L6228 DMOS DRIVER FOR BIPOLAR STEPPER MOTOR ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ OPERATING SUPPLY VOLTAGE FROM 8 TO 52V 2.8A OUTPUT PEAK CURRENT (1.4A RMS) RDS(ON) 0.73Ω TYP. VALUE @ Tj = 25°C OPERATING FREQUENCY UP TO 100KHz NON DISSIPATIVE OVERCURRENT PROTECTION DUAL INDEPENDENT CONSTANT tOFF PWM CURRENT CONTROLLERS FAST/SLOW DECAY MODE SELECTION FAST DECAY QUASI-SYNCHRONOUS RECTIFICATION DECODING LOGIC FOR STEPPER MOTOR FULL AND HALF STEP DRIVE CROSS CONDUCTION PROTECTION THERMAL SHUTDOWN UNDER VOLTAGE LOCKOUT INTEGRATED FAST FREE WHEELING DIODES TYPICAL APPLICATIONS ■ BIPOLAR STEPPER MOTOR DESCRIPTION The L6228 is a DMOS Fully Integrated Stepper Motor Driver with non-dissipative Overcurrent Protection, realized in MultiPower-BCD technology, which com- PowerDIP24 (20+2+2) PowerSO36 SO24 (20+2+2) ORDERING NUMBERS: L6228N (PowerDIP24) L6228PD (PowerSO36) L6228D (SO24) bines isolated DMOS Power Transistors with CMOS and bipolar circuits on the same chip. The device includes all the circuitry needed to drive a two-phase bipolar stepper motor including: a dual DMOS Full Bridge, the constant off time PWM Current Controller that performs the chopping regulation and the Phase Sequence Generator, that generates the stepping sequence. Available in PowerDIP24 (20+2+2), PowerSO36 and SO24 (20+2+2) packages, the L6228 features a non-dissipative overcurrent protection on the high side Power MOSFETs and thermal shutdown. BLOCK DIAGRAM VBOOT VCP VBOOT VBOOT VBOOT 10V 10V OCDA OCDB OVER CURRENT DETECTION THERMAL PROTECTION EN OUT1A SENSEA PWM HALF/FULL RESET OUT2A GATE LOGIC CONTROL CLOCK VSA CHARGE PUMP STEPPING SEQUENCE GENERATION ONE SHOT MONOSTABLE CW/CCW MASKING TIME + SENSE COMPARATOR VREFA RCA BRIDGE A VOLTAGE REGULATOR 10V 5V VSB OVER CURRENT DETECTION OUT1B OUT2B SENSEB GATE LOGIC VREFB BRIDGE B RCB D01IN1225 September 2003 This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice. 1/26 L6228 ABSOLUTE MAXIMUM RATINGS Symbol VS VOD VBOOT Parameter Test conditions Value Unit Supply Voltage VSA = VSB = VS 60 V Differential Voltage between VSA, OUT1A, OUT2A, SENSEA and VSB, OUT1B, OUT2B, SENSEB VSA = VSB = VS = 60V; VSENSEA = VSENSEB = GND 60 V Bootstrap Peak Voltage VSA = VSB = VS VS + 10 V VIN,VEN Input and Enable Voltage Range -0.3 to +7 V VREFA, VREFB Voltage Range at pins VREFA and VREFB -0.3 to +7 V -0.3 to +7 V -1 to +4 V VRCA, VRCB Voltage Range at pins RCA and RCB VSENSEA, VSENSEB Voltage Range at pins SENSEA and SENSEB IS(peak) Pulsed Supply Current (for each VS pin), internally limited by the overcurrent protection VSA = VSB = VS; tPULSE < 1ms 3.55 A RMS Supply Current (for each VS pin) VSA = VSB = VS 1.4 A -40 to 150 °C IS Tstg, TOP Storage and Operating Temperature Range RECOMMENDED OPERATING CONDITIONS Symbol VS VOD VREFA, VREFB VSENSEA, VSENSEB IOUT 2/26 Parameter Test Conditions Supply Voltage VSA = VSB = VS Differential Voltage Between VSA, OUT1A, OUT2A, SENSEA and VSB, OUT1B, OUT2B, SENSEB VSA = VSB = VS; VSENSEA = VSENSEB Voltage Range at pins VREFA and VREFB Voltage Range at pins SENSEA and SENSEB (pulsed tW < trr) (DC) MIN MAX Unit 8 52 V 52 V -0.1 5 V -6 -1 6 1 V V 1.4 A +125 °C 100 KHz RMS Output Current Tj Operating Junction Temperature fsw Switching Frequency -25 L6228 THERMAL DATA Symbol Description Rth-j-pins Maximum Thermal Resistance Junction-Pins Rth-j-case Maximum Thermal Resistance Junction-Case PowerDIP24 SO24 PowerSO36 Unit 19 15 - °C/W - - 2 °C/W 44 55 - °C/W Rth-j-amb1 Maximum Thermal Resistance Junction-Ambient Rth-j-amb1 Maximum Thermal Resistance Junction-Ambient (2) - - 36 °C/W Rth-j-amb1 Maximum Thermal Resistance Junction-Ambient (3) - - 16 °C/W Rth-j-amb2 Maximum Thermal Resistance Junction-Ambient (4) 59 78 63 °C/W (1) (2) (3) (4) (1) Mounted on a multi-layer FR4 PCB with a dissipating copper surface on the bottom side of 6cm2 (with a thickness of 35µm). Mounted on a multi-layer FR4 PCB with a dissipating copper surface on the top side of 6cm2 (with a thickness of 35µm). Mounted on a multi-layer FR4 PCB with a dissipating copper surface on the top side of 6cm2 (with a thickness of 35µm), 16 via holes and a ground layer. Mounted on a multi-layer FR4 PCB without any heat sinking surface on the board. PIN CONNECTIONS (Top View) CLOCK 1 24 VREFA CW/CCW 2 23 RESET SENSEA 3 22 VCP GND 1 36 GND N.C. 2 35 N.C. N.C. 3 34 N.C. VSA 4 33 VSB OUT2A 5 32 OUT2B RCA 4 21 OUT2A N.C. 6 31 N.C. OUT1A 5 20 VSA VCP 7 30 VBOOT GND 6 19 GND RESET 8 29 EN GND 7 18 GND VREFA 9 28 CONTROL OUT1B 8 17 VSB CLOCK 10 27 HALF/FULL RCB 9 16 OUT2B CW/CCW 11 26 VREFB 12 25 SENSEB 10 15 VBOOT SENSEA SENSEB RCB VREFB 11 14 EN HALF/FULL 12 13 CONTROL D99IN1083 RCA 13 24 N.C. 14 23 N.C. OUT1A 15 22 OUT1B N.C. 16 21 N.C. N.C. 17 20 N.C. GND 18 19 GND D99IN1084 PowerDIP24/SO24 (5) PowerSO36 (5) The slug is internally connected to pins 1,18,19 and 36 (GND pins). 