MAXQ3180 Datasheet, PDF (9/48 Pages) Maxim Integrated Products – Low-Power, Multifunction, Polyphase AFE

Low-Power, Multifunction, Polyphase AFE
Reset Sources
There are several different sources that can cause the
MAXQ3180 to undergo a reset cycle. For any type of
hardware reset, the RESET pin is driven low when a
reset occurs.
External Reset
This hardware reset is initiated by an external source
(such as the master controller or a manual pushbutton
press) driving the RESET pin on the MAXQ3180 low.
The RESET line must be held low for at least four cycles
of the currently selected clock for the external reset to
take effect. Once the external reset takes effect, it
remains in effect indefinitely as long as RESET is held
low. Once the external reset has been released, the
MAXQ3180 clears all registers to their default states
and resumes execution in Initialization Mode.
When an external reset occurs outside of Stop Mode,
execution (in Initialization Mode) resumes after four
cycles of the currently selected clock (external high-fre-
quency crystal for Run Mode, 1MHz internal RC oscilla-
tor for LPMM Mode). As the MAXQ3180 enters
Initialization Mode, the LOWPM bit is always cleared to
0, meaning that the MAXQ3180 always switches to the
high-frequency clock before it begins accepting com-
mands in Initialization Mode.
When an external reset occurs from Stop Mode, execu-
tion (in Initialization Mode) resumes after 128 cycles of
the internal RC oscillator (or approximately 128μs).
Power-On Reset
When the MAXQ3180 is first powered up, or when the
power supply, DV_DD, drops below the V_RST power-fail
trip point (outside of Stop Mode), the MAXQ3180 is
held in power-on reset. Once the power supply rises
above the V_RST level, the power-on reset state is
released and all registers are reset to their defaults and
execution resumes in Initialization Mode. The high-fre-
quency external crystal (LOWPM = 0) is always select-
ed as the clock source following any power-on or
brownout reset.
In Stop Mode brownout detection is disabled, so a
power-on reset does not occur until DV_DD drops to a
lower level (V_POR). From the master’s perspective,
power-on resets and brownout resets both cause the
MAXQ3180 to reset in the same way.
Watchdog Reset
The MAXQ3180 includes a hardware watchdog timer that
is armed and periodically reset automatically during nor-
mal operation. Under normal circumstances, the
MAXQ3180 always resets the watchdog timer often
enough to prevent it from expiring. However, if an internal
CLOCK
RESET
RESET
SAMPLING
INTERNAL
RESET
Figure 2. External Reset
BEGIN RUNNING IN INITIALIZATION MODE
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