MAX6819 Datasheet, PDF (1/8 Pages) Maxim Integrated Products – SOT23 Power-Supply Sequencers

19-1951; Rev 2; 4/02
SOT23 Power-Supply Sequencers
General Description
The MAX6819/MAX6820 are power-supply sequencers
for dual-voltage microprocessors (µPs) 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°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
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°C to +125°C Operating Temperature Range
o Small 6-Pin SOT23 Package
Ordering Information
PART
TEMP RANGE
PIN-
TOP
PACKAGE MARK
MAX6819UT-T -40°C to +125°C 6 SOT23-6 AARF
MAX6820UT-T -40°C to +125°C 6 SOT23-6 AARG
Products must be ordered in 2,500 piece increments.
Typical Operating Circuits
PRIMARY SUPPLY
(3.3V)
SECONDARY SUPPLY
(1.8V)
VCC2
GATE
MAX6819
VCC1
GND
DUAL-SUPPLY
BOARD OR µP
SETV
EN
ON
OFF
Pin Configurations
TOP VIEW
Pin Configurations and Typical Operating Circuits
continued at end of data sheet.
VCC1 1
6 VCC2
MAX6819
GND 2
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’s website at www.maxim-ic.com.