Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - system monitor Dual voltage detector SOIC 16

General Description

The MAX696/MAX697 supervisory circuits reduce the

complexity and number of components required for

power-supply monitoring and battery-control functions

in microprocessor (μP) systems. These include μP reset

and backup-battery switchover, watchdog timer, CMOS

RAM write protection, and power-failure warning. The

MAX696/MAX697 significantly improve system reliability

and accuracy compared to that obtained with separate

ICs or discrete components.

The MAX696 and MAX697 are supplied in 16-pin pack-

ages and perform six functions:

1) A reset output during power-up, power-down, and

brownout conditions. The threshold for this “lowline”

reset is adjustable by an external voltagedivider.

2) A reset pulse if the optional watchdog timer has not

been toggled within a specified time.

3) Individual outputs for low-line and watchdog fault con-

ditions.

4) The reset time may be left at its default value of 50ms,

or may be varied with an external capacitor or clock

pulses.

5) A separate 1.3V threshold detector for power-fail warn-

ing, low-battery detection, or to monitor a power supply

other than V

The MAX696 also has battery-backup switching for CMOS

RAM, CMOS microprocessor, or other lowpower logic.

The MAX697 lacks battery-backup switching, but has

write-protection pins (CE IN and CE OUT) for CMOS

RAM or EPROM. In addition, it consumes less than 250

microamperes.

Applications

● Computers

● Controllers

● Intelligent Instruments

● Critical μP Power Monitoring

Features

● Adjustable Low-Line Monitor and Power-Down Reset

● Power-OK/Reset Time Delay

● Watchdog Timer—100ms, 1.6s, or Adjustable

● Minimum Component Count

● 1μA Standby Current

● Battery-Backup Power Switching (MAX696)

● On-Board Gating of Chip-Enable Signals (MAX697)

● Separate Monitor for Power-Fail or Low-Battery

Warning

Typical Operating Circuit appears at end of data sheet.

Pin Configurations continued at end of data sheet.

Ordering Information continued at end of data sheet.

19-0829; Rev 5; 7/14

Devices in PDIP and SO packages are available in both leaded

and lead(Pb)-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.

PART TEMP RANGE PIN-PACKAGE

MAX696C/D 0°C to +70°C Dice

MAX696CPE 0°C to +70°C 16 PDIP

MAX696CWE 0°C to +70°C 16 Wide SO

MAX696EPE -40°C to +85°C 16 PDIP

MAX696EJE -40°C to +85°C 16 CERDIP

MAX696EWE -40°C to +85°C 16 Wide SO

MAX696MJE -55°C to +125°C 16 CERDIP

OUT

BATT

GND

LLIN

N.C.

BATT ON

PFI

WDI

OSC IN

OSC SEL

PFO

LOW LINE

TOP VIEW

RESET

WDO

MAX696

MAX696/MAX697 Microprocessor Supervisory Circuits

Ordering Information

Pin Congurations

Summary of content (16 pages)

