19-1951; Rev 2; 4/02
SOT23 Power-Supply Sequencers
General Description
The MAX6819/MAX6820 are power-supply sequencers
for dual-voltage microprocessors (碌Ps) and multivolt-
age 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 charac-
teristics 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 ref-
erence/comparator with externally adjustable thresh-
olds to monitor the primary power supply. When the
primary supply is below the desired threshold, an exter-
nal 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 R
DS-
ON
voltage drop. The devices can be connected to
support various supply sequencing priorities such as
V
I/O
before V
CORE
or V
CORE
before V
I/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掳C to +125掳C) and are available in space-saving
6-pin SOT23 packages.
Features
o
Adjustable Primary Supply Voltage Monitor
(Monitors Down to 0.62V)
o
Internal Charge Pump to Enhance External
Secondary Supply N-Channel MOSFET Switch
o
Delay from Primary Supply Good to Secondary
Supply Enabled
Factory Fixed 200ms (MAX6819)
Capacitor Adjustable (MAX6820)
o
Logic Driven ENABLE Input (MAX6819)
o
Immune to Short Voltage Transients
o
Few External Components
o
-40掳C to +125掳C Operating Temperature Range
o
Small 6-Pin SOT23 Package
MAX6819/MAX6820
Ordering Information
PART
MAX6819UT-T
MAX6820UT-T
TEMP RANGE
-40掳C to +125掳C
-40掳C to +125掳C
PIN-
PACKAGE
6 SOT23-6
6 SOT23-6
TOP
MARK
AARF
AARG
Products must be ordered in 2,500 piece increments.
Typical Operating Circuits
PRIMARY SUPPLY
(3.3V)
SECONDARY SUPPLY
(1.8V)
V
CC2
GATE
DUAL-SUPPLY
BOARD OR
碌P
MAX6819
V
CC1
GND
Applications
Dual-Voltage Microprocessors
Multivoltage Systems
Digital Signal Processors
Power PC鈩?Series Processors
TOP VIEW
ON
SETV
EN
OFF
Pin Configurations
Pin Configurations and Typical Operating Circuits
continued at end of data sheet.
V
CC1
1
6
V
CC2
GND
2
MAX6819
5
GATE
Power PC is a trademark of IBM corp.
SETV
3
4
EN
SOT23-6
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim鈥檚 website at www.maxim-ic.com.
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