Datasheet

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General Description

The MAX807 microprocessor (µP) supervisory circuit

reduces the complexity and number of components

needed to monitor power-supply and battery-control func-

tions in µP systems. A 70µA supply current makes the

MAX807 ideal for use in portable equipment, while a 2ns

chip-enable propagation delay and 250mA output current

capability (20mA in battery-backup mode) make it suit-

able for larger, higher-performance equipment.

The MAX807 comes in 16-pin DIP, SO, and TSSOP pack-

ages, and provides the following functions:

•µP reset. The active-low RESET output is asserted dur-

ing power-up, power-down, and brownout conditions,

and is guaranteed to be in the correct state for V

down to 1V.

• Active-high RESET output.

• Manual-reset input.

• Two-stage power-fail warning. A separate low-line

comparator compares V

to a threshold 52mV above

the reset threshold. This low-line comparator is more

accurate than those in previous µP supervisors.

• Backup-battery switchover for CMOS RAM, real-time

clocks, µPs, or other low-power logic.

• Write protection of CMOS RAM or EEPROM.

• 2.275V threshold detector provides for power-fail

warning and low-battery detection, or monitors a

power supply other than +5V.

• BATT OK status flag indicates that the backup-battery

voltage is above +2.275V.

• Watchdog-fault output—asserted if the watchdog input

has not been toggled within a preset timeout period.

Applications

Computers

Controllers

Intelligent Instruments

Critical µP Power Monitoring

Portable/Battery-Powered Equipment

Features

♦ Precision 4.675V (MAX807L), 4.425V (MAX807M),

or 4.575V (MAX807N) Voltage Monitoring

♦ 200ms Power-OK/Reset Time Delay

♦ RESET and RESET Outputs

♦ Independent Watchdog Timer

♦ 1µA Standby Current

♦ Power Switching

250mA in V

Mode

20mA in Battery-Backup Mode

♦ On-Board Gating of Chip-Enable Signals;

2ns CE Gate Propagation Delay

♦ MaxCap

and SuperCap

Compatible

♦ Voltage Monitor for Power Fail

♦ Backup-Battery Monitor

♦ Guaranteed RESET Valid to V

= 1V

♦ ±1.5% Low-Line Threshold Accuracy 52mV above

Reset Threshold

MAX807L/M/N

Full-Featured µP Supervisory Circuit with

±1.5% Reset Accuracy

________________________________________________________________ Maxim Integrated Products 1

19-0433; Rev 4; 11/05

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.

RESET

WDO

CE IN

GND

OUT

BATT

TOP VIEW

MAX807

CE OUT

WDI

LOW LINE

BATT OK

PFI

PFO

BATT ON

DIP/SO/TSSOP

Pin Configuration

Ordering Information and Typical Operating Circuit appear at end of data sheet.

SuperCap is a registered trademark of Baknor Industries. MaxCap is a registered trademark of Cesiwid, Inc.

Summary of content (16 pages)

