Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - system monitor Reserve capacity circuit SOIC 8

_______________General Description

The MAX801/MAX808 microprocessor (µP) supervisory

circuits monitor and control the activities of +5V µPs by

providing backup-battery switchover, low-line indica-

tion, and µP reset. Additional features include a watch-

dog for the MAX801 and CMOS RAM write protection

for the MAX808.

The MAX801/MAX808 offer a choice of reset-threshold

voltage (denoted by suffix letter): 4.675V (L), 4.575V

(N), and 4.425V (M). These devices are available in

8-pin DIP and SO packages.

________________________Applications

Computers

Controllers

Intelligent Instruments

Critical µP Power Monitoring

Portable/Battery-Powered Equipment

Embedded Systems

____________________________Features

♦ Precision Voltage Monitoring, ±1.5% Reset

Accuracy

♦ 200ms Power-OK/Reset Time Delay

♦ RESET Output (MAX808)

RESET and RESET Outputs (MAX801)

♦ Watchdog Timer (MAX801)

♦ On-Board Gating of Chip-Enable Signals (MAX808):

Memory Write-Cycle Completion

3ns CE Gate Propagation Delay

♦ 1µA Standby Current

♦ Power Switching:

250mA in V

Mode

20mA in Battery-Backup Mode

♦ MaxCap™/SuperCap™ Compatible

♦ RESET Guaranteed Valid to V

= 1V

♦ Low-Line Threshold 52mV Above Reset

Threshold

MAX801L/M/N, MAX808L/M/N

8-Pin µP Supervisory Circuits

with ±1.5% Reset Accuracy

________________________________________________________________ Maxim Integrated Products 1

0.1μF

μP

POWER

POWER FOR

CMOS RAM

NMI

BATT

OUT

+5V

GND

RESET

FROM I/O SYSTEM OR

ADDRESS DECODER

TO CMOS RAM

CE IN

CE OUT

LOWLINE

RESET

MAX808

µP SYSTEM

__________Typical Operating Circuit

19-1086; Rev 1; 11/05

PART*

MAX801_CPA

MAX801_CSA

MAX801_EPA -40°C to +85°C

0°C to +70°C

TEMP RANGE PIN-PACKAGE

8 Plastic DIP

8 SO

8 Plastic DIP

______________Ordering Information

MaxCap is a trademark of The Carborundum Corp.

SuperCap is a trademark of Baknor Industries.

Pin Configurations appear at end of data sheet.

MAX801_ESA

MAX801_MJA

MAX808_CPA

0°C to +70°C

-55°C to +125°C

-40°C to +85°C 8 SO

8 CERDIP**

8 Plastic DIP

MAX808_CSA 0°C to +70°C 8 SO

MAX808_EPA

MAX808_ESA

MAX808_MJA -55°C to +125°C

-40°C to +85°C

-40°C to +85°C 8 Plastic DIP

8 SO

8 CERDIP**

*These parts offer a choice of reset threshold voltage. From the

table below, select the suffix corresponding to the desired thresh-

old and insert it into the blank to complete the part number.

**Contact factory for availability and processing to MIL-STD-883.

Devices in PDIP, SO and µMAX packages are available in both

leaded and lead-free packaging. Specify lead free by adding the

+ symbol at the end of the part number when ordering. Lead free

not available for CERDIP package.

RESET THRESHOLD (V)

L 4.60 4.675

N 4.50

4.75

M 4.35

4.575 4.65

4.425 4.50

MIN MAX

SUFFIX

TYP

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 (12 pages)