3/26 L6228 PIN DESCRIPTION PACKAGE SO24/ PowerDIP24 PowerSO36 PIN # PIN # 1 Name Type 10 CLOCK Logic Input Step Clock input. The state machine makes one step on each rising edge. 2 11 CW/CCW Logic Input Selects the direction of the rotation. HIGH logic level sets clockwise direction, whereas LOW logic level sets counterclockwise direction. If not used, it has to be connected to GND or +5V. 3 12 SENSEA Power Supply Bridge A Source Pin. This pin must be connected to Power Ground through a sensing power resistor. 4 13 RCA RC Pin 5 15 OUT1A Power Output 6, 7, 18, 19 1, 18, 19, 36 GND GND 8 22 OUT1B Power Output 9 24 RCB RC Pin 10 25 SENSEB Power Supply Bridge B Source Pin. This pin must be connected to Power Ground through a sensing power resistor. 11 26 VREFB Analog Input Bridge B Current Controller Reference Voltage. Do not leave this pin open or connected to GND. 12 27 HALF/FULL Logic Input Step Mode Selector. HIGH logic level sets HALF STEP Mode, LOW logic level sets FULL STEP Mode. If not used, it has to be connected to GND or +5V. 13 28 CONTROL Logic Input Decay Mode Selector. HIGH logic level sets SLOW DECAY Mode. LOW logic level sets FAST DECAY Mode. If not used, it has to be connected to GND or +5V. 14 29 EN Logic Input (6) Chip Enable. LOW logic level switches OFF all Power MOSFETs of both Bridge A and Bridge B. This pin is also connected to the collector of the Overcurrent and Thermal Protection to implement over current protection. If not used, it has to be connected to +5V through a resistor. 15 30 VBOOT Supply Voltage 16 32 OUT2B Power Output Bridge B Output 2. 17 33 VSB Power Supply Bridge B Power Supply Voltage. It must be connected to the Supply Voltage together with pin VSA 20 4 VSA Power Supply Bridge A Power Supply Voltage. It must be connected to the Supply Voltage together with pin VSB 4/26 Function RC Network Pin. A parallel RC network connected between this pin and ground sets the Current Controller OFF-Time of the Bridge A. Bridge A Output 1. Ground terminals. In PowerDIP24 and SO24 packages, these pins are also used for heat dissipation toward the PCB. On PowerSO36 package the slug is connected to these pins. Bridge B Output 1. RC Network Pin. A parallel RC network connected between this pin and ground sets the Current Controller OFF-Time of the Bridge B. Bootstrap Voltage needed for driving the upper Power MOSFETs of both Bridge A and Bridge B. L6228 PIN DESCRIPTION (continued) PACKAGE SO24/ PowerDIP24 PowerSO36 PIN # PIN # 21 (6) Name Type Function 5 OUT2A Power Output 22 7 VCP Output 23 8 RESET Logic Input 24 9 VREFA Analog Input Bridge A Output 2. Charge Pump Oscillator Output. Reset Pin. LOW logic level restores the Home State (State 1) on the Phase Sequence Generator State Machine. If not used, it has to be connected to +5V. Bridge A Current Controller Reference Voltage. Do not leave this pin open or connected to GND. Also connected at the output drain of the Over current and Thermal protection MOSFET. Therefore, it has to be driven putting in series a resistor with a value in the range of 2.2KΩ - 180KΩ, recommended 100KΩ. ELECTRICAL CHARACTERISTICS (Tamb = 25°C, Vs = 48V, unless otherwise specified) Symbol Min Typ Max Unit VSth(ON) Turn-on Threshold 5.8 6.3 6.8 V VSth(OFF) Turn-off Threshold 5 5.5 6 V 5 10 mA IS Tj(OFF) Parameter Quiescent Supply Current Test Conditions All Bridges OFF; Tj = -25°C to 125°C (7) Thermal Shutdown Temperature °C 165 Output DMOS Transistors RDS(ON) IDSS High-Side + Low-Side Switch ON Tj = 25 °C Resistance Tj =125 °C (7) Leakage Current 1.47 1.69 Ω 2.35 2.70 Ω 2 mA EN = Low; OUT = VS EN = Low; OUT = GND -0.3 mA Source Drain Diodes VSD Forward ON Voltage ISD = 1.4A, EN = LOW 1.15 1.3 V trr Reverse Recovery Time If = 1.4A 300 ns tfr Forward Recovery Time 200 ns Logic Inputs (EN, CONTROL, HALF/FULL, CLOCK, RESET, CW/CCW) VIL Low level logic input voltage -0.3 0.8 V VIH High level logic