Behavioural mixed-signal modelPololu #1182 (A4988 carrier)a4988_module
A4988 stepper driver module
Microstepping driver for one bipolar stepper motor, 8–35 V, up to 2 A per coil (about 1 A without heatsink). Each rising edge on STEP moves one step in the direction of DIR; MS1–MS3 select full, half, quarter, eighth or sixteenth steps. The coil current is chopped (30 µs off-time, mixed decay) to I = VREF / (8 · 0.068 Ω) · sin/cos of the step angle; set VREF with the trimmer. ENABLE high switches the outputs off; RESET and SLEEP must be high (tie RST to SLP).
Key data
- Category
- Modules
- Simulation model
- Behavioural mixed-signal model
- Manufacturer part number
- Pololu #1182 (A4988 carrier)
- Reference prefix
- U
- Pins
- 16
- Land pattern
- Pololu_Breakout-16_15.2x20.3mm
Simulation model
A behavioural model implements the interface of the chip (registers, protocol, timing) at its pins. The pins are connected to the analog circuit like CMOS pins.
- Model
- a4988
- Supply pins
- 2 / 1
Pins 16
| Pin | Name | Use |
|---|---|---|
| 9 | ENInput pin | Enable, active low: high switches the outputs off |
| 10 | MS1Input pin | Microstep select 1 |
| 11 | MS2Input pin | Microstep select 2 |
| 12 | MS3Input pin | Microstep select 3 |
| 13 | RSTInput pin | Reset, active low: tie to SLP for normal operation |
| 14 | SLPInput pin | Sleep, active low: high = driver on |
| 15 | STEPInput pin | Step pulse: each rising edge moves one (micro)step |
| 16 | DIRInput pin | Direction of rotation |
| 8 | VMOTSupply pin | Motor supply 8–35 V: 100 µF close to the module |
| 7 | GNDGround pin | Motor ground |
| 6 | 2BOutput pin | Coil 2 (B) terminal |
| 5 | 2AOutput pin | Coil 2 (B) terminal |
| 4 | 1AOutput pin | Coil 1 (A) terminal |
| 3 | 1BOutput pin | Coil 1 (A) terminal |
| 2 | VDDSupply pin | Logic supply 3–5.5 V |
| 1 | GNDGround pin | Logic ground |
Parameters 2
VREF (trimmer)
vrefliveDefault0.544 V
Current limit I = VREF / (8 · RS): 0.544 V = 1 A
Current sense resistors
rsDefault0.068 Ω
Pololu carriers since 2017: 0.068 Ω (older green boards 0.05 Ω)
PCB
Verified land pattern
Pololu_Breakout-16_15.2x20.3mm