LV8728MR Stepper Motor Driver, PWM, Constant-Current Control, 1/128 step Overview The LV8728MR is a PWM current-controlled micro step stepper motor driver. This driver can perform eight types of excitation mode from Full step to 1/128 step and can drive simply by the CLK input. www.onsemi.com Function Single-channel PWM current control stepper motor driver BiCDMOS process IC Output on-resistance (upper side: 0.3 ; lower side: 0.25 ; total of upper and lower: 0.55 ; Ta = 25C, IO = 2.0A) Full, Half, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128 step excitation mode are selectable Advance the excitation step with the only step signal input Available forward reverse control IO max = 2.0A Over-current protection circuit Thermal shutdown circuit Input pull down resistance With reset pin and enable pin. MFP30KR (375mil) ORDERING INFORMATION Ordering Code: LV8728MR-AH Package MFP30KR (Pb-Free / Halogen Free) Shipping (quantity/packing) 1000 / Tape & Reel Typical Applications Printer (Multi-function printer, 3D printer, etc.) Security camera Scanner Stage light † For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. http://www.onsemi.com/pub_link/Collateral/BRD8011-D.PDF Maximum Ratings (Note 1) Parameter Symbol Conditions Ratings Unit Maximum supply voltage VM max VM , VM1 , VM2 36 Maximum output current IO max Per 1ch 2.0 V A Maximum logic input voltage VIN max ST , MD1 , MD2 , MD3 , OE , RST , FR , STEP 6 V Maximum FDT input voltage VFDT max 6 V Maximum VREF input voltage VREF max 6 V Maximum MO input voltage VMO max 6 V Maximum DOWN input voltage VDOWN max 6 V Allowable power dissipation (Note 2) Pd max 1.55 W Operating temperature Topr -30 to +85 C Storage temperature Tstg -55 to +150 C 1. Stresses exceeding those listed in the Absolute Maximum Rating table may damage the device. If any of these limits are exceeded, device functionality should not be assumed, damage may occur and reliability may be affected. 2. Specified circuit board: 76.1mm114.3mm1.6mm, glass epoxy board. © Semiconductor Components Industries, LLC, 2016 June 2016 - Rev. 1 1 Publication Order Number: LV8728MR/D LV8728MR Recommended Operating Ranges (Note 3) Parameter Symbol Conditions Ratings Supply voltage range VM VM , VM1 , VM2 Logic input voltage VIN ST , MD1 , MD2 , MD3 , OE , RST , FR , STEP FDT input voltage range VREF input voltage range Unit 9 to 32 V 0 to 5 V VFDT 0 to 5 V VREF 0 to 3 V 3. Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond the Recommended Operating Ranges limits may affect device reliability. Electrical Characteristics at Ta=25°C, VM=24V, VREF=1.5V unless otherwise noted. (Note 4) Parameter Symbol Conditions Ratings min typ max Unit Standby mode current drain IMst ST = “L” , VM+VM1+VM2 70 100 A Current drain IM 3.3 4.6 mA Thermal shutdown temperature Thermal hysteresis width TSD ST = “H”, OE = “H”, no load VM+VM1+VM2 Guaranteed by design 180 200 C TSD Guaranteed by design Logic pin input current IINL ST , MD1 , MD2 , MD3 , OE , RST , FR , STEP , VIN = 0.8V ST , MD1 , MD2 , MD3 , OE , RST , FR , STEP , VIN = 5V IINH Logic input voltage High VINH ST , MD1 , MD2 , MD3 , OE , RST , Low VINL FR , STEP 150 3 8 15 A 30 50 70 A 2.0 5.0 V 0 0.8 V FDT pin high level voltage Vfdth 3.5 FDT pin middle level voltage Vfdtm 1.1 FDT pin low level voltage Vfdtl V 3.1 V 0.8 V Chopping frequency Fch OSC1 pin charge/discharge current Chopping oscillation circuit threshold voltage Iosc1 Vtup1 0.8 1 1.2 V Vtdown1 0.3 0.5 0.7 V VREF pin input voltage Iref DOWN output residual voltage VOlDOWN Idown = 1mA 40 100 mV MO pin residual voltage VOlMO Imo = 1mA 40 100 mV Hold current switching frequency OSC2 pin charge/discharge current Hold current