TB62217AFG Datasheet, PDF (58/61 Pages) Toshiba Semiconductor – PWM drive Stepping Motor Driver / Brush DC Motor Driver Selectable, DC-DC Converter and Reset function IC

Operating Time of The Motor Over Current Protection Circuit
(ISD dead band time and ISD operating time)
TB62217AFG
fosc_M oscillation
(chopping reference waveform)
Output stop (RESET state)

Fosc
(OSC_M)
Dead band time
ISD BLANK time

min
max
ISD operating time

Time when over current starts flowing through the output stage (over current state start)

Reference diagram: Timing chart showing over current flowing through a motor
The over current protection circuit has the dead band time to avoid detecting over current accidentally from
current spikes in switching. The dead band time is in synchronization with the frequency of the OSC for setting
up the chopping frequency (OSC_M).
The time between the instant when over current starts flowing through the output stage and the instant
when the output stops is as follows:
When dead band time = 4 × fosc_M period
Minimum: 4 × fosc_M period
Maximum: 8 × fosc_M period (+ synchronization time + 1 fosc_M time)
However, the operating time stated above applies when the over current flows ideally. The over current circuit
may not work depending on the output control mode and timing.
Therefore, a protection fuse needs to be inserted in the VM power supply.
(The required rating of the fuse varies depending on the conditions under which the IC is used. Therefore,
select a rating that will not cause the maximum power dissipation of the IC to be exceeded and that will not
pose any problem.)
58
2004-11-12