8

Section 3

Operation of the IM2000S

Section Over view

This section covers the operation of the various circuits contained within the IM2000S Microstepping Controller ASIC.

These are:

!

Protection Inputs

!

Microstep Select (MSEL) Inputs

!

Step/Direction Inputs

!

Chip Select (CSEL) Input

!

Full Step Output

!

Dual PWM

!

Power Control Outputs

!

Controling the Output Current

!

Chopping Oscillator

!

Reset Input

!

External Look-up Table

!

Buss/Standalone Mode

Pr otection Inputs

The IM2000S has four inputs which will disable the PWM and driver control outputs to protect against external faults.

These inputs include:

!

Over Temperature

!

Phase A and Phase B Short Circuit

!

Over Voltage

All four inputs are buffered using Schmitt triggered buffers and are internally AND’ed together. These inputs may be

used independently or tied together for wired OR’ed protection circuits. Unused inputs must be tied to a logic HIGH

state.

Upon detection of a fault condition the IM2000S will latch the condition and set the fault output pin to a logic HIGH

state. At this time the phase control outputs, phase enable outputs and PWM are disabled. The IM2000S must be reset by

either pulling the reset input LOW, or cycling power to clear the fault condition and re-enable the PWM and driver

control outputs. Figures 3.1 and 3.2 illustrate possible application/interface of the overcurrent and over temperature

inputs.

Figure 3.1: Overcurrent Protection Example

Figure 3.2: Thermal Protection Example

+5V

Thermostat

Output to

OVTMP

10 kOhm

10 kOhm

Output to

OVCA/OVCB

Comparator

Input from

Sense Resistor

+5V

*

*Set Reference for

Maximum

Allowable Current

+5V

_

+