SLUS527 – DECEMBER 2002 FEATURES D Designed for Off-Line Charger Design for D D D D D D D D D DESCRIPTION Single-Cell Li-Ion Packs Provides Control Feedback to a Primary-Side Controller Robust Battery Insertion and Removal Detection Charge Current and Voltage Regulation Feedback to Primary-Side for High-Accuracy Charging Charge Termination by Minimum Current and Time Pre-Charge Conditioning Regulator with Safety Timer Charge Status Outputs for LED or Host Processor Interface Indicates Chargein-Progress, Charge Completion, and Fault Conditions Temperature Monitoring Before and During Charge Short-Circuit Protection Small, 14-Pin TSSOP Package APPLICATIONS D Cradle Chargers for Digital Cameras D Desktop Chargers D Handheld Devices The bq24901 Li-Ion charge management devices are designed specifically for off-line charger applications. The bq24901 resides on the secondary-side of the transformer and provides the control feedback to a variety of primary side controllers. The bq24901 offers current or voltage regulation feedback, temperature monitoring, charge status, and adjustable charge termination, in a single monolithic device. During battery-absent or charge-complete conditions, the bq24901 continuously regulates the secondary-side voltage, used as VCC supply to the device. The bq24901 features a time-limited precon– ditioning phase to condition deeply discharged cells. The pre-conditioning phase is achieved by linear regulation in the secondary side. Following preconditioning, the bq24901 regulates the charge current to the value set by the external current sense resistor. Once the battery reaches the charge voltage, the voltage regulation loop takes over and completes the charge cycle. The accuracy of the voltage regulation is better than ±30mV. Charge is terminated based on minimum current. The minimum current level is set through TADJ pin. An internal five-hour charge timer provides a backup for charge termination. The bq24901 is designed to reliably detect battery insertion and removal conditions, including packs with open protectors. Other standard features include a recharge feature activated when the battery voltage falls below the VRCH threshold. Copyright 2002, Texas Instruments Incorporated !" # $%&" !# '%($!" )!"&* )%$"# $ " #'&$$!"# '& "+& "& # &,!# #"% &"# #"!)!) -!!".* )%$" '$&##/ )&# " &$&##!(. $(%)& "&#"/ !(( '!! &"&#* www.ti.com 1 SLUS527 – DECEMBER 2002 DESCRIPTION (continued) In addition to the standard features, the bq24901 offers battery temperature monitoring and status display. The temperature-sense circuit continuously measures battery temperature using an external thermistor and suspends charge until the battery temperature is within the user–defined thresholds. The STAT pins indicate conditions of operation of the charger. These outputs can be used to drive an LED or interface to a host microcontroller. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. ORDERING INFORMATION TA CHARGE REGULATION VOLTAGE PACKAGE DEVICES(1) TOP SIDE MARKINGS –20°C to 85°C 4.2 V bq24901PW bq24901 (1) The PW package is also available taped and reeled. Add an R suffix to the device type (i.e., bq24901PWR) for quantities of 2,500 devices per reel. PACKAGE DISSIPATION RATING TABLE PACKAGE θJA TA ≤ 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C PW 110°C/ W 907 mW 9.07 mW/°C/ ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range unless otherwise noted(1) Supply voltage, VCC I Input t voltage lt range, VI bq24901 UNIT with respect to VSS 11.5 V SNS, BAT, STAT1, STAT2, VCOMP, ICOMP, SCOMP, OPTD, CC (all with respect to Vss) 11.5 TADJ, VREF (all with respect to Vss) TS (with respect to Vss) Output sink/source current, IO O tp t sink current Output c rrent V 7 –0.3 to VCC + 0.3 V STAT1, STAT2, OPTD 20 CC 80 VREF 1 mA Operating free-air temperature range, TA –40 to 100 Junction temperature range, TJ –40 to 125 Storage temperature, Tstg –65 to 150 °C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 