MC33340/D MC33340 MC33342 MC33340P MC33342P MC33340D MC33342D MC33340/342 LM317 - Datasheet Archive

 

MC33340 MC33342 Battery Fast Charge Controllers The MC33340 and MC33342 are monolithic control IC's that are specifically

 

Order this document by MC33340/D MC33340/D MC33340 MC33340 MC33342 MC33342 Battery Fast Charge Controllers The MC33340 MC33340 and MC33342 MC33342 are monolithic control IC's that are specifically designed as fast charge controllers for Nickel Cadmium (NiCd) and Nickel Metal Hydride (NiMH) batteries. These devices feature negative slope voltage detection as the primary means for fast charge termination. Accurate detection is ensured by an output that momentarily interrupts the charge current for precise voltage sampling. An additional secondary backup termination method can be selected that consists of either a programmable time or temperature limit. Protective features include battery over and undervoltage detection, latched over temperature detection, and power supply input undervoltage lockout with hysteresis. Fast charge holdoff time is the only difference between the MC33340 MC33340 and the MC33342 MC33342. The MC33340 MC33340 has a typical holdoff time of 177 seconds and the MC33342 MC33342 has a typical holdoff time of 708 seconds. · Negative Slope Voltage Detection with 4.0 mV Sensitivity · · · · · · · · · BATTERY FAST CHARGE CONTROLLERS SEMICONDUCTOR TECHNICAL DATA Accurate Zero Current Battery Voltage Sensing P SUFFIX PLASTIC PACKAGE CASE 626 High Noise Immunity with Synchronous VFC/Logic Programmable 1 to 4 Hour Fast Charge Time Limit 8 Programmable Over/Under Temperature Detection 1 Battery Over and Undervoltage Fast Charge Protection Power Supply Input Undervoltage Lockout with Hysteresis Operating Voltage Range of 3.0 V to 18 V 177 seconds Fast Change Hold­off Time (MC33340 MC33340) D SUFFIX PLASTIC PACKAGE CASE 751 (SO­8) 8 708 seconds Fast Change Hold­off Time (MC33342 MC33342) 1 DC Input Regulator Simplified Block Diagram VCC 1 PIN CONNECTIONS Undervoltage Lockout Internal Bias Vsen 8 VCC Voltage to Frequency Converter Ck High F/V R Over Q Battery Detect R Battery Pack S Gnd 4 t1/Tref High ­V Detect Counter Timer t2 t2/Tsen 6 Vsen Gate t3/Tref Low ORDERING INFORMATION 5 3 F/T Gnd 5 t3/Tref Low (Top View) 7 t3 Fast/ Trickle 6 t2/Tsen Fast/Trickle Output 3 Under t1 2 7 t1/Tref High Vsen Gate Output 2 Temp Detect Low Vsen Gate 8 VCC Vsen Input 1 Over Temp Latch t/T Time/ Temp Select VCC 4 This device contains 2,512 active transistors. Device Operating Temperature Range MC33340P MC33340P MC33342P MC33342P MC33340D MC33340D Plastic DIP TA = ­25° to +85°C MC33342D MC33342D © Motorola, Inc. 1999 MOTOROLA ANALOG IC DEVICE DATA Package Plastic DIP SO­8 SO­8 Rev 3 1 2 MOTOROLA ANALOG IC DEVICE DATA Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁ Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁ Á Á Á Á Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁ Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ Á Á Á Á Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁ Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁ Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Á Á Á Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á NOTES: 1. Whichever voltage is lower. 2. Tested junction temperature range for the MC33340/342 MC33340/342: Tlow = ­25°C Power Supply Current (Pins 5, 6, 7 Open) Start­Up (VCC = 2.9 V) Operating (VCC = 6.0 V) Thigh = +85°C Symbol Min Typ Max Unit ­Vth Vth(OV) Vth(UV) IIB Rin ­ 1.9 0.95 ­ ­ ­4.0 2.0 1.0 10 6.0 ­ 2.1 1.05 ­ ­ mV V mV nA M Iin Iin VIO VH(T) Vth(t/T) ­24 ­ ­30 1.0 ­36 2.0 µA % ­ ­ ­ 5.0 44 VCC ­0.7 ­ ­ ­ mV mV V Internal Clock Oscillator Frequency Vsen Gate Output (Pin 2) Gate Time Gate Repetition Rate fOSC tgate ­ 760 ­ kHz ­ ­ 33 1.38 ­ ­ ms s Fast Charge Holdoff from ­V Detection MC33340 MC33340 MC33342 MC33342 thold ­ ­ 177 708 ­ ­ Ioff VOL ­ ­ 10 1.2 ­ ­ nA V Ioff VOL ­ ­ 10 1.0 ­ ­ nA V Vth(on) Vth(off) ­ 2.75 3.0 2.85 3.1 ­ V V ­ ­ 0.65 0.61 2.0 2.0 ICC mA TOTAL DEVICE (Pin 8) Start­Up Threshold (VCC Increasing, TA = 25°C) Turn­Off Threshold (VCC Decreasing, TA = 25°C) UNDERVOLTAGE LOCKOUT (Pin 8) Off­State Leakage Current (VO = 20 V) Low State Saturation Voltage (Isink = 10 mA) FAST/TRICKLE OUTPUT (Pin 3) Vsen