FET Drive Simple Sequencers®
ADM6819/ADM6820
FUNCTIONAL BLOCK DIAGRAM
FEATURES
V
V
V
V
CC1
CC2
CC1
CC2
Single chip enables power supply sequencing of two
supplies
Q1
OUT
V
V
CC2
CC1
On-board charge pump fully enhances N-channel FET
Adjustable primary supply monitor to 0.618 V
Delay from primary supply to secondary supply enabled
Fixed 300 ms delay (ADM6819)
Capacitor adjustable delay (ADM6820)
Logic/analog driven enable input (ADM6819)
−40°C to +85°C operating range
CHARGE
PUMP
V
FET
UVLO
R1
R2
LOGIC
SETV
GATE
FET
DRIVER
0.618V
Packaged in small 6-lead SOT-23 package
Pin-to-pin compatibility with MAX6819/MAX6820
TIMER
ADM6819/
ADM6820
0.618V
APPLICATIONS
Multivoltage systems
GND
EN (ADM6819) - DIGITAL/ANALOG
SETD (ADM6820)
Figure 1.
Dual voltage microprocessors/FPGAs/ASICs/DSPs
Network processors
Telecom and datacom systems
PC/server applications
GENERAL DESCRIPTION
The ADM6819 and ADM6820 are simple power supply sequencers
with FET drive capability for enhancing N-channel MOSFETs.
These devices can monitor a primary supply voltage and
enable/disable an external N-channel FET for a secondary
supply. The ADM6819 has the ability to monitor two supplies.
When more than two voltages require sequencing, multiple
ADM6819/ADM6820 devices can be cascaded to achieve this.
The devices operate over a supply range of 2.95 V to 5.5 V.
The ADM6819 features an enable (EN) pin that is fed to the
input of an additional comparator and reference circuit. This
pin can be used as a digital enable or a secondary power good
comparator to monitor a second supply and enables the GATE
only if both supplies are valid. When both inputs of the internal
comparators are above the threshold, a fixed 300 ms timeout
occurs before the GATE is driven high and the secondary
supply is enabled.
An internal comparator monitors the primary supply using the
VSET pin. The input to this comparator is externally set via a
resistor divider from the primary supply. When the voltage at
the VSET pin rises above the comparator threshold, an internal
charge pump on the GATE output enhances the secondary
supply FET.
The ADM6820 has only one comparator that is on the SETV
pin. It also features a timeout period that is adjustable via a
single external capacitor on the SETD pin.
The ADM6819/ADM6820 are packaged in small 6-lead SOT-23
packages.
Rev. 0
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