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1 features safe management of fast charge for nicd, nimh, or li- ion battery packs high-frequency switching con - troller for efficient and simple charger design pre-charge qualification for detecting shorted, damaged, or overheated cells fast-charge termination by ? t/ ? t minimum current (li-ion), maximum tempera- ture, and maximum charge time selectable top-off mode for achieving maximum capacity in nimh batteries programmable trickle-charge mode for reviving deeply dis- charged batteries and for post- charge maintenance built-in battery removal and insertion detection sleep mode for low power consumption general description the bq2000t is a programmable, monolithic ic for fast-charge manage - ment of nickel cadmium (nicd), nickel metal-hydride (nimh), or lith - ium-ion (li-ion) batteries in single- or multi-chemistry applications. the bq2000t detects the battery chemis - try and proceeds with the optimal charging and termination algorithms. this process eliminates undesirable undercharged or overcharged condi - tions and allows accurate and safe termination of fast charge. depending on the chemistry, the bq2000t provides a number of charge termination criteria: rate of temperature rise, ? t/ ? t (for nicd and nimh) minimum charging current (for li-ion) maximum temperature maximum charge time for safety, the bq2000t inhibits fast charge until the battery voltage and temperature are within user-defined limits. if the battery voltage is below the low-voltage threshold, the bq2000t uses trickle-charge to condition the battery. for nimh batteries, the bq2000t provides an optional top-off charge to maximize the battery capacity. the integrated high-frequency com - parator allows the bq2000t to be the basis for a complete, high-efficiency power-conversion circuit for both nickel-based and lithium-based chemistries. bq2000t sns current-sense input v ss system ground led charge-status output bat battery-voltage input 1 pn-2000.eps 8-pin dip or narrow soic or tssop 2 3 4 8 7 6 5 sns led bat v ss mod v cc ts rc pin connections pin names programmable multi-chemistry fast-charge management ic slus149a?february 2000 ts temperature-sense input rc timer-program input v cc supply-voltage input mod modulation-control output
2 pin descriptions sns current-sense input enables the bq2000t to sense the battery current via the voltage developed on this pin by an external sense-resistor connected in series with the battery pack v ss system ground led charge-status output open-drain output that indicates the charg - ing status by turning on, turning off, or flashing an external led bat battery-voltage input battery-voltage sense input. a simple resistive divider, across the battery terminals, generates this input. ts temperature-sense input input for an external battery-temperature monitoring circuit. an external resistive di- vider network with a negative tempera- ture-coefficient thermistor sets the lower and upper temperature thresholds. rc timer-program input rc input used to program the maximum charge-time, hold-off period, and trickle rate during the charge cycle, and to disable or enable top-off charge v cc supply-voltage input mod modulation-control output push-pull output that controls the charging current to the battery. mod switches high to enable charging current to flow and low to inhibit charging- cur rent flow. functional description the bq2000t is a versatile, multi-chemistry battery- charge control device. see figure 1 for a functional block diagram and figure 2 for the state diagram. bq2000t bd2000t.eps voltage reference internal osc clock phase generator adc osc sns ts mod rc bat led v cc v ss timer ? t/ ? t alu voltage comparator voltage comparator charge control figure 1. functional block diagram
3 bq2000t charge initialization 4.0v < v c c < 6.0v sleep mode charge suspended battery conditioning current regulation voltage regulation current taper or time = mto time < mto and v ba t > v m cv maintenance charge done top-off yes no v c c reset or battery replacement or capacity depletion (li-ion) v cc reset v bat > v m cv time = mto or v ts < v tco ? t/ ? t (after hold-off period), or v t s < v tc o or time = mto battery voltage (checked at all times) battery temperature (checked at all times) top-off selected? v b at < v slp v bat < v m cv v t s > v ht f v ba t < v lb at or v t s > v ltf v lb at < v b at < v m cv and v ht f < v ts < v ltf v l bat < v b at < v m cv and v h tf < v ts < v l tf v ts < v ht f v sl p < v ba t < v cc v m cv < v bat < v s lp sd2000t.eps v b at > v m cv figure 2. state diagram