input voltage 2 7 V IIL Low Level Logic Input Current GND Logic Input Voltage IIH High Level Logic Input Current 7V Logic Input Voltage -10 µA 10 µA 5/26 L6228 ELECTRICAL CHARACTERISTICS (continued) (Tamb = 25°C, Vs = 48V, unless otherwise specified) Symbol Parameter Vth(ON) Turn-on Input Threshold Vth(OFF) Turn-off Input Threshold Vth(HYS) Input Threshold Hysteresis Test Conditions Min Typ Max Unit 1.8 2.0 V 0.8 1.3 V 0.25 0.5 V Switching Characteristics tD(ON)EN Enable to Output Turn-on Delay Time (8) ILOAD =1.4A, Resistive Load 500 650 800 ns tD(OFF)EN Enable to Output Turn-off Delay Time (8) ILOAD =1.4A, Resistive Load 500 800 1000 ns tRISE Output Rise Time (8) ILOAD =1.4A, Resistive Load 40 250 ns tFALL Output Fall Time (8) ILOAD =1.4A, Resistive Load 40 250 ns tDCLK Clock to Output Delay Time (9) ILOAD =1.4A, Resistive Load 2 µs tCLK(min)L Minimum Clock Time (10) 1 µs tCLK(min) Minimum Clock Time (10) 1 µs 100 KHz H fCLK Clock Frequency tS(MIN) Minimum Set-up Time (11) 1 µs tH(MIN) Minimum Hold Time (11) 1 µs tR(MIN) Minimum Reset Time (11) 1 µs 1 µs tRCLK(MIN Minimum Reset to Clock Delay ) Time (11) tDT Dead Time Protection fCP Charge Pump Frequency 0.5 1 0.6 Tj = -25°C to 125°C (7) µs 1 MHz PWM Comparator and Monostable IRCA, IRCB Source Current at pins RCA and RCB Voffset Offset Voltage on Sense Comparator tPROP Turn OFF Propagation Delay (12) tBLANK Internal Blanking Time on SENSE pins tON(MIN) tOFF 6/26 VRCA = VRCB = 2.5V VREFA, VREFB = 0.5V Minimum On Time PWM Recirculation Time 3.5 5.5 mA ±5 mV 500 ns 1 µs 2.5 3 µs ROFF = 20KΩ; COFF = 1nF 13 µs ROFF = 100KΩ; COFF = 1nF 61 µs L6228 ELECTRICAL CHARACTERISTICS (continued) (Tamb = 25°C, Vs = 48V, unless otherwise specified) Symbol Parameter Test Conditions IBIAS Input Bias Current at pins VREFA and VREFB Min Typ Max Unit 10 µA 2.8 3.55 A 60 Ω Over Current Protection ISOVER Input Supply Overcurrent Protection Threshold Tj = -25°C to 125°C (7) ROPDR Open Drain ON Resistance I = 4mA 40 tOCD(ON) OCD Turn-on Delay Time (13) I = 4mA; CEN < 100pF 200 ns tOCD(OFF) OCD Turn-off Delay Time (13) I = 4mA; CEN < 100pF 100 ns (7) (8) (9) (10) (11) (12) (13) 2 Tested at 25°C in a restricted range and guaranteed by characterization. See Fig. 1. See Fig. 2. See Fig. 3. See Fig. 4. Measured applying a voltage of 1V to pin SENSE and a voltage drop from 2V to 0V to pin VREF. See Fig. 5. Figure 1. Switching Characteristic Definition EN Vth(ON) Vth(OFF) t IOUT 90% 10% t D01IN1316 tFALL tD(OFF)EN tRISE tD(ON)EN 7/26 L6228 Figure 2. Clock to Output Delay Time CLOCK Vth(ON) t IOUT t D01IN1317 tDCLK Figure 3. Minimum Timing Definition; Clock Input CLOCK Vth(ON) Vth(OFF) tCLK(MIN)L Vth(OFF) tCLK(MIN)H D01IN1318 Figure 4. Minimum Timing Definition; Logic Inputs CLOCK Vth(ON) LOGIC INPUTS tS(MIN) RESET Vth(OFF) Vth(ON) tR(MIN) 8/26 tH(MIN) tRCLK(MIN) D01IN1319 L6228 Figure 5. Overcurrent Detection Timing Definition IOUT ISOVER ON BRIDGE OFF VEN 90% 10% tOCD(ON) tOCD(OFF) D02IN1399 9/26 L6228 CIRCUIT DESCRIPTION POWER STAGES and CHARGE PUMP The L6228 integrates two independent Power MOS Full Bridges. Each Power MOS has an RDS(ON) = 0.73Ω (typical value @ 25°C), with intrinsic fast freewheeling diode. Switching patterns are generated by the PWM Current Controller and the Phase Sequence Generator (see below). Cross conduction protection is achieved using a dead time (tDT = 1µs typical value) between the switch off and switch on of two Power MOSFETSs in one leg of a bridge. Pins VSA and VSB MUST be connected together to the supply voltage VS. The device operates with a supply voltage in the range from 8V to 52V. It has to be noticed that the RDS(ON) increases of some percents when the supply voltage is in the range from 8V to 12V. Using N-Channel Power MOS for the upper transistors in the bridge requires a gate drive voltage above the power supply voltage. The bootstrapped supply voltage VBOOT is obtained through an internal Oscillator and few external components to realize a charge pump circuit as shown in Figure 6. The oscillator output (VCP) is a square wave at 600KHz (typical) with 10V amplitude. Recommended values/part numbers for the charge pump circuit are shown in Table 1. LOGIC INPUTS Pins CONTROL, HALF/FULL, CLOCK, RESET and CW/CCW are TTL/CMOS and uC compatible logic inputs. The internal structure is shown in Fig. 7. Typical value for turn-on and turn-off thresholds are