BQ2002CSNTRG4

bq2002C NiCd/NiMH Fast-Charge Management IC Features General Description ➤ The bq2002C Fast-Charge IC is a lowcost CMOS battery-charge controller providing reliable charge termination for both NiCd and NiMH battery applications. Controlling a current-limited or constant-current supply allows the bq2002C to be the basis for a costeffective stand-alone or system-integrated charger. The bq2002C integrates fast charge with pulsed-trickle control in a single IC for charging one or more NiCd or NiMH battery cells. ➤ ➤ Fast charge of nickel cadmium or nickel-metal hydride batteries Direct LED output displays charge status Fast-charge termination by -∆V, maximum voltage, maximum temperature, and maximum time ➤ Internal band-gap voltage reference ➤ Selectable pulse-trickle charge rates ➤ Low-power mode ➤ 8-pin 300-mil DIP or 150-mil SOIC Pin Connections Fast charge is initiated on application of the charging supply or battery replacement. 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: n Peak voltage detection (PVD) n Negative delta voltage (-∆V) n Maximum voltage n Maximum temperature n Maximum time After fast charge, the bq2002C pulsetrickles the battery per the preconfigured limits. Fast charge may be inhibited using the INH pin. The bq2002C may also be placed in lowstandby-power mode to reduce system power consumption. Pin Names TM 1 8 CC LED 2 7 INH BAT 3 6 VCC VSS 4 5 TS TM Timer mode select input TS Temperature sense input LED Charging status output VCC Supply voltage input BAT Battery voltage input INH Charge inhibit input VSS System ground CC Charge control output 8-Pin DIP or Narrow SOIC PN-200201.eps SLUS136 - AUGUST 2011 1 bq2002C TM Charge control output CC Pin Descriptions An open-drain output used to control the charging current to the battery. CC switching to high impedance (Z) enables charging current to flow, and low to inhibit charging current. CC is modulated to provide pulse trickle. Timer mode input A three-level input that controls the settings for the fast charge safety timer, voltage termination mode, pulse-trickle, and voltage hold-off time. LED Functional Description Charging output status Open-drain output that indicates the charging status. BAT Figure 2 shows a state diagram and Figure 3 shows a block diagram of the bq2002C. Battery input voltage Battery Voltage and Temperature Measurements The battery voltage sense input. The input to this pin is created by a high-impedance resistor divider network connected between the positive and negative terminals of the battery. VSS System ground TS Temperature sense input 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 =N-1 RB2 Input for an external battery temperature monitoring thermistor. VCC 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 battery terminal. See Figure 1. Supply voltage input 5.0V ± 20% power input. INH Charge inhibit input Note: This resistor-divider network input impedance to end-to-end should be at least 200kΩ and less than 1 MΩ. When high, INH suspends the fast charge in progress. When returned low, the IC resumes operation at the point where initially suspended. A ground-referenced negative temperature coefficient thermistor placed near the battery may be used as a lowcost temperature-to-voltage transducer. The temperature sense voltage input at TS is developed using a resistorthermistor network between VCC and VSS. See Figure 1. VCC PACK + RT RB1 VCC R3 BAT bq2002C TM RB2 TS N T C bq2002C R4 VSS VSS BAT pin connection Mid-level setting for TM Thermistor connection NTC = negative temperature coefficient thermistor. Fg2002/C.eps Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration 2 bq2002C Battery Voltage too High? Chip on 4.0V VCC VBAT > 2V VBAT < 2V Battery Voltage too Low? VBAT < 0.84V 0.84V < VBAT VTS > VCC/2 VTS < VCC/2 Battery Temperature? Charge Pending Fast LED = Low VBAT > 0.84V and VBAT < 2V and VTS > VCC/2 VBAT > 2V or VTS < VCC/2 or PVD or - V or Maximum Time Out Trickle LED = Flash VBAT > 2V VBAT 2V Trickle LED = Z SD2002C.eps Figure 2. State Diagram Clock Phase Generator OSC TM Timing Control Sample History Voltage Reference PVD, - V ALU A to D Converter INH Charge-Control State Machine LBAT Check HTF TCO Check Check Power-On Reset CC LED TS Power Down VCC MCV Check BAT VSS Bd2002CEG.eps Figure 3. Block Diagram 3 bq2002C VCC = 0 Fast Charging Pulse-Trickle Fast Charging 1s CC Output See Table 1 Charge initiated by application of power Charge initiated by battery replacement LED TD2002C1.eps Figure 4. Charge Cycle Phases pending state. In this state pulse trickle charge is applied to the battery and the LED flashes until the voltage and temperature come into the allowed fast charge range or VBAT rises above VMCV. Anytime VBAT ≥ VMCV, the IC enters the Charge Complete/Battery Absent state. In this state the LED is off and trickle charge is applied to the battery until the next new charge cycle begins. Starting A Charge Cycle Either of two events starts a charge cycle (see Figure 4): 1. Application of power to VCC or 2. Voltage at the BAT pin falling through the maximum cell voltage VMCV where Fast charge continues until termination by one or more of the five possible termination conditions: VMCV = 2V ±5%. If the battery is within the configured temperature and voltage limits, the IC begins fast charge. The valid battery voltage range is VLBAT < VBAT < VMCV, where VLBAT = 0.175 ∗ VCC ±20% The valid temperature range is VTS > VHTF where VHTF = 0.6 ∗ VCC ±5%. n Peak voltage detection (PVD) n Negative delta voltage (-∆V) n Maximum voltage n Maximum temperature n Maximum time If VBAT ≤ VLBAT or VTS ≤ VHTF, the IC enters the charge- Table 1. Fast-Charge Safety Time/Hold-Off Table Corresponding Fast-Charge Rate TM Termination Typical FastCharge Time Limits (minutes) C/2 Mid PVD 160 300 C/32 73 18.7 1C Low PVD 80 150 C/32 37 18.7 2C High -∆V 40 75 C/32 18 9.4 Notes: Typical PVD and -∆V Hold-Off Time (seconds) Typical conditions = 25°C, VCC = 5.0V Mid = 0.5 * VCC ±0.5V Tolerance on all timing is ±12%. 4 PulseTrickle Rate PulseTrickle Pulse Width (ms) Maximum Synchronized Sampling Period (seconds) bq2002C _______________________________________________________________________ PVD and -∆V Termination There are two modes for voltage termination, depending on the state of TM. For -∆V (TM = high), if VBAT is lower than any previously measured value by 12mV ±3mV, fast charge is terminated. For PVD (TM = low or mid), a decrease of 2.5mV ±2.5mV terminates fast charge. The PVD and -∆V tests are valid in the range 1V