AS8410 PWM DC Motor Regulator Data Sheet (Preliminary) Rev. 1.0, December 2000 PWM DC Motor Regulator – Data Sheet AS8410 1 Key Features The AS8410 builds up a complete PWM DC Motor current regulation loop with an external n-channel power FET. A full diagnosis of motor failures with stand-alone failure handling procedures is integrated. One of the most important features of this ASSP namely in automotive applications is the slew rate regulated switching of the external power FET. This technology enables two features of the DC motor regulator, which was up to now impossible to realise at the same time: • An excellent EMC behaviour (very low RF emission in the whole frequency range) • A high power efficiency > 95 % (fall / rise time < 150 ns) A short overview of the main features of the AS8410 is given here below: Main properties: • Complete PWM DC motor regulator with an external power FET • Single voltage supply in the range VB = 6 V … 35 V (Vpumpmax = 45 V) • Analogue motor current regulation loop (two modes: set value as digital duty ratio of a low frequency (e.g. 10 Hz) or as an analogue voltage in the range Vin = 0 … 5 V) • High power efficiency of the whole regulator module (> 95 %) • Low RF emission in the whole frequency range • Fully protected, analogue / digital failure handling procedures (see below: Security functions) • • Simple programming possibilities for different classes of DC motors and different operating modes (set value input, over temperature-handling procedure) Applicable directly on the automotive board supply battery (burst and surge) • Automatic sleep mode controlled by the set value Security functions: 1. Extensive diagnosis of the DC motor and the power FET, failures handling procedures and report of the failures: 1.1 Over current detection and protection 1.2 No load detection of the motor 1.3 Open wire detection (motor or power switch) 1.4 Short circuit of the power switch detection 1.5 Blocked motor detection and protection 1.6 Short-circuited motor segments detection and protection 1.7 Protection of the power FET and the ASIC, if the motor works in generator mode 2. Over- / Under Voltage detection and protection 3. Over Temperature detection and protection in two modes Rev. 1.0, December 2000 page 2 of 19 PWM DC Motor Regulator – Data Sheet AS8410 2 General Description Package and Marking Package: SOIC16 wide outline SOIC16 Marking AS8410 ASSP number YY WW XXX Production year Production week Assembly-ID A A1 A2 B C D E e H h L α SOIC16 wide outline (measure in mm) min. nom. max. 2,46 2,56 2,64 0,13 0,22 0,29 2,29 2,34 2,39 0,35 0,41 0,48 0,23 0,25 0,32 10.21 10.34 10.46 7,42 7,52 7,59 1.27 BSC 10.16 10.31 10.41 0.25 0.33 0.41 0,61 0,81 1,02 0° 5° 8° Table 2.1: Dimensions and marking Fig. 2.1 Dimensions and marking Rev. 1.0, December 2000 page 3 of 19 PWM DC Motor Regulator – Data Sheet AS8410 Maximal Ratings (ASSP out of operation) Symbol Vbat Vpump VDD IIMmax Parameter Supply voltage Pumped supply Regulated 5V-supply Maximal input currents min -0,5 -0,5 -0,5 -30 max 50 50 7 30 Unit V V V mA VINA Analogue input voltage - 0.3 35 V Isrc1 or Isrc2 Input currents at pins SRC1 or 2 mA SRC2 Storage Temperature -55 150 °C ΘSTG Solder Temperature 260 °C ΘLEAD PTOT Maximal power dissipation 0.4 W ESD Electrostatic discharge voltage 1000 V 1 GND = Ground 2 except for Pins SRC1 and SRC2 3 260 °C for 10 s (reflow soldering), 360 °C for 3 s (manual soldering) 4 HBM: R = 1.5 kΩ, C = 100 pF Rev. 1.0, December 2000 Note 1 VIN < VIN min or VIN > Vbat 2 3 4 page 4 of 19 PWM DC Motor Regulator – Data Sheet AS8410 Operating Conditions The following conditions are valid in the temperature range ΘRT = -40 °C to +120 °C and the supply voltage range Vbat = 6.5 V to 35 V. Symbol Parameter min typ Vbat Supply voltage 6.5 12 IDDA Current consumption in sleep mode (power down mode) IDDB Current consumption (at Vbat in normal mode 1 or 2) Vpump Pumped supply voltage 11 Vbat+10 VDD Regulated 5V-supply 4,7 5,0 ISRC1, max. current into the current ISRC2 inputs SRC1 or SRC2 