GATE OUTPUT (Pin 2) Off­State Leakage Current (VO = 20 V) Low State Saturation Voltage (Isink = 10 mA) s INTERNAL TIMING Input Offset Voltage, Over and Under Temperature Comparators Under Temperature Comparator Hysteresis (Pin 5) Temperature Select Threshold Programing Inputs (Vin = 1.5 V) Input Current Input Current Matching TIME/TEMPERATURE INPUTS (Pins 5, 6, 7) Input Sensitivity for ­V Detection Overvoltage Threshold Undervoltage Threshold Input Bias Current Input Resistance BATTERY SENSE INPUT (Pin 1) Characteristic ambient temperature range that applies (Note 2), unless otherwise noted.) ELECTRICAL CHARACTERISTICS (VCC = 6.0 V, for typical values TA = 25°C, for min/max values TA is the operating NOTE: ESD data available upon request. TJ TA Tstg Thermal Resistance, Junction­to­Air P Suffix, DIP Plastic Package, Case 626 D Suffix, SO­8 Plastic Package, Case 751 Operating Junction Temperature Operating Ambient Temperature (Note 2) Storage Temperature °C °C °C 100 178 +150 ­25 to +85 ­55 to +150 Symbol Value Unit VCC 18 V V VIR(t/T) VIR(sen) ­1.0 to VCC ­1.0 to VCC + 0.6 or ­1.0 to 10 VO(gate) IO(gate) 20 50 V mA VO(F/T) IO(F/T) RJA 20 50 V mA Fast/Trickle Output (Pin 3) Voltage Current Power Supply Voltage (Pin 8) Input Voltage Range Time/Temperature Select (Pins 5, 6, 7) Battery Sense, Note 1 (Pin 1) Vsen Gate Output (Pin 2) Voltage Current Rating °C/W MAXIMUM RATINGS MC33340 MC33340 MC33342 MC33342 Figure 1. Battery Sense Input Thresholds versus Temperature 2.10 VCC = 6.0 V 2.00 1.90 1.02 1.00 0.98 ­ 50 ­ 25 0 25 50 75 100 125 f OSC, OSCILLATOR FREQUENCY CHANGE (%) V th, OVER/UNDERVOLTAGE THRESHOLDS (V) MC33340 MC33340 MC33342 MC33342 Figure 2. Oscillator Frequency versus Temperature 16 VCC = 6.0 V 8.0 0 ­8.0 ­16 ­ 50 ­ 25 0 25 50 75 100 125 TA, AMBIENT TEMPERATURE (°C) Figure 3. Temperature Select Threshold Voltage versus Temperature Figure 4. Saturation Voltage versus Sink Current Vsen Gate and Fast/Trickle Outputs 0 ­0.2 VOL , SINK SATURATION VOLTAGE (V) V th(t/T), TEMPERATURE SELECT THRESHOLD VOLTAGE (V TA, AMBIENT TEMPERATURE (°C) VCC = 6.0 V VCC Threshold voltage is measured with respect to VCC. ­0.4 Time mode is selected if any of the three inputs are above the threshold. ­0.6 Temperature mode is selected when all three inputs are below the threshold. ­0.8 ­1.0 ­50 3.2 VCC = 6.0 V TA = 25°C 2.4 Vsen Gate Pin 2 1.6 Fast/Trickle Pin 3 0.8 0 ­25 0 25 50 75 100 125 0 8.0 16 24 32 TA, AMBIENT TEMPERATURE (°C) Figure 5. Undervoltage Lockout Thresholds versus Temperature Figure 6. Supply Current versus Supply Voltage 1.0 TA = 25°C Startup Threshold (VCC Increasing) 3.0 ICC , SUPPLY CURRENT (mA) VCC , SUPPLY VOLTAGE (V) 3.1 2.9 2.8 2.7 ­ 50 40 Isink, SINK SATURATION (mA) Minimum Operating Threshold (VCC Decreasing) 0.8 0.6 0.4 0.2 0 ­ 25 0 25 50 75 TA, AMBIENT TEMPERATURE (°C) MOTOROLA ANALOG IC DEVICE DATA 100 125 0 4.0 8.0 12 16 VCC, SUPPLY VOLTAGE (V) 3 MC33340 MC33340 MC33342 MC33342 INTRODUCTION counter for detection of a negative slope in battery voltage. A timer with three programming inputs is available to provide backup charge termination. Alternatively, these inputs can be used to monitor the battery pack temperature and to set the over and under temperature limits also for backup charge termination. Two active low open collector outputs are provided to interface this controller with the external charging circuit. The first output furnishes a gating pulse that momentarily interrupts the charge current. This allows an accurate method of sampling the battery voltage by eliminating voltage drops that are associated with high charge currents and wiring resistances. Also, any noise voltages generated by the charging circuitry are eliminated. The second output is designed to switch the charging source between fast and trickle modes based upon the results of voltage, time, or temperature. These outputs normally connect directly to a linear or switching regulator control circuit in non­isolated primary or secondary side applications. Both outputs can be used to drive optoisolators in primary side applications that require galvanic isolation. Figure 8 shows the typical charge characteristics for NiCd and NiMh batteries. Nickel Cadmium and Nickel Metal Hydride batteries require precise charge