Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - system monitor Serialiser TQFN 24

General Description

The MAX6877/MAX6878/MAX6879 multivoltage power

trackers/sequencers/supervisors monitor up to three

system voltages and provide proper power-up and

power-down control for systems requiring voltage track-

ing or sequencing. These devices ensure controlled

voltage tracking within a specified range or sequencing

in the proper order as system power supplies are

enabled. The MAX6877/MAX6878/MAX6879 generate

all required voltages and timing to control up to three

external n-channel pass FETs for the OUT1/OUT2/

OUT3 supply voltages (see the Selector Guide for dif-

ferent features of each device).

The MAX6877/MAX6878/MAX6879 feature adjustable

undervoltage thresholds for each input supply. When all

the voltages are above these adjustable thresholds, the

devices turn on the external n-channel MOSFETs to

either sequence or track the voltages to the system.

During voltage-tracking mode, the voltage at the GATE

of each MOSFET is increased to slowly bring up all

supplies at a controlled slew rate. The MAX6877/

MAX6878/MAX6879 feature an autoretry or latch-off

mode with capacitor-adjusted timing.

These devices also provide a controlled power-down

(tracking mode) when the system shuts off in an orderly

manner. When an unexpected fault occurs, the outputs

are all pulled down simultaneously with an internal

100Ω pulldown to help discharge capactive loads at

the MOSFET’s source. The MAX6877/MAX6878/

MAX6879 feature independent internal charge pumps

to fully enhance the external FETs for low-voltage drop

at highpass current. The MAX6877 and MAX6878 also

feature a power-good output with a selectable timeout

period that can be used for system reset.

The MAX6877/MAX6878/MAX6879 are available in

small 4mm x 4mm 24-pin and 16-pin thin QFN pack-

ages and are fully specified over the -40°C to +85°C

extended operating temperature range.

Applications

Multivoltage Systems

Networking Systems

Telecom

Storage Equipment

Servers/Workstations

Features

♦ Pin-Selectable Tracking or Sequencing Control

for Up to Three Supply Voltages

♦ Capacitor-Adjustable Power-Up/Down Tracking

Slew Rate

♦ Capacitor-Adjustable Power-Up Sequencing Delay

♦ Internal Charge Pumps to Enhance External

n-Channel FETs

♦ Capacitor-Adjustable Timeout Period Power-Good

Output (MAX6877/MAX6878)

♦ Adjustable Undervoltage Lockout or

Logic-Enable Input

♦ Internal 100Ω Pulldown for Each Output to

Discharge Capacitive Load Quickly

♦ 0.5V to 5.5V Nominal IN_/OUT_ Range

♦ 2.7V to 5.5V Operating Voltage Range

♦ Immune to Short Voltage Transients

♦ Small 4mm x 4mm 24-Pin or 16-Pin Thin QFN

Packages

MAX6877/MAX6878/MAX6879

Dual-/Triple-Voltage, Power-Supply

Trackers/Sequencers/Supervisors

________________________________________________________________ Maxim Integrated Products 1

ABP

SET2

SET1

EN/UV

GATE3

FAULT

PG/RST

OUT2

MARGIN

IN3

456

1718 16 14 13

IN2

IN1

TIMEOUT

*EXPOSED PADDLE CONNECTED TO GND.

SLEW

DELAY

GND

EP*

MAX6877

SET3

OUT3

GATE1

LTCH/RTR

OUT1

TRK/SEQ

GATE2

4mm x 4mm THIN QFN

TOP VIEW

Pin Configurations

Ordering Information

19-3771; Rev 1; 10/05

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.

Ordering Information continued at end of data sheet.

+Denotes lead-free package.

EVALUATION KIT

AVAILABLE

Selector Guide appears at end of data sheet.

PART

TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX6877ETG+

-40°C to +85°C 24 Thin QFN

T2444-4

Pin Configurations continued at end of data sheet.