VIN Voltage at set value input pin IN GND - 0,3 VMODE Voltage at the MODE pin GND - 0,3 VCMP, VCMN Vout Iout Voltage at the current measGND - 3,5 urement input pins CMp, CMN Voltage at the output pin OUT GND - 0,3 Max. output current at pin OUT -300 (t < 1µs) Vanalog Analogue input voltage GND - 0,3 1 2 3 4 5 max 35 400 Unit V µA 10 mA 45 5,3 400 V V µA Vbat + 0,5 Vbat + 0,5 V V Vbat + 0,5 V Vpump 300 V mA VDD + 0,5 V Note 1 2 3 4 5 valid in mode 2 only (MODE = low) and Vbat = 12 V without output current at pin OUT the inputs SRC1 and SRC2 must be current limited by the external circuitry (max. 400 µA) max. duration of the current pulse = 1µs valid for the pins OSC, TP, Cint1, Cint2 Rev. 1.0, December 2000 page 5 of 19 PWM DC Motor Regulator – Data Sheet AS8410 Pinout and Package Description Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Name Vpump Pump_ctrl Vbat VDD MODE IN OSC Cint2 Cint1 TP CMp CMn SRC1 SRC2 GND OUT Typ Output Output Power Output Input Input Input Input Input Input Input Input Input Input Power Output Description Pumped supply voltage: Vpump = Vbat + 10 V Connection of the capacitor Cp1 of the charge pump positive supply voltage 5V regulator output Selection of the operating mode Set value input Connection of the reference current resistor (1 V output) RC filter of the set value Connection of the capacitor of the regulation loop Temperature measurement input Motor current measurement input (positive side) Motor current measurement input (negative side) Slew rate regulation input (rising edge) Slew rate regulation input (falling edge) Ground Power FET control output (Gate drive) Fig 2.2 Pinning of the SOIC16 package Rev. 1.0, December 2000 page 6 of 19 PWM DC Motor Regulator – Data Sheet AS8410 3 Applications Fig. 3.1 Operating mode 1 (OM1) of the motor regulator (e.g. automotive application) Fig. 3.2 Operating mode 2 (OM2) of the motor regulator Rev. 1.0, December 2000 page 7 of 19 PWM DC Motor Regulator – Data Sheet AS8410 Meaning and Settings of the external devices Symbol ROSC Rmeas Rint2 Cint2 Cint1 SRC1 SRC2 RIN RMODE RTP1 RTP2 Description Typical value Application Note Regulation loop settings / slew rate regulation Resistor of the referThe voltage at the pin OSC is regu100 kΩ ence current generalated to VOSC = 1 V. The reference curtion Iref rent is therefore 10 µA. This current is used for three functions: 1. The oscillator frequency (Iref = 10µA generates fOSC = 18 kHz, fOSC is a linear function of Iref) 2. Generation of the internal set value voltage in OM1 together with the resistor Rint2. 100% set value is build by a voltage of 2 V at pin Cint2: VCint2(100%) = Iref * Rint2 = 2 V 3. Reference current for the power FET driver / Slew rate regulation (linear function between Iref and driver output current IOUT) Dependent on the The voltage drop over the Rmeas must Motor current measurement resistor nominal motor be 50 mV for the nominal motor curcurrent Imotor_nom rent: Rmeas = 50 mV / Imotor_nom Resistor to convert VCint2(100%) = Iref * Rint2 = 2 V 200 kΩ the incoming duty ratio of the set value in OM1 to the set value voltage VCint2 Filter capacitor of the Dependent on the incoming PWM fre> 2.2 µF set value conversion quency fIN_PWM in OM1 fIN_PWM = 10 Hz à Cint2 > 2.2 µF Capacitor to set the 100 nF The time constant of the failure hanregulation loop time dling Tfail is determined by the max. constant and failure current at pin Cint2 (ICint1_max = 10 µA handling time con… 15 µA) and the min. voltage to start stant the PWM generator (1.66 V): Tfail = (Cint1 * 1.66 V ) / ICint1_max Feedback circuitry of Dependent on the Application Support of Austria Mikro the slew rate regulaapplication (motor Systeme AG will be guaranteed tion and environment) Protection Resistors Protection resistor of Needed in automotive applications 330 Ω the pin IN Protection resistor of Needed in automotive applications 1 kΩ the pin MODE Temperature Sensor Resistor divider of the RTP1 + RTP2 < 10 kΩ The threshold voltage at the pin TP temperature sensor must be 