termination control to maximize cell capacity and operating time while preventing overcharging. Overcharging can result in a reduction of battery life as well as physical harm to the end user. Since most portable applications require the batteries to be charged rapidly, a primary and usually a secondary or redundant charge sensing technique is employed into the charging system. It is also desirable to disable rapid charging if the battery voltage or temperature is either too high or too low. In order to address these issues, an economical and flexible fast charge controller was developed. The MC33340/342 MC33340/342 contains many of the building blocks and protection features that are employed in modern high performance battery charger controllers that are specifically designed for Nickel Cadmium and Nickel Metal Hydride batteries. The device is designed to interface with either primary or secondary side regulators for easy implementation of a complete charging system. A representative block diagram in a typical charging application is shown in Figure 7. The battery voltage is monitored by the Vsen input that internally connects to a voltage to frequency converter and Figure 7. Typical Battery Charging Application Regulator DC Input MC33340 MC33340 or MC33342 MC33342 Reg Control Undervoltage Lockout Internal Bias R2 VCC 8 VCC Voltage to Frequency Converter Vsen 1 2.9 V Ck High 2.0 V 1.0 V F/V R Over Battery Detect Q R Battery Pack S Temp Detect Under Low ­V Detect Counter Timer Vsen Gate 30 µA t1 30 µA t2 30 µA t3 3 Fast/ Trickle R2 4 t/T F/T + R1 Gnd VBatt ­1 Vsen t1/Tref High 7 Vsen Gate 2 RNTC Over Temp Latch R1 Charge Status T Time/ Temp Select SW1 t2/Tsen 6 t3/Tref Low 5 R3 SW2 SW3 R4 VCC 0.7 V 4 MOTOROLA ANALOG IC DEVICE DATA MC33340 MC33340 MC33342 MC33342 Figure 8. Typical Charge Characteristics for NiCd and NiMh Batteries 1.6 Vmax ­V 70 dV 60 CELL VOLTAGE (V) Tmax 1.4 50 1.3 40 Voltage 1.2 30 Temperature 1.1 CELL TEMPERATURE (° C) dt 1.5 20 Relative Pressure 1.0 0 40 80 120 CHARGE INPUT PERCENT OF CAPACITY 10 160 OPERATING DESCRIPTION The MC33340/342 MC33340/342 starts up in the fast charge mode when power is applied to VCC. A change to the trickle mode can occur as a result of three possible conditions. The first is if the Vsen input voltage is above 2.0 V or below 1.0 V. Above 2.0 V indicates that the battery pack is open or disconnected, while below 1.0 V indicates the possibility of a shorted or defective cell. The second condition is when the MC33340/342 MC33340/342 detects a fully charged battery by measuring a negative slope in battery voltage. The MC33340/342 MC33340/342 recognize a negative voltage slope after the preset holdoff time (thold) has elapsed during a fast charge cycle. This indicates that the battery pack is fully charged. The third condition is either due to the battery pack being out of a programmed temperature range, or that the preset timer period has been exceeded. There are three conditions that will cause the controller to return from trickle to fast charge mode. The first is if the Vsen input voltage moved to within the 1.0 to 2.0 V range from initially being either too high or too low. The second is if the battery pack temperature moved to within the programmed temperature range, but only from initially being too cold. Third is by cycling VCC off and then back on causing the internal logic to reset. A concise description of the major circuit blocks is given below. Negative Slope Voltage Detection A representative block diagram of the negative slope voltage detector is shown in Figure 9. It includes a Synchronous Voltage to Frequency Converter, a Sample Timer, and a Ratchet Counter. The Vsen pin is the input for the Voltage to Frequency Converter (VFC), and it connects to the rechargeable battery pack terminals through a resistive voltage divider. The input has an impedance of approximately 6.0 M and a maximum voltage range of ­1.0 V to VCC + 0.6 V or 0 V to 10 V, whichever is lower. The 10 V upper limit is set by an internal zener clamp that provides protection in the event of an electrostatic discharge. The VFC is a charge­balanced synchronous type which generates output pulses at a rate of FV = Vsen (24 kHz). The Sample Timer circuit provides a 95 kHz system clock