switching frequency threshold voltage Fdown Cosc2 = 1500pF 1.12 1.6 2.08 Hz Iosc2 7 10 13 A Vtup2 0.8 1 1.2 V Vtdown2 0.3 0.5 0.7 V VREG1 output voltage Vreg1 4.7 5 5.3 V VREG2 output voltage Vreg2 18 19 20 V Output on-resistance Ronu IO = 2.0A, upper side ON resistance 0.3 0.42 Ω Rond IO = 2.0A, lower side ON resistance 0.25 0.35 Ω IOleak VD VM = 36V 50 A ID = -2.0A VRF VREF = 1.5V, Current ratio 100% Output leakage current Diode forward voltage Current setting reference voltage Cosc1 = 100pF C 40 VREF = 1.5V 70 100 130 kHz 7 10 13 A A -0.5 0.285 1.1 1.4 V 0.3 0.315 V 4. Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product performance may not be indicated by the Electrical Characteristics if operated under different conditions. www.onsemi.com 2 LV8728MR Package Dimensions unit : mm SOIC30 W / MFP30KR (375 mil) CASE 751CH ISSUE A 15.55 MAX 15.2 0~10 0.1 0.2 0.65 0.3 10.5 (4.4) (5.1) 0.1 LASER MARKED INDEX 7.9 30 1 2 +0.15 0.35 −0.05 1.0 0.25 0.15 S 0.1 0.10 S 0.1 (2.25) 2.45 MAX (0.6) 1.15 SOLDERING FOOTPRINT* 9.75 (Unit: mm) 1.00 0.50 NOTE: The measurements are not to guarantee but for reference only. www.onsemi.com 3 +0.15 −0.05 LV8728MR Pin Assignment 1 VREG2 VREG1 30 2 VM 3 OUT1A MD1 28 4 PGND1 MD2 27 5 VM1 MD3 26 6 RF1 OE 25 7 OUT1B RST 24 8 NC GND 23 9 OUT2A ST 29 FR 22 10 RF2 STEP 21 11 VM2 OSC1 20 12 PGND2 OSC2 19 13 OUT2B FDT 18 14 GND DOWN 17 15 VREF MO 16 Pd max – Ta Allowable power dissipation, Pdmax - W 1.8 Mounted on a board (76.1mm×114.3mm×1.6, Glass epoxy) 1.6 1.55 1.4 1.2 1 Independent IC 0.8 0.806 0.8 0.6 0.416 0.4 0.2 0 -20 0 20 40 60 Ambient temperature, Ta - C www.onsemi.com 4 80 100 LV8728MR RF2 OUT2B OUT2A VM2 VM1 OUT1B OUT1A RF1 VREG2 Block Diagram VM Output preamplifier stage PGND2 Output preamplifier stage PGND1 Output preamplifier stage Output preamplifier stage Regulator 2 MO VREG1 Regulator 1 Output control logic VREF Current select circuit Current select circuit Oscillator circuit Decay Mode setting circuit TSD www.onsemi.com 5 OSC1 FDT OE RST FR STEP MD3 MD2 MD1 OSC2 UVLO ST GND DOWN LV8728MR Pin Functions Pin No. Pin Name Pin Function 21 22 24 25 26 27 28 STEP FR RST OE MD3 MD2 MD1 Step clock pulse signal input pin Forward / Reverse signal input pin Reset signal input pin Output enable signal input pin Excitation mode switching pin Excitation mode switching pin Excitation mode switching pin 29 ST Chip enable pin 3 4 5 6 OUT1A PGND1 VM1 RF1 7 9 10 OUT1B OUT2A RF2 11 12 13 VM2 PGND2 OUT2B Channel 1 output A pin Channel 1 Power ground pin Channel 1 motor power supply pin Channel 1 current sense resistor pin Channel 1 output B pin Channel 2 output A pin Channel 2 current sense resistor pin Channel 2 motor power supply pin Channel 2 Power ground pin Channel 2 output B pin 15 VREF Equivalent Circuit Constant-current control reference voltage input pin. Continued on next page www.onsemi.com 6 LV8728MR Continued from preceding page Pin No. Pin Name Pin Function Equivalent Circuit 1 VREG2 Internal regulator capacitor connection pin. 30 VREG1 Internal regulator capacitor connection pin. 16 17 MO DOWN Output pin for position detecting Output pin for holding current reduction 19 OSC2 Capacitor connection pin for STEP signal off detection time setting When not using the current reduction by DOWN pin, need to connect OSC2 pin to GND at 10kΩ (recommended value). 20 OSC1 Capacitor connection pin for chopping frequency setting. 