0.5 *VDD or (RTP1 = RTP2) Rev. 1.0, December 2000 page 8 of 19 PWM DC Motor Regulator – Data Sheet AS8410 VTP < 0.5 *VDD à over temp. VTP > 0.5 *VDD à no over temp. Cp1 Cp2 D1 D2 CVDD CVbat Df Tr1 Charge pump and 5V Regulator Charge pump capaci- 100 nF … 200 nF The capacitor value is dependent on tors the external power FET to drive (Cgate_source) Diodes of the charge Vbreak > Vbat + 10 V pump Imax > 50 mA Filter capacitor of the 100 nF 5V regulator Filter Capacitor of the The capacitor value is dependent on 1000 µF Vbat the motor power. Typical value: 1000 µF pro 100 W motor power in automotive application. Power Switch and Free wheel diode Free wheel diode Dependent on the max. motor current Power FET and voltage Austria Mikro Systeme International AG gives all necessary application support to the user of this PWM DC Motor Regulator device AS8410. Rev. 1.0, December 2000 page 9 of 19 PWM DC Motor Regulator – Data Sheet AS8410 4 Functional Description and Electrical Parameters The main functions of this PWM-Switch-Regulator are summarised in section 1.3. The normal regulation loop is build by an analogue difference-integrator, both the input set value at pin IN and the measured motor current (at pins CMp and CMn) are transformed to the chip internal control signals. The difference signal is integrated on the capacitor connected to the pin Cint1 and the voltage at this pin is controlling the PWM generator and closes so the regulation loop. So the regulation time constant can be determined in width range by the external capacitor at the pin Cint1. The AS8410 can be used in two different modes controlled by the pin MODE : Operating Mode 1 (OM1: VMODE = high): - The set value must be given at pin IN as the duty ration of a low frequency digital signal (fIN > 10 Hz). - The Over Temperature reaction: 100 % duty ratio of the FET-driver output (permanent switch on the motor) as long as the temperature is higher than the predefined threshold value (typical automotive application, the heating source is not the electrical system but the combustion engine). Operating Mode 2 (OM2: VMODE = low): - The set value must be given at pin IN as analogue voltage in the range VIN = 0 … 5 V - The Over Temperature reaction: The motor is regulated down to not cross the predefined temperature threshold (like a thermostat if the heating source is the electrical system itself). The adaptation of the AS8410 to the DC motor (nominal motor current and power FET) will be realised by the value of the motor current measurement resistor Rmeas and by the slew rate controlling currents into the pins SRC1 and SRC2 as described in section 3.4.1. The detection of the different kinds of motor failures is realised by comparing the actual measured motor working point and the normal motor characteristic. Each motor failure is then treated by the AS8410 with an adapted failure handling procedure described in section 3.4.2. A failure report signal is generated and sent to the pin IN by pull down this pin. Also the over temperature and the over / under voltage failure are treated by the AS8410 itself. Rev. 1.0, December 2000 page 10 of 19 PWM DC Motor Regulator – Data Sheet AS8410 Figure 4.1: Simplified Block diagram of the AS8410 Rev. 1.0, December 2000 page 11 of 19 PWM DC Motor Regulator – Data Sheet AS8410 4.1 Normal Operating Mode (regulation loop) The regulation loop of the AS8410 consist of the following functional blocks: 1. Analogue / Digital Interface with signal conditioning (set value input / failure signal output IN, modus input MODE and low pass filter input Cint2) 2. Regulator characteristic generator (high resolution of the set value for set values < 50 % and lower resolution for set values 50 % … 100 %) 3. Difference generator at the pin Cint1 (VCint1 = (set value) – (motor current value) ) 4. PWM generator (controlled by the voltage VCint1 and the 20 kHz oscillator) 5. Power FET driver with slew rate regulation controlling the external power FET gate connected at pin OUT 6. Motor current measurement unit (measuring and converting the voltage over the external resistor Rmeas connected at the pins CMp and CMn) 7. Oscillator (20 kHz) and reference current generator (regulated VOSC = 1 V at pin OSC with external resistor Rosc = 100 kΩ ) 8. Charge pump with external capacitors at the pins Pump_ctrl and Vpump 9. 