initiation and charge qualification the bq2000t initiates a charge cycle when it detects application of power to v cc battery replacement exit from sleep mode capacity depletion (li-ion only) immediately following initiation, the ic enters a charge-qualification mode. the bq2000t charge qualifi - cation is based on battery voltage and temperature. if voltage on pin bat is less than the internal threshold, v lbat , the bq2000t enters the charge-pending state. this condition indicates the possiblility of a defective or shorted battery pack. in an attempt to revive a fully depleted pack, the bq2000t enables the mod pin to trickle-charge at a rate of once every 1.0s. as explained in the section ?top-off and pulse-trickle charge,? the trickle pulse-width is user-selectable and is set by the value of the resistance connected to pin rc. during this period, the led pin blinks at a 1hz rate, indicating the pending status of the charger. similarly, the bq2000t suspends fast charge if the battery temperature is outside the v ltf to v htf range. (see table 4.) for safety reasons, however, it disables the pulse trickle, in the case of a battery over-temperature condition (i.e., v ts with a trickle maintenance-charge that continues as long as the voltage on pin bat remains below v mcv . lithium-ion batteries the bq2000t uses a two-phase fast-charge algorithm for li-ion batteries (figure 3). in phase one, the bq2000t regulates constant current until v bat rises to v mcv . the bq2000t then moves to phase two, regulates the battery with constant voltage of v mcv , and terminates when the charging current falls below the i min threshold. a new charge cycle is started if the cell voltage falls below the v rch threshold. during the current-regulation phase, the bq2000t monitors charge time, battery temperature, and battery voltage for adherence to the termination criteria. during the final constant-voltage stage, in addition to the charge time and temperature, it monitors the charge current as a termination criterion. there is no post-charge maintenance mode for li-ion batteries. charge termination maximum charge time (nicd, nimh, and li-ion) the bq2000t sets the maximum charge-time through pin rc. with the proper selection of external resistor and capacitor, various time-out values may be achieved. figure 4 shows a typical connection. the following equation shows the relationship between the r mto and c mto values and the maximum charge time (mto) for the bq2000t: mto = r mto ? c mto ? 35,988 mto is measured in minutes, r mto in ohms, and c mto in farads. ( note: r mto and c mto values also determine other features of the device. see tables 2 and 3 for de - tails.) for li-ion cells, the bq2000t resets the mto when the battery reaches the constant-voltage phase of the charge. this feature provides the additional charge time required for li-ion cells. maximum temperature (nicd, nimh, li-ion) a negative-coefficient thermistor, referenced to v ss and placed in thermal contact with the battery, may be used as a temperature-sensing device. figure 5 shows a typi- cal temperature-sensing circuit. during fast charge, the bq2000t compares the battery temperature to an internal high-temperature cutoff threshold, v tco . as shown in table 4, high-temperature termination occurs when voltage at pin ts is less than this threshold. ? t/ ? t (nicd, nimh) when fast charging, the bq2000t monitors the voltage at pin ts for rate of temperature change detection, ? t/ ? t. the bq2000t samples the voltage at the ts pin every 16s and compares it to the value measured 2 sam - ples earlier. this feature terminates fast charge if this voltage declines at a rate of v 161 v min cc ? ? ? ? ? ? figure 5 shows a typical connection diagram. minimum current (li-ion only) the bq2000t monitors the charging current during the voltage-regulation phase of li-ion batteries. fast charge is terminated when the current is tapered off to 7% of the maximum charging current. please note that this threshold is different for the bq2000. initial hold-off period the values of the external resistor and capacitor con - nected to pin rc set the initial hold-off period. during this period, the bq2000t avoids early termination by disabling the ? t/ ? t feature. this period is fixed at the 5 battery chemistry charge algorithm nicd or nimh 1. charge qualification 2. trickle charge, if required 3. fast charge (constant current) 4. charge termination ( ? t/ ? t, time) 5. top-off (optional) 6. trickle charge li-ion 1. charge qualification 2. trickle charge, if required 3. two-step fast charge (constant current followed by constant voltage) 4. charge termination (minimum current, time) table 1. charge algorithm bq2000t
