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1 features ? fast charge of nickel cadmium or nickel-metal hydride batter - ies ? direct led output displays charge status ? fast-charge termination by rate of rise of temperature, maximum voltage, maximum temperature, and maximum time ? internal band-gap voltage ref - erence ? optional top-off charge (bq2002t only) ? selectable pulse-trickle charge rates (bq2002t only) ? low-power mode ? 8-pin 300-mil dip or 150-mil soic general description the bq2002d/t fast-charge ic are low-cost cmos battery-c harge control - lers able to provide reliable charge ter - mination for both nicd and nimh bat - tery applications. controlling a current-limited or constant -current supply allows the bq2002d/t to be the basis for a cost-effective stand-alone or system- integrated c harger. the bq2002d/t integrates fast charge with optional top-off and pulsed-trickle con - trol in a single ic for charging one or more nicd or nimh battery cells. fast charge is initiated on application of the charging supply or battery re - placement. for safety, fast charge is inhibited if the battery temperature and voltage are outside configured limits. fast charge is terminated by any of the following: rate of temperature rise maximum voltage maximum temperature maximum time after fast charge, the bq2002t option - ally tops-off and pulse-trickles the battery per the pre-configured limits. fast charge may be inhibited using the inh pin. the bq2002d/t may be placed in low-standby-power mode to reduce system power consumption. nicd/nimh fast-charge management ics bq2002d/t tm timer mode select input led charging status output bat battery voltage input v ss system ground 1 pn-200201.eps 8-pin dip or narrow soic 2 3 4 8 7 6 5 tm led bat v ss cc inh v cc ts ts temperature sense input v cc supply voltage input inh charge inhibit input cc charge control output pin connections pin names bq2002d/t selection guide part no. tco htf ltf fast charge time-out top-off maintenance bq2002d 0.225 ? v cc 0.25 ? v cc 0.4 ? v cc c/4 320 min c/64 c/256 1c 80 min c/16 c/256 2c 40 min none c/128 bq2002t 0.225 ? v cc 0.25 ? v cc none c/4 440 min none none 1c 110 min none none 2c 55 min none none 1/99 d
pin descriptions tm timer mode input a three-level input that controls the settings for the fast charge safety timer, voltage ter - mination mode, top-off, pulse-trickle, and voltage hold-off time. led charging output status open-drain output that indicates the charging status. bat battery input voltage the battery voltage sense input. the input to this pin is created by a high-impedance re - sistor divider network connected between the positive and negative terminals of the battery. v ss system ground ts temperature sense input input for an external battery temperature monitoring thermistor. v cc supply voltage input 5.0v 20% power input. inh charge inhibit input when high, inh suspends the fast charge in progress. when returned low, the ic re - sumes operation at the point where initially suspended. cc charge control output an open-drain output used to control the charging current to the battery. cc switch - ing to high impedance (z) enables charging current to flow, and low to inhibit charging current. cc is modulated to provide top-off, if enabled, and pulse trickle. functional description figures 2 and 3 show state diagrams of bq2002d/t and figure 4 shows the block diagram of the bq2002d/t battery voltage and temperature measurements battery voltage and temperature are monitored for maximum allowable values. the voltage presented on the battery sense input, bat, should represent a single-cell potential for the battery under charge. a resistor-divider ratio of: rb1 rb2 = n - 1 is recommended to maintain the battery voltage within the valid range, where n is the number of cells, rb1 is the resistor connected to the positive battery terminal, and rb2 is the resistor connected to the negative bat- tery terminal. see figure 1. 2 bq2002d/t f2002dt1.eps bq2002d/t bat v ss n t c bq2002d/t v cc v cc pack + t s v ss bat pin connection thermistor connection tm ntc = negative temperature coefficient thermistor. rt1 rt2 r3 r4 rb1 rb2 mid-level setting for tm figure 1. voltage and temperature monitoring and tm pin configuration
3 bq2002d/t chip on v cc 4.0v battery voltage too high? battery temperature? charge pending fast charge, cc = z led = low sd2002d.eps v bat < 2v v bat < 2v and v bat > 2v off, cc = low led = low off, cc = low led = z v bat > 2v v bat 2v v ts > 0.25v v cc v ts > 0.25v v cc v ts < 0.25v v cc v bat > 2v or v ts < 0.25v v cc or maximum time out t/ t or figure 2. bq2002d state diagram chip on v cc 4.0v battery voltage too high? ( t/ t or maximum time out) and tm = high battery temperature? charge pending fast led = low top-off led = z sd2002t.eps v bat < 2v v bat > 2v 0.25 v cc < v ts < 0.6 v cc trickle led = low trickle led = z v bat > 2v or v ts < 0.225 v cc or maximum time out v bat > 2v or v ts < 0.225 v cc or (( t/ t or maximum time out) and tm = high) v bat < 2v and v ts < 0.6 v cc and v ts > 0.25 v cc v bat > 2v v bat 2v v ts > 0.6 v cc or v ts < 0.25 v cc figure 3. bq2002t state diagram