PAGE 1
9-0433; Rev 4; 11/05 Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy The MAX807 microprocessor (µP) supervisory circuit reduces the complexity and number of components needed to monitor power-supply and battery-control functions in µP systems. A 70µA supply current makes the MAX807 ideal for use in portable equipment, while a 2ns chip-enable propagation delay and 250mA output current capability (20mA in battery-backup mode) make it suitable for larger, higher-performance equipment.
PAGE 2
MAX807L/M/N Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy ABSOLUTE MAXIMUM RATINGS Input Voltages (with respect to GND) VCC ..........................................................................-0.3V to 6V VBATT .......................................................................-0.3V to 6V All Other Inputs......................................-0.3V to (VOUT + 0.3V) Input Current VCC Peak ...........................................................................1.
PAGE 3
Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy (V CC = 4.60V to 5.5V for the MAX807L, VCC = 4.50V to 5.5V for the MAX807N, VCC = 4.35V to 5.5V for the MAX807M, VBATT = 2.8V, VPFI = 0V, TA = TMIN to TMAX. Typical values are tested with VCC = 5V and TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN Sink current Source current, VCC = 0V, VBATT = 2.
PAGE 4
MAX807L/M/N Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy ELECTRICAL CHARACTERISTICS (continued) (V CC = 4.60V to 5.5V for the MAX807L, V CC = 4.50V to 5.5V for the MAX807N, V CC = 4.35V to 5.5V for the MAX807M, VBATT = 2.8V, VPFI = 0V, TA = TMIN to TMAX. Typical values are tested with VCC = 5V and TA = +25°C, unless otherwise noted.) PARAMETER PFI Input Threshold SYMBOL VPFT CONDITIONS VPFI falling VPFI rising MIN TYP MAX UNITS 2.20 2.22 2.265 2.285 20 ±0.005 2.33 2.
PAGE 5
Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy 76 74 72 70 68 66 64 MAX807-03 MAX807-02 6 5 2.5 PROPAGATION DELAY (ns) BATTERY SUPPLY CURRENT (µA) 78 VCC SUPPLY CURRENT (µA) 3.0 MAX807-01 80 CHIP-ENABLE PROPAGATION DELAY vs. TEMPERATURE BATTERY SUPPLY CURRENT vs. TEMPERATURE (BATTERY-BACKUP MODE) VCC SUPPLY CURRENT vs. TEMPERATURE (NORMAL OPERATING MODE) 2.0 1.5 1.0 4 3 2 1 0.
PAGE 6
Typical Operating Characteristics (contiued) (VCC = 5V, VBATT = 2.8V, PFI = 0, no load, TA = +25°C, unless otherwise noted.) 4.70 N VERSION 4.65 4.60 4.55 M VERSION 4.50 4.45 VCC FALLING AT 1mV/µs 30 25 20 15 10 5 35 -60 -40 -20 0 25 20 15 10 5 0 -60 -40 -20 0 20 40 60 80 100 120 140 VCC FALLING AT 1mV/µs 30 0 4.40 MAX807-12 MAX807-11 35 40 -60 -40 -20 0 20 40 60 80 100 120 140 20 40 60 80 100 120 140 TEMPERATURE (°C) TEMPERATURE (°C) BATTERY CURRENT vs.
PAGE 7
Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy PIN NAME FUNCTION 1 PFI Power-Fail Input. When PFI is less than VPFT (2.265V), PFO goes low. Connect to ground when unused. 2 PFO Power-Fail Output. This CMOS-logic output goes low when PFI is less than VPFT (2.265V). Valid for VCC ≥ 4V. PFO swings between VCC and GND. 3 VCC Input Supply Voltage, nominally +5V. Bypass with a 0.1µF capacitor to GND. 4 WDI Watchdog Input.
PAGE 8
MAX807L/M/N Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy Detailed Description The MAX807 µP supervisory circuit provides powersupply monitoring, backup-battery switchover, and program execution watchdog functions in µP systems (Figure 1). Use of BiCMOS technology results in an improved 1.5% reset-threshold precision, while keeping supply currents typically below 70µA.
PAGE 9
Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy VCC VCC VLOW LINE VLOW LINE VRESET tRP VRESET (MAX801) VRESET tRP VRESET (MAX808) VCE OUT MAX807L/M/N VRST + VLR VRST VRST VLL VBATT VCE OUT VBATT SHOWN FOR VCC = 5V to 0, VBATT = 2.8V, CE IN = GND SHOWN FOR VCC = 0 to 5V, VBATT = 2.8V, CE IN = GND Figure 2a. Timing Diagram, VCC Rising The RESET output is active low and implemented with a strong pulldown/relatively weak pullup structure.
PAGE 10
MAX807L/M/N Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy 1µs MIN MR 170ns RESET CE IN 0V CE OUT 28µs TYP Figure 4. Manual-Reset Timing Diagram Watchdog Output WDO remains high if there is a transition or pulse at WDI during the watchdog-timeout period. WDO goes low if no transition occurs at WDI during the watchdogtimeout period. The watchdog function is disabled and WDO is a logic high when V CC is below the reset threshold or WDI is an open circuit.
PAGE 11
Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy MAX807L/M/N VRST MAX VCC RESET THRESHOLD VCC CE IN MAX807 CE OUT 28µs 26µs CE IN CE OUT 26µs 50pF CLOAD 50Ω DRIVER RESET GND RESET Figure 7. Reset and Chip-Enable Timing (see the Chip-Enable Propagation Delay vs. CE OUT Load Capacitance graph in the Typical Operating Characteristics).
PAGE 12
MAX807L/M/N Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy VIN VCC R1 MAX807 PFI VCC R1 PFO PFI R2 MAX807 PFO R2 MR GND GND VCC VIN VCC PFO PFO VL VTRIP = R2 (VPFT + VPFH) ( VL = R2 (VPFT) 1 1 VTRIP ( R1 + R2 ) – 1 1 + R1 R2 ) VCC R1 VCC – R1 VIN 0V VTRIP = VPFT WHERE VPFT = 2.265V VPFH = 20mV NOTE: VTRIP, VL ARE NEGATIVE. a) VTRIP ( R1 + R2 R2 VIN ) R1 + R2 VH = (VPFT + VPFH) R2 ( b) VH ) Figure 10.
PAGE 13
Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy PIN NAME 1 PFI The power-fail comparator remains active in battery-backup mode for VCC ≥ 4V. FUNCTION 2 PFO The power-fail comparator remains active in battery-backup mode for VCC ≥ 4V. Below 4V, PFO is forced low. 3 VCC Battery switchover comparator monitors VCC for active switchover.
PAGE 14
MAX807L/M/N Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy BATT OK Output The BATT OK comparator monitors the backup battery voltage, comparing it with a 2.265V reference (VCC ≥ 4V). BATT OK remains high as long as the backup battery voltage remains above 2.265V, signaling that the backup battery has sufficient voltage to maintain the memory of static RAM. When the battery voltage drops below 2.265V, the BATT OK output drops low, signaling that the backup battery needs to be changed.
PAGE 15
Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy Negative-Going VCC Transients While issuing resets to the µP during power-up, powerdown, and brownout conditions, these supervisors are relatively immune to short-duration negative-going VCC transients (glitches). It is usually undesirable to reset the µP when VCC experiences only small glitches. The Typical Operating Characteristics show Maximum Transient Duration vs. Reset Comparator Overdrive, for which reset pulses are not generated.
PAGE 16
MAX807L/M/N Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy Typical Operating Circuit Ordering Information PART† +5V 0.1µF 0.1µF VCC BATT ON OUT BATT CMOS RAM REALTIME CLOCK 0.