Using the HT13R90 in Simple Charger Applications

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Domenic Blake
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1 Using the HT13R90 in Simple Charger Applications D/N: HA0148E Introduction This product is a simple Ni-MH charger, which can charge AA and AAA cell types. The charger has only a time setup function. When power is applied the timing begins and continues until the time has elapsed at which point the charger stops automatically when the charging indicator light will extinguish. HT13R90 Characteristics Operating voltage: 2.2V~5.5V 40-bit programmable timer (max. over one year timer) 3 kinds of operating modes (continuous mode, one period mode and one pulse mode) One timer output Two LED or Buzzer output for indicating status Adjustable 5% internal RC or 32768Hz crystal Oscillator with quickly startup circuit (need to automatically turn off for power saving issue) Option OTP 22 4 bits for mode setting 8-pin DIP/SOP package 1

2 Block Diagram Description Using the HT13R90 in Simple Charger Applications Power Supply Charger Circuit Battery Power: supplies power to the charger HT13R90: controls charging time, setup time and control until charger stops charging Charger circuit: battery charging circuit Battery: Ni-MH or NiCD battery Hardware Circuit Introduction Figure 1 Overall Hardware Circuit Diagram 2

3 Circuit Section The power supply supplies power to the charger and uses a transformer, bridge rectifier, filter capacitors and LM7805 voltage regulator. See Figure 2. Figure 2 Power Supply Circuit T1 is a transformer which after rectification provides a 12V DC output with a power rating of 2W to provide enough current for charging. D1-D4 are four IN1004 diodes which together form a rectifier bridge, and convert AC voltage to DC voltage. C1 is a filter capacitor, to stabilize the VDD supply line. P1 is a LM7805 regulator to provide a 5V supply. HT13R90 Time Control IC The HT13R90 is used as a timer to control the charging time. See Figure 3 for the circuit details. Figure 3 HT13R90 charger timer IC 3

4 The HT13R90 has two outputs LED1 and LED2 which output a carrier wave with a 64Hz frequency and which drive two 8050 transistor switches. The function of the carrier wave is to allow time division charging, when LED1 is high then LED2 is low. For the same time there is only one 8050 channel. Some of the HT13R90 functions are setup using configuration options. Table 1 - HT13R90 configuration options Function LOCK: option table lock all setting 0 = unlock 1 = lock RCADJ6~0: RC oscillator frequency adjusting Valid value range is from 0 to 127 (totally 128 sections). 0 represent the highest frequency, 127 represent the lowest frequency. for each section, the frequency deviation is around 0.75%. OSC : oscillator type definition 0 = oscillator 1 = internal RC oscillator OSCON: oscillator keep on in standby mode 0 = oscillator turn off 1 = oscillator on PCR0M0~2: TMR0 Prescaler ((PCR0) output clock selection 000=fSYS 001=fSYS/2 010=fSYS/4 011=fSYS/8 100=fSYS/16 101=fSYS/32 110=fSYS/ = erved PCR1M0~4: TMR1 Prescaler (PCR1) output clock selection = TMR0_OV 00001~10010 = TMR0_OV/2 ~ TMR0_OV/(2^18) 10011~11111 = erved OMOD1:0 = Operating mode selection 00 = Mode 0 (continuous mode) 01 = Mode 1 (one period mode) 10 = Mode 2 (one pulse mode) 11 = reserved OACT = LED0 Pad Active high or low setting 0 = Active Low 1 = Active High LxACT: LEDx ACTIVE High/Low setting (x=1 or 2) Selection Unlock 0 Internal RC oscillator Oscillator turn off fsys TMR0_OV/(216) Mode 2 (one pulse mode) active high LED1: high active 4

5 Function 0 = Low active (Low to Driving LED) 1 = High active (High to Driving LED) LxOUT0~1: LEDx Output state (x=1 or 2) 00 = None. (No output) 01 = When Active (Output when LED0 pad at Active state) 10 = When Inactive (Output when LED0 pad at Inactive state) 11 = Both Active and Inactive (Output when LED0 pad both state) L2CMP: LED2 complement output setting 0 = LED1/2 standalone 1 = LED2 output is complement to LED1 in its Active state. (ignore L2 Options except L2ACT, L2OUT) LxMOD[2:0]:LEDx Output Mode setting (x=1 or 2) 000 = normal (output the LxFREQ defining waveform) 001 = 2 Combo (output LxFREQ and LxFREQ/2 Logical AND result) 010 = 3 Combo (output LxFREQ, LxFREQ/2, LxFREQ/4 Logical AND result ) 011 = reserved. 100 = one shot (out put one cycle of LxFREQ defining waveform) 101, 110 = reserved 111 = Level (ignore the LxFREQ setting) LxFREQ0~2: LEDx Output square waveform (x=1 or 2) 000 = TMR0_OV/2 001 = TMR0_OV/4 010 = TMR0_OV/8 011 = TMR0_OV/ = TMR0_OV/ = TMR0_OV/ = TMR0_OV/ = TMR0_OV/256 LxCARR0~2: LEDx Carrier waveform definition (x=1 or 2) 000 = No carrier 001=fSYS/2 010=fSYS/4 011=fSYS/8 100=fSYS/16 101=fSYS/32 110=fSYS/ = TMR0_OV/2 TMR0[7:0] = TMR0 count register preload value. Valid value range is from 0 to 255, Count No = 256-TMR0 TMR1A[7:0] = TMR1 first count register preload value Valid value range is from 0 to 255, Count No = 256-TMR1A TMR1B[7:0]= TMR1 second count register preload value Valid value range is from 0 to 255, Count No = 256-TMR1B Selection LED2: low active LED1 LED2: both active and inactive LED1/2 standalone LED1 LED2: level LED1 LED2: TMR0_OV/4 LED1 LED2: TMR0_OV/2 0H 50H 0H 5

