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General Description

The MAX703/MAX704 microprocessor (μP) supervisory

circuits reduce the complexity and number of components

required for power-supply monitoring and battery control

functions in μP systems. These devices significantly

improve system reliability and accuracy compared to that

obtained with separate ICs or discrete components.

The MAX703/MAX704 are available in 8-pin DIP and SO

packages and provide four functions:

1) An active-low reset during power-up, power-down, and

brownout conditions.

2) Battery-backup switching for CMOS RAM, CMOS μPs,

or other low-power logic circuitry.

3) A 1.25V threshold detector for power-fail warning,

low-battery detection, or for monitoring a power supply

other than +5V.

4) An active-low manual reset input.

The MAX703 and MAX704 differ only in their supplyvolt-

age monitor levels. The MAX703 generates a reset when

the supply drops below 4.65V, while the MAX704 gener-

ates a reset below 4.40V.

Applications

● Computers

● Controllers

● Intelligent Instruments

● Critical μP Power Monitoring

Features

● Battery-Backup Power Switching

● Precision Supply-Voltage Monitor

• 4.65V (MAX703)

• 4.40V (MAX704)

● 200ms Reset Pulse Width

● Debounced TTL/CMOS-Compatible Manual Reset

Input

● 200μA Quiescent Current

● 50nA Quiescent Current in Battery-Backup Mode

● Voltage Monitor for Power-Fail or Low-Battery

Warning

● 8-Pin DIP and SO Packages

● Guaranteed RESET Assertion to V

= 1V

19-0130; Rev 3; 5/14

*Dice are tested at T

= +25°C only.

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

Devices in PDIP and SO packages are available in both leaded

and lead(Pb)-free packaging. Specify lead(Pb)-free by adding

the “+” symbol at the end of the part number when ordering.

Lead(Pb)-free not available for CERDIP package.

PART TEMP RANGE PIN-PACKAGE

MAX703C/D 0°C to +70°C Dice*

MAX703CPA 0°C to +70°C 8 PDIP

MAX703CSA 0°C to +70°C 8 SO

MAX703EPA -40°C to +85°C 8 PDIP

MAX703ESA -40°C to +85°C 8 SO

MAX703MJA -55°C to +125°C 8 CERDIP**

MAX704C/D 0°C to +70°C Dice*

MAX704CPA 0°C to +70°C 8 PDIP

MAX704CSA 0°C to +70°C 8 SO

MAX704EPA -40°C to +85°C 8 PDIP

MAX704ESA -40°C to +85°C 8 SO

MAX704MJA -55°C to +125°C 8 CERDIP**

UNREGULATED DC REGULATED +5V

CMOS RAM

MICROPROCESSOR

3.6V

LITHIUM

BATTERY

PFI

PUSHBUTTON

SWITCH

0.1µF

OUT

BATT

NMI

GND

BUS

RESET

PFO

MAX703

MAX704

PFOPFI

MAX703

MAX704

BATT

RESETV

GND

OUT

DIP/SO

TOP VIEW

MAX703/MAX704 Low-Cost Microprocessor Supervisory

Circuits with Battery Backup

Typical Operating Circuit

Pin Conguration

Ordering Information

Summary of content (10 pages)

PAGE 1
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup General Description The MAX703/MAX704 microprocessor (μP) supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery control functions in μP systems. These devices significantly improve system reliability and accuracy compared to that obtained with separate ICs or discrete components.
PAGE 2
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup Absolute Maximum Ratings Terminal Voltage (with respect to GND) Rate-of-Rise VBATT, VCC................................................100V/μs VCC...................................................................-0.3V to +6.0V Operating Temperature Range VBATT................................................................-0.3V to +6.0V C Suffix................................................................
PAGE 3
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup Electrical Characteristics (continued) (VCC = +4.75V to +5.5V for MAX703, VCC = +4.5V to +5.5V for MAX704, VBATT = 2.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL MR Input Threshold CONDITIONS VIL Low VIH High MR Pulse Width tMR MR to RESET Delay tMD MIN TYP MAX UNITS 0.8 V 2.0 150 ns 250 ns MR Pullup Current MR = 0V 100 250 600 µA PFI Input Threshold VCC = 5V 1.20 1.25 1.
PAGE 4
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup Pin Description PIN NAME FUNCTION 1 VOUT Supply Output for CMOS RAM. When VCC is above the reset threshold, VOUT connects to VCC through a p-channel MOSFET switch. When VCC is below the reset threshold, the higher of VCC or VBATT is connected to VOUT. 2 VCC +5V Supply Input 3 GND Ground 4 PFI Power-Fail Comparator Input. When PFI is less than 1.25V, PFO goes low; otherwise PFO remains high.
PAGE 5
MAX703/MAX704 Detailed Description RESET Output A μP’s reset input starts the μP in a known state. Whenever the μP is in an unknown state, it should be held in reset. The MAX703/MAX704 assert reset when VCC is low, preventing code-execution errors during power-up, power-down, or brownout conditions. When VBATT is 2V or more, RESET is always valid, irrespective of VCC. On power-up, as VCC rises, RESET remains low.
PAGE 6
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup drops to more than 1V below VBATT, the internal switchover comparator shuts off and the supply current falls to less than 1μA. +5V VOUT VCC Manual Reset TO STATIC RAM MAX704 The manual reset input (MR) allows RESET to be activated by a pushbutton switch. The switch is effectively debounced by the 140ms minimum reset pulse width. Because it is TTL/CMOS compatible, MR can be driven by an external logic line.
PAGE 7
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup Ensuring a Valid RESET Output Down to VCC = 0V When VCC falls below 1V, the MAX703/MAX704 RESET output no longer sinks current; it becomes an open circuit. High-impedance CMOS logic inputs can drift to undetermined voltages if left as open circuits. If a pulldown resistor is added to the RESET pin as shown in Figure 6, any stray charge or leakage currents will flow to ground, holding RESET low.
PAGE 8
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup Using the Power-Fail Comparator to Assert Reset In addition to asserting reset at the VCC reset threshold voltage, reset can also be asserted at the PFI input threshold voltage. Connect PFO to MR to initiate a reset pulse when the monitored supply drops below a userspecified threshold or when VCC falls below the reset threshold. For additional noise rejection, place a capacitor between PFI and GND. Table 3.
PAGE 9
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup Chip Topography Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. 0.070” [1.778mm] VOUT VBATT VCC RESET WDI GND PFI 0.065” [1.
PAGE 10
MAX703/MAX704 Low-Cost Microprocessor Supervisory Circuits with Battery Backup Revision History REVISION NUMBER REVISION DATE 3 5/14 PAGES CHANGED DESCRIPTION Removed “Automotive Systems” from the Applications section 1 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.