Datasheet
Table Of Contents
- Table 1. Device summary
- 1 Block diagram
- 2 Electrical data
- 3 Electrical characteristics
- 4 Pin connection
- 5 Typical applications
- 6 Functional description
- 6.1 Device power-up
- 6.2 Logic I/O
- 6.3 Charge pump
- 6.4 Microstepping
- 6.5 Absolute position counter
- 6.6 Programmable speed profiles
- 6.7 Motor control commands
- 6.8 Internal oscillator and oscillator driver
- 6.9 Overcurrent detection
- 6.10 Undervoltage lockout (UVLO)
- 6.11 Thermal warning and thermal shutdown
- 6.12 Reset and standby
- 6.13 External switch (SW pin)
- 6.14 Programmable DMOS slew rate, deadtime and blanking time
- 6.15 Integrated analog-to-digital converter
- 6.16 Internal voltage regulator
- 6.17 BUSY\SYNC pin
- 6.18 FLAG pin
- 7 Phase current control
- 8 Serial interface
- 9 Programming manual
- 9.1 Registers and flags description
- Table 9. Register map
- 9.1.1 ABS_POS
- 9.1.2 EL_POS
- 9.1.3 MARK
- 9.1.4 SPEED
- 9.1.5 ACC
- 9.1.6 DEC
- 9.1.7 MAX_SPEED
- 9.1.8 MIN_SPEED
- 9.1.9 FS_SPD
- 9.1.10 KVAL_HOLD, KVAL_RUN, KVAL_ACC and KVAL_DEC
- 9.1.11 INT_SPEED
- 9.1.12 ST_SLP
- 9.1.13 FN_SLP_ACC
- 9.1.14 FN_SLP_DEC
- 9.1.15 K_THERM
- 9.1.16 ADC_OUT
- 9.1.17 OCD_TH
- 9.1.18 STALL_TH
- 9.1.19 STEP_MODE
- 9.1.20 ALARM_EN
- 9.1.21 CONFIG
- Table 22. CONFIG register
- Table 23. Oscillator management
- Table 24. External switch hard stop interrupt mode
- Table 25. Overcurrent event
- Table 26. Programmable power bridge output slew rate values
- Table 27. Motor supply voltage compensation enable
- Table 28. PWM frequency: integer division factor
- Table 29. PWM frequency: multiplication factor
- Table 30. Available PWM frequencies [kHz]: 8-MHz oscillator frequency
- Table 31. Available PWM frequencies [kHz]: 16-MHz oscillator frequency
- Table 32. Available PWM frequencies [kHz]: 24-MHz oscillator frequency
- Table 33. Available PWM frequencies [kHz]: 32-MHz oscillator frequency
- 9.1.22 STATUS
- 9.2 Application commands
- Table 37. Application commands
- 9.2.1 Command management
- 9.2.2 Nop
- 9.2.3 SetParam (PARAM, VALUE)
- 9.2.4 GetParam (PARAM)
- 9.2.5 Run (DIR, SPD)
- 9.2.6 StepClock (DIR)
- 9.2.7 Move (DIR, N_STEP)
- 9.2.8 GoTo (ABS_POS)
- 9.2.9 GoTo_DIR (DIR, ABS_POS)
- 9.2.10 GoUntil (ACT, DIR, SPD)
- 9.2.11 ReleaseSW (ACT, DIR)
- 9.2.12 GoHome
- 9.2.13 GoMark
- 9.2.14 ResetPos
- 9.2.15 ResetDevice
- 9.2.16 SoftStop
- 9.2.17 HardStop
- 9.2.18 SoftHiZ
- 9.2.19 HardHiZ
- 9.2.20 GetStatus
- 9.1 Registers and flags description
- 10 Package information
- 11 Revision history
Phase current control L6470
34/73 DocID16737 Rev 7
7 Phase current control
The L6470 controls the phase current applying a sinusoidal voltage to motor windings.
Phase current amplitude is not directly controlled but depends on phase voltage amplitude,
load torque, motor electrical characteristics and rotation speed. Sinewave amplitude is
proportional to the motor supply voltage multiplied by a coefficient (K
VAL
). K
VAL
ranges from
0 to 100% and the sinewave amplitude can be obtained through the following formula:
Equation 1
Different K
VAL
values can be programmed for acceleration, deceleration and constant speed
phases and when the motor is stopped (HOLD phase) through the KVAL_ACC, KVAL_DEC,
KVAL_RUN and KVAL_HOLD registers (see Section 9.1.10 on page 44). KVAL value is
calculated according to the following formula:
Equation 2
where K
VAL_X
is the starting K
VAL
value programmed for present motion phase (KVAL_ACC,
KVAL_DEC, KVAL_RUN or KVAL_HOLD), BEMF_COMP is the BEMF compensation curve
value, VSCOMP and K_THERM are the motor supply voltage and winding resistance
compensation factors and microstep is the current microstep value (fraction of target peak
current).
The L6470 device offers various methods to guarantee a stable current value, allowing the
compensation of:
low speed optimization (Section 7.3)
back electromotive force value (Section 7.4)
motor supply voltage variation (Section 7.5)
windings resistance variation (Section 7.6).
7.1 PWM sinewave generators
The two voltage sinewaves applied to the stepper motor phases are generated by two PWM
modulators.
The PWM frequency (f
PWM
) is proportional to the oscillator frequency (f
OSC
) and can be
obtained through the following formula:
Equation 3
'N' is the integer division factor and 'm' is the multiplication factor. 'N' and 'm' values can be
programmed by the F_PWM_INT and F_PWM_DEC parameters in the CONFIG register
(see Table 28 on page 52 and Table 29 on page 52, Section 9.1.21 on page 49).
Available PWM frequencies are listed in Section 9.1.21 from Table 30 on page 53 to
Table 33 on page 54.
V
OUT
V
S
K
VAL
=
K
VAL
K
VAL_X
BEMF_COMP+VSCOMP K_THERMmicrostep=
f
PWM
f
OSC
512 N
------------------ m=