14 23 GND GND Ground pin www.onsemi.com 7 LV8728MR Functional Description 3. STEP pin function 1. Input Pin Function Each input terminal has the function to prevent the flow of the current from an input to a power supply. Therefore, Even if a power supply (VM) is turned off in the state that applied voltage to an input terminal, the electric current does not flow into the power supply. Input Operating mode ST STEP Low Don’t care Standby mode High Excitation step is proceeded High Excitation step is kept 2. Stand-by function When ST pin is at low levels, the IC enters stand-by mode, all logic is reset and output is turned OFF. When ST pin is at high levels, the stand-by mode is released. 4. Input Timing Tsteph/Tstepl: Clock H/L pulse width (min 500ns) Tds: Data set-up time (min 500ns) Tdh: Data hold time (min 500ns) 5. Position detection monitor function The MO position detection monitoring pin is an open drain type. When the excitation position is in the initial position, the MO output is placed in the ON state. (Refer to "Examples of current waveforms in each of the excitation modes.") MO Status ON Initial position OFF Except initial position www.onsemi.com 8 LV8728MR 6. Excitation mode setting function Set the excitation setting as shown in the following Input table by setting MD1 pin, MD2 pin and MD3 pin. Excitation Initial position MD3 MD2 MD1 mode 1ch current 2ch current Low Low Low Full step 100% -100% Low Low High Half step 100% 0% 0% Low High Low 1/4 step 100% Low High High 1/8 step 100% 0% High Low Low 1/16 step 100% 0% 0% High Low High 1/32 step 100% High High Low 1/64 step 100% 0% High High High 1/128 step 100% 0% The initial position is also the default state at start-up and excitation position at counter-reset in each excitation mode. 7. Output enable function When the OE pin is set Low, the output is forced OFF and goes to high impedance. However, the internal logic circuits are operating, so the excitation position proceeds when the STEP is input. Therefore, when OE pin is returned to High, the output level conforms to the excitation position that is advanced by the STEP input. OE Operating mode Low Output OFF High Output ON 8. Reset function When the RST pin is set Low, the excitation position of the output is set to the initial position forcibly and MO pin output is turn ON state. And then by setting RST pin is High, the excitation position moves forward with the next step signal. RST www.onsemi.com 9 Operating mode Low Reset status High Normal operation LV8728MR 12. Chopping frequency setting For constant-current control, LV8728 performs PWM operation at the chopping frequency determined by the capacitor (COSC1) connected between the OSC1 pin and GND. The calculation for the value of chopping frequency is: 9. Forward / Reverse switching The internal D/A converter proceeds by a bit on the rising edge of the step signal input to the STP pin. In addition, CW and CCW mode are switched by FR pin setting. In CW mode, the channel 2 current phase is delayed by 90° relative to the channel 1 current. In CCW mode, the channel 2 current phase is advanced by 90° relative to the channel 1 current. FR 1 1 Where, Fch : Chopping frequency [Hz] IOSC1 : Charge/ Discharge current of OSC1pin [A]. IOSC1 is 10uA (typ) by electrical Characteristics. COSC1 : Capacitor for chopping frequency setting [F] Operating mode Low Clockwise (CW) High Counter-clockwise(CCW) CW mode FR CCW mode CW mode For example, when COSC1=100pF and IOSC1=10uA (typ), the chopping frequency is shown below: STEP Excitation Position (1) (2) (3) (4) (5) (6) (5) (4) (3) (4) (5) 10 100 1ch output 10. Decay mode setting Current Decay method is selectable as shown below by applied voltage to the FDT pin. Decay mode SLOW Decay MIXED Decay 0V to 0.8V FAST Decay 13. Blanking time If, when exercising PWM constant-current chopping control over the motor current, the mode is switched from decay to charge, the recovery current of the parasitic diode