Datasheet

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General Description

The MAX16997/MAX16998 are microprocessor (µP)

supervisory circuits for high-input-voltage and low-qui-

escent-current applications. These devices detect

downstream circuit failures and provide switchover to

redundant circuitry. See the

Selector Guide

for the dif-

ferent versions of this product family.

The MAX16997/MAX16998 family has four independent

inputs for reset and watchdog functions. SWT and SRT

inputs independently set the timeout periods of watch-

dog and reset timers through external capacitors.

RESETIN/EN monitor voltages at respective inputs. A

resistive voltage-divider sets the reset threshold.

The MAX16998A/B/D generate two output signals,

RESET and ENABLE. RESET asserts whenever

RESETIN drops below its threshold voltage or when the

watchdog timer detects a timing fault at WDI. Once

asserted, and after all reset conditions are removed,

RESET remains low for the reset timeout period, t

RESET

and then goes high. The MAX16997A generates one

output signal (ENABLE) based on the voltage level at

EN and the signal at WDI.

The MAX16997A does not have a RESET output. The

watchdog is disabled if the voltage at EN is below its

threshold. The MAX16997A watchdog timer starts tim-

ing when the voltage at EN becomes higher than the

preset threshold voltage level. Each time EN rises

above the preset threshold voltage, the initial watchdog

timeout period is 8 times the normal watchdog timeout

period (t

The MAX16997/MAX16998 are available in 8-pin lead-

free µMAX

packages and are fully specified over the

-40°C to +125°C automotive temperature range.

Applications

Automotive

Industrial

Features

o Wide 5V to 40V Input Voltage Range

o 18µA Quiescent Current (Typical at +125°C)

o Capacitor-Adjustable Timeout Period for

Watchdog and Reset

o Windowed Watchdog Timer Options

(MAX16998B/D)

o External Voltage Monitoring (RESETIN for the

MAX16998A/B/D and EN for the MAX16997A)

o Car Battery-Compatible EN Input

o TTL- and CMOS-Compatible Open-Drain Outputs

o 18V Maximum Open-Drain Reset Output Voltage

o 28V Maximum Open-Drain Enable Output Voltage

o Power-On/Power-Off Reset Functionality

(MAX16998A/B/D Only)

o AEC-Q100 Qualified

o -40°C to +125°C Operating Temperature Range

o Small (3mm x 3mm) µMAX Package

o WDI Narrow Pulse Immunity

MAX16997/MAX16998

High-Voltage Watchdog Timers with

Adjustable Timeout Delay

________________________________________________________________

Maxim Integrated Products

PART TEMP RANGE PIN-PACKAGE

MAX16997AAUA+ -40°C to +125°C 8 µMAX

MAX16997AAUA/V+ -40°C to +125°C 8 µMAX

MAX16998AAUA+ -40°C to +125°C 8 µMAX

MAX16998AAUA/V+ -40°C to +125°C 8 µMAX

MAX16998BAUA+ -40°C to +125°C 8 µMAX

MAX16998BAUA/V+ -40°C to +125°C 8 µMAX

MAX16998DAUA+ -40°C to +125°C 8 µMAX

MAX16998DAUA/V+ -40°C to +125°C 8 µMAX

PART

WATCHDOG

WINDOW SIZE (%)

ENABLE RESET EN RESETIN

MAX16997A 100 ✓ — ✓ —

MAX16998A 100 ✓✓ — ✓

MAX16998B 50 ✓✓ — ✓

MAX16998D 75 ✓✓ — ✓

Selector Guide

Ordering Information

19-4000; Rev 2; 8/09

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

+Denotes a lead(Pb)-free/RoHS-compliant package.

/V Denotes Automotive qualified part.