respectively Vth(ON)= 1.8V and Vth(OFF)= 1.3V. Pin EN (Enable) has identical input structure with the exception that the drain of the Overcurrent and thermal protection MOSFET is also connected to this pin. Due to this connection some care needs to be taken in driving this pin. The EN input may be driven in one of two configurations as shown in Fig. 8 or 9. If driven by an open drain (collector) structure, a pull-up resistor REN and a capacitor CEN are connected as shown in Fig. 8. If the driver is a standard Push-Pull structure the resistor REN and the capacitor CEN are connected as shown in Fig. 9. The resistor REN should be chosen in the range from 2.2KΩ to 180KΩ. Recommended values for REN and CEN are respectively 100KΩ and 5.6nF. More information on selecting the values is found in the Overcurrent Protection section. Figure 7. Logic Inputs Internal Structure 5V Table 1. Charge Pump External Components Values CBOOT 220nF CP 10nF RP 100Ω D1 1N4148 ESD PROTECTION D01IN1329 Figure 8. EN Pin Open Collector Driving 5V D2 5V REN 1N4148 OPEN COLLECTOR OUTPUT Figure 6. Charge Pump Circuit EN CEN ESD PROTECTION D01IN1330 VS D1 CBOOT Figure 9. EN Pin Push-Pull Driving D2 5V RP CP VCP PUSH-PULL OUTPUT VBOOT VSA VSB D01IN1328 REN EN CEN ESD PROTECTION D01IN1331 10/26 L6228 PWM CURRENT CONTROL The L6228 includes a constant off time PWM current controller for each of the two bridges. The current control circuit senses the bridge current by sensing the voltage drop across an external sense resistor connected between the source of the two lower power MOS transistors and ground, as shown in Figure 10. As the current in the motor builds up the voltage across the sense resistor increases proportionally. When the voltage drop across the sense resistor becomes greater than the voltage at the reference input (VREFA or VREFB) the sense comparator triggers the monostable switching the bridge off. The power MOS remain off for the time set by the monostable and the motor current recirculates as defined by the selected decay mode, described in the next section. When the monostable times out the bridge will again turn on. Since the internal dead time, used to prevent cross conduction in the bridge, delays the turn on of the power MOS, the effective off time is the sum of the monostable time plus the dead time. Figure 10. PWM Current Controller Simplified Schematic VSA (or B) TO GATE LOGIC BLANKING TIME MONOSTABLE 1µs FROM THE LOW-SIDE GATE DRIVERS 2H 5mA S Q (0) (1) MONOSTABLE SET 1H IOUT BLANKER R OUT2A(or B) DRIVERS + DEAD TIME - DRIVERS + DEAD TIME + 5V 2 PHASE STEPPER MOTOR OUT1A(or B) 2.5V SENSE COMPARATOR 2L 1L + COMPARATOR OUTPUT RCA(or B) COFF ROFF - VREFA(or B) SENSEA(or B) RSENSE D01IN1332 Figure 11 shows the typical operating waveforms of the output current, the voltage drop across the sensing resistor, the RC pin voltage and the status of the bridge. More details regarding the Synchronous Rectification and the output stage configuration are included in the next section. Immediately after the Power MOS turns on, a high peak current flows through the sensing resistor due to the reverse recovery of the freewheeling diodes. The L6228 provides a 1µs Blanking Time tBLANK that inhibits the comparator output so that this current spike cannot prematurely re-trigger the monostable. 11/26 L6228 Figure 11. Output Current Regulation Waveforms IOUT VREF RSENSE tOFF tON tOFF 1µs tBLANK 1µs tBLANK VSENSE VREF Slow Decay 0 Slow Decay ay ay c Fast De c Fast De tRCRISE VRC tRCRISE 5V 2.5V tRCFALL tRCFALL 1µs tDT 1µs tDT ON OFF SYNCHRONOUS OR QUASI SYNCHRONOUS RECTIFICATION D01IN1334 B C D A B C D Figure 12 shows the magnitude of the Off Time tOFF versus COFF and ROFF values. It can be approximately calculated from the equations: tRCFALL = 0.6 · ROFF · COFF tOFF = tRCFALL + tDT = 0.6 · ROFF · COFF + tDT where ROFF and COFF are the external component values and tDT is the internally generated Dead Time with: 20KΩ ≤ ROFF ≤ 100KΩ 0.47nF ≤ COFF ≤ 100nF tDT = 1µs (typical value) Therefore: tOFF(MIN) = 6.6µs tOFF(MAX) = 6ms These values allow a sufficient range of tOFF to implement the drive circuit for most motors. The capacitor value chosen for COFF also affects the Rise Time tRCRISE of the voltage at the pin RCOFF. The Rise Time tRCRISE will only be an issue if the capacitor is not completely charged before the next time the monostable is triggered. Therefore, the on time tON, which depends by motors and supply parameters, has to be bigger than tRCRISE for allowing a good current regulation by the PWM stage. Furthermore, the on time tON can not be smaller than the minimum on time tON(MIN). 