5V-regulator with bandgap reference 4.1.1 Analogue / Digital Interface, Signal Conditioning This interface consists of the three pins MODE, IN and Cint2. The interface sets the operating mode by the signal MODE, monitors and converts the input set value at the pin IN and drives the pin IN to the low level in case of a detected failure in operating mode 1. In operating mode 1 (OM1) the incoming low frequency PWM signal is converted in a dc voltage by switching a current Icint2 = 10 µA with the incoming duty ratio to the pin Cint2 with Rint2 / Cint2 (typical: 200 kΩ / 2.2 µF). Vcint2 must be in the range Vcint2 = 0 … 2 V. The monitor of the set value VCint2 generates two internal logical signal P00 and P10 to treat the sleep / wake function and the input failure detection in operating mode 1, the hysteresis of these detections is given in Fig. 4.2. Symbol Meaning MODE Operating mode of the AS8410 P00 P10 Detection of the 5 % threshold value of the set value Detection of the 10 % threshold value of the set value Rev. 1.0, December 2000 Meaning of the level MODE = high Ü Operating mode 1 (OM1) MODE = low P00 = high P00 = low P10 = high P10 = low Ü Ü Ü Ü Ü Operating mode 2 (OM2) Set value < 5 % Set value > 5 % Set value = 5 % ... 17.5 %) Set value outside of this range page 12 of 19 PWM DC Motor Regulator – Data Sheet AS8410 Fig. 4.2 Monitoring of the set value (generation of the signals P00 and P10) Symbol Parameter min typ max Unit 4,3 Vbat V V Note Operating Mode selection MODE VMODE_low Low-level of MODE VMODE_high High-level of MODE fIN Duty VIN_low VIN_high ICint2 VIN_OM2 IIN_high IIN_failure 5,7 Set value input signal IN (OM1) Frequency of the PWM set value input 10 Duty ratio of the PWM input 0 Low-level of the PWM input 0 High-level of the PWM input 3,65 Switched current high level at pin Cint2 9,8 10,0 Set value input signal IN (OM2) Input voltage range of VIN (0 % … 100 %) 0 Signal conditioning of the signal at the pin IN High level current at pin IN (internal pull up) 2.7 Failure signal current at pin IN (internal pull down) 3.0 Rev. 1.0, December 2000 Hz % V V 100 3,35 Vbat 10,4 µA 5 V 3.6 10.0 mA mA page 13 of 19 PWM DC Motor Regulator – Data Sheet AS8410 4.1.2 Regulator Characteristic, PWM Generator The external set value, incoming at pin IN, is transformed in both modes (OM1 and OM2) to the internal dc voltage in the range 0 … 2 V corresponding to 0 % … 100 % set value. A function generator transforms then this set value voltage to a function with two different gradients: a) The input range 0 % … 50 % is transformed to the output range 0 % … 20 % b) The input range 50 % … 100 % is transformed to the output range In this way the resolution of the set value input is higher in the first half of the input range (low motor currents: 0% … 20%) than in the second half one (higher motor currents 20% … 100%). A special behaviour is implemented for very low input set values in the following way for the operating mode 1 (OM1) and operating mode 2 (OM2): a) OM2: For low input set values (< 10%) the system is put in sleep mode Condition: (P00 or P10) and (/MODE) b) OM1: For very low input set values (0 < set value < 5%, duty ratio nearly or equal 0 is taken as input failure: short circuit of the input line to ground), the internal set value is put to 100 % àsecurity mode: The motor is permanently switched on and so cooling the heating engine. For input set values in the range 5% < set value < 10% the system is put in a special sleep mode. The difference of the set value output of this block and the internal control value coming from the motor measurement unit is controlling the PWM generator (voltage at the pin Cint1) and so generating the duty ratio of the 20 kHz PWM signal what controls the power FET driver. The time constant of this regulation loop can be chosen in very width ranges by the external capacitor connected at the pin Cint1. 