300 (1) Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. RECOMMENDED OPERATING CONDITIONS MIN Supply voltage, VCC Operating free-air temperature, TA 2 www.ti.com MAX UNIT 3 10 V –20 85 °C SLUS527 – DECEMBER 2002 ELECTRICAL CHARACTERISTICS Over recommended operating free-air temperature and supply voltage (unless otherwise noted) TEST CONDITIONS PARAMETER MIN TYP MAX UNIT SUPPLY CURRENT ICC(VCC) IIB(BAT) Input current IIB(TS) IIB(SNS) Input bias current on TS pin Input bias current on BAT pin Input bias current on SNS pin IIB(TADJ) Input bias current on TADJ pin BATTERY VOLTAGE and VCC REGULATION VO(REG) VCC Output voltage VCC > VCC(min) VI(BAT) > VO(REG), when not in charge 2 VI(TS) = 2.5 V VCC = 6 V, VI(SNS) = 6 V when not in charge VI(TADJ) = VREF 1 0°C ≤ TA ≤ 70°C Supply voltage mA 1 1 µA A 1 4.17 4.20 4.23 5.8 6.0 6.3 184 200 216 mV VCC V V CURRENT REGULATION Current regulation threshold voltage V(SNS) Voltage at pin SNS relative to BAT, 0°C ≤ TA ≤ 70°C, V(LOWV)≤ V(SNS)≤ VO(REG) Input common mode range on SNS pin V(UVT) PRE-CHARGE AND SHORT-CIRCUIT CURRENT REGULATION Pre-charge voltage threshold ISC Short-circuit current CHARGE TERMINATION DETECTION Charge termination current detect threshold V(ITERM) Voltage at pin SNS relative to BAT pin, 0°C ≤ TA ≤ 70°C V(UVT) ≤ VI(BAT) ≤ V(LOWV) 0°C ≤ TA ≤ 70°C, 0 ≤ VI(BAT) ≤ V(UVT) Voltage at pin SNS relative to BAT pin, 0°C ≤ TA ≤ 70°C TADJ pin tied to VREF pin, VI(SNS) = VO(REG)VI(BAT) > V(RCH) Voltage at pin SNS relative to BAT pin, 0°C ≤ TA ≤ 70°C TADJ pin tied to VSS pin, VI(SNS) = VO(REG)VI(BAT) > V(RCH) 10 20 5.4 16 20 30 mV 30.0 mA 24 mV 7.5 10.0 12.5 VO(REG) –210 VO(REG) – 160 VO(REG) – 110 V(EN-TERM) Enable termination voltage (VI(SNS) – VI(BAT)) < V(ITERM) , VBAT increasing above threshold t(TRMDET2) Falling-edge delay for termination detection (VSNS – VBAT) increasing above threshold, VI(BAT) > V(EN–TERM), 100 ns fall time 2 mV overdrive 100 µs t(TRMDET1) Rising-edge delay for termination detection (VSNS – VBAT) increasing above threshold, VI(BAT) > V(EN–TERM), 100 ns fall time 2 mV overdrive 20 ms V TEMPERATURE COMPARATOR V(LTF) V(HTF) Cold temperature threshold voltage V(TCO) Cutoff temperature threshold voltage Hot temperature threshold voltage LTF hysteresis VTS, VTS, VCC ≥ 3.5 V VCC ≥ 3.5 V VTS, VCC ≥ 3.5 V Hysteresis for LTF threshold voltage 72.6 73.5 74.1 33.7 34.4 35.1 28.7 29.3 29.9 0.1 0.6 1.1 3.00 3.05 3.15 %VCC LOW BATTERY VOLTAGE (LOWV) THRESHOLD COMPARATOR V(LOWV) (1) V Ensured by design. Not production tested. www.ti.com 3 SLUS527 – DECEMBER 2002 ELECTRICAL CHARACTERISTICS (continued) Over recommended operating free-air temperature and supply voltage (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT BATTERY RECHARGE THRESHOLD (VRCH) COMPARATOR V(RCH) VO(REG) – 0.24 Recharge threshold voltage VO(REG) – 0.12 V V POWER-ON RESET (POR) V(POR) TIMERS POR threshold voltage t(PRECHG) Precharge time t(CHG) Charge time VI(BAT) < V(LOWV) V(LOWV) < VI(BAT) < VO(REG), (VI(SNS) – VI(BAT)) < V(ITERM) 2.60 2.70 2.85 1,350 1,800 2,250 13,500 18,000 22,500 s OPTO-DRIVER PIN (OPTD) VSAT(OPTD) Output saturation voltage I(OPTDLKG) Opto-driver leakage current gM Transconductance Gain-bandwidth product IO(OPTD) = 10 mA V(OPTD) = 5 V, VI(BAT) < VO(REG) VCC = 5.8 V, (VI(SNS) – VI(BAT)) < 184 mV IO(OPTD) = 5 mA IO(OPTD) = 5 mA, RLOAD = 100 Ω 5 100 mV 100 µA 500 S 1 MHz DISCHARGE CURRENT, DISCHARGE VOLTAGE, CONDITION CURRENT AND WAKE CURRENT 1 V≤ VI(BAT) ≤ 4.2 V I(DISCHG) t(DISCHG1) Discharge current 60 300 800 Discharge time 1 250 310 370 t(DISCHG2) V(DISCHG) Discharge time 2 20 25 30 1.5 2.0 2.5 Discharge voltage(1) 0.8 Batter detection current Battery c rrent I(DETECT_min) at VCC = 5.8 V,VI(BAT) = 4.2 V I(DETECT_max) at VCC = 6 V, VI(BAT) = 0 V 0.8 I(WK_SRC) current source 1 Wake current, I(WK_SRC_min) at VCC = 5.8 V,VI(BAT) = 4.2 V I(WK_SRC_max) at VCC = 6 V, VI(BAT) = 0 V Wake current, c rrent source so rce 