In the world of bipolar stepper motors, what is dead time and blanking time?
"Dead time" is the time in a half bridge driver between say the top switch being turned off and the bottom switch being turned on.


In  a half bridge driver a top switch can connect one side of the load to V+ and a low switch can connect the same point to ground. 

If both switches are turned on at once then V+ is connected to ground via the two switches.
This is a generally undesired situation :-).
This is known as 'shoot through" for obvuiousish reasons and "is to be avoided".

To stop this happening the drive logic is arranged to never allow both switches to be turned on at the same time. When a half bridge output is switched from say high (top on, bottom off) to low (bottom on, top off) a delay is inserted in the middle of the transition . Both switches are turned off for this period.  


"Blanking time" is a period when an input is ignored by the system so that transients which occur at this point will not disturb proper measurement. 


"Blanking" is often used on a current sense or voltage sense input at the beginning of a cycle when the switching transient is still settling.

For example, if a stepper motor phase is enabled an another is disabled, there will often be switching spikes on the current waveform.  These may be due to incomplete mutual coupling between inductors in a system (leakage inductance) or to parasitic capacitances charging or discharging.

If a current limit is set, then if the spike are sensed by the monitoring circuitry the IC may "trip" incorrectly. If the input is ignored for a set period after switching until transients will/should have settled or been damped then the actual current can be sensed.




Note that while the terms are usually used as above, other variations may be used. eg It is not unknown for the term "blanking time" to be used to cover the situation described under "dead time" above. This is not usual but needs to be known . Here is an example where the term blanking time is used extensively BUT what is meant is dead time or time between two switching actions. This may have been caused by translation into English. 

Here is a normal use of the term blanking time

International Rectifier - Using The Current Sensing IR212X Gate Drive IC

This example is typical enought to be worth quoting. In this case the blanking time is not at the start of the cycle but is used to deal with transients from the start of the cycle. 


A typical connection for the IR2125 is shown in fig 2). The typical connection for the IR2121 is similar, but this
time its a low side drive and no bootstrap diode is needed (pin 1 &amp; pin 8 are connected internally) . Again the
CS pin is the pin used for sensing the current. 

Again there is a blanking time to ensure there is no nuisance
tripping, but the operation is slightly different. When the voltage at the CS pin reaches the threshold (230mV
nominal), the IC will detect the overcurrent condition. At this point the IC will wait for a time equal to the
blanking time (500ns nominal) to filter out the noise spike caused by the switching action of the power device.

After the blanking time has elapsed if a CS voltage above the threshold is still present, the output driver is
switched into a linear mode with a feedback amplifier controlling the output gate drive voltage. The amplifier
and the output power switch form a negative feedback loop which controls and settles the gate drive voltage to
a lower value in order to keep the switch current limited to the preset value determined by the sensing resistor
between the CS pin and VS(IR21