4.1.3 Power FET driver, Slew rate regulation The Power FET driver is controlled in two different ways: First by the digital output of the PWM generator to realise the duty ratio of the motor drive and so to regulate the motor current in the closed loop. Second by the analogue motor voltage to regulate the slew rate during the rising and falling edge of the motor voltage. This control is executed by an external feedback of the motor voltage to the pins SRC1 (rising edge) and SRC2 (falling edge). The two currents incoming to these pins are amplified by a factor of about 1000 and drive then the gate of the external power FET. The supply voltage of this driver is about 10 V higher than the Vbat (n-channel power FET) and is delivered by the on chip charge pump at pin Vpump. Symbol Vpump VSRC1/SRC2 ISRC1 or ISRC2 IOUT IOUT/ISRC1 IOUT/ISRC2 IOUT/ISRC1 IOUT/ISRC2 tS Parameter min typ max Unit Pumped supply voltage Voltage at the pins SRC1 or SRC2 Input current into the pins SRC1 or SRC2 11 Vbat+10 0.70 43,00 0.90 400 V V Output current pin OUT Current amplification factor (high currents) -300 900 1100 300 1600 Current amplification factor (low currents) 900 1400 1700 Delay Rev. 1.0, December 2000 100 Note 1 µA mA 2 3 4 ns page 14 of 19 PWM DC Motor Regulator – Data Sheet AS8410 This input must be current limited by the external circuitry (max. 400 µA). max. pulse duration = 1µs 3 valid for IOUT = 5 mA ... 300 mA and Vbat = 12 V , Vpump = 22 V 4 valid for IOUT = 1 mA ... 5 mA and VDDA = 12 V , Vpump = 22 V (For a fixed output current the tolerance of the current amplification factor is less than 10%.) 1 2 4.1.4 Charge pump The charge pump generates a supply voltage about 10 V higher than the system supply voltage Vbat (Vpump = Vbat + 10 V) to drive the gate of the external high side power FET switch. In the case of the min. supply voltage Vbat = 6 V, the pumped voltage Vpump is about 11 V. The load current of the external capacitors Cp1 and Cp2 is limited to max. 40 mA to prevent RF emissions by high current peaks. Symbol Parameter min typ max Unit Note 1 VPP Pumped voltage difference 9,0 10,0 12,0 V VPP = (Vpump – Vbat) ICp1, ICp2 Currents to the external capacitors 40 mA DV Ripple of the pumped voltage Vpump 0,50 0,70 V f PWM Frequency (internal oscillator) 18 kHz 1 valid for Vbat = (12.. 33) V (for Vbat = 6 V is VPP = 5 V), Vpump = Vbat + VPP 2 valid for IVpump = 300 mA ( pulse duration < 1µs and fOSC = 18 kHz ), Cp1 = Cp2 = 400 nF 4.1.5 2 Motor current measurement unit The motor measurement unit works with an external current measurement resistor in the high side motor line. The nominal measurement differential voltage (VCMp – VCMn)nom is fixed to 50 mV (corresponding to 100% of the motor current). So the value of this measurement resistor is given by Rmeas = 50 mV / Imotor_nom . The over current detection is fixed by a motor current 60 % over the nominal motor current (Imotor_over = 1.6 * Imotor_nom). The switch off of the motor in case of an over current (or short circuit of the motor) is realised in less than 2 µs. Symbol Parameter min typ max Unit VCMp/CMn Common mode voltage at the pins -1.15 Vbat V CMn or CMp VCM_diff_nom Nominal differential voltage of the 50 mV motor current measurement input (VCMp – VCMn)nom VCM_diff_over Threshold voltage of the over current 1,6 * VCM_diff_nom detection FI Relative motor current measurement 2 % error 1 Imotor_nom = VCM_diff_nom / Rmeas Rmeas is the motor current measurement resistor. 