signal (SCK) to the VFC. This signal synchronizes the FV output to the other Sample Timer outputs used within the detector. At 1.38 second intervals the Vsen Gate output goes MOTOROLA ANALOG IC DEVICE DATA low for a 33 ms period. This output is used to momentarily interrupt the external charging power source so that a precise voltage measurement can be taken. As the Vsen Gate goes low, the internal Preset control line is driven high for 11 ms. During this time, the battery voltage at the Vsen input is allowed to stabilize and the previous FV count is preloaded. At the Preset high­to­low transition, the Convert line goes high for 22 ms. This gates the FV pulses into the ratchet counter for a comparison to the preloaded count. Since the Convert time is derived from the same clock that controls the VFC, the number of FV pulses is independent of the clock frequency. If the new sample has more counts than were preloaded, it becomes the new peak count and the cycle is repeated 1.38 seconds later. If the new sample has two fewer counts, a less than peak voltage event has occurred, and a register is initialized. If two successive less than peak voltage events occur, the ­V `AND' gate output goes high and the Fast/Trickle output is latched in a low state, signifying that the battery pack has reached full charge status. Negative slope voltage detection starts after 60 ms have elapsed in the fast charge mode. This does not affect the Fast/Trickle output until the holdoff time (thold) has elapsed during the fast charge mode. Two scenarios then exist. Trickle mode holdoff is implemented to ignore any initial drop in voltage that may occur when charging batteries that have been stored for an extended time period. If the negative slope voltage detector senses that initial drop during the holdoff time, and the input voltage rises as the battery charges, the Fast/Trickle output will remain open. However, if the negative slope voltage detector senses a negative drop in voltage during the holdoff time and the input voltage never rises above that last detected level, the Fast/Trickle output will latch into a low state. The negative slope voltage detector has a maximum resolution of 2.0 V divided by 1023, or 1.955 mV per count with an uncertainty of ±1.0 count. This yields a detection range of 1.955 mV to 5.865 mV. In order to obtain maximum sensing accuracy, the R2/R1 voltage divider must be adjusted so that the Vsen input voltage is slightly less than 2.0 V when the battery pack is fully charged. Voltage variations due to temperature and cell manufacturing must be considered. 5 MC33340 MC33340 MC33342 MC33342 Figure 9. Negative Slope Voltage Detector Battery Detect Low High UVLO FV = Vsen (24 kHz) Ck SCK 95 kHz Rachet Counter Preset Convert Vsen Input Synchronous Voltage to Frequency Converter Trickle Mode Holdoff ­V F/T Logic Over Under Charge Temperature Timer Vsen Gate Sample Timer Vsen Gate 1.38 s Preset 11 ms Convert 22 ms Rachet Counter Convert 0 to 1023 FV Pulses 6 MOTOROLA ANALOG IC DEVICE DATA MC33340 MC33340 MC33342 MC33342 that present at t2/Tsen, and less than VCC ­ 0.7 V. Under extremely cold conditions, it is possible that the thermistor resistance can become too high, allowing the t2/Tsen input to go above VCC ­ 0.7 V, and activate the timer. This condition can be prevented by placing a resistor in parallel with the thermistor. Note that the time/temperature threshold of VCC ­ 0.7 V is a typical value at room temperature. Refer to the Electrical Characteristics table and to Figure 3 for additional information. The upper comparator senses the presence of an over temperature condition. When the upper temperature limit is exceeded, the comparator output sets the Over Temperature Latch and the charger is switched to trickle mode. Once the latch is set, the charger cannot be returned to fast charge, even after the temperature falls below the limit. This feature prevents the battery pack from being continuously temperature cycled and overcharged. The latch can be reset by removing and reconnecting the battery pack or by cycling the power supply voltage. If the charger does not require either the time or temperature backup features, they can both be easily disabled. This is accomplished by biasing the t3/Tref