Data Sheet

AMIS−30543
http://onsemi.com
29
Error Output
This is a digital output to flag a problem to the external
microcontroller. The signal on this output is active low and
the logic combination of:
NOT(ERRB) = <TW> OR <TSD> OR <OVCXij> OR
<OVCYij> OR <OPENi> OR <CPFAIL>
Logic Supply Regulator
AMIS−30543 has an on−chip 5 V low−drop regulator
with external capacitor to supply the digital part of the chip,
some low−voltage analog blocks and external circuitry. The
voltage level is derived from an internal bandgap reference.
To calculate the available drive−current for external
circuitry, the specified I
load
should be reduced with the
consumption of internal circuitry (unloaded outputs) and the
loads connected to logic outputs. See Table 4. DC
parameters
Power−On Reset (POR) Function
The open drain output pin POR
/WD provides an “active
low” reset for external purposes. At powerup of
AMIS−30543, this pin will be kept low for some time to reset
for example an external microcontroller. A small analogue
filter avoids resetting due to spikes or noise on the V
DD
supply.
t
PU
t
POR
t
RF
VBB
V
DDH
VDD
V
DDL
t
PD
<t
RF
t
t
POR/WD pin
Figure 16. Power−on−Reset Timing Diagram
Watchdog Function
The watchdog function is enabled/disabled through
<WDEN> bit (Table 11: SPI CONTROL REGISTERS).
Once this bit has been set to “1” (watchdog enable), the
microcontroller needs to re−write this bit to clear an internal
timer before the watchdog timeout interval expires. In case
the timer is activated and WDEN is acknowledged too early
(before t
WDPR
) or not within the interval (after t
WDTO
), then
a reset of the microcontroller will occur through POR
/WD
pin. In addition, a warm/cold boot bit <WD> is available (see
Tables 14 and 15) for further processing when the external
microcontroller is alive again.
CLR pin (=Hard Reset)
Logic 0 on CLR pin allows normal operation of the chip.
To reset the complete digital inside AMIS−30543, the input
CLR needs to be pulled to logic 1 during minimum time
given by t
CLR
(Table 5 AC Parameters). This reset function
clears all internal registers without the need of a
power−cycle, except in sleep mode. Logic 0 on CLR pin
resumes normal operation again.
The voltage regulator and charge pump remains
functional during and after the reset and the POR
/WD pin is
not activated. Watchdog function is reset completely.
Sleep Mode
The bit <SLP> in SPI Control Register 2 (See Table 10)
is provided to enter a so−called “sleep mode”. This mode
allows reduction of current−consumption when the motor is
not in operation. The effect of sleep mode is as follows:
• The drivers are put in HiZ
• All analog circuits are disabled and in low−power mode
• All internal registers are maintaining their logic content
• NXT and DIR inputs are forbidden
• SPI communication remains possible (slight current
increase during SPI communication)
• Oscillator and digital clocks are silent, except during
SPI communication
• Registers cannot be cleared by using the CLR pin
VBB should be minimum 9 V to be able to enter
Sleep Mode.