6 bq2000t f2000ttmc.eps bq2000t 2 7 battery pack 5 r t2 r t1 v ss v cc v cc ts n t c figure 5. temperature monitoring configuration f2000t rci.eps bq2000t 2 v cc rc 7 6 c mto r mto v ss figure 4. typical connection for the rc input f2000tbvd.eps bat+ bq2000t 2 4 r b1 r b2 v ss bat figure 6. battery voltage divider
programmed value of the maximum charge time divided by 32. hold-off period = maximum time - out 32 top-off and pulse-trickle charge an optional top-off charge is available for nicd or nimh batteries. top-off may be desirable on batteries that have a tendency to terminate charge before reaching full capacity. to enable this option, the capacitance value of c mto connected to pin rc (figure 4) should be greater than 0.13 f, and the value of the resistor connected to this pin should be less than 15k . to disable top-off, the capacitance value should be less than 0.07 f. the toler - ance of the capacitor needs to be taken into account in component selection. once enabled, the top-off is performed over a period equal to the maximum charge time at a rate of 1 16 that of fast charge. following top-off, the bq2000t trickle-charges the bat- tery by enabling the mod to charge at a rate of once ev- ery 1.0 second. the trickle pulse-width is user-selectable and is set by the value of the resistor r mto , which is on pin rc. figure 7 shows the relationship between the trickle pulse-width and the value of r mto . the typical tolerance of the pulsewidth below 150k is 10%. during top-off and trickle-charge, the bq2000t monitors battery voltage and temperature. these functions are suspended if the battery voltage rises above the maximum cell voltage (v mcv ) or if the temperature exceeds the high-temperature fault threshold (v htf ). charge current control the bq2000t controls the charge current through the mod output pin. the current-control circuit supports a switching-current regulator with frequencies up to 500khz. the bq2000t monitors charge current at the sns input by the voltage drop across a sense-resistor, r sns , in series with the battery pack. see figure 9 for a typical current-sensing circuit. r sns is sized to provide the desired fast-charge current (i max ): i max = 0.05 r sns if the voltage at the sns pin is greater than v snslo or less than v snshi , the bq2000t switches the mod output high to pass charge current to the battery. when the sns voltage is less than v snslo or greater than v snshi , the bq2000t switches the mod output low to shut off charging current to the battery. figure 8 shows a typical multi-chemistry charge circuit. voltage input as shown in figure 6, a resistor voltage-divider between the battery pack?s positive terminal and v ss scales the battery voltage measured at pin bat. for li-ion battery packs, the resistor values r b1 and r b2 are calculated by the following equation: r r n v v b1 b2 cell mcv =? ? ? ? ? ? ? ? 1 where n is the number of cells in series and v cell is the manufacturer-specified charging voltage. the end-to-end input impedance of this resistive divider network should be at least 200k and no more than 1m . 7 bq2000t 1 246810 50 100 150 200 250 2 3 4 20 40 60 pulsewidth?ms r mto ?k 80 100 120 140 160 2000pnvb3.eps shows tolerance figure 7. relationship between trickle pulse-width and value of r mto
8 bq2000t bat+ q1 fmmt718 d2 zhcs1000 l1 47uh c8 1000pf r9 120 ohms q2 mmbt3904lt1 c6 47uf d5 mmsd914lt d3 mmsd914lt d4 s1a dc+ r7 1k d1 red r2 2k c3 10uf d6 bzt52-c5v1 r1 100k c4 0.0022uf vcc c7 4.7pf c9 0.33uf rc 6 led 3 bat 4 vss 2 ts 5 vcc 7 sns 1 mod 8 u1 bq2000t q3 mmbt3904lt1 r8 220 ohms r13 10.5k r4 210k c5 10uf bat - therm chemistry r5 pn1031a02.eps 200k r6 221k r12 100k r14 23.2k c1 0.1 r11 6.81k c10 0.01uf c2 0.1 r10 1.1k r3 0.05 ohm notes: 1. for li-ion, the chemistry is left floating. for nicd/nimh, the chemistry is tied to bat- 2. dc input voltage: 9?16v 4. l1: 3l global p/n pksmd-1005-470k-1a 3. charge current: 1a figure 8. single-cell li-ion, three-cell nicd/nimh 1a charger