may flow to the current sensing resistance, causing noise to be carried on the current sensing resistance pin, and this may result in erroneous detection. To prevent this erroneous detection, a blanking period is provided to prevent the noise occurring during mode switching from being received. During the blanking time, even if noise is generated in sense resistor, a mode does not switch from CHARGE to DECAY. In this IC, the blanking time is fixed to approximately 1s. 11. Output current setting Output current is set as shown below by the VREF pin (applied voltage) and a resistance value between RF1 (2) pin and GND. 5∙ The setting current value above is a 100% output current in each excitation mode. Where, IOUT : Coil current [A] RRFx : Resistor between RF1 (2) and GND [Ω] VREF : Input voltage at the VREF pin [V] For example, when VREF = 1.1V and RF1 (2) resistance is 0.22Ω, the setting current is shown below: 5 1.1 0.22 100 The higher the chopping frequency is, the greater the output switching loss becomes. As a result, heat generation issue arises. The lower the chopping frequency is, the lesser the heat generation becomes. However, current ripple occurs. Since noise increases when switching of chopping takes place, you need to adjust frequency with the influence to the other devices into consideration. 2ch output FDT voltage 3.5V to 5.0V 1.1V to 3.1V or Open 10 10 1.0 www.onsemi.com 10 LV8728MR 14. DOWN output pin for holding current reduction The DOWN output pin is an open drain type. When DOWN pin is turned ON, the motor is holding current. DOWN Status ON Holding current OFF Normal operation For example, when V1=5V, R1=68kΩ, R2=30kΩ, R3=5kΩ, RRF1 (2) =0.22Ω, the VREF voltage is shown below: RRF1 (2) is Resistor between RF1 (2) and GND [Ω] VREF is input voltage at the VREF pin [V] When the DOWN is turned OFF 5 30 1.53 68 30 To avoid to applying high current to a motor coil for long term at one position, the DOWN output may be used to reduce the reference current. The DOWN is asserted when the step clock interval is longer than TDOWN (STEP signal off detection time). With the circuit is shown in below. VREF voltage can be reduced when the DOWN is turned ON. The open-drain output in once turned ON, is turned OFF at the next rising edge of STP. 5 1.53 0.22 1.39 When the DOWN is turned ON, combined resistor of R2 and R3 is about 4.3kΩ. 5 4.3 0.3 68 4.3 0.3 5 0.22 0.27 15. SETP signal off detection time setting STEP signal off time is determined by the capacitor (COSC2) connected between the OSC2 pin and GND. When this function is unused, connect OSC2 pin to GND at 10kohm (recommendation). The calculation for the value of STEP signal off detection time is: 2 0.4 10 Where, TDOWN : STEP signal off detection time [Sec] COSC2 : Capacitor for STEP signal off time [F] For example, when COSC2=1500pF, the STEP signal off detection time is shown below: 1500 www.onsemi.com 11 10 0.6 0.4 10 LV8728MR 16. Output current vector locus (one step is normalized to 90 degrees) (Full step) Current setting ratio in each excitation mode STEP θ0 θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8 θ9 θ10 θ11 θ12 θ13 θ14 θ15 θ16 θ17 θ18 θ19 θ20 θ21 θ22 θ23 θ24 θ25 1/128 step (%) 1ch 2ch 100 0 100 1 100 2 100 4 100 5 100 6 100 7 100 9 100 10 99 11 99 12 99 13 99 15 99 16 99 17 98 18 98 20 98 21 98 22 97 23 97 24 97 25 96 27 96 28 96 29 95 30 1/64 step (%) 1ch 2ch 100 0 100 2 100 5 100 7 100 10 99 12 99 15 99 17 98 20 98 22 97 24 96 27 96 29 1/32 step (%) 1ch 2ch 100 0 100 5 100 10 99 15 98 20 97 24 96 29 1/16 step (%) 1ch 2ch 100 0 100 10 98 20 96 29 1/8 step (%) 1ch 2ch 100 0 98 1/4 step (%) 1ch 2ch 100 0 Half step (%) 1ch 2ch 100 0 Full step (%) 1ch 