2 Over current detection at Imotor_over = 1,6 * Imotor_nom 3 FI < 2 % of Imotor_nom , FI = (Imotor – Imotor_meas) / Imotor_nom valid for static VCMp/CMn or for: Vbat = 12 V , Vpump = 22 V , switching edges of VCMp/CMn (VCMp/CMn_min = -0.7 V and VCMp/CMn_max = Vbat) with trise/fall > 200 ns Rev. 1.0, December 2000 Note 1 2 3 page 15 of 19 PWM DC Motor Regulator – Data Sheet AS8410 4.1.6 Oscillator, Reference Voltage / Current Generator The oscillator is used to control the PWM generator and the charge pump with a frequency of typical 18 kHz. The reference current Iref of this oscillator is generated by a temperature compensated voltage regulator which delivers a stable voltage of 1 V at pin OSC, the ROSC = 100 kΩ at this pin generates the reference current. This reference current is used for other functions of this chip too (see section 3). Symbol VOSC f OSC Trise/fall Iref 1 Parameter Reference voltage at pin OSC Oscillator frequency Rise or fall time of the clock Reference current min 0.96 17,0 typ 1.00 18,0 9,6 10,0 max 1.04 19,0 100 10,4 Unit V kHz ns µA Note 1 Iref must be generated by the external resistor ROSC = 100 kΩ at the pin OSC 4.1.7 5V Regulator (bandgap reference) The 5V-regulator generates the supply voltage for all internal low voltage blocks and the rough reference voltage for the 1 V-regulator to generate the reference current Iref. This regulated 5 V supply can also be used externally (e.g. for the temperature sensor at pin TP). This externally usable 5 V will be switched off in the sleep mode. Symbol Parameter Vbat VDD Supply voltage of the regulator Regulated voltage IVDD_OUT External load current at pin VDD 1 external capacitor to ground CVDD = 100 nF 4.1.8 min typ max Unit 6,5 4,7 12 5,0 35 5,3 3 V V mA Note 1 Failures Detection, Failure Handling Procedures Three different kinds of failure detections and protections are implemented: 1. Failure detection of the load circuit (DC motor and power FET) 1.1 Over current detection and protection 1.2 No load detection of the motor and protection 1.3 Open wire detection (motor or power switch) 1.4 Short circuit of the power switch detection 1.5 Blocked motor detection and protection 1.6 Short-circuited motor segments detection and protection 1.7 Protection of the power FET and the ASIC, if the motor works in generator mode 2. Failure detection of the supply voltage Vbat (Over- / Under Voltage) 3. Over Temperature detection and protection in two modes Rev. 1.0, December 2000 page 16 of 19 PWM DC Motor Regulator – Data Sheet AS8410 For all detected failures an adequate failure handling procedure is integrated to fully protect the motor regulator module. This failure procedures works without interaction of the controlling µP and so the AS8410 can also be used to develop regulator modules without µP. Nevertheless the most important failures are reported in operating mode 1 (OM1) by pull down the set value input pin IN with a current source (3 mA … 10 mA). 4.1.8.1 Motor Failures The principle of the load circuit (motor and power FET) failure detection and handling procedures is the following: a) Motor failure detection principle: The motor current at the high side of the motor and the average value of the motor voltage is permanently measured. In this way the actual motor working point is monitored and permanently compared with the normal motor characteristic. This comparison delivers then the different motor or power FET failures. b) Failure handling procedures: After the detection of any motor or power FET failure, the control of the motor is taken by internal settings (no longer by the input set value IN) to protect the whole system. After a predefined time the AS8410 restarts the control by the input set value again and monitors the motor and power FET. This procedure is repeated up the failure disappears (or the controlling µP is executing a protection reaction by itself). The main internal setting values and reactions of the different load circuit failures in OM1 are listed here below: 1. Over current or short circuit of the motor Handling: a) switch off the motor immediately (delay < 1 µs) b) report of the failure at the pin IN c) check the failure condition again after a waiting time d) reuse the input set value, if the over current condition is over 2. No load of the motor Handling: a) report of the failure at the pin IN b) internal setting of the set value to 75 % c) reuse the input