12/26 L6228 t O N > t O N ( MIN ) = 2.5µ s (typ. value) t O N > t RCRISE – t DT tRCRISE = 600 · COFF Figure 13 shows the lower limit for the on time tON for having a good PWM current regulation capacity. It has to be said that tON is always bigger than tON(MIN) because the device imposes this condition, but it can be smaller than tRCRISE - tDT. In this last case the device continues to work but the off time tOFF is not more constant. So, small COFF value gives more flexibility for the applications (allows smaller on time and, therefore, higher switching frequency), but, the smaller is the value for COFF, the more influential will be the noises on the circuit performance. Figure 12. tOFF versus COFF and ROFF 4 1 .10 R off = 100kΩ 3 1 .10 R off = 47kΩ toff [µs] R off = 20kΩ 100 10 1 0.1 1 10 100 Coff [nF] Figure 13. Area where tON can vary maintaining the PWM regulation. ton(min) [us] 100 10 2.5µs (typ. value) 1 0.1 1 10 100 Coff [nF] 13/26 L6228 DECAY MODES The CONTROL input is used to select the behavior of the bridge during the off time. When the CONTROL pin is low, the Fast Decay mode is selected and both transistors in the bridge are switched off during the off time. When the CONTROL pin is high, the Slow Decay mode is selected and only the low side transistor of the bridge is switched off during the off time. Figure 14 shows the operation of the bridge in the Fast Decay mode. At the start of the off time, both of the power MOS are switched off and the current recirculates through the two opposite free wheeling diodes. The current decays with a high di/dt since the voltage across the coil is essentially the power supply voltage. After the dead time, the lower power MOS in parallel with the conducting diode is turned on in synchronous rectification mode. In applications where the motor current is low it is possible that the current can decay completely to zero during the off time. At this point if both of the power MOS were operating in the synchronous rectification mode it would then be possible for the current to build in the opposite direction. To prevent this only the lower power MOS is operated in synchronous rectification mode. This operation is called Quasi-Synchronous Rectification Mode. When the monostable times out, the power MOS are turned on again after some delay set by the dead time to prevent cross conduction. Figure 15 shows the operation of the bridge in the Slow Decay mode. At the start of the off time, the lower power MOS is switched off and the current recirculates around the upper half of the bridge. Since the voltage across the coil is low, the current decays slowly. After the dead time the upper power MOS is operated in the synchronous rectification mode. When the monostable times out, the lower power MOS is turned on again after some delay set by the dead time to prevent cross conduction. Figure 14. Fast Decay Mode Output Stage Configurations A) ON TIME B) 1µs DEAD TIME D01IN1335 C) QUASI-SYNCHRONOUS RECTIFICATION D) 1µs SLOW DECAY Figure 15. Slow Decay Mode Output Stage Configurations A) ON TIME B) 1µs DEAD TIME D01IN1336 C) SYNCHRONOUS RECTIFICATION D) 1µs DEAD TIME STEPPING SEQUENCE GENERATION The phase sequence generator is a state machine that provides the phase and enable inputs for the two bridges to drive a stepper motor in either full step or half step. Two full step modes are possible, the Normal Drive Mode where both phases are energized each step and the Wave Drive Mode where only one phase is energized at a 14/26 L6228 time. The drive mode is selected by the HALF/FULL input and the current state of the sequence generator as described below. A rising edge of the CLOCK input advances the state machine to the next state. The direction of rotation is set by the CW/CCW input. The RESET input resets the state machine to state. HALF STEP MODE A HIGH logic level on the HALF/FULL input selects Half Step Mode. Figure 16 shows the motor current waveforms and the state diagram for the Phase Sequencer Generator. At Start-Up or after a RESET the Phase Sequencer is at state 1. After each clock pulse the state changes following the