2 I(WK_SINK_min) at VCC = 5.8 V, VI(BAT) = 4.2 V I(WK_SINK_max) at VCC = 6 V,VI(BAT) = 0 V 0 I(WK_SINK) I(DETECT) t(WK) Wake time CHARGE STATUS OUTPUT (STAT1/STAT2) VOL(STATx) Low-level output saturation voltage VOLTAGE REFERENCE OUTPUT (VREF) VREF voltage threshold V mA 30 1000 IO(STATx) = 10 mA, VCC ≥ 3.5 V 0°C ≤ TA ≤ 70°C ms 30 100 0 V < IO(VREF) < 500 µA, µA 1.18 125 µA A 150 ms 0.5 V 1.22 V CHARGE CONTROL OUTPUT (CC) VOL COUT Low-level output voltage (FstChg) Output capacitance IO(CC) = 40 mA (sink) LDO to BAT, LDO to VSS 0.45 V 0.1 10.0 µF 2.00 2.15 V UNDERVOLTAGE THRESHOLD SHORT-CIRCUIT PROTECTION V(UVT) (1) 4 Undervoltage threshold voltage Ensured by design. Not production tested. www.ti.com SLUS527 – DECEMBER 2002 PW PACKAGE† (TOP VIEW) OPTD VCC SCOMP ICOMP VCOMP STAT1 STAT2 1 2 3 4 5 6 7 14 13 12 11 10 9 8 VSS CC SNS BAT TS VREF TADJ TERMINAL FUNCTIONS TERMINAL NAME NO. I/O DESCRIPTION BAT 11 I Battery voltage sense input. This input is tied directly to the positive side of the battery pack. CC 13 O Charge control output. CC is an open-drain pulldown output that is used to drive an external pass transistor for charge current and voltage control ICOMP 4 I Current loop compensation. This is the compensation for the fast charge current regulation loop. OPTD 1 O Optocoupler driver output. This open-collector output is used to provide feedback to the primary side by driving an external optocoupler. SCOMP 3 I Supply loop compensation. This is the compensation for the VCC supply regulation loop. SNS 12 I Current sense input. Battery current is sensed via the voltage developed on this pin by an external sense resistor. STAT1 6 O Charge status output 1 (open drain) STAT2 7 O Charge status output 2 (open drain) TADJ 8 I Termination adjust. This input is used to set the minimum current termination level during voltage regulation phase. TS 10 I Temperature sense Input. Input for an external battery temperature monitoring. VCC 2 I VCOMP 5 I VCC supply input. Voltage loop compensation. This is the compensation for the battery regulation loop VREF 9 O Voltage reference output. This buffered output provides the internal bandgap voltage. VSS 14 – Ground input. www.ti.com 5 SLUS527 – DECEMBER 2002 FUNCTIONAL BLOCK DIAGRAM VCC CC SNS 2 13 12 11 BAT + + SHUTDOWN POR FILTER SHUTDOWN ITERM FILTER DECODE LOGIC AND RAMP CONTROL PRECHARGE Term_det_EN (to SM) VUVT TERMINATION ILIM BYPASS SUSPEND TS 10 BAT_PRS_wake (to SM) BAT LTF FILTER VHEG – 100 mV SHUT DOWN WAKE_SRC WAKE HTF BAT VCC TCO VREF TADJ 9 8 + CHARGE DISCHARGE CHARGE CONTROL, TIMER, AND DISPLAY LOGIC VBANDGAP ICHARGE_SINK IDSCHRG TERMINATION PRECHARGE SUSPEND FASTCHARGE ITERM START–UP LOGIC VIBAT Term_det_EN BAT_PRS_wake 6 STAT1 7 STAT2 4 ICOMP 5 VCOMP DISC_RES VCC + SHUTDOWN SCOMP 3 OPTD 1 FILTER RAMP CONTROL VICHG FASTCHARGE + + VBANDGAP VBANDGAP SHUTDOWN VSS SUSPEND 14 DISC_RES TERMINATION UDG–02182 6 www.ti.com SLUS527 – DECEMBER 2002 APPLICATION INFORMATION The bq24901 supports a precision current and voltage regulated li-ion charging system suitable for single-cells. Figure 1 shows the typical application diagram, Figure 2 shows a typical charge profile, and Figure 3 shows an operational flow chart. XMFR D2 OPTO1 L1 D1 N1 Q1 COUT N2 C1 bq24901 C3 N3 PRIMARY SIDE CONTROLLER RS 1 OPTD 2 VCC 3 VSS 14 OPTO1 CC 13 SCOMP SNS 12 4 ICOMP BAT 11 5 VCOMP 6 STAT1 VREF 9 7 STAT2 TADJ 8 VCC + TS 10 BATTERY PACK VCC VCC UDG–02180 Figure 1. Typical Application Diagram Current Regulation Phase Voltage Regulation Phase Regulation Voltage Regulation Current Charge Voltage Minimum Charge Voltage Charge Current Pre-Conditioning and Taper Detect Fast Charge Timer Pre-Charge Timer Figure 2. Typical Charge Profile www.ti.com 7 SLUS527 – DECEMBER 2002 APPLICATION INFORMATION POR Check for battery Presence Battery Present? No Indicate BATTERY ABSENT Yes Suspend charge TS pin in LTF to HTF range? No Indicate CHARGE SUSPEND Yes VBAT <VLOWV Yes Regulate IPRECHG