ADM6819/ADM6820

Rev. 0

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FEATURES

Single chip enables power supply sequencing of two

supplies

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

Packaged in small 6-lead SOT-23 package

Pin-to-pin compatibility with MAX6819/MAX6820

APPLICATIONS

Multivoltage systems

Dual voltage microprocessors/FPGAs/ASICs/DSPs

Network processors

Telecom and datacom systems

PC/server applications

FUNCTIONAL BLOCK DIAGRAM

Q1

GATE

LOGIC

SETV

EN (ADM6819) - DIGITAL/ANALOG

SETD (ADM6820)

0.618V

0.618V

GND

R1

R2

ADM6819/

ADM6820

FET

DRIVER

CHARGE

PUMP

TIMER

UVLO

Figure 1.

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.

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 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.

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.