2ch 20 Continued on next page www.onsemi.com 12 LV8728MR Continued from preceding page STEP θ26 θ27 θ28 θ29 θ30 θ31 θ32 θ33 θ34 θ35 θ36 θ37 θ38 θ39 θ40 θ41 θ42 θ43 θ44 θ45 θ46 θ47 θ48 θ49 θ50 θ51 θ52 θ53 θ54 θ55 θ56 θ57 θ58 θ59 θ60 θ61 θ62 θ63 θ64 θ65 θ66 θ67 θ68 θ69 θ70 θ71 θ72 θ73 θ74 θ75 θ76 θ77 θ78 θ79 θ80 θ81 θ82 θ83 θ84 θ85 θ86 θ87 θ88 θ89 θ90 1/128 step 1ch 2ch 95 31 95 33 94 34 94 35 93 36 93 37 92 38 92 39 91 41 91 42 90 43 90 44 89 45 89 46 88 47 88 48 87 49 86 50 86 51 85 52 84 53 84 55 83 56 82 57 82 58 81 59 80 60 80 61 79 62 78 62 77 63 77 64 76 65 75 66 74 67 73 68 72 69 72 70 71 71 70 72 69 72 68 73 67 74 66 75 65 76 64 77 63 77 62 78 62 79 61 80 60 80 59 81 58 82 57 82 56 83 55 84 53 84 52 85 51 86 50 86 49 87 48 88 47 88 46 89 45 89 1/64 step (%) 1ch 2ch 95 31 94 34 93 36 92 38 91 41 90 43 89 45 88 47 87 49 86 51 84 53 83 56 82 58 80 60 79 62 77 63 76 65 74 67 72 69 71 71 69 72 67 74 65 76 63 77 62 79 60 80 58 82 56 83 53 84 51 86 49 87 47 88 45 89 1/32 step (%) 1ch 2ch 94 34 92 38 90 43 88 47 86 51 83 56 80 60 77 63 74 67 71 71 67 74 63 77 60 80 56 83 51 86 47 88 1/16 step (%) 1ch 2ch 92 38 88 47 83 56 77 63 71 71 63 77 56 83 47 88 1/8 step (%) 1ch 2ch 92 38 83 56 71 71 56 83 1/4 step (%) 1ch 2ch 92 38 71 71 Half step (%) 1ch 2ch 71 71 Full step (%) 1ch 2ch 100 100 Continued on next page www.onsemi.com 13 LV8728MR Continued from preceding page STEP θ91 θ92 θ93 θ94 θ95 θ96 θ97 θ98 θ99 θ100 θ101 θ102 θ103 θ104 θ105 θ106 θ107 θ108 θ109 θ110 θ111 θ112 θ113 θ114 θ115 θ116 θ117 θ118 θ119 θ120 θ121 θ122 θ123 θ124 θ125 θ126 θ127 θ128 1/128 step 1ch 2ch 44 90 43 90 42 91 41 91 39 92 38 92 37 93 36 93 35 94 34 94 33 95 31 95 30 95 29 96 28 96 27 96 25 97 24 97 23 97 22 98 21 98 20 98 18 98 17 99 16 99 15 99 13 99 12 99 11 99 10 100 9 100 7 100 6 100 5 100 4 100 2 100 1 100 0 100 1/64 step (%) 1ch 2ch 43 90 41 91 38 92 36 93 34 94 31 95 29 96 27 96 24 97 22 98 20 98 17 99 15 99 12 99 10 100 7 100 5 100 2 100 0 100 1/32 step (%) 1ch 2ch 43 90 38 92 34 94 29 96 24 97 20 98 15 99 10 100 5 100 0 100 1/16 step (%) 1ch 2ch 38 92 29 96 20 98 10 100 0 100 1/8 step (%) 1ch 2ch 38 92 20 98 0 100 www.onsemi.com 14 1/4 step (%) 1ch 2ch 38 92 0 100 Half step (%) 1ch 2ch 0 100 Full step (%) 1ch 2ch LV8728MR 17. Current wave example in each excitation mode (Full, Half, 1/16, 1/128 step) Full step (CW mode) STEP MO (%) 100 I1 0 -100 (%) 100 I2 0 -100 Half step (CW mode) STEP MO (%) 100 I1 0 -100 (%) 100 I2 0 -100 www.onsemi.com 15 LV8728MR 1/16 step (CW mode) STEP MO [%] 100 50 I1 0 -50 -100 [%] 100 50 I2 0 -50 -100 1/128 step (CW mode) www.onsemi.com 16 LV8728MR 18. Current control operation FAST Decay current control: When FDT pin voltage is 0.8V or less, the constant- current control is operated in FAST Decay mode. (Sine-wave increasing direction) STEP Setting current Setting current Coil current Blanking Tim e (Forced CHARGE) Fch Current mode Chopping period CHARGE FAST CHARGE FAST (Sine-wave decreasing direction) STEP S e ttin g c u rre n t C o il c u rre n t B la n k in g T im e (F o rc e d C H A R G E ) S e ttin g c u rre n t C h o p p in g p e rio d Fch C u rre n t m o d e CHARGE FA S T B la n k in g T im e The current control of FAST Decay operates with the follow sequence. The IC enters CHARGE mode at a rising edge of the chopping oscillation. The CHARGE of the blanking time is forced regardless of the magnitude of the coil current (ICOIL) and set current (IREF). The blanking time is approximately 1μs. After the period of the blanking time, The IC operates in CHARGE mode until ICOIL ≥ IREF. After that, the mode switches to the FAST Decay FA S T CHARGE FA S T mode and the coil current is attenuated until the end of a chopping