®L297STEPPER MOTOR CONTROLLERSNORMAL/WAVE DRIVEHALF/FULL STEP MODESCLOCKWISE/ANTICLOCKWISE DIRECTIONSWITCHMODE LOAD CURRENT REGULA-TIONPROGRAMMABLE LOAD CURRENTFEW EXTERNAL COMPONENTSRESET INPUT & HOME OUTPUTENABLE INPUTDESCRIPTIONThe L297 Stepper Motor Controller IC generatesfour phase drive signals for two phase bipolar andfour phase unipolar step motors in microcomputer-controlled applications. The motor can be driven inhalf step, normal and wawe drive modes and on-chip PWM chopper circuits permit switch-modecontrol of the current in the windings. A feature ofDecember 2001Symbol Parameter Value UnitVsSupply voltage 10 VViInput signals 7VPtotTotal power dissipation (Tamb = 70°C)1WTstg, TjStorage and junction temperature -40 to + 150°CABSOLUTE MAXIMUM RATINGSthis device is that it requires only clock, directionand mode input signals. Since the phase are gen-erated internally the burden on the microprocessor,and the programmer, is greatly reduced. Mountedin DIP20 and SO20 packages, the L297 can beused with monolithic bridge drives such as theL298N or L293E, or with discrete transistors anddarlingtons.TWO PHASE BIPOLAR STEPPER MOTOR CONTROL CIRCUIT DIP20 SO20ORDERING NUMBERS : L297/1 (DIP20) L297D (SO20)1/11PIN CONNECTION (Top view)BLOCK DIAGRAM (L297/1 - L297D)2/11L297/1L297DL297N°NAME FUNCTION1 SYNC Output of the on-chip chopper oscillator.The SYNC connections The SYNC connections of all L297s to besynchronized are connected together and the oscillatorcomponents are omitted on all but one. If an external clock sourceis used it is injected at this terminal.2 GND Ground connection.3 HOME Open collector output that indicates when the L297 is in its initialstate (ABCD = 0101).The transistor is open when this signal is active.4 A Motor phase A drive signal for power stage.5INH1 Active low inhibit control for driver stage of A and B phases.When a bipolar bridge is used this signal can be used to ensurefast decay of load current when a winding is de-energized. Alsoused by chopper to regulate load current if CONTROL input is low.6 B Motor phase B drive signal for power stage.7 C Motor phase C drive signal for power stage.8INH2 Active low inhibit control for drive stages of C and D phases.Same functions as INH1.9 D Motor phase D drive signal for power stage.10 ENABLE Chip enable input. When low (inactive) INH1, INH2, A, B, C and Dare brought low.11 CONTROL Control input that defines action of chopper.When low chopper acts on INH1 and INH2; when high chopperacts on phase lines ABCD.12 Vs5V supply input.13 SENS2Input for load current sense voltage from power stages of phasesC and D.14 SENS1Input for load current sense voltage from power stages of phasesA and B.15 VrefReference voltage for chopper circuit. A voltage applied to this pindetermines the peak load current.16 OSCAn RC network (R to VCC, C to ground) connected to this terminaldetermines the chopper rate. This terminal is connected to groundon all but one device in synchronized multi - L297 configurations. f≅ 1/0.69 RC17 CW/CCW Clockwise/counterclockwise direction control input.Physical direction of motor rotation also depends on connectionof windings.Synchronized internally therefore direction can be changed at anytime.18CLOCK Step clock. An active low pulse on this input advances the motorone increment. The step occurs on the rising edge of this signal.PIN FUNCTIONS - L297/1 - L297D3/11L297N°NAME FUNCTION19 HALF/FULL Half/full step select input. When high selects half step operation,when low selects full step operation. One-phase-on full step modeis obtained by selecting FULL when the L297’s translator is at aneven-numbered state.Two-phase-on full step mode is set by selecting FULL when thetranslator is at an odd numbered position. (The home position isdesignate state 1).20RESET Reset input. An active low pulse on this input restores thetranslator to the home position (state 1, ABCD = 0101).PIN FUNCTIONS - L297/1 - L297D (continued)CIRCUIT OPERATIONThe L297 is intended for use with a dual bridgedriver, quad darlington array or discrete powerdevices in step motor driving applications. It re-ceives step clock, direction and mode signals fromthe systems controller (usually a microcomputerchip) and generates control signals for the powerstage.The principal functions are a translator, which gen-erates the motor phase sequences, and a dualPWM chopper circuit which regulates the current inthe motor windings. The translator generates threedifferent sequences, selected by the HALF/FULLinput. These are normal (two phases energised),wave drive (one phase energised) and half-step(alternately one phase energised/two phases en-ergised). Two inhibit signals are also generated bythe L297 in half step and wave drive modes. Thesesignals, which connect directly to the L298’s enableinputs, are intended to speed current decay whena winding is de-energised. When the L297 is usedto drive a unipolar motor the chopper acts on theselines.An input called CONTROL determines whether thechopper will act on the phase lines ABCD or theinhibit lines INH1 and INH2. When the phase linesare chopped the non-active phase line of each pair(AB or CD) is activated (rather than interrupting theline then active). In L297 + L298 configurations thistechnique reduces dissipation in the load currentsense resistors.A common on-chip oscillator drives the dual chop-per. It supplies pulses at the chopper rate which setthe two flip-flops FF1 and FF2. When the current ina winding reaches the programmed peak value thevoltage across the sense resistor (connected toone of the sense inputs SENS1 or SENS2) equalsVref and the corresponding comparator resets itsflip flop, interrupting the drive current until the nextoscillator pulse arrives. The peak current for bothwindings is programmed by a voltage divider on theVref input.Ground noise problems in multiple configurationscan be avoided by synchronising the chopper os-cillators. This is done by connecting all the SYNCpins together, mounting the oscillator RC networkon one device only and grounding the OSC pin onall other devices.Symbol Parameter DIP20 SO20 UnitRth-j-ambThermal resistance junction-ambient max 80 100°C/WTHERMAL DATA4/11L297MOTOR DRIVING PHASE SEQUENCESThe L297’s translator generates phase sequencesfor normal drive, wave drive and half step modes.The state sequences and output waveforms forthese three modes are shown below. In all casesthe translator advances