The MAX6819/MAX6820 are power-supply sequencers
for dual-voltage microprocessors (μPs) and multivoltage
systems. These devices monitor a primary supply voltage
and enable/disable an external n-channel MOSFET
switch for a secondary supply voltage. The MAX6819/
MAX6820 control local component voltage sequencing
when system power-on/power-off characteristics cannot
be guaranteed (supplies come from a multivoltage system
bus, silver box, or must be sequenced in different
modes for components on the same board). These small
power-supply sequencers improve system reliability.
The MAX6819/MAX6820 include an internal voltage reference/
comparator with externally adjustable thresholds
to monitor the primary power supply. When the
primary supply is below the desired threshold, an external
secondary supply MOSFET switch is disabled.
When the primary supply exceeds the threshold, an
internal charge pump is activated and the external
MOSFET switch is enabled to connect the secondary
supply to the load. The charge pump fully enhances the
n-channel MOSFET switch to provide a very low RDSON
voltage drop. The devices can be connected to
support various supply sequencing priorities such as
VI/O before VCORE or VCORE before VI/O.
The MAX6819 features a logic-driven EN input to
enable/disable the external MOSFET drive and includes
an internally fixed 200ms enable timeout period
(VPRIMARY GOOD to VSECONDARY ENABLE). The
MAX6820 allows the enable timeout period to be
adjusted with a single external capacitor. Both devices
are specified over the automotive temperature range
(-40°C to +125°C) and are available in space-saving
6-pin SOT23 packages.
Applications
Dual-Voltage Microprocessors
Multivoltage Systems
Digital Signal Processors
Power PC? Series Processors