sequence 1,2,3,4,5,6,7,8,… if CW/ CCW is high (Clockwise movement) or 1,8,7,6,5,4,3,2,… if CW/CCW is low (Counterclockwise movement). NORMAL DRIVE MODE (Full-step two-phase-on) A LOW level on the HALF/FULL input selects the Full Step mode. When the low level is applied when the state machine is at an ODD numbered state the Normal Drive Mode is selected. Figure Fig. 17 shows the motor current waveform state diagram for the state machine of the Phase Sequencer Generator. The Normal Drive Mode can easily be selected by holding the HALF/FULL input low and applying a RESET. AT start -up or after a RESET the State Machine is in state1. While the HALF/FULL input is kept low, state changes following the sequence 1,3,5,7,… if CW/CCW is high (Clockwise movement) or 1,7,5,3,… if CW/CCW is low (Counterclockwise movement). WAVE DRIVE MODE (Full-step one-phase-on) A LOW level on the pin HALF/FULL input selects the Full Step mode. When the low level is applied when the state machine is at an EVEN numbered state the Wave Drive Mode is selected. Figure 18 shows the motor current waveform and the state diagram for the state machine of the Phase Sequence Generator. To enter the Wave Drive Mode the state machine must be in an EVEN numbered state. The most direct method to select the Wave Drive Mode is to first apply a RESET, then while keeping the HALF/FULL input high apply one pulse to the clock input then take the HALF/FULL input low. This sequence first forces the state machine to sate 1. The clock pulse, with the HALF/FULL input high advances the state machine from state 1 to either state 2 or 8 depending on the CW/CCW input. Starting from this point, after each clock pulse (rising edge) will advance the state machine following the sequence 2,4,6,8,… if CW/CCW is high (Clockwise movement) or 8,6,4,2,… if CW/ CCW is low (Counterclockwise movement). Figure 16. Half Step Mode IOUTA 3 4 2 1 5 6 8 IOUTB 7 Start Up or Reset CLOCK 1 2 3 4 5 6 7 8 D01IN1320 Figure 17. Normal Drive Mode IOUTA 3 4 2 1 5 IOUTB 6 8 7 CLOCK Start Up or Reset 1 3 5 7 1 3 5 7 D01IN1322 15/26 L6228 Figure 18. Wave Drive Mode IOUTA 3 4 5 IOUTB 6 2 1 7 8 CLOCK Start Up or Reset 2 4 6 8 2 4 6 8 D01IN1321 NON-DISSIPATIVE OVERCURRENT PROTECTION The L6228 integrates an Overcurrent Detection Circuit (OCD) for full protection. This circuit provides protection against a short circuit to ground or between two phases of the bridge. With this internal over current detection, the external current sense resistor normally used and its associated power dissipation are eliminated. Figure 19 shows a simplified schematic of the overcurrent detection circuit. To implement the over current detection, a sensing element that delivers a small but precise fraction of the output current is implemented with each high side power MOS. Since this current is a small fraction of the output current there is very little additional power dissipation. This current is compared with an internal reference current IREF. When the output current reaches the detection threshold (typically 2.8A) the OCD comparator signals a fault condition. When a fault condition is detected, the EN pin is pulled below the turn off threshold (1.3V typical) by an internal open drain MOS with a pull down capability of 4mA. By using an external R-C on the EN pin, the off time before recovering normal operation can be easily programmed by means of the accurate thresholds of the logic inputs. Figure 19. Overcurrent Protection Simplified Schematic OUT1A VSA OUT2A POWER SENSE 1 cell HIGH SIDE DMOSs OF THE BRIDGE A I1A POWER DMOS n cells TO GATE LOGIC µC or LOGIC POWER DMOS n cells POWER SENSE 1 cell + OCD COMPARATOR VDD I2A I1A / n I2A / n (I1A+I2A) / n REN. CEN. EN IREF INTERNAL OPEN-DRAIN RDS(ON) 40Ω TYP. OVER TEMPERATURE OCD COMPARATOR FROM THE BRIDGE B D01IN1337 16/26 L6228 Figure 20 shows the Overcurrent Detection operation. The Disable Time tDISABLE before recovering normal operation can be easily programmed by means of the accurate thresholds of the logic inputs. It is affected whether by CEN and REN values and its magnitude is reported in Figure 21. The Delay Time tDELAY before turning off the bridge when an overcurrent has been detected depends only by CEN value. Its magnitude is reported in Figure 22. CEN is also used for providing immunity to pin EN against fast transient noises. Therefore the value of CEN should be