Pin Configurations appear at end of data sheet.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

Summary of content (16 pages)

PAGE 1
9-4000; Rev 2; 8/09 High-Voltage Watchdog Timers with Adjustable Timeout Delay The MAX16997/MAX16998 are microprocessor (µP) supervisory circuits for high-input-voltage and low-quiescent-current applications. These devices detect downstream circuit failures and provide switchover to redundant circuitry. See the Selector Guide for the different versions of this product family. The MAX16997/MAX16998 family has four independent inputs for reset and watchdog functions.
PAGE 2
MAX16997/MAX16998 High-Voltage Watchdog Timers with Adjustable Timeout Delay ABSOLUTE MAXIMUM RATINGS Junction-to-Case Thermal Resistance (θJC) (Note 1) ......42°C/W Junction-to-Ambient Thermal Resistance (θJA ) (Note 1).....206.3°C/W Operating Temperature Range (TA) ..................-40°C to +125°C Junction Temperature (TJ) ...............................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) ........................
PAGE 3
High-Voltage Watchdog Timers with Adjustable Timeout Delay MAX16997/MAX16998 ELECTRICAL CHARACTERISTICS (continued) (VIN = 14V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS WATCHDOG TIMER VIH WDI Input Threshold 2.
PAGE 4
Typical Operating Characteristics (continued) (CSWT = CSRT = 1500pF, TA = +25°C, unless otherwise noted.) 18.0 17.5 17.0 16.5 16.0 1.25 1.23 1.20 1.15 1.13 1.10 1.35 RISING 1.30 1.25 1.20 FALLING 1.15 1.10 1.05 1.00 TEMPERATURE (°C) SUPPLY VOLTAGE (V) RESETIN TO RESET DELAY vs. TEMPERATURE RESETIN/WATCHDOG PERIOD vs. SUPPLY VOLTAGE RESETIN/WATCHDOG PERIOD vs. SUPPLY VOLTAGE 50mV OVERDRIVE 0.
PAGE 5
High-Voltage Watchdog Timers with Adjustable Timeout Delay PIN NAME FUNCTION MAX16997A MAX16998A/B/D 1 1 IN Power-Supply Input. Bypass IN to GND with a 0.1µF capacitor. 2 — EN High-Impedance Input to the Enable Comparator. Depending on the voltage level at EN, the internal watchdog timer is turned on or off (see the EN Input section). 3, 7 — N.C. No Connection. Not internally connected. Watchdog Timeout Adjustment Input.
PAGE 6
High-Voltage Watchdog Timers with Adjustable Timeout Delay MAX16997/MAX16998 Functional Diagram IN MAX16997/MAX16998 PREG RESET VBG RESETIN (MAX16998) EN (MAX16997) WDI BUFFER ENABLE MAX16997A/ MAX16998A/B/D LOGIC IRAMP VBG SRT (MAX16998) IRAMP VBG SWT GND 6 _______________________________________________________________________________________
PAGE 7
High-Voltage Watchdog Timers with Adjustable Timeout Delay VEN VHYST VPON tWP tWD tWDI tWP INITIAL tWP tWP tWDI tWP tWP tWDI tWDI WDI 1 3 2 1 2 3 ENABLE tWP INITIAL = WATCHDOG TIMEOUT PERIOD x 8 tWP = WATCHDOG TIMEOUT PERIOD 3 CONSECUTIVE tWP WITHOUT TRIGGER ENABLE GOES LOW tWDI = WDI TRIGGER PERIOD 3 CONSECUTIVE WATCHDOG TRIGGER (WDI) ENABLE GOES ACTIVE HIGH Figure 1.
PAGE 8
High-Voltage Watchdog Timers with Adjustable Timeout Delay MAX16997/MAX16998 Timing Diagrams (continued) VRESETIN VHYST VPON PROPER WATCHDOG TRIGGER RESETS THE INTERNAL ENABLE COUNTER tOW tRESET tWDI tCW tWDI tWP tWP tWP tWDI tWDI WDI tWP 1 1 2 2 3 3 RESET ENABLE tRESET = RESET TIMEOUT PERIOD tOW = T OPEN WINDOW 3 CONSECUTIVE RESETS ENABLE GOES ACTIVE LOW tCW = T CLOSED WINDOW tWP = tCW + tOW tWDI = WDI TRIGGER PERIOD 3 CONSECUTIVE WATCHDOG TRIGGER (WDI) ENABLE GOES ACTIVE HIGH
PAGE 9