Reset and Start T30min timer Indicate Charge– In–Progress No Suspend charge Reset and Start T5hr timer TS pin in LTF to TCO range? Regulate Current or Voltage Yes No Indicate CHARGE SUSPEND No TS pin in LTF to HTF range? Indicate Charge– In–Progress No VBAT <VLOWV Yes Suspend charge TS pin in LTF to TCO range? Yes No Indicate CHARGE SUSPEND Yes T30min Expired? No No TS pin in LTF to HTF range? T5hr Expired? Yes No Yes Reset and Start T30min timer Yes Reset and Start T5hr timer VBAT <VLOWV Yes No – Fault Condition – Enable IDETECT No ITERM detection? Indicate Fault No Yes – Turn off charge – Enable IDISCHG for tDISCHG2 Battery Replaced? Indicate Charge– In–Progress Yes Charge Complete VBAT < VRCH ? No Indicate DONE Battery Removed Yes Indicate BATTERY ABSENT Figure 3. Operational Flow Chart 8 www.ti.com SLUS527 – DECEMBER 2002 APPLICATION INFORMATION Charge Qualification and Pre-Conditioning The bq24901 starts a charge cycle when power is applied and a battery is present. Charge qualification is based on battery temperature and voltage. The device suspends charge if the battery temperature is outside the VLTF to VHTF and waits until the battery temperature is within the allowed range. The device also checks the battery voltage. If the battery voltage is below the low-voltage threshold, VLOWV, the device use pre-conditioning current, IPRECHG, to charge the battery. Temperature Sense (TS) Input The bq24901 continuously monitors battery temperature by measuring the voltage between the TS pin and Vss. A negative temperature coefficient thermistor (NTC) and an external voltage divider typically develop this voltage. The bq24901 compares this voltage against its internal thresholds to determine if charging is allowed. To initiate a charge cycle, the battery temperature must be within the VLTF to VHTF thresholds. If battery temperature is outside of this range, the device suspends charge and waits until the battery temperature is within the VLTF to VHTF range. During the charge cycle (both pre-charge and fast charge) the battery temperature must be within the VLTF to VTCO thresholds. If battery temperature is outside of this range, the bq24901 suspends charge and waits until the battery temperature is within the VLTF to VHTF range. The device suspends charge by turning off the CC pin and holding the timer value (i.e. timers are not reset during a suspend condition). Figure 4 summarizes this operation. VCC Charge Suspend VLTF VHTF VTCO Charge Suspend Temperature Range to Initiate Charge Temperature Range During Charge Cycle Charge Suspend Charge Suspend VSS Figure 4. Temperature Sense Input Thresholds www.ti.com 9 SLUS527 – DECEMBER 2002 APPLICATION INFORMATION VCC Regulation During the following conditions the bq24901 regulates the VCC power and the device remains active. Loop compensation for VCC regulation is achieved through SCOMP pin. D D D D D Battery absent condition Pre-charge Charge suspend Fault Done Voltage Monitoring and Regulation Voltage regulation feedback is through pin BAT. This input is tied directly to the positive side of the battery pack. Loop compensation for voltage regulation is achieved through VCOMP pin. Current Regulation The bq24901 provides current regulation while the battery pack voltage is less than the regulation voltage, VREG. The device monitors charge current at the SNS input by the voltage drop across an external sense-resistor, RSNS, in series with the battery pack. Charge current feedback, applied through pin SNS, maintains regulation around a threshold of VSNS. The formula in equation (1) calculates the value of the sense resistor. R SNS + V (SNS) I (CHG) (1) where: D I(CHG) is the desired charging circuit Loop compensation for current regulation is accomplished via the ICOMP pin. 10 www.ti.com SLUS527 – DECEMBER 2002 APPLICATION INFORMATION Current Regulation Ramp-Up and Ramp-Down Both current regulation loops ramp up and down when transitioning from pre-charge