chosen as big as possible according to the maximum tolerable Delay Time and the REN value should be chosen according to the desired Disable Time. The resistor REN should be chosen in the range from 2.2KΩ to 180KΩ. Recommended values for REN and CEN are respectively 100KΩ and 5.6nF that allow obtaining 200µs Disable Time. Figure 20. Overcurrent Protection Waveforms IOUT ISOVER VEN VDD Vth(ON) Vth(OFF) VEN(LOW) ON OCD OFF ON tDELAY BRIDGE tDISABLE OFF tOCD(ON) tEN(FALL) tOCD(OFF) tD(OFF)EN tEN(RISE) tD(ON)EN D02IN1400 17/26 L6228 Figure 21. tDISABLE versus C EN and REN (VDD = 5V). R EN = 2 20 kΩ 3 1 .1 0 R EN = 1 00 kΩ R EN = 47 k Ω R EN = 33 k Ω tDISABLE [µs] R EN = 10 k Ω 100 10 1 1 10 100 C E N [n F ] Figure 22. tDELAY versus CEN (VDD = 5V). tdelay [µs] 10 1 0.1 1 10 Cen [nF] 100 THERMAL PROTECTION In addition to the Ovecurrent Protection, the L6228 integrates a Thermal Protection for preventing the device destruction in case of junction over temperature. It works sensing the die temperature by means of a sensible element integrated in the die. The device switch-off when the junction temperature reaches 165°C (typ. value) with 15°C hysteresis (typ. value). 18/26 L6228 APPLICATION INFORMATION A typical Bipolar Stepper Motor Driver application using L6228 is shown in Fig. 23. Typical component values for the application are shown in Table 2. A high quality ceramic capacitor in the range of 100 to 200 nF should be placed between the power pins (VSA and VSB) and ground near the L6228 to improve the high frequency filtering on the power supply and reduce high frequency transients generated by the switching. The capacitor connected from the EN input to ground sets the shut down time when an over current is detected (see Overcurrent Protection). The two current sensing inputs (SENSEA and SENSEB) should be connected to the sensing resistors with a trace length as short as possible in the layout. The sense resistors should be non-inductive resistors to minimize the di/dt transients across the resistor. To increase noise immunity, unused logic pins (except EN) are best connected to 5V (High Logic Level) or GND (Low Logic Level) (see pin description). It is recommended to keep Power Ground and Signal Ground separated on PCB. Table 2. Component Values for Typical Application C1 100µF D1 1N4148 C2 100nF D2 1N4148 CA 1nF RA 39KΩ CB 1nF RB 39KΩ CBOOT 220nF REN 100KΩ CP 10nF RP 100Ω CEN 5.6nF RSENSEA 0.6Ω CREF 68nF RSENSEB 0.6Ω Figure 23. Typical Application + VS 8-52VDC VSA C1 POWER GROUND - SIGNAL GROUND VSB C2 D1 CBOOT RP CP 20 17 VBOOT RSENSEB 11 VREFA VREF = 0-1V VREFB CREF VCP 22 D2 RSENSEA 24 SENSEA SENSEB OUT1A OUT2A 23 14 3 10 5 21 13 GND GND GND GND 18 12 1 HALF/FULL CLOCK FAST/SLOW DECAY HALF/FULL CLOCK CW/CCW CW/CCW CA 4 RCA RA CB 19 6 7 ENABLE CONTROL 8 16 RESET REN CEN 2 OUT2B EN 15 M OUT1B RESET 9 RCB D01IN1341 RB 19/26 L6228 Output Current Capability and IC Power Dissipation In Fig. 24, 25, 26 and 27 are shown the approximate relation between the output current and the IC power dissipation using PWM current control driving a two-phase stepper motor, for different driving sequences: – HALF STEP mode (Fig. 24) in which alternately one phase / two phases are energized. – NORMAL DRIVE (FULL-STEP TWO PHASE ON) mode (Fig. 25) in which two phases are energized during each step. – WAVE DRIVE (FULL-STEP ONE PHASE ON) mode (Fig. 26) in which only one phase is energized at each step. – MICROSTEPPING mode (Fig. 27), in which the current follows a sine-wave profile, provided through the Vref pins. For a given output current and driving sequence the power dissipated by the IC can be easily evaluated, in order to establish which package should be used and how large must be the on-board copper dissipating area to guarantee a safe operating junction temperature (125°C maximum). Figure 24. IC Power Dissipation versus Output Current in HALF STEP Mode. HALF STEP 10 IA I OUT 8 IB 6 PD [W] I OUT 4 Test Conditions: Supply Voltage = 24V No PWM f SW = 30 kHz (slow decay) 2 0 0 0.25 0.5 0.75 1 1.25 1.5 I OUT [A] Figure 25. IC Power Dissipation versus Output Current in NORMAL Mode (full step two phase on). NORM AL DRIVE IA 10 8 I OUT IB 6 I OUT PD [W ] 4 Test Conditions: Supply Volt age =24 V 2 0 0 0.25 0.5 0.75 1 I OUT [A ] 20/26 1.25 1.5 No PWM f SW = 30 kHz (slow decay) L6228 Figure 26. IC Power Dissipation versus Output Current