Low input to a voltage greater than t2/Tsen, and by grounding the t1/Tref High input. Under these conditions, the Time/Temp Select comparator output is low, indicating that the temperature mode is selected, and that the t2/Tsen input is biased within the limits of an artificial temperature window. Charging of battery packs that are used in portable power tool applications typically use temperature as the only means for fast charge termination. The MC33340/342 MC33340/342 can be configured in this manner by constantly resetting the ­V detection logic. This is accomplished by biasing the Vsen input to 1.5 V from a two resistor divider that is connected between the positive battery pack terminal and ground. The Vsen Gate output is also connected to the Vsen input. Now, each time that the Sample Timer causes the Vsen output to go low, the Vsen input will be pulled below the undervoltage threshold of 1.0 V. This causes a reset of the ­V logic every 1.38 seconds, thus disabling detection. Fast Charge Timer A programmable backup charge timer is available for fast charge termination. The timer is activated by the Time/Temp Select comparator, and is programmed from the t1/Tref High, t2/Tsen, and t3/Tref Low inputs. If one or more of these inputs is allowed to go above VCC ­ 0.7 V or is left open, the comparator output will switch high, indicating that the timer feature is desired. The three inputs allow one of seven possible fast charge time limits to be selected. The programmable time limits, rounded to the nearest whole minute, are shown in Figure 10. Over/Under Temperature Detection A backup over/under temperature detector is available and can be used in place of the timer for fast charge termination. The timer is disabled by the Time/Temp Select comparator when each of the three programming inputs are held below VCC ­ 0.7 V. Temperature sensing is accomplished by placing a negative temperature coefficient (NTC) thermistor in thermal contact with the battery pack. The thermistor connects to the t2/Tsen input which has a 30 µA current source pull­up for developing a temperature dependent voltage. The temperature limits are set by a resistor that connects from the t1/Tref High and the t3/Tref Low inputs to ground. Since all three inputs contain matched 30 µA current source pull­ups, the required programming resistor values are identical to that of the thermistor at the desired over and under trip temperature. The temperature window detector is composed of two comparators with a common input that connects to the t2/Tsen input. The lower comparator senses the presence of an under temperature condition. When the lower temperature limit is exceeded, the charger is switched to the trickle mode. The comparator has 44 mV of hysteresis to prevent erratic switching between the fast and trickle modes as the lower temperature limit is crossed. The amount of temperature rise to overcome the hysteresis is determined by the thermistor's rate of resistance change or sensitivity at the under temperature trip point. The required resistance change is: VH(T) 44 mV DR(TLow T High) 1.46 k I 30 mA in The resistance change approximates a thermal hysteresis of 2°C with a 10 k thermistor operating at 0°C. The under temperature fast charge inhibit feature can be disabled by biasing the t3/Tref Low input to a voltage that is greater than ³ + + + Operating Logic The order of events in the charging process is controlled by the logic circuitry. Each event is dependent upon the input conditions and the chosen method of charge termination. A table summary containing all of the possible operating modes is shown in Figure 11. Figure 10. Fast Charge Backup Termination Time/Temperature Limit Programming Inputs Backup Termination Mode t3/Tref Low (Pin 5) t2/Tsen (Pin 6) t1/Tref High (Pin 7) Time Limit Fast Charge (Minutes) Time Open Open Open 283 Time Open Open Gnd 247 Time Open Gnd Open 212 Time Open Gnd Gnd 177 Time Gnd Open Open 141 Time Gnd Open Gnd 106 Time Gnd Gnd Open 71 Temperature 0 V to VCC ­ 0.7 V 0 V to VCC ­ 0.7 V 0 V to VCC ­ 0.7 V Timer Disabled MOTOROLA ANALOG IC DEVICE DATA 7 MC33340 MC33340 MC33342 MC33342 Figure 11. Controller Operating Mode Table Input Condition Vsen Input Voltage: >1.0 V and 1.0 V and 3.0 V and 0.6 V and