PAGE 1
9-1086; Rev 1; 11/05 8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy The MAX801/MAX808 microprocessor (µP) supervisory circuits monitor and control the activities of +5V µPs by providing backup-battery switchover, low-line indication, and µP reset. Additional features include a watchdog for the MAX801 and CMOS RAM write protection for the MAX808. The MAX801/MAX808 offer a choice of reset-threshold voltage (denoted by suffix letter): 4.675V (L), 4.575V (N), and 4.425V (M).
PAGE 2
MAX801L/M/N, MAX808L/M/N 8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy ABSOLUTE MAXIMUM RATINGS Input Voltage (with respect to GND) VCC .......................................................................-0.3V to +6V VBATT ....................................................................-0.3V to +6V All Other Pins........................................-0.3V to (VOUT + 0.3V) Input Current VCC Peak ..........................................................................1.
PAGE 3
8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy (VCC = 4.6V to 5.5V for the MAX80_L, VCC = 4.5V to 5.5V for the MAX80_N, VCC = 4.35V to 5.5V for the MAX80_M; VBATT = 2.8V; TA = TMIN to TMAX. Typical values are at VCC = 5V and TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS RESET AND LOW-LINE Reset Threshold VRST VCC rising and falling MAX80_L 4.600 4.675 4.750 MAX80_N 4.500 4.575 4.650 MAX80_M 4.350 4.425 4.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (VCC = 4.6V to 5.5V for the MAX80_L, VCC = 4.5V to 5.5V for the MAX80_N, VCC = 4.35V to 5.5V for the MAX80_M; VBATT = 2.8V; TA = TMIN to TMAX. Typical values are at VCC = 5V and TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS ±0.00002 ±1 µA 150 Ω CHIP-ENABLE GATING (MAX808) CE IN Leakage Current VCC = 4.
PAGE 5
8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy 4 2 0 50 MAX801/808-05 VBATT = 2.0V 20 15 VBATT = 2.8V 10 VBATT = 4.5V 1.5 IOUT = 250mA 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 -60 -40 -20 0 100 -60 -40 -20 0 20 40 60 80 100 120 140 20 40 60 80 100 120 140 CLOAD (pF) TEMPERATURE (°C) TEMPERATURE (°C) RESET THRESHOLD vs. TEMPERATURE RESET TIMEOUT PERIOD vs. TEMPERATURE (VCC RISING) LOWLINE to RESET THRESHOLD vs. TEMPERATURE (VCC FALLING) 4.60 MAX80_N 4.55 4.50 4.
PAGE 6
____________________________Typical Operating Characteristics (continued) (VCC = 5V, VBATT = 2.8V, no load, TA = +25°C, unless otherwise noted.) BATTERY CURRENT vs. INPUT SUPPLY VOLTAGE 12 10 8 6 4 MAX801/808-14 1000 VBATT TO VOUT VOLTAGE (mV) 14 BATTERY CURRENT (µA) BATT to OUT VOLTAGE vs. OUTPUT CURRENT MAX801/808-13 16 VCC = 0V SLOPE = 12Ω 100 2 0 10 2.6 2.7 2.8 2.9 3.0 1 10 100 VCC (V) IOUT (mA) VCC to OUT VOLTAGE vs. OUTPUT CURRENT MAXIMUM TRANSIENT DURATION vs.
PAGE 7
8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy PIN NAME FUNCTION MAX801 MAX808 5 — RESET — 5 CE OUT 6 — WDI — 6 CE IN Chip-Enable Input Active-High Reset Output. RESET is the inverse of RESET. It is a CMOS output that sources and sinks current. RESET swings between VCC and GND. Chip-Enable Output. Output to the chip-enable gating circuit. CE OUT is pulled up to the higher of VCC or VBATT when the chip-enable gate is disabled. Watchdog Input.
PAGE 8
MAX801L/M/N, MAX808L/M/N 8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy VRST VLL VRST + VLR VRST VCC VCC VLOWLINE VLOWLINE VRESET tRP VRESET VRESET (MAX801) tRP VRESET (MAX801) VCE OUT (MAX808) VCE OUT (MAX808) VBATT SHOWN FOR VCC = 0V to 5V, VBATT = 2.8V, CE IN = GND tLL tRD tRD tRCE VBATT SHOWN FOR VCC = 5V to 0V, VBATT = 2.8V, CE IN = GND Figure 2a. Timing Diagram, VCC Rising Figure 2b.
PAGE 9
8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy VCC LOWLINE TO μP NMI P VCC MAX801L/M/N, MAX808L/M/N 4.5V to 5.5V REGULATOR MAX801 MAX808 CHOLD CONTROL CIRCUITRY MAX801 MAX808 OUT 0.1μF CHOLD > ILOAD x tSHDN VLR GND BATT P P Figure 3. Using LOWLINE to Provide a Power-Fail Warning to the µP Figure 4.
PAGE 10
MAX801L/M/N, MAX808L/M/N 8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy MAX801 Watchdog Timer The watchdog monitors the µP’s activity. If the µP does not toggle the watchdog input (WDI) within 1.6sec, reset asserts for the reset timeout period. The internal 1.6sec timer is cleared when reset asserts or when a transition (low-to-high or high-to-low) occurs at WDI while reset is not asserted. The timer remains cleared and does not count as long as reset is asserted.
PAGE 11
8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy +5V VCC BATT MAX808 CE IN VCC 1N4148 0.47F CE OUT 50pF CLOAD 50Ω DRIVER OUT GND MAX801 MAX808 GND Figure 7. MAX808 CE Gate Test Circuit Figure 8. Using the MAX801/MAX808 with a SuperCap Chip-Enable Output In enabled mode, CE OUT’s impedance is equivalent to 75Ω in series with the source driving CE IN. In disabled mode, the 75Ω transmission gate is off and CE OUT is actively pulled to the higher of V CC or V BATT .
PAGE 12
MAX801L/M/N, MAX808L/M/N 8-Pin µP Supervisory Circuits with ±1.5% Reset Accuracy Watchdog Software Considerations To help the watchdog timer keep a closer watch on software execution, you can set and reset the watchdog input at different points in the program, rather than “pulsing” the watchdog input high-low-high or low-highlow. This technique avoids a “stuck” loop, where the watchdog timer continues to be reset within the loop, keeping the watchdog from timing out.