period. If ICOIL > IREF state exists when the end of blanking time, the coil current is attenuated by the FAST Decay mode until the end of a chopping period. Since the attenuation of the current is fast, it is early that the coil current follows the set current. However, the current ripple value may be higher. www.onsemi.com 17 LV8728MR MIXED Decay current control: When FDT pin voltage is between 1.1V and 3.1V or Open, the constant- current control is operated in MIXED Decay mode. (Sine-wave increasing direction) STEP Setting current Setting current Coil current Blanking time (Forced CHARGE) Fch Current mode CHARGE SLOW FAST CHARGE SLOW FAST (Sine-wave decreasing direction) STEP Setting current Coil current Blanking time (Forced CHARGE) Setting current Fch Current mode CHARGE SLOW FAST Forced CHARGE The current control of MIXED Decay operates with the follow sequence. The IC enters CHARGE mode at a rising edge of the chopping oscillation. The CHARGE of the blanking time is forced regardless of the magnitude of the coil current (ICOIL) and set current (IREF). The blanking time is approximately 1μs. In a period of Blanking Time, the coil current (ICOIL) and the setting current (IREF) are compared. If an ICOIL < IREF state exists during the charge period: The IC operates in CHARGE mode until ICOIL ≥ IREF. After that, it switches to SLOW DECAY mode and then switches to FAST DECAY mode in the last approximately 1μs of the period. FAST CHARGE SLOW If no ICOIL < IREF state exists during the charge period: The IC switches to FAST DECAY mode and the coil current is attenuated with the FAST DECAY operation until the end of a chopping period. The above operation is repeated. Normally, the IC operates in SLOW (+ FAST) Decay mode at the sine wave increasing direction, and the IC operates in FAST Decay mode at the sine wave decreasing direction until the current is attenuated. And then the IC operates in SLOW Decay mode when the current reaches the set value. www.onsemi.com 18 LV8728MR SLOW Decay current control: When FDT pin voltage is 3.5V or more, the constant- current control is operated in SLOW Decay mode. (Sine-wave increasing direction) STEP Setting current Setting current Coil current Blanking Time (Forced CHARGE) Fch Chopping period CHARGE Current mode CHARGE SLOW SLOW (Sine-wave decreasing direction) STEP Setting current Coil current Blanking Time Forced CHARGE) Setting current Chopping period Fch Current mode CHARGE SLOW Blanking Time SLOW Blanking Time SLOW If ICOIL > IREF state exists when the end of blanking time, the coil current is attenuated by the SLOW Decay mode until the end of a chopping period. The current control of SLOW Decay operates with the follow sequence. The IC enters CHARGE mode at a rising edge of the chopping oscillation. The CHARGE of the blanking time is forced regardless of the magnitude of the coil current (ICOIL) and set current (IREF). The blanking time is approximately 1μs. After the period of the blanking time, The IC operates in CHARGE mode until ICOIL ≥ IREF. After that, the mode switches to the SLOW Decay mode and the coil current is attenuated until the end of a chopping period. Since the attenuation of the current is slow, it may be slow that the coil current follows the set current. Or the coil current may not follow a set current. www.onsemi.com 19 LV8728MR 19. Over-current protection function This IC incorporates an over current protection circuit that, when the output has been shorted by an event such as shorting to power, shorting to ground and shorting to other output. And it switches the output to the standby mode in order to prevent the IC from being damaged. Three over-current detection