Actuator modules

AXA-002 — DRV8871 high-current DC motor driver PMOD module

Catalog #2 in the AruviX actuator line, level L2. TI DRV8871 single H-bridge: 3.6 A peak, 6.5–45 V, resistor-programmed current limit — the feature the TB6612 slot (AXA-001) lacks.

Level L2 ERC clean DRC clean Fab package 8 components

3D render of the AXA-002 PCB — Rendered from the PCB layout. No physical board has been manufactured.

Circuit review & bench-test guide →

Components#

Every placed component, with the reason it is on the board. Extracted directly from the schematic, so this cannot drift from the design.

Ref	Value	What it does on this board	Part number	Footprint
`C1`	10uF 50V X7R	VM bulk reservoir for motor switching current	`GRM31CR71H106KA12L` Murata	`C_1210_3225Metric`
`C2`	10uF 50V X7R	VM bulk reservoir for motor switching current	`GRM31CR71H106KA12L` Murata	`C_1210_3225Metric`
`C3`	100nF 50V X7R	VM high-frequency decoupling at the driver (50 V rated for the 45 V rail)	`GRM188R71H104KA93D` Murata	`C_0603_1608Metric`
`J1`	PMOD PLUG 2x6	PMOD peripheral plug (Digilent spec 1.2)	not selected generic	`PinHeader_2x06_P2.54mm_Horizontal`
`J2`	VM IN 6.5-45V	Motor supply input: 1 VM (6.5-45 V), 2 GND (joins PMOD GND here)	not selected Phoenix Contact	`TerminalBlock_Phoenix_MKDS-1,5-2-5.08_1x02_P5.08mm_Horizontal`
`J3`	MOTOR	Motor output: 1 OUT1, 2 OUT2	not selected Phoenix Contact	`TerminalBlock_Phoenix_MKDS-1,5-2-5.08_1x02_P5.08mm_Horizontal`
`R1`	30.9k 1%	Current-limit set: I_TRIP = 64 V / R_ILIM(kOhm) = 2.07 A	`RC0603FR-0730K9L` Yageo Datasheet ↗	`R_0603_1608Metric`
`U1`	DRV8871DDA	Brushed DC motor driver, 3.6 A peak, 6.5-45 V, resistor-set current limit	`DRV8871DDA` Texas Instruments Datasheet ↗	`Texas_HTSOP-8-1EP_3.9x4.9mm_P1.27mm_EP2.95x4.9mm_Mask2.4x3.1mm_ThermalVias`

Signals#

Net labels used in the schematic, which are also the names the HDL top level should use.

3V3 GND ILIM IN1 IN2 OUT1 OUT2 VMOT

Production status#

Schematic ERC	0 violations
PCB layout	complete
DRC	0 violations
Fab package	exported (24 gerbers + drill + CPL + BOM)
Fabricated	no — design stage only

Source: boards/actuator-modules/axa-002-hc-motor

Catalog #2 in the AruviX actuator line (../README.md), level L2. TI DRV8871 single H-bridge: 3.6 A peak, 6.5–45 V, resistor-programmed current limit — the feature the TB6612 slot (AXA-001) lacks.

Status: schematic generated, ERC clean (0/0), netlist reviewed. PCB layout not started. Not released.

What it teaches#

High-current PWM drive with hardware current regulation: the IN1/IN2 truth table (forward / reverse / brake / coast), and why a stalled motor does not smoke the driver — when winding current reaches I_TRIP the bridge chops automatically. Compare stall behaviour against AXA-001 to see the lesson.

Design#

DRV8871DDA (TI), HTSOP-8 with PowerPAD.
Motor power (VM, 6.5–45 V) enters on the J2 screw terminal only — never through the PMOD. Grounds join on the module.
6.5 V minimum: the DRV8871 UVLO sits at ~6.5 V, so this module will not run from a 5 V USB brick. Use 2S/3S LiPo, 12 V, or 24 V supplies.
Current limit: DRV8871 datasheet formula I_TRIP (A) = 64 V / R_ILIM (kΩ). Fitted R1 = 30.9 kΩ (E96, RC0603FR-0730K9L) → I_TRIP = 64 / 30.9 = 2.07 A. Swap R1 to move the limit (e.g. 21.0 k → 3.0 A, 64 k → 1.0 A).
Bulk: 2× 10 µF 50 V X7R 1210 (GRM31CR71H106KA12L) + 100 nF 50 V 0603 (GRM188R71H104KA93D) on VM — all rated for the full 45 V rail.
Motor output OUT1/OUT2 → J3 (MKDS 1x02 screw terminal).
Both PMOD lines are host-driven, so no 100 Ω series resistors (the line rule applies to module-driven lines only).
Flyback: internal H-bridge body diodes (line flyback rule satisfied internally).
Line-rule exception (documented, same as AXA-001): the DRV8871 has no fault output pin, so no fault signal returns to the PMOD. Current limiting is internal and autonomous.

PMOD pin	1	2	3	4	5	6	7	8	9	10	11	12
Net	IN1	IN2	NC	NC	GND	3V3	NC	NC	NC	NC	GND	3V3

IN1/IN2: 10 forward, 01 reverse, 11 brake (low-side slow decay), 00 coast (device sleeps after 1 ms).

Regenerate#

python3 generate_design.py

Remaining for release#

[ ] PCB layout (20 × 40 mm actuator outline, PowerPAD thermal vias), DRC, fab outputs
[ ] hdl/: pwm_gen + direction controller reuse from AXA-001, testbench, ECP5 demo
[ ] BOM export and availability check, design-review checklist