Maxim Integrated MAXQ7666 - Manual (Page 75)

SECTION 2: POWER-SUPPLY/SUPERVISORY MONITORING MODULE
The MAXQ7665/MAXQ7666 power-supply/supervisory monitoring module supports dedicated supply pins to independently power analog,
digital I/O, and digital core functions. The analog functions and digital I/O are powered from an external +5V supply, while the internal digi-
tal core is powered from a +3.3V supply, which can be supplied by an on-chip linear regulator. Except where explicitly noted, the MAXQ7665
and MAXQ7666 support identical features.
The MAXQ7665/MAXQ7666 power-supply/supervisory monitoring module features include the following.
• Dedicated analog supply (+5.0V) and ground pins
• Dedicated digital I/O supply (+5.0V) and ground pins
• Dedicated digital core supply (+3.3V) and ground pins
• On-chip +3.3V linear regulator
• Digital core brownout interrupt and reset voltage monitors
• Digital I/O brownout voltage monitor (can also be used to monitor analog supply)
• User-programmable thresholds for digital core brownout reset and interrupt generation
• User-programmable thresholds for digital I/O brownout interrupt generation
• Five reset sources: power-on, brownout, external, WDT, and internal system
2.1 Architecture
Figure 2-1 shows a simplified functional block diagram of the MAXQ7665/MAXQ7666 power-supply/supervisory monitoring module.
The MAXQ7665/MAXQ7666 microcontrollers are +5V-powered devices. Three power supplies are used to operate the various mod-
ules in the microcontroller. The MAXQ7665/MAXQ7666’s digital I/O supply (DVDDIO) uses two +5.0V supply pins to power the digital
I/Os. An internal +3.3V linear regulator powers the digital core functions composed of internal CPU, memory, oscillator, and digital
peripherals. If required, an external +3.3V supply (DVDD) can instead be used by disabling (
REGEN pin connected to DVDDIO) the
internal regulator. The analog module uses a separate power-supply line (AVDD) to allow additional filtering to maintain superior ana-
log performance.
The MAXQ7665/MAXQ7666 contain two brownout power-supply monitors. One power-supply monitor is dedicated to the DVDDIO for
brownouts, while the other monitors brownouts of the DVDD core supply of the microcontroller, and can actually cause a reset if DVDD
is too low. The AVDD supply can be connected to the DVDDIO supply lines, and can then also be monitored by the DVDDIO monitor.
The power-on reset circuit is integrated into the DVDD power-supply monitor and the default trip level is between 2.7V and 2.99V. The
DVDDIO and DVDD brownout detection thresholds are user selectable, and can be configured independently to interrupt the micro-
controller when either of the selected thresholds are crossed.
MAXQ7665/MAXQ7666 User’s Guide
2-3
Maxim Integrated