note: this resistor-divider network input impedance to end-to-end should be at least 200k ? and less than 1 m ? . a ground-referenced negative temperature coefficient ther - mistor placed in proximity to the battery may be used as a low-cost temperature-to-voltage transducer. the tempera - ture sense voltage input at ts is developed using a resistor-thermistor network between v cc and v ss . see figure 1. starting a charge cycle either of two events starts a charge cycle (see figure 5): 1. application of power to v cc or 2. voltage at the bat pin falling through the maximum cell voltage where: v mcv = 2v 5%. if the battery is within the configured temperature and voltage limits, the ic begins fast charge. the valid bat - tery voltage range is v bat nique minimizes the effect of any ac line ripple that may feed through the power supply from either 50hz or 60hz ac sources. tolerance on all timing is 20%. maximum voltage, temperature, and time any time the voltage on the bat pin exceeds the maxi- mum cell voltage, v mcv , fast charge or optional top-off charge is terminated. maximum temperature termination occurs anytime the voltage on the ts pin falls below the temperature cut-off threshold v tco where: v tco = 0.225 ? v cc 5% maximum charge time is configured using the tm pin. time settings are available for corresponding charge rates of c/4, 1c, and 2c. maximum time-out termina- tion is enforced on the fast-charge phase, then reset, and 5 bq2002d/t corresponding fast-charge rate tm typical fast-charge and top-off time limits (minutes) top-off rate pulse- trickle rate pulse- trickle period (ms) bq2002d c/4 mid 440 na na na 1c low 110 na na na 2c high 55 na na na bq2002t c/4 mid 320 c/64 c/256 18.3 1c low 80 c/16 c/256 73.1 2c high 40 disabled c/128 73.1 notes: typical conditions = 25c, v cc = 5.0v. mid = 0.5 * v cc 0.5v tolerance on all timing is 20% table 1. fast-charge safety time/top-off table td2002f1.eps fast charging v cc = 0 fast charging cc output led s s charge initiated by application of power charge initiated by battery replacement pulse-trickle top-off (optional, bq2002t only) (optional, bq2002t only) 286 see table 1 s 286 4576 figure 5. charge cycle phases
enforced again on the top-off phase, if selected (bq2002t only). there is no time limit on the trickle-charge phase. top-off charge?bq2002t only an optional top-off charge phase may be selected to follow fast charge termination for 1c and c/4 rates. this phase may be necessary on nimh or other bat - tery chemistries that have a tendency to terminate charge prior to reaching full capacity. with top-off en - abled, charging continues at a reduced rate after fast-charge termination for a period of time selected by the tm pin. (see table 1.) during top-off, the cc pin is modulated at a duty cycle of 286 s active for every 4290 s inactive. this modulation results in an average rate 1/16th that of the fast charge rate. maxi - mum voltage, time, and temperature are the only ter - mination methods enabled during top-off. pulse-trickle charge?bq2002t only pulse-trickle is used to compensate for self-discharge while the battery is idle in the charger. the battery is pulse-trickle charged by driving the cc pin active for a period of 286 s for every 72.9ms of inactivity for 1c and 2c selections, and 286 s for every 17.9ms of inactivity for c/4 selection. this results in a trickle rate of c/256 for the top-off enabled mode and c/128 otherwise. tm pin the tm pin is a three-level pin used to select the charge timer, top-off, voltage termination mode, trickle rate, and voltage hold-off period options. table 1 de - scribes the states selected by the tm pin. the mid- level selection input is developed by a resistor di - vider between v cc and ground that fixes the voltage on tm at v cc /2 0.5v. see figure 5. charge status indication in the fast charge and charge pending states, and when - ever the inhibit pin is active, the led pin goes low. the led pin is driven to the high-z state for all other condi - tions. figure 3 outlines the state of the led pin during charge. charge inhibit fast charge and top-off may be inhibited by using the inh pin. when high, inh sus pends all fast charge and top-off activity and the internal charge timer. inh freezes the current state of led until inhibit is re - moved. temperature monitoring is not affected by the inh pin. during charge inhibit, the bq2002d/t contin - ues to pulse-trickle charge the battery per the tm selec - tion. when inh returns low, charge control and the charge timer resume from the point where inh became active. the v ts sample history is cleared by inh. low-power mode the ic enters a low-power state when v bat is driven above the power-down threshold (v pd ) where: v pd = v cc - (1v 0.5v) both the cc pin and the led pin are driven to the high-z state. the operating current is reduced to less than 1 a in this mode. when v bat returns to a value below v pd , the ic pulse-trickle charges until the next new charge cycle begins. 6 bq2002d/t