Summary of content (24 pages)

PAGE 1
9-3771; Rev 1; 10/05 KIT ATION EVALU E L B AVAILA Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors Features The MAX6877/MAX6878/MAX6879 multivoltage power trackers/sequencers/supervisors monitor up to three system voltages and provide proper power-up and power-down control for systems requiring voltage tracking or sequencing. These devices ensure controlled voltage tracking within a specified range or sequencing in the proper order as system power supplies are enabled.
PAGE 2
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND, unless otherwise noted.) IN1, IN2, IN3, VCC ....................................................-0.3V to +6V ABP .....................................-0.3V to the highest of VIN1 - VIN3 or VCC SET1, SET2, SET3 ....................................................-0.3V to +6V GATE1, GATE2, GATE3 .........................................-0.
PAGE 3
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors (VCC, IN1, IN2, or IN3 = +2.7V to +5.5V, EN/UV = MARGIN = ABP, TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL Power-Good Threshold Hysteresis VHYS_PG CONDITIONS % 2.5 4 µA During power-up and power-down, VGATE_ = 5V 2.5 4 µA GATE_ Pullup Current IGUP IGD tD-GATE UNITS During power-up and power-down, VGATE_ = 1V ISOURCE = 0.
PAGE 4
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors EN/UV BUS VOLTAGE MONITORED THROUGH EN/UV INPUT EN/UV VEN_F VEN_R EN/UV IN1 = 2.5V IN2 = 1.8V IN_ IN3 = 0.7V MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS CAPACITORADJUSTED SLEW RATE OUT1 = 2.5V OUT2 = 1.8V OUT_ OUT3 = 0.7V tDELAY PG/RST tTIMEOUT Figure 1.
PAGE 5
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors VEN_R MAX6877/MAX6878/MAX6879 BUS VOLTAGE MONITORED THROUGH EN/UV INPUT EN/UV EN/UV VEN_F IN1 GOES BELOW SET1 THRESHOLD IN1 = 2.5V IN2 = 1.8V IN3 = 0.7V IN_ MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS CAPACITORADJUSTED SLEW RATE OUT1 = 2.5V OUT2 = 1.8V OUT3 = 0.7V OUT_ tDELAY tTIMEOUT PG/RST FAULT = HIGH FORCED INTO QUICK SHUTDOWN AFTER NORMAL SHUTDOWN WHEN IN1 GOES BELOW ITS SET VOLTAGE Figure 2.
PAGE 6
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors EN/UV BUS VOLTAGE MONITORED THROUGH EN/UV INPUT VEN_R EN/UV VEN_F IN1 = 2.5V IN2 = 1.8V IN3 = 0.7V IN_ MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS CAPACITORADJUSTED SLEW RATE OUT1 = 2.5V OUT2 = 1.8V OUT_ OUT3 = 0.7V tDELAY tDELAY tDELAY PG/RST tTIMEOUT Figure 3.
PAGE 7
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors MAX6877/MAX6878/MAX6879 EN/UV EN/UV BUS VOLTAGE MONITORED THROUGH EN/UV INPUT VEN_R IN1 = 2.5V IN2 = 1.8V IN_ IN3 = 0.7V MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS CAPACITORADJUSTED SLEW RATE OUT_ FORCED BELOW VTH_PG OUT1 = 3.3V OUT2 = 1.8V OUT_ OUT3 = 0.7V tDELAY tDELAY PG/RST tDELAY tTIMEOUT FAULT FORCED INTO QUICK SHUTDOWN WHEN OUT1 FALLS BELOW 92.5% of IN1 Figure 4.
PAGE 8
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors EN/UV EN/UV BUS VOLTAGE MONITORED THROUGH EN/UV INPUT VEN_F VEN_R IN1 = 2.5V IN2 = 1.8V IN3 = 0.7V IN_ MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS CAPACITORADJUSTED SLEW RATE OUT1 = 2.5V OUT2 = 1.8V OUT_ OUT3 = 0.7V tDELAY *tTIMEOUT PG/RST = LOW *ANY POWER-DOWN CONDITION BEFORE tTIMEOUT (PG/RST ASSERTED) CAUSES A SHUTDOWN. Figure 5.