a nicd or nimh battery pack consisting of n se- ries-cells may benefit by the selection of the r b1 value to be n-1 times larger than the r b2 value. in a mixed-chemistry design, a common voltage-divider is used as long as the maximum charge voltage of the nickel-based pack is below that of the li-ion pack. oth- erwise, different scaling is required. temperature monitoring the bq2000t measures the temperature by the voltage at the ts pin. this voltage is typically generated by a negative-temperature-coefficient thermistor. the bq2000t compares this voltage against its internal threshold voltages to determine if charging is safe. these thresholds are the following: high-temperature cutoff voltage: v tco = 0.225 ? v cc this voltage corresponds to the maximum temperature (tco) at which fast charging is allowed. the bq2000t terminates fast charge if the voltage on pin ts falls below v tco . high-temperature fault voltage: v htf = 0.25 ? v cc this voltage corresponds to the temperature (htf) at which fast charging is allowed to begin. low-temperature fault voltage: v ltf = 0.5 ? v cc this voltage corresponds to the minimum temperature 9 bq2000t parameter value maximum cell voltage (v mcv )2v minimum pre-charge qualification voltage (v lbat ) 950mv high-temperature cutoff voltage (v tco ) 0.225 ? v cc high-temperature fault voltage (v htf ) 0.25 ? v cc low-temperature fault voltage (v ltf ) 0.5 ? v cc bq2000t fast-charge maximum time out (mto) r mto ? c mto ? 35,988 fast-charge charging current (i max ) 0.05/r sns hold-off period mto/32 top-off charging current (optional) i max /16 top-off period (optional) mto trickle-charge frequency 1hz trickle-charge pulse-width see figure 7 table 2. summary of nicd or nimh charging characteristics parameter value maximum cell voltage (v mcv )2v minimum pre-charge qualification voltage (v lbat ) 950mv high-temperature cutoff voltage (v tco ) 0.225 ? v cc high-temperature fault voltage (v htf ) 0.25 ? v cc low-temperature fault voltage (v ltf ) 0.5 ? v cc bq2000t fast-charge maximum time-out (mto) 2 ? r mto ? c mto ? 35,988 fast-charge charging current (i max) 0.05/r sns hold-off period mto/32 minimum current (for fast-charge termination) i max /14 trickle-charge frequency (before fast charge only) 1hz trickle-charge pulse-width (before fast charge only) see figure 7 table 3. summary of li-ion charging characteristics
(ltf) at which fast charging or top-off is allowed. if the voltage on pin ts rises above v ltf, the bq2000t suspends fast charge or top-off but does not terminate charge. when the voltage falls back below v ltf, fast charge or top-off resumes from the point where suspended. trickle-charge is allowed during this condition. table 4 summarizes these various conditions. charge status display the charge status is indicated by open-drain output led. table 5 summarizes the display output of the bq2000t. sleep mode the bq2000t features a sleep mode for low power con - sumption. this mode is enabled when the voltage at pin bat is above the low-power-mode threshold, v slp . dur- ing sleep mode, the bq2000t shuts down all internal cir- cuits, drives the led output to high-impedance state, and drives pin mod to low. restoring bat below the v mcv threshold initiates the ic and starts a fast-charge cycle. 10 bq2000t table 5. charge status display charge action state led status battery absent high impedance pre-charge qualification 1hz flash trickle charge (before fast charge) 1hz flash fast charging low top-off or trickle (after fast charge, nicd, nimh only) high impedance charge complete high impedance sleep mode high impedance charge suspended (v ts > v ltf ) 1hz flash temperature condition action v ts > v ltf cold battery?checked at all times suspends fast charge or top-off and timer allows trickle charge?led flashes at 1hz rate during pre-charge qualification and fast charge v htf 11 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, ex - cluding v cc relative to v ss -0.3 +7.0 v t opr operating ambient temperature -20 +70 c t stg storage temperature -40 +125 c t solder soldering temperature - +260 c 10s max. note: permanent device damage may occur if absolute maximum ratings are exceeded. functional operation should be limited to the recommended dc operating conditions detailed in this data sheet. exposure to conditions beyond the operational limits for extended periods of time may affect device reliability. dc thresholds (t a =t opr ;v cc = 5v 20% unless otherwise specified) symbol