set value, if the no load condition is over 3. Open wire (motor or power FET line) Handling: a) report of the failure at the pin IN b) internal setting of the set value to 75 % c) reuse the input set value, if the open wire condition is over 4. Short-circuited power switch (power FET) Handling: a) report of the failure at the pin IN b) internal setting of the set value to 75 % c) reuse the input set value, if the short-circuit condition is over 5. Mechanically blocked motor Handling: a) report of the failure at the pin IN b) pull down the motor c) check the failure condition again after a waiting time d) reuse the input set value, if the blocked motor condition is over Rev. 1.0, December 2000 page 17 of 19 PWM DC Motor Regulator – Data Sheet AS8410 6. Short-circuited commutator segments (dirt of the lamellas) Handling: a) internal setting of the set value to 100 % (cleaning of the lamellas) b) regulation of the motor with adapted characteristic or switch off the motor if the motor current cross over the over current threshold c) reuse the input set value, if the short-circuit condition is over 7. Protection function for the power FET and the AS8410 itself, if the motor works as generator due to its mechanical inertia Handling: a) The gate potential of the power FET is permanently monitored, if this potential is to high in the switch off case of the driver, the power FET gate will be protected b) If the power FET gate is returned in the normal region (the motor speed of the off switched motor is low enough), the normal driver function is reused. The figure 4.3 is showing an example of the sequence of AS8410 internal events during failures handling procedure in a reduced time scale. Fig. 4.3 Example of a failure handling procedure Rev. 1.0, December 2000 page 18 of 19 PWM DC Motor Regulator – Data Sheet AS8410 4.1.8.2 Over / Under Voltage Detection and Protection The over / under voltage detection is used to prevent undefined system status. Over or under voltage detected: Handling: a) switch off the motor b) reuse the input set value, if the supply voltage returns in the permissible range Symbol Vbat Vbat_min Vbat_max 4.1.8.3 Parameter Monitored supply voltage Threshold voltage of the under voltage detection Threshold voltage of the over voltage detection min typ max Unit Note 5 6,2 12 6,50 50 6,7 V V falling 32 33 34 V rising Over Temperature Detection and Protection The over temperature detection is realised with an external temperature sensor (e.g. NTC resistor) connected to the pin TP and the supply VDD. The threshold value of the temperature detection is fixed at the voltage level VrefT = 0.5 *VDD at the pin TP. Symbol Parameter VDD VrefT min typ 5V supply at pin VDD 4,7 5,00 Threshold voltage of the temperature 0.5*VDD detection VrefT_hys Hysteresis of the threshold voltage 50 1 Over temperature if VTP < 0.5*VDD No over temperature if VTP > 0.5*VDD Cross current of the external resistor divider must be > 1 mA max Unit 5,3 V V Note 1 mV Handling of the over temperature failure: Operating Mode 1 (VMODE = high): - The Over Temperature reaction: 100 % duty ratio of the FET-driver output (permanent switch on the motor) as long as the temperature is higher than the predefined threshold value (typical automotive application, the heating source is not the electrical system but the combustion engine to be cooled). Operating Mode 2 (VMODE = low): - The Over Temperature reaction: The motor is regulated down to not cross the predefined temperature threshold (like a thermostat if the heating source is the electrical system itself). Copyright 2000, Austria Mikro Systeme International AG, Schloß Premstätten, 8141 Unterpremstätten, Austria. Tel.: +43-(0)3136-500-0, Fax: +43-(0)3136-52501, E-Mail: [email protected] All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing by the copyright holder. To the best of its knowledge, Austria Mikro Systeme International asserts that the information contained in this publication is accurate and correct. Rev. 1.0, December 2000 page 19 of 19