PAGE 1
MAX696/MAX697 Microprocessor Supervisory Circuits General Description Features The MAX696 and MAX697 are supplied in 16-pin packages and perform six functions: Ordering Information The MAX696/MAX697 supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery-control functions in microprocessor (μP) systems. These include μP reset and backup-battery switchover, watchdog timer, CMOS RAM write protection, and power-failure warning.
PAGE 2
MAX696/MAX697 Microprocessor Supervisory Circuits Absolute Maximum Ratings Terminal Voltage (with respect to GND) VCC.......................................................................-0.3V to +6V VBATT...................................................................-0.3V to +6V All Other Inputs (Note 1).....................-0.3V to (VOUT + 0.5V) Input Current VCC................................................................................200mA VBATT...............................................
PAGE 3
MAX696/MAX697 Microprocessor Supervisory Circuits Electrical Characteristics (continued) (VCC = full operating range, VBATT = 2.8V, TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS Clock cycles Watchdog Timeout Period, External Clock Long period 4032 4097 Short period 960 1025 Minimum WDI Input Pulse Width VIL = 0.4V, VIH = 3.5V, VCC = 5V 200 RESET and RESET Output Voltage (Note 2) 0.4 ISINK = 1.6mA, 3V < VCC < 5.5V 0.4 ISOURCE = 1µA, VCC = 5V V 3.
PAGE 4
MAX696/MAX697 Microprocessor Supervisory Circuits Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) MAX696 SUPPLY CURRENT AS A FUNCTION OF SUPPLY VOLTAGE 1.50 1.25 VCC MODE 1.00 1.00 0.75 0.75 0.50 0.50 BATTERY MODE TA = 25°C 0.25 0 2 3 4 5 SUPPLY CURRENT (µA) BATTERY MODE SUPPLY CURRENT (mA) VCC MODE 1.25 1.50 0.
PAGE 5
MAX696/MAX697 Microprocessor Supervisory Circuits Pin Description PIN NAME FUNCTION MAX696 MAX697 1 — VBATT Backup-Battery Input. Connect to ground if a backup battery is not used. 2 — VOUT The higher of VCC or VBATT is internally switched to VOUT. Connect VOUT to VCC if VOUT and VBATT are not used. 3 3 VCC +5V Input 4 5 GND 0V Ground Reference for All Signals 5 — BATT ON BATT ON goes High when VOUT is Internally Switched to the VBATT Input.
PAGE 6
MAX696/MAX697 Microprocessor Supervisory Circuits Pin Description (continued) PIN NAME MAX696 MAX697 — 1 TEST — 12 CE OUT — 13 CE IN FUNCTION Used During Maxim Manufacture Only. Always ground this pin. CE OUT goes low only when CE IN is low and LLIN is above 1.3V. See Figure 5. The Input to the CE Gating Circuit. Connect to GND or VOUT if not used. +5V VCC INPUT 0.1µF 0.
PAGE 7
MAX696/MAX697 Microprocessor Supervisory Circuits Watchdog Timer low for 50ms after LLIN rises above 1.3V. This prevents repeated toggling of RESET even if the VCC power drops out and recovers with each power line cycle. The microprocessor drives the watchdog input (WDI) with an I/O line. When OSC IN and OSC SEL are unconnected, the microprocessor must toggle the WDI pin once every 1.6 seconds to verify proper software execution.
PAGE 8
MAX696/MAX697 Microprocessor Supervisory Circuits MAX697 The MAX697 is nearly identical to the MAX696. The MAX697 lacks the battery-backup feature, so it does not have the VBATT, VOUT, or BATT ON pins. This allows the MAX697 to consume less than 250 microamperes, and it allows the inclusion of RAM write-protection pins. See Figure 2.
PAGE 9
MAX696/MAX697 Microprocessor Supervisory Circuits The MAX696 operates with battery voltages from 2.0V to 4.25V. The battery voltage should not be within 0.5V of VCC, or switchover may occur. High-value capacitors, either standard electrolytic or the farad-size doublelayer capacitors, can also be used for short-term memory backup. The capacitor charging voltage should include a diode to limit the fully charged voltage to approximately 0.5V less than VCC.
PAGE 10
MAX696/MAX697 Microprocessor Supervisory Circuits LLIN RESET OUTPUT 1.312V 50ms 1.3V 1.312V 1.3V 50ms LOW LINE OUTPUT (MAX697) CE IN (MAX697) CE OUT Figure 5. MAX697 Reset Timing CE Gating and RAM Write Protection The MAX697 uses two pins to control the CE or WRITE inputs of CMOS RAMs. When LLIN is > 1.3V, CE OUT is a buffered replica of CE IN, with a 50ns propagation delay. If LLIN input falls below 1.3V (1.2V min, 1.4V max), an internal gate forces CE OUT high, independent of CE IN.
PAGE 11
MAX696/MAX697 Microprocessor Supervisory Circuits PRESCALER WATCHDOG INPUT VCC 10.24kHz FROM INTERNAL OSCILLATOR OR EXTERNALLY SET FREQUENCY FROM OSC IN PIN Q6 2.7V + HI IF WATCHDOG INPUT IS FLOATING WATCHDOG TIMEOUT SELECT RESET COUNTER + - R WATCHDOG COUNTER Q10/12 WATCHDOG TIMEOUT SELECTOR LOGIC Q11 Q13 Q15 R 1.0V TRANSITION DETECTOR GOES HIGH AT THE END OF WATCHDOG TIMEOUT PERIOD FOR EACH TRANSITION S LOW LINE (HI IF LLIN < 1.
PAGE 12
MAX696/MAX697 Microprocessor Supervisory Circuits Applications Information Adding Hysteresis to the Power-Fail Comparator Since the power-fail comparator circuit is noninverting, hysteresis can be added by connecting a resistor between the PFO output and the PFI input as shown in Figure 7. When PFO is low, resistor R3 sinks current from the summing junction at the PFI pin. When PFO is high, the series combination of R3 and R4 source current into the PFI summing junction.
PAGE 13
MAX696/MAX697 Microprocessor Supervisory Circuits Table 1. MAX696 and MAX697 Reset Pulse Width and Watchdog Timeout Selections (Notes 1, 2) WATCHDOG TIMEOUT PERIOD OSC SEL (Note 3) OSC IN IMMEDIATELY AFTER RESET NORMAL RESET TIMEOUT PERIOD Low External Clock Input 1024 clocks 4096 clocks 512 clocks Low External Capacitor 400ms/47pF x C 1.6s/47pF x C 200ms/47pF x C High/Floating Low 100ms 1.6s 50ms High/Floating Floating 1.6s 1.
PAGE 14
MAX696/MAX697 Microprocessor Supervisory Circuits Typical Operating Circuit -5V POWER TO CMOS RAM VOUT VCC P POWER VBATT µP SYSTEM MAX696 RESET RESET LLIN PFI µP RESET PFO µP NMI WDI I/O LINE GND Pin Configurations (continued) Ordering Information PART TEMP RANGE PIN-PACKAGE MAX697C/D 0°C to +70°C Dice MAX697CPE 0°C to +70°C 16 PDIP MAX697CWE 0°C to +70°C 16 Wide SO MAX697EPE -40°C to +85°C 16 PDIP MAX697EJE -40°C to +85°C 16 CERDIP MAX697EWE -40°C to +85°C 16 Wide SO
PAGE 15
MAX696/MAX697 Microprocessor Supervisory Circuits Chip Topography MAX697 TEST RESET MAX696 RESET VOUT VBATT RESET RESET VCC VCC WDO WDO CE IN CE OUT 0.116” [2.95mm] LLIN 0.116” [2.95mm] LLIN GND GND BATT ON WDI LOW LINE OSC IN OSC PFI PFO SEL WDI LOW LINE 0.084” [2.13mm] OSC IN OSC PFI PFO SEL 0.084” [2.13mm] Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages.
PAGE 16
MAX696/MAX697 Microprocessor Supervisory Circuits Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 4 5/14 No /V OPNs; removed automotive reference from Applications section 5 7/14 Corrected typos in Figures 4, 5; updated Reset Output section DESCRIPTION 1 9, 10 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.