High-Voltage Watchdog Timers with Adjustable Timeout Delay The MAX16997/MAX16998 are µP supervisory circuits for high-input-voltage and low-quiescent-current applications. These devices improve system reliability by monitoring the sub-system for software code execution errors. The MAX16997A/MAX16998A/B/D detect downstream circuit failures, and provide switchover to redundant circuitry. These devices provide complete adjustability for reset and watchdog functions.
PAGE 10
MAX16997/MAX16998 High-Voltage Watchdog Timers with Adjustable Timeout Delay VIN VIN = 1.1V VRESETIN VHYST VPON tRESET tRESET tRESET tRESET RESET ENABLE tWP tWP tWP tCW ≤ tWDI ≤ tWP tWDI tWDI tWDI tWDI tWDI tWDI WDI tCW tWDI tWDI THE THREE CONSECUTIVE RESET COULD BE CAUSED BY THREE TIMEOUTS AS SHOWN HERE OR BY THREE WDI FALLING EDGE OUTSIDE THE OPEN WINDOW, OR A COMBINATION OF ANY RESET CONDITIONS EXCEPT VRESETIN DROPS TOO LOW.
PAGE 11
High-Voltage Watchdog Timers with Adjustable Timeout Delay VIN VCC MAX16998A/B/D R1 RESETIN ⎡R ⎤ VTH = VPON ⎢ 1 + 1⎥ ⎣ R2 ⎦ R2 where VTH is the desired reset threshold voltage, and V PON = 1.235V. To simplify the resistor selection, choose a value for R2 (< than 1MΩ) and calculate R1. ⎡ V ⎤ R1 = R2 ⎢ TH − 1⎥ ⎣ VPON ⎦ EN Input The MAX16997A provides a high-impedance input (EN) to the enable comparator. Based on the voltage level at EN, the watchdog timer is turned on or off.
PAGE 12
MAX16997/MAX16998 High-Voltage Watchdog Timers with Adjustable Timeout Delay WDI falling edge occurs within the watchdog timeout period (tWP) and is considered a late fault that asserts RESET. In case 3, the WDI falling edge occurs within the open window period and is considered a good WDI signal falling edge. In this case, RESET stays high. In case 4, the WDI falling edge occurs within the indeterminate region. In this case, the RESET state is indeterminate.
PAGE 13
High-Voltage Watchdog Timers with Adjustable Timeout Delay As shown in Figure 9, the open-drain RESET output can operate in the 2.5V to 18V range. This allows the device to interface a µP with other logic levels. WDI Glitch Immunity For additional glitch immunity, connect an RC lowpass filter as close as possible to WDI (see Figure 10). For example, for glitches with duration of 1µs, a 12kΩ resistor and a 47pF capacitor will provide immunity.
PAGE 14
MAX16997/MAX16998 High-Voltage Watchdog Timers with Adjustable Timeout Delay VBATT IN SRT EN ENABLE BACKUP CIRCUITRY, PERIPHERAL VCC 5V REGULATOR MAX16998A/B/D VCC R1 RESET RESET RESETIN µC R2 SWT I/O WDI GND GND Figure 11. MAX16998A/B/D Switch Over to Backup Circuitry VBATT BACKUP CIRCUITRY FLAGS IN BACKUP CIRCUITRY, PERIPHERAL ENABLE 5V REGULATOR VCC MAX16997A LDO R1 µC EN R2 RESET SWT WDI WATCHDOG I/O 5V I/O GND GND SEPARATE WATCHDOG Figure 12.
PAGE 15
High-Voltage Watchdog Timers with Adjustable Timeout Delay TOP VIEW IN 1 EN 2 N.C. 3 SWT 4 + MAX16997A IN 1 N.C. RESETIN 2 6 WDI SRT 3 5 GND SWT 4 8 ENABLE 7 8 MAX16998A/B/D ENABLE 7 RESET 6 WDI 5 GND µMAX µMAX Package Information Chip Information PROCESS: BiCMOS + For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
PAGE 16
MAX16997/MAX16998 High-Voltage Watchdog Timers with Adjustable Timeout Delay Revision History REVISION NUMBER REVISION DATE DESCRIPTION 0 2/08 Initial release 1 4/09 Added bullet to Features section, revised Electrical Characteristics table. 2 8/09 Added automotive qualified parts. PAGES CHANGED — 1, 2, 3 1 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.