7 bq2002d/t absolute maximum ratings symbol parameter minimum maximum unit notes v cc v cc relative to v ss -0.3 +7.0 v v t dc voltage applied on any pin excluding v cc relative to v ss -0.3 +7.0 v t opr operating ambient temperature 0 +70 c commercial t stg storage temperature -40 +85 c t solder soldering temperature - +260 c 10 sec max. t bias temperature under bias -40 +85 c note: permanent device damage may occur if absolute maximum ratings are exceeded. functional opera - tion should be limited to the recommended dc operating conditions detailed in this data sheet. expo - sure to conditions beyond the operational limits for extended periods of time may affect device reliability. dc thresholds (t a = 0 to 70c; v cc 20%) symbol parameter rating tolerance unit notes v tco temperature cutoff 0.225 * v cc 5% v v ts v tco terminates fast charge and top-off v htf high-temperature fault 0.25 ? v cc 5% v v ts v htf inhibits fast charge start v ltf low-temperature fault 0.4 ? v cc 5% v v ts v ltf inhibits fast charge start (bq2002t only) v mcv maximum cell voltage 2 5% v v bat v mcv inhibits/terminates fast charge
8 bq2002d/t recommended dc operating conditions (t a = 0 to 70c) symbol condition minimum typical maximum unit notes v cc supply voltage 4.0 5.0 6.0 v v bat battery input 0 - v cc v v ts thermistor input 0.5 - v cc vv ts < 0.5v prohibited v ih logic input high 0.5 - - v inh logic input high v cc - 0.5 - - v tm v im logic input mid v cc 2 - 0.5 - v cc 2 05 + . vtm v il logic input low - - 0.1 v inh logic input low - - 0.5 v tm v ol logic output low - - 0.8 v led ,cc,i ol = 10ma v pd power down v cc - 1.5 - v cc - 0.5 v v bat v pd max. powers down bq2002d/t; v bat < v pd min. = normal operation. i cc supply current - - 500 a outputs unloaded, v cc = 5.1v i sb standby current - - 1 av cc = 5.1v, v bat = v pd i ol led , cc sink 10 - - ma @v ol = v ss + 0.8v i l input leakage - - 1 a inh, cc, v = v ss to v cc i oz output leakage in high-z state -5 - - a led ,cc note: all voltages relative to v ss .
9 impedance symbol parameter minimum typical maximum unit r bat battery input impedance 50 - - m ? r ts ts input impedance 50 - - m ? timing (t a = 0 to +70c; v cc 10%) symbol parameter minimum typical maximum unit notes d fcv time-base variation -20 - 20 % note: typical is at t a = 25c, v cc = 5.0v. bq2002d/t
10 bq2002d/t d e1 e c e l g b a a1 b1 s 8-pin dip ( pn ) 8-pin pn ( 0.300" dip ) dimension inches millimeters min. max. min. max. a 0.160 0.180 4.06 4.57 a1 0.015 0.040 0.38 1.02 b 0.015 0.022 0.38 0.56 b1 0.055 0.065 1.40 1.65 c 0.008 0.013 0.20 0.33 d 0.350 0.380 8.89 9.65 e 0.300 0.325 7.62 8.26 e1 0.230 0.280 5.84 7.11 e 0.300 0.370 7.62 9.40 g 0.090 0.110 2.29 2.79 l 0.115 0.150 2.92 3.81 s 0.020 0.040 0.51 1.02 8-pin soic narrow (sn) 8-pin sn ( 0.150" soic ) dimension inches millimeters min. max. min. max. a 0.060 0.070 1.52 1.78 a1 0.004 0.010 0.10 0.25 b 0.013 0.020 0.33 0.51 c 0.007 0.010 0.18 0.25 d 0.185 0.200 4.70 5.08 e 0.150 0.160 3.81 4.06 e 0.045 0.055 1.14 1.40 h 0.225 0.245 5.72 6.22 l 0.015 0.035 0.38 0.89
11 bq2002d/t ordering information data sheet revision history change no. page no. description nature of change 13 was: table 1 gave the bq2002t operational summary. is: figure 2 gives the bq2002t operational summary. changed table to figure. 1 5 added top-off values. added column and val - ues. 2 all revised and expanded this data sheet 3 all revised and included bq2002d addition of device notes: change 1 = sept. 1996 b changes from aug. 1994. change 2 = aug. 1997 c changes from sept. 1996 b. change 3 = jan. 1999 d changes from aug. 1997 c. bq2002x package option: pn = 8-pin plastic dip sn = 8-pin narrow soic device: bq2002d fast-charge ic bq2002t fast-charge ic
12 bq2002d/t 17919 waterview parkway dallas, tx 75252 fax: (972) 437-9198 tel: (972) 437-9195 www.benchmarq.com or www.unitrode.com copyright ? 1999, unitrode corporation all rights reserved. no part of this data sheet may be reproduced in any form or means, without express permission from unitrode. unitrode reserves the right to make changes in its prod - ucts without notice. unitrode assumes no responsibility for use of any products or circuitry described within. no license for use of intel - lectual property (patents, copyrights, or other rights) owned by unitrode or other parties is granted or implied. unitrode does not authorize the use of its components in life-support systems where failure or malfunction may cause injury to the user. if unitrode components are used in life-support systems, the user assumes all responsibili - ties and indemnifies unitrode from all liability or damages. benchmarq is a registered trademark of unitrode corporation printed in u.s.a.

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