.6A current-limited power supply provided Advanced Power Solutions. Since many power supplies have built-in current limiting, very external components required this charging method. this circuit tied directly VSS. This signals stay high until termination condition met. When high, transistor turned hence pulling gate MOSFET low. This turns MOSFET supplies current battery current limit source (2.6A). zener diode placed between source gate ensure FET's maximum source-drain voltage exceeded. When termination condition reached, goes turn terminate fastcharge current.
Table Operation Summary
Charge Status Conditions (VBAT VSNS) VMCV Rising edge DCMD Power applied voltage CCMD DCMD DCMD Low, CCMD Rising Edge (power already present) DCMD High, CCMD Falling Edge (power already present) Fast-charge initiated temperature voltage outside limits. Discharge initiated with temperature voltage within limits. Fast-charge initiated with temperature voltage within limits. Exceed five termination conditions. Charge complete top-off enabled without exceeding temperature voltage limits. Trickle current provided external resistor after fast-charge/top-off. Pulse current provided pulsing after fast-charge/top-off. Status Status Status (Low) (High) (sec) (sec) Continuous Continuous
Battery Absent Initiate Discharge
Initiate Fast-Charge
Continuous
Charge Pending Discharge Fast-Charge Charge Complete
VSNS 0.050VCC, VSNS 0.044VCC, High MAX2003A: Activate 0.5sec every 4sec period. MAX2003: Active 4sec every 34sec period. Pulsed according charge rate (Table
High
0.125 1.375 Continuous 0.125
1.375 0.125 0.125
Top-Off Charge
0.125
0.125
Constant TrickleCharge (MAX2003) Pulsed TrickleCharge (MAX2003A)
0.125 0.125
0.125 0.125
NiCd/NiMH Battery Fast-Charge Controllers
Chip Topography
CCMD DCMD
MAX2003/MAX2003A
DVEN
0.089" (2.261mm)
TEMP
0.086" (2.184mm)
TRANSISTOR COUNT: 5514 SUBSTRATE CONNECTED
_Package Information
SOICN.EPS
NiCd/NiMH Battery Fast-Charge Controllers MAX2003/MAX2003A
_Package Information (continued)
SOICW.EPS
PDIPN.EPS

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