to fast charge, and when going in and out of fault/suspend mode where the LDO needs to be turned hard on or off. Figure 5 demonstrates the typical stepping ramp. 300 Fastcharge 275 VFB – Feedback Voltage – mV Pre-Charge 250 225 Pre-Charge Regulator Reference 200 150 125 100 75 Fastcharge Regulator Reference 50 25 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 75 tCHG – Time – ms Step Count Figure 5. Typical Current Regulation Ramp From/To Pre-Charge/Fastcharge www.ti.com 11 SLUS527 – DECEMBER 2002 APPLICATION INFORMATION Battery Insertion and Removal Detection The bq24901 reliably detects insertion and removal of battery packs under various conditions. This includes the battery packs with open or closed protectors. Figure 6 shows the flow chart. Table 1 provides a summary of various battery insertion and removal conditions. Begin Battery Detection Enable IDSCHG for tDSCHG Yes VBAT > VDSCHG ? No Enable IWAKE1 orWAKE2 I for tWAKE In Voltage Regulation ? Yes Battery Absent No Battery Present Figure 6. Battery Detection Summary 12 www.ti.com SLUS527 – DECEMBER 2002 APPLICATION INFORMATION Table 1. State Machine Status STATE MACHINE STATUS BATTERY PACK STATUS 1 Following power-on reset (POR) New pack insertion. 2 Following POR New deeply-discharged battery (with an open protector inserted). 3 Pre-conditioning Pack is removed. 4 Fastcharge (current or voltage regulation) Pack is removed. 5 Charge suspend Pack is removed. 6 Charge suspend Pack is removed. A new pack with normal temperature inserted. 7 Charge suspend Pack is removed. A new pack with abnormal temperature inserted. 8 Charge suspend Pack is removed. A pack with open protector and normal temperature inserted 9 Charge suspend Pack is removed. A pack with open protector and abnormal temperature inserted 10 Timer fault Pack remains in charger. ACTION h The device remains in the battery presence detection loop until a new battery is detected. h Depending on the battery voltage, the device either enters pre–charge or fast charge. h The device remains in the battery presence detection loop until a new battery is detected. h Depending on the battery voltage, the device either enters pre–charge or fast charge. h The device enters fast charge (since the output capacitor rises above V LOWV) and terminates immediately due to ITERM detection. h The device then enables I DISCHG for tDISCHG2. In the absence of a battery, the BAT voltage falls below VRCH, prompting the device to indicate BATTERY ABSENT. If the battery is present the BAT voltage does not fall below VRCH and therefore device assumes a battery is still connected and indicates DONE on STAT pins. h The device terminates immediately due to I TERM detection. h The device then enables I DISCHG for tDISCHG2. In the absence of a battery, the BAT voltage falls below VRCH, prompting the device to indicate BATTERY ABSENT. If the battery is present the BAT voltage does not fall below VRCH and therefore device assumes a battery is still connected and indicates DONE on STAT pins. h The device remains the charge suspend mode as long as the TS pin voltage is outside the VLTF to VHTF range. h The device leaves the charge-suspend mode and resumes charging depending on the battery voltage. h The device resets the timers only if it enters a charge mode different from where the initial charge suspend condition happened (for instance from pre-charge to fast or vice versa) h The device remains the charge suspend mode as long as the TS pin voltage is outside the VLTF to VHTF range. h Once temperature returns to normal, item 6 in this table applies. h The device leaves the charge suspend mode. h The device enters pre-charge (since the voltage is below V LOWV). This action closes the protector and charging resumes. h The device remains the charge suspend mode as long as the TS pin voltage is outside the VLTF to VHTF range. h Once temperature returns to normal, item 8 in this table applies. h The device remains in the fault condition until POR or battery removal is detected. 