Datasheet

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General Description

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 sys-

tem 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-

voltage drop. The devices can be connected to

support various supply sequencing priorities such as

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

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

♦ 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

MAX6819/MAX6820

SOT23 Power-Supply Sequencers

________________________________________________________________ Maxim Integrated Products 1

19-1951; Rev 3; 12/05

Ordering Information

PART

TEMP RANGE

PIN-

PACKAGE

TOP

M ARK

MAX6819UT-T

-40°C to +125°C 6 SOT23-6

AARF

MAX6820UT-T

-40°C to +125°C 6 SOT23-6

AARG

Pin Configurations

GND

ENSETV

16V

CC2

5 GATE

CC1

MAX6819

SOT23-6

TOP VIEW

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

ENSETV

CC2

GATE

DUAL-SUPPLY

BOARD OR µP

PRIMARY SUPPLY

(3.3V)

SECONDARY SUPPLY

(1.8V)

CC1

GND

OFF

MAX6819

Pin Configurations and Typical Operating Circuits

continued at end of data sheet.

Power PC is a trademark of IBM corp.

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.

Summary of content (8 pages)

PAGE 1
9-1951; 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.
PAGE 2
MAX6819/MAX6820 SOT23 Power-Supply Sequencers ABSOLUTE MAXIMUM RATINGS Referenced to GND VCC1, VCC2, EN .....................................................-0.3V to +6.0V SETV, SETD..................-0.3V to the higher of (VCC1 + 0.3V) and (VCC2 + 0.3V) GATE ...................................................................-0.3V to +12.0V Input Current/Output Current (all pins) ...............................20mA Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23 (derate 8.7mW/°C above +70°C)........
PAGE 3
SOT23 Power-Supply Sequencers GATE TURN-ON TIME tDELAY vs. TEMPERATURE MAX6819 toc02 MAX6819 toc01 250 240 230 tDELAY (ms) 220 210 200 190 VGATE 5V/div 180 170 160 CLOAD = 1500pF (MAX6819) 150 -40 -20 0 20 40 60 80 100 120 1ms/div TEMPERATURE (°C) GATE TURN-OFF TIME VCC2 vs. GATE VOLTAGE MAX6819 toc03 MAX6819 toc04 12 10 8 VGATE (V) VSETV 500mV/div VGATE 5V/div VCC1 = +3.3V VSETV = 1V 6 4 2 CLOAD = 1500pF 0 20µs/div 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VCC2 (V) VCC2 vs.
PAGE 4
Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. TEMPERATURE VSETV vs. TEMPERATURE 0.63 0.62 0.61 108 106 ICC1 104 VEN = 2V VSETV = 2V VCC2 = +3.3V VCC1 = +5V 100 0 20 40 60 80 100 120 -40 -20 0 20 40 60 80 ICC2 vs. VCC2 ICC2 vs. VCC2 120 100 120 MAX6819 toc10 TEMPERATURE (°C) MAX6819 toc09 TEMPERATURE (°C) 140 140 120 100 ICC2 (µA) 100 80 80 60 60 VCC1 = 0 VEN = 2V VSETV = 2V 40 20 VCC1 = 3.
PAGE 5
SOT23 Power-Supply Sequencers PIN FUNCTION NAME MAX6819 MAX6820 1 1 VCC1 Supply Voltage 1. Either VCC1 or VCC2 must be greater than the UVLO to enable external MOSFET drive. 2 2 GND Ground 3 3 SETV Sequence Threshold Set. Connect to an external resistor-divider network to set the VCC1 threshold that enables GATE turn-on. The internal reference is 0.618V. 4 — EN Active-High Enable. GATE drive is enabled tDELAY after EN is driven high.
PAGE 6
MAX6819/MAX6820 SOT23 Power-Supply Sequencers Applications Information Adjusting tDELAY The MAX6820 features a capacitor adjustable sequence delay. The adjustable delay provides power sequencing for a wide range of devices with different power-supply delay requirements. Connect a capacitor (CSET) between SETD and GND to adjust the delay time (Figure 2). Calculate the sequence delay time as follows: tDELAY (s) = 2.
PAGE 7
SOT23 Power-Supply Sequencers MAX6819/MAX6820 VEN/VSETV 50% O tON VCC2 + 5.5V 90% GATE 10% O tOFF tDELAY 10% Figure 3. Timing Diagram 5(V) PRIMARY VOLTAGE SUPPLY 3.3(V) SECONDARY VOLTAGE SUPPLY 1.8(V) THIRD VOLTAGE SUPPLY GATE VCC2 VCC2 MAX6819 MAX6820 GND VCC1 GATE MAX6819 MAX6820 GND VCC1 MULTISUPPLY BOARD OR µP R3 R1 SETV SETD/EN R2 SETV SETD/EN R4 Figure 4.
PAGE 8
Typical Operating Circuits (continued) PRIMARY SUPPLY (1.8V) Pin Configurations (continued) VCC1 1 6 VCC2 5 GATE 4 SETD DC/DC SECONDARY SUPPLY (3.3V) GND 2 VCC2 MAX6820 GATE MAX6820 VCC1 GND SETV SETD DUAL-SUPPLY BOARD OR µP SETV 3 SOT23-6 R1 R2 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 6LSOT.