PAGE 9
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors MAX6877/MAX6878/MAX6879 EN/UV EN/UV BUS VOLTAGE MONITORED THROUGH EN/UV INPUT VEN_R VEN_F IN1 = 2.5V IN2 = 1.8V IN3 = 0.7V IN_ MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS CAPACITORADJUSTED SLEW RATE OUT1 = 2.5V OUT2 = 1.8V OUT_ OUT3 = 0.7V tDELAY tDELAY tDELAY *tTIMEOUT PG/RST = LOW *ANY POWER-DOWN CONDITION BEFORE tTIMEOUT (PG/RST ASSERTED) CAUSES A SHUTDOWN. Figure 6.
PAGE 10
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors EN/UV VEN_R OUT2 AND OUT3 ARE WAITING OUT1 IS SLOW OUT_ OUT2 AND OUT3 ARE WAITING 125mV OUT1 IS SLOW tDELAY tDELAY tFAULT tFAULT tRETRY FAULT tFAULT AND tRETRY NOT TO SCALE ALL SET_ > 0.5V AND VCC OR IN_ ≥ 2.7V Figure 7.
PAGE 11
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors (VCC_ = 2.7V to 5.5V, CSLEW = 200pF, EN = MARGIN = ABP, TA = +25°C, unless otherwise noted.) VCC SUPPLY CURRENT vs. INPUT VOLTAGE NORMALIZED POWER-GOOD TIMEOUT vs. TEMPERATURE 1.1 TA = +25°C TA = -40°C 0.9 0.8 3.0 3.5 4.0 4.5 5.0 0.95 0.90 0.85 MAX6877 toc03 100 10 1 0.80 5.5 -40 -15 10 35 60 0.1 0.0001 85 0.001 0.01 TEMPERATURE (°C) CTIMEOUT (µF) NORMALIZED SET_ THRESHOLD vs.
PAGE 12
Typical Operating Characteristics (continued) (VCC_ = 2.7V to 5.5V, CSLEW = 200pF, EN = MARGIN = ABP, TA = +25°C, unless otherwise noted.) GATE_ VOLTAGE LOW vs. GATE SINK CURRENT GATE_ OUTPUT VOLTAGE HIGH vs. GATE SOURCE CURRENT 1.2 1.0 0.8 0.6 0.4 MAX6877 toc12 MAX6877 toc11 9 GATE_ VOLTAGE HIGH (V) 1.4 TRACKING MODE 10 MAX6877 toc10 1.
PAGE 13
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors PIN MAX6877 MAX6878 MAX6879 NAME FUNCTION 1 1 — VCC Optional Supply Voltage Input. Connect VCC to an alternate (i.e., always-on) supply if desired. Leave VCC unconnected, if not used. VCC allows IN_ supplies less than UVLO to be tracked. VCC is internally pulled down by a 100kΩ resistor. 2 2 1 ABP Internal Supply Bypass Input. Bypass ABP with a 1µF capacitor to GND.
PAGE 14
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors Pin Description (continued) PIN NAME FUNCTION MAX6877 MAX6878 MAX6879 14 14 — PG/RST Power-Good Output, Open-Drain. PG_RST asserts high tTIMEOUT after all OUT_ voltages exceed the VTH_PG thresholds. 15 15 10 FAULT Tracking Fault Alert Output, Active Low, Open-Drain.
PAGE 15
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors IN1 TO LOAD VCC IN2 IN3 IN1 OUT1 GATE1 ABP INTERNAL VCC/UVLO IN1 CHARGE PUMP MAX6877 SET1 RAMP GENERATOR IN2 COMP GATE CONTROLLER SET2 IN3 COMP CONTROL LOGIC IN2 TO OUT2 CONTROL BLOCK SET3 VBUS COMP GATE2 OUT2 OUT1 OUT2 TRACKING MONITORS EN/UVLO COMP OUT3 IN1 IN3 TO OUT3 CONTROL BLOCK GATE3 OUT3 IN2 IN3 VREF PG CIRCUIT MARGIN GND DELAY SLEW TIMEOUT CSLEW CTIMEOUT PG/RST FAULT TRK/SEQ LTCH/RTR ______________
PAGE 16
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors Detailed Description The MAX6877/MAX6878/MAX6879 multivoltage power trackers/sequencers/supervisors monitor up to three system voltages and provide proper power-up and power-down control for systems requiring voltage tracking or sequencing. These devices ensure controlled voltage tracking with a specified range or sequencing in the proper order as system power supplies are enabled.