modes are shown in the next page. When the over current is detected, the over current protection circuit operates. If the short status continues for the period of internal timer (≈2μs), the output of 1ch/ 2ch is turned off. If the short status exceeds the timer latch time (≈256us) set in the internal timer, the output is turned on again and detects short status again. If short is detected again, all the outputs of 1ch/ 2ch are switched to standby mode and the status is kept. To cancel the standby status, set ST=”L”. H-bridge Output state Output ON Fault Detection Release Output ON Output OFF Timer latch period (typ:256µs) 2µs Over-current Detected Output OFF 2µs Over-current Detected Internal counter 1st counter 1st counter 1st counter 1st counter start stop start stop 2nd counter start 2nd counter stop protection of the final product because it operates when the temperature exceed the junction temperature of Tjmax=150°C. TSD = 180°C (typ) ΔTSD = 40°C (typ) 20. Thermal shutdown function The thermal shutdown circuit is incorporated and the output is turned Off when junction temperature Tj exceeds 180°C. As the temperature falls by hysteresis, the output turned on again (automatic restoration). The thermal shutdown circuit does not guarantee the www.onsemi.com 20 LV8728MR 21. Over current detection mode Short to Power VM VM Tr1 Tr3 ON OUTA M Tr2 OFF RF OFF OUTB Tr1 OFF OUTA Tr4 Tr2 ON ON Tr3 1. High current flows if OUTB short to VM and Tr4 are ON. 2. If RF voltage> setting voltage, then the mode switches to SLOW decay. 3. If the voltage between Drain and Source of Tr4 exceeds the reference voltage for 2μs, short status is detected. OFF OUTB M Tr4 ON RF Short-circuit Detection (left schematic) 1. High current flows if OUTA short to GND and Tr1 are ON 2. If the voltage between Drain and Source of Tr1 exceeds the reference voltage for 2μs, short status is detected. Short to GND (right schematic) 1. Without going through RF resistor, current control does not operate and current will continue to increase in CHARGE mode. 2. If the voltage between Drain and Source of Tr1 exceeds the reference voltage for 2μs, short status is detected. 1. Without L load, high current flows. 2. If RF voltage> setting voltage, then the mode switches to SLOW decay. 3. During load short stay in SLOW decay mode, current does not flow and over current state is not detected. Then the mode is switched to FAST decay according to chopping cycle. 4. Since FAST state is short (≈1μs), switches to CHARGE mode before short is detected. 5. If voltage between Drain and Source exceeds the reference voltage continuously during blanking time at the start of CHARGE mode (Tr1), CHARGE state is fixed (even if RF voltage exceeds the setting voltage, the mode is not switched to SLOW decay). After 2us or so, short is detected. Load short www.onsemi.com 21 LV8728MR Application Circuit Example Calculation for each constant setting according to the above circuit diagram is as follows. For example, when VREF=1.1V, IOSC1=10uA (typ) and COSC1=100pF Coil current 1.1 5 0.22 1.0 Chopping frequency 10 10 100 10 STEP signal off detection time 1500 10 0.6 100 0.4 10 www.onsemi.com 22 LV8728MR ON Semiconductor and the ON Semiconductor logo are trademarks of Semiconductor Components Industries, LLC dba ON Semiconductor or its subsidiaries in the United States and/or other countries. ON Semiconductor owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of ON Semiconductor’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent-Marking.pdf. ON Semiconductor reserves the right to make changes without further notice to any products herein. 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