Differential Axis

For information on ESD protection please see: >>>HERE<<<
Each differential axis output is made up of 7 components
- The Differential Driver IC which makes the differential Step and direction signals for the motor.
- The Step+ and the Step- has a TVS diode across it to help protect from static discharges and external voltages that may be accidentally applied to the outputs from external sources.
- The Direction+ and the Direction- has a TVS diode across it to help protect from static discharges and external voltages that may be accidentally applied to the outputs from external sources.
- The TVS diodes are do not affect the Step and Direction output from the Differential driver unless a voltage exceeding 5 volts is applied to it in which case it will permanently short circuit to MASSO GND to protect the Drive IC and at the same time will disable the driver output on that line. Note: The TVS diode package is a dual protection diode so it is possible to trip half of the IC disabling one line and not the other line.
- A tripped TVS diode package can range in look from normal to being burnt and testing can be done using the diode test on a multimeter.
- Because the TVS diode is not required for normal axis operation the diode can be removed from the board and axis operation will resume if this is the only fault. The Diode package can then be replaced or left off the board in which case it will continue to work but there will be no protection for the differential driver IC. If the Diode package is removed clean the pads and ensure that there are no solder bridges are present between pads.
- The Step + , Step - , Direction + and Direction - each pass through their own 0 ohm resistor which can act as a fuse in extreme cases.

X & Y axis Quadruple Differential Line Driver - TEXAS INSTRUMENTS - DS26LS31CM
Z axis Quadruple Differential Line Driver - TEXAS INSTRUMENTS - DS26LS31CM
A & B axis Quadruple Differential Line Driver - TEXAS INSTRUMENTS - DS26LS31CM
Step+ & Step- protection TVS diode - Bourns - CDSOT23-SM712
Direction+ & Direction- protection 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


Testing TVS diode - Bourns - CDSOT23-SM712
- The Protection diode packs can be tested using a meter set to Diode test as follows
- Turn MASSO Off and leave it off for all testing.
- Disconnect all wiring from the axis
- Set meter for Diode test mode
- Connect the Black meter lead to MASSO GND and using the Red meter lead measure the S+, S-, D+ & D- in turn
- All should read the same and show no reading eg OL on the meter. Some meters may show OL , 1 or -1 on the screen to indicate an open circuit. This is what you see on the screen when the meter is not connected to anything when in Diode mode.
NOTE: a reading a 0 indicates a short circuit. - Connect the Red meter lead to MASSO GND and using the Black meter lead measure the S+, S-, D+ & D- in turn.
- All 4 outputs should give the same reading of 0.67 nominal.
- Compare with a known good axis to ensure that you get the expected results
Testing Resistors - WALSIN - WR04X000 PTL
- There are 4 protection resistors per Axis, one for each pin on the output and they can act as a fuse i extreme cases.
- The resistors can be tested by measuring continuity between the output pin and each side of the appropriate resistor.
Blue S+
Green S-
Red D+
Yellow D- - Continuity tests can also be done from the output pin all the way to the Differential Driver IC output pin to ensure continuity.
- Compare with a known good axis to ensure that you get the expected results