PAGE 17
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors The slew rate for the reference ramp voltage is capacitor adjustable. Connect a capacitor from SLEW to ground to select the desired OUT_ slew rate. When all OUT_ voltages have exceeded the VTH_PG percentage of the IN_ voltage (external n-channel FET is saturated), PG/RST asserts high after tTIMEOUT indicating successful tracking. Sequencing The sequencing operation can be initiated after all input conditions for power-up are met VEN/UV > 1.
PAGE 18
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors VIN_ Limiting Inrush Current The capacitor connected at SLEW controls the OUT_S slew rate, thus controlling the inrush current required to charge the load capacitor at the outputs (OUT_). Using the programmed slew rate, limit the inrush current by using the following formula: IINRUSH = COUT x SR where IINRUSH is in amperes, COUT is in farads, and SR is in V/s. IN_ R1 MAX6877 MAX6878 SET_ MAX6879 R2 Figure 9.
PAGE 19
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors Outputs GATE_ The MAX6877/MAX6878/MAX6879 feature up to three GATE_ outputs to drive up to three external n-channel FET gates. The following conditions must be met before GATE_ begins enhancing the external n-channel FET_: 1) All SET_ inputs (SET1–SET3) are above their 0.5V thresholds. 2) At least one IN_ input or VCC is above the minimum operating voltage (2.7V). 3) EN/UV > 1.25V.
PAGE 20
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors When a fault is detected, for a period of tRETRY, GATE_ remains off and the 100Ω pulldowns are turned on. After the tRETRY period, the device waits tDELAY and retries power-up if all power-up conditions are met (see Figure 8). These include all VSET_ > 0.5V, EN/UV > VEN_R, OUT_ voltages < VTH_PL. The autoretry period, tRETRY, is a function of CSLEW; see Table 1.
PAGE 21
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors IN1 OUT1 IN2 OUT2 IN3 OUT3 0.1µF IN1 IN2 0.1µF 0.
PAGE 22
Ordering Information (continued) TEMP RANGE PINPACKAGE PKG CODE MAX6878ETG+ -40°C to +85°C 24 Thin QFN T2444-4 MAX6879ETE+ -40°C to +85°C 16 Thin QFN T1644-4 PART Chip Information PROCESS: BiCMOS +Denotes lead-free package. Pin Configurations (continued) GATE2 19 12 TRK/SEQ OUT1 20 11 LTCH/RTR GATE1 21 10 TIMEOUT 9 SLEW MAX6878 N.C. 22 EP* IN2 23 + 1 2 3 4 5 6 ABP N.C.
PAGE 23
Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors 24L QFN THIN.EPS PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 E 1 2 ______________________________________________________________________________________ 23 MAX6877/MAX6878/MAX6879 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.
PAGE 24
MAX6877/MAX6878/MAX6879 Dual-/Triple-Voltage, Power-Supply Trackers/Sequencers/Supervisors Package Information (continued) (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.) PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 E 2 2 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product.