19-1951; Rev 3; 12/05
SOT23 Power-Supply Sequencers
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
(V PRIMARY GOOD to V SECONDARY 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.
Features
♦ Adjustable Primary Supply Voltage Monitor
(Monitors Down to 0.62V)
♦ Internal Charge Pump to Enhance External
Secondary Supply n-Channel MOSFET Switch
♦ Delay from Primary Supply Good to Secondary
Supply Enabled
Factory Fixed 200ms (MAX6819)
Capacitor Adjustable (MAX6820)
♦ Logic Driven ENABLE Input (MAX6819)
♦ Immune to Short Voltage Transients
♦ Few External Components
♦ -40°C to +125°C Operating Temperature Range
♦ Small 6-Pin SOT23 Package
Ordering Information
TEMP RANGE
PINPACKAGE
TOP
MARK
MAX6819UT-T
-40°C to +125°C
6 SOT23-6
AARF
MAX6820UT-T
-40°C to +125°C
6 SOT23-6
AARG
PART
Products must be ordered in 2,500 piece increments.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Typical Operating Circuits
PRIMARY SUPPLY
(3.3V)
SECONDARY SUPPLY
(1.8V)
VCC2
Applications
GATE
DUAL-SUPPLY
BOARD OR µP
MAX6819
VCC1
GND
SETV
EN
Dual-Voltage Microprocessors
ON
Multivoltage Systems
OFF
Digital Signal Processors
Power PC™ Series Processors
Pin Configurations
TOP VIEW
Pin Configurations and Typical Operating Circuits
continued at end of data sheet.
VCC1 1
GND 2
Power PC is a trademark of IBM corp.
6
SETV 3
5
GATE
4
MAX6819
VCC2
EN
SOT23-6
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX6819/MAX6820
General Description
