For information on ESD protection, please see: HERE

Differential Axis Overview

Each differential axis output consists of seven key components:

1. Differential Driver IC
   Generates the differential Step and Direction signals for the motor.

    

2. Step+ and Step- TVS Protection Diode
   A TVS diode is connected across Step+ and Step- to protect against static discharge and accidental external voltages.

    

3. Direction+ and Direction- TVS Protection Diode
   A TVS diode is connected across Direction+ and Direction- for the same protection.

    

4. TVS Diode Operation
   The TVS diodes do not affect normal Step and Direction signals.
   If a voltage exceeding 5 V is applied, the diode will permanently short to MASSO GND to protect the driver IC.
   This will disable the affected output line.

    

   Note: The TVS diode package contains dual protection diodes. It is possible for only one line to fail while the other continues to operate.

    

5. TVS Diode Failure Identification
   A failed TVS diode may appear visually normal or burnt.
   Testing must be performed using a multimeter in diode test mode.

    

6. TVS Diode Removal
   The TVS diode is not required for normal axis operation.
   If it is the only fault, removing the diode will restore axis function.
   The diode may be replaced or left off the board.
   If left off, the axis will operate normally but without ESD protection.

    

   When removing the diode, clean the pads and ensure no solder bridges remain.

    

7. 0-Ohm Protection Resistors
   Step+ , Step- , Direction+ , and Direction- each pass through a 0-ohm resistor, which can act as a fuse in extreme fault conditions.

Components Used

	X & Y Axis Differential Driver – Texas Instruments – DS26LS31CM
	Z Axis Differential Driver – Texas Instruments – DS26LS31CM
	A & B Axis Differential Driver – Texas Instruments – DS26LS31CM
	Step+/Step- TVS Diode – Bourns – CDSOT23-SM712
	Direction+/Direction- TVS Diode – Bourns – CDSOT23-SM712
	Step+ 0-ohm Resistor – WALSIN – WR04X000 PTL
	Step- 0-ohm Resistor – WALSIN – WR04X000 PTL
	Direction+ 0-ohm Resistor – WALSIN – WR04X000 PTL
	Direction- 0-ohm Resistor – WALSIN – WR04X000 PTL

Identifying components on the Board

	X Axis
	Y Axis
	Z Axis
	A Axis
	B Axis
	14 Pin Chip
	14 Pin Chip
	14 Pin Chip

Testing TVS Diodes - Bourns – CDSOT23-SM712

TVS diode packs can be tested using a multimeter set to Diode Test mode.

Test Procedure

• Turn MASSO OFF and leave it off for all testing.

• Disconnect all axis wiring.

• Set the meter to Diode Test mode.

   

Test 1

• Connect the black probe to MASSO GND.

• Use the red probe to measure S+ , S- , D+ , D- individually.

• All readings should show open circuit (OL, 1, or -1 depending on meter).

• Note: A reading of 0 indicates a short circuit.

   

Test 2

• Connect the red probe to MASSO GND.

• Use the black probe to measure S+ , S- , D+ , D- individually.

• All outputs should read approximately 0.67 V.

• Compare results with a known good axis.

Testing Protection Resistors - WALSIN – WR04X000 PTL

Each axis contains four 0-ohm protection resistors, one per output:

	S+
	S-
	D+
	D-

Test Procedure

• Measure continuity between the output pin and each side of the corresponding resistor.

• Continuity can also be checked from the output pin through to the Differential Driver IC output pin.

Compare results with a known good axis.