AMIS-30421 Datasheet, PDF (24/41 Pages) ON Semiconductor – Micro-Stepping Stepper Motor Bridge Controller

AMIS−30421
VBB
t
VERRb
t
Charge Pump Failure
during start up
Charge Pump Failure longer than 250 us
due to slow voltage slope Error is latched.
Figure 23. Charge Pump Failure
Watchdog
When V_BB is applied, the WDb−pin is kept low for t_por
(Table 5). This can for instance be used to reset an external
microcontroller at power up.
The WDb−pin also has a second function, a Watchdog
function. When the watchdog is enabled (<WDEN> = ‘1’),
a timer will start counting up. When the counter reaches a
certain value (<WDT[3:0]>), the <WD> SPI bit will be set
and the WDb−pin will be pulled low for a time equal to t_POR
to reset the external microcontroller. To avoid that the
microcontroller gets reset, the microcontroller needs to
re−enable the watchdog before the count value is reached (=
write ‘1’ to <WDEN> before <WDT[3:0]> is reached). This
functionality can be used to reset a “stuck” microcontroller.
The SPI bit <WD> can be used to detect a cold or warm
boot. When powering the application (cold boot), <WD>
will be zero. If the microcontroller has been reset by the
WDb−pin (warm boot), <WD> bit will be ‘1’. The
microcontroller can use this information to detect a cold or
warm boot.
It’s forbidden to re−enable the watchdog too fast
(minimum time between re−enabling must be above t_WDPR
(see Figure 4)). One may also not enable the watchdog too
fast after power up (see t_DSPI, Figure 4).
A small analogue filter avoids resetting due to spikes or
noise on the VDD supply (t_rf).
During and after power up the WDb−pin is an open drain
output. One can change this to a push−pull output by using
SPI bit <IO_OT>.
Error Output
The error output (ERRb−pin) will be activated if an error
is reported. Next errors will be reported:
• Thermal Warning
• Thermal Shutdown
• Overcurrent
• Open Coil
• Charge Pump Failure
• All errors except a Thermal Warning will disable the
H−bridge drivers to protect the motor driver
(<MOTEN> = ‘0’). To reset the error one needs to read
out the error. Only when all errors are reset it will be
possible to re−enable the motor driver (<MOTEN> =
‘1’).
Keep in mind that during power up a charge pump failure
will be reported during the first 250us but will not be latched
(see also Charge Pump Failure).
During and after power up the ERRb−pin is an open drain
output. One can change this to a push−pull output with SPI
bit <IO_OT>.
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