11 Timer fault Pack is removed. h Once in the fault mode, the device applies the I DETECT current to the output. The purpose of this current is to detect the removal of the pack. h If voltage regulation can be maintained with I DETECT current, the device assumes the pack has been removed (and only output capacitor is present). h The device then awaits battery insertion as outlined item 1 of this table. 12 Timer fault Pack is removed. A new pack is inserted. h See item 11 in this table. 13 Timer fault Pack is removed. A new pack with open protector is inserted. h See items 11 and 12 in this table. 14 Timer fault Pack remains in charger. 15 Done Pack is removed. h The bq24901 in the Done state as long as the pack voltage is above the V RCH threshold. While in the done state there is no current flow to the battery (zero current) h While in the DONE state, the device monitors the BAT voltage and initiates a new cycle once the BAT voltage falls below VRCH threshold (this happens as the output capacitor discharges through the input leakage on the BAT pin). h While in the DONE state, the device monitors the BAT voltage and initiates a new cycle once the BAT voltage falls below VRCH threshold (this happen as the output capacitor discharges through the input leakage on the BAT pin). www.ti.com 13 SLUS527 – DECEMBER 2002 APPLICATION INFORMATION Charge Termination and Re-Charge The bq24901 monitors the charging current during voltage regulation. The device declares a DONE condition and terminates charge when then the current tapers off to charge termination current detect threshold. The charge termination level is set through TADJ pin as detailed in Table 2 and Figure 7. Table 2. Charge Termination Adjustment TADJ INPUT TERMINATION LEVEL V SNS Connected directly to VREF pin 10 V SNS Connected directly to VSS pin Connected directly to the mid-point of a resistor divider between VREF and VSS pins (see Figure 8) ǒ 20 Ǔ ǒ Ǔ R2 V SNS V SNS ) 20 20 (R1 ) R2) NOTE: VSNS is the current regulation threshold. VREF R1 TADJ R2 Figure 7. Charge Termination Adjustment Connection The bq24901 also features two internal digital filters for detecting termination threshold. The digital filters, with tTERMDET1 and tTERMDET2 response times, are designed to reduce the possibility of early termination due to line or switching frequency noise. A new charge cycle is initiated when one of the following conditions are detected: 1. Battery voltage falls below the VRCH threshold 2. New battery insertion (once battery falls below the VRCH threshold) 3. Power-on reset (POR) 14 www.ti.com SLUS527 – DECEMBER 2002 APPLICATION INFORMATION Charge Timers The bq24901 provides two charge timers to protect the battery during pre-charge and charge phases. The first timer, T30min, is reset at the beginning of a new charge cycle and initiated in the pre-charge phase. During pre-charge, if the timer expires before the battery rises above the VLOWV threshold, a fault condition is annunciated. Power-on reset or battery replacement clears the fault. The second timer, T5hr, is reset at the beginning of a new charge cycle and is initiated at the beginning of the charge phase. A fault condition is annunciated if the battery current fails to reach charge termination current detect threshold, ITERM, during charge. Power-on reset or battery replacement clears the fault. Charge Status Display The open-drain STAT1 and STAT2 outputs indicate various charger operations as shown in the Table 3. Table 3. Charge Termination Adjustment CHARGE STATE STAT1 OFF(1) STAT2 Charge-in-progress ON OFF Charge done OFF ON Charge suspend (temperature) OFF OFF Battery absent OFF Timer fault OFF OFF (1) OFF means the open-drain output transistor on the STATx pin is in an off state. www.ti.com 15 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. 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