6 By setting the required configuration options any time can be setup. The charging time is determined according to the battery capacity and is set according to the following method: When the charging current less than or equal to 5% of battery capacity: Charging time (hours) = battery capacity (mah) 1.6 charging current (ma) When the charging current is greater than 5% of the battery capacity and less than or equal to 10%: Charging time (hours) = battery capacity (mah) 1.5 Charging current (ma) When the charging current is greater than 10% of battery capacity and less than or equal to 15%: Charging time (hours) = battery capacity (mah) 1.3 Charging current (ma) When the charging current is greater than 15% of battery capacity and less than or equal to 20%: Charging time (hours) = battery capacity (mah) 1.2 Charging current (ma) When the charging current is greater than 20% of the battery capacity: Charging time (hours) = battery capacity (mah) 1.1 Charging current (ma) To charge a GP 1300mAH capacity battery, the charging current is 140mA, which meets the third condition, therefore the charging time will be 13 hours. The actual time can be extended by 1 hour, giving a final time of 14 hours. 6

7 Charger Circuit The charger circuit is simple and only uses 8050 transistors as switches to control the charger. The circuit is shown in Figure 4. Figure 4 Charger Circuit Because the charger design can charge two batteries at the same time, therefore there are two separate charger circuits which use the Q1 and Q transistors to control the charger. The HT13R90 two outputs LED1 and LED2 are output control signals. In the figure BT1-BT8 are the battery positive and negative terminals. Among these BT1 and BT5 are the positive terminals (AA and AAA cells use the same positive terminals), BT2 and BT4 are the AA negative terminals while BT6 and BT8 are the AAA cell negative terminals. During charging, the LED1 and LED2 outputs will output a low frequency complimentary square wave, to control the two charger circuits. When the charging time has elapsed the output will stop, however the LED1 and LED2 conditions are complimentary and when one is high the other is low. When the LED1 and LED2 lines are high this enables the battery charging. Therefore two transistors, Q2 and Q4 are used to control when Q1 and Q2 are switched off when the time has elapsed to stop the charging process. 7

8 PCB Layout Product Picture Second set of AAA cells LED illuminated during charging Second set of AA cells First set of AA cells First set of AAA cells 8

9 BOM Designator LibRef Description Footprint Comment BT1 BT2 BT4 BT5 BT6 BT8 POSITION POSITION C1 Cap Pol3 Polarized Capacitor (Surface Mount) cap150 Cap Pol3 C2 CAPNP CAPNP C3 Cap Pol3 Polarized Capacitor (Surface Mount) CAP100 Cap Pol3 C4 Cap Semi Capacitor (Semiconductor SIM Model) CAPNP200 Cap Semi C5 Cap Capacitor CAPNP200 Cap D1 Diode Default Diode DIODE 4001 IN4001 D2 Diode Default Diode DIODE 4001 IN4001 D3 Diode Default Diode DIODE 4001 IN4001 D4 Diode Default Diode DIODE 4001 IN4001 DS1 LED0 Typical INFRARED GaAs LED LED LED DS2 LED0 Typical INFRARED GaAs LED LED LED P1 LM7805 Regulator 5V TO220 LM7805 Q1 NPN NPN Bipolar Transistor TO Q2 NPN NPN Bipolar Transistor TO Q3 NPN NPN Bipolar Transistor TO Q4 NPN NPN Bipolar Transistor TO R1 Thermistor res0.4 R2 Thermistor res0.4 R3 Thermistor res0.4 R4 Thermistor res0.4 R5 Thermistor res0.4 R6 Thermistor res0.4 R7 Thermistor res0.4 T1 Trans Cupl Transformer (Coupled Inductor Model) Trans Cupl Trans Cupl U1 Component_1 DIP8 HT13R90 9

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