in WAVE Mode (full step one phase on). WAVE DRIVE 10 IA I OUT 8 IB 6 PD [W] I OUT 4 Test Conditions: Supply Voltage = 24V 2 0 0 0.25 0.5 0.75 1 No PW M fSW = 3 0 kHz (slow decay) 1.25 1.5 I OUT [A] Figure 27. IC Power Dissipation versus Output Current in MICROSTEPPING Mode. MICROSTEPPING 10 IA I OUT 8 I OUT 6 IB PD [W] 4 2 0 0 0.25 0.5 0.75 1 I OUT [A] 1.25 1.5 Test Conditions: Supply Voltage = 24V f SW = 30 kHz (slow decay) f SW = 50 kHz (slow decay) Thermal Management In most applications the power dissipation in the IC is the main factor that sets the maximum current that can be delivered by the device in a safe operating condition. Therefore, it has to be taken into account very carefully. Besides the available space on the PCB, the right package should be chosen considering the power dissipation. Heat sinking can be achieved using copper on the PCB with proper area and thickness. Figures 28, 29 and 30 show the Junction-to-Ambient Thermal Resistance values for the PowerSO36, PowerDIP24 and SO24 packages. For instance, using a PowerSO package with copper slug soldered on a 1.5mm copper thickness FR4 board with 6cm2 dissipating footprint (copper thickness of 35µm), the Rth(j-amb) is about 35°C/W. Fig. 31 shows mounting methods for this package. Using a multi-layer board with vias to a ground plane, thermal impedance can be reduced down to 15°C/W. 21/26 L6228 Figure 28. PowerSO36 Junction-Ambient Thermal Resistance versus On-Board Copper Area. ºC / W 43 38 33 W ith o ut G ro u nd La yer 28 W ith Gro un d La yer W ith Gro un d La yer+ 16 via H o le s 23 On-Board Copper Area 18 13 1 2 3 4 5 6 7 8 9 10 11 12 13 s q. cm Figure 29. PowerDIP24 Junction-Ambient Thermal Resistance versus On-Board Copper Area. ºC / W On-Board Copper Area 49 48 C o p pe r Are a is o n Bo tto m S id e 47 C o p pe r Are a is o n To p S i de 46 45 44 43 42 41 40 39 1 2 3 4 5 6 7 8 9 10 11 12 s q . cm Figure 30. SO24 Junction-Ambient Thermal Resistance versus On-Board Copper Area. On-Board Copper Area ºC / W 68 66 64 62 60 C o pp er A re a is o n T op S id e 58 56 54 52 50 48 1 2 3 4 5 6 7 8 9 10 11 12 s q. cm Figure 31. Mounting the PowerSO Package. Slug soldered to PCB with dissipating area 22/26 Slug soldered to PCB with dissipating area plus ground layer Slug soldered to PCB with dissipating area plus ground layer contacted through via holes L6228 DIM. A a1 a2 a3 b c D (1) D1 E e e3 E1 (1) E2 E3 E4 G H h L N S MIN. mm TYP. 0.10 0 0.22 0.23 15.80 9.40 13.90 MAX. 3.60 0.30 3.30 0.10 0.38 0.32 16.00 9.80 14.50 inch TYP. MIN. 0.004 0 0.008 0.009 0.622 0.370 0.547 0.65 11.05 10.90 0.0256 0.435 11.10 0.429 2.90 6.20 0.228 3.20 0.114 0.10 0 15.90 0.610 1.10 1.10 0.031 10°(max.) 8 °(max.) 5.80 2.90 0 15.50 0.80 OUTLINE AND MECHANICAL DATA MAX. 0.141 0.012 0.130 0.004 0.015 0.012 0.630 0.385 0.570 0.437 0.114 0.244 0.126 0.004 0.626 0.043 0.043 PowerSO36 (1): "D" and "E1" do not include mold flash or protrusions - Mold flash or protrusions shall not exceed 0.15mm (0.006 inch) - Critical dimensions are "a3", "E" and "G". N N a2 e A DETAIL A A c a1 DETAIL B E e3 H DETAIL A lead D slug a3 36 BOTTOM VIEW 19 E3 B E1 E2 D1 DETAIL B 0.35 Gage Plane 1 1 -C- 8 S h x 45˚ b ⊕ 0.12 L SEATING PLANE G M AB PSO36MEC C (COPLANARITY) 23/26 L6228 mm DIM. MIN. TYP. A A1 inch MAX. MIN. TYP. 4.320 0.380 A2 0.170 0.015 3.300 0.130 B 0.410 0.460 0.510 0.016 0.018 0.020 B1 1.400 1.520 1.650 0.055 0.060 0.065 c 0.200 0.250 0.300 0.008 0.010 0.012 D 31.62 31.75 31.88 1.245 1.250 1.255 E 7.620 8.260 0.300 e 2.54 E1 6.350 e1 L 6.600 M 0.325 0.100 6.860 0.250 0.260 0.270 0.300 7.620 3.180 OUTLINE AND MECHANICAL DATA MAX. 3.430 0.125 0.135 Powerdip 24 0˚ min, 15˚ max. E1 A2 A A1 L B B1 e e1 D 24 13 c 1 12 M SDIP24L 24/26 L6228 mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. A 2.35 2.65 0.093 0.104 A1 0.10 0.30 0.004 0.012 B 0.33 0.51 0.013 0.200 C 0.23 0.32 0.009 0.013 D (1) 15.20 15.60 0.598 0.614 E 7.40 7.60 0.291 0.299 e 1.27 10.0 10.65 0.394 0.419 h 0.25 0;75 0.010 0.030 L 0.40 1.27 0.016 0.050 ddd Weight: 0.60gr 0.050 H k OUTLINE AND MECHANICAL DATA 0˚ (min.), 8˚ (max.) 0.10 0.004 (1) “D” dimension does not include mold flash, protusions or gate burrs. Mold flash, protusions or gate burrs shall not exceed 0.15mm per side. SO24 0070769 C 25/26 L6228 Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics. 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