parameter rating tolerance unit notes v tco temperature cutoff 0.225 * v cc 5% v voltage at pin ts v htf high-temperature fault 0.25 * v cc 5% v voltage at pin ts v ltf low-temperature fault 0.5 * v cc 5% v voltage at pin ts v mcv maximum cell voltage 2.00 0.75% v v bat > v mcv inhibits fast charge v lbat minimum cell voltage 950 5% mv voltage at pin bat v therm ts input change for ? t/ ? t detection ? v 161 cc 25% v/min v snshi high threshold at sns, resulting in mod-low 50 10 mv voltage at pin sns v snslo low threshold at sns, resulting in mod-high -50 10 mv voltage at pin sns v slp sleep-mode input threshold v cc - 1 0.5 v applied to pin bat v rch recharge threshold v mcv - 0.1 0.02 v at pin bat bq2000t
12 bq2000t impedance symbol parameter minimum typical maximum unit r bat battery input impedance 10 - - m r ts ts input impedance 10 - - m r sns sns input impedance 10 - - m recommended dc operating conditions (t a =t opr) symbol condition minimum typical maximum unit notes v cc supply voltage 4.0 5.0 6.0 v i cc supply current - 0.5 1 ma exclusive of external loads i ccs sleep current - - 5 a v bat =v slp v ts thermistor input 0.5 - v cc vv ts < 0.5v prohibited v oh output high v cc - 0.2 - - v mod, i oh = 20ma v ol output low - - 0.2 v mod, led, i ol = 20ma i oz high-impedance leakage current --5 a led i snk sink current - - 20 ma mod, led r mto charge timer resistor 2 - 250 k c mto charge timer capacitor 0.001 - 1.0 f note: all voltages relative to v ss except as noted. timing (t a =t opr ;v cc = 5v 20% unless otherwise specified) symbol parameter minimum typical maximum unit d mto mto time-base variation -5 - +5 % f trkl pulse-trickle frequency 0.9 1.0 1.1 hz
13 bq2000t ordering information bq2000t package option: pn = 8-pin narrow plastic dip sn = 8-pin narrow soic ts = 8-pin tssop device: bq2000t multi-chemistry fast-charge ic with ? t/ ? t detection change no. page no. description nature of change 1 5 minimum current termination was: 14% is: 7% 1 3 added state diagram 17 changed capacitor value for en - abling top-off was: 0.13 f is: 0.26 f 1 8 figure 8 schematic updated 110v tco , v htf , v ltf tolerance updated 29 minimum current (for fast charge termination) was: i max /7 is: i max /14 note: change 1 = may 1999 b changes to final from jan. 1999 preliminary data sheet. change 2 = february 2000 changes from may 1999 b. data sheet revision history
14 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 bq2000t
15 bq2000t dimension millimeters inches min. max. min. max. a - 1.10 - 0.043 a1 0.05 0.15 0.002 0.006 b 0.18 0.30 0.007 0.012 c 0.09 0.18 0.004 0.007 d 2.90 3.10 0.115 0.122 e 4.30 4.48 0.169 0.176 e 0.65bsc 0.0256bsc h 6.25 6.50 0.246 0.256 l 0.50 0.70 0.020 0.028 notes: 1. controlling dimension: millimeters. inches shown for reference only. 2 'd' and 'e' do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.15mm per side 3 each lead centerline shall be located within 0.10mm of its exact true position. 4. leads shall be coplanar within 0.08mm at the seating plane. 5 dimension 'b' does not include dambar protrusion. the dambar protrusion(s) shall not cause the lead width to exceed 'b' maximum by more than 0.08mm. 6 dimension applies to the flat section of the lead between 0.10mm and 0.25mm from the lead tip. 7 'a1' is defined as the distance from the seating plane to the lowest point of the package body (base plane). 8-pin tssop ~ ts package suffix
important notice texas instruments and its subsidiaries (ti) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. all products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. ti warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with ti's standard warranty. testing and other quality control techniques are utilized to the extent ti deems necessary to support this warranty. specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. customers are responsible for their applications using ti components. in order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. ti assumes no liability for applications assistance or customer product design. ti does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of ti covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. ti's publication of information regarding any third party's products or services does not constitute ti's approval, warranty or endorsement thereof. copyright ? 2000, texas instruments incorporated

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