Document
19-0366; Rev 6; 3/10
MAX793/MAX794/MAX795
3.0V/3.3V Adjustable Microprocessor Supervisory Circuits
General Description
The MAX793/MAX794/MAX795 microprocessor (µP) supervisory circuits monitor and control the activities of +3.0V/+3.3V µPs by providing backup-battery switchover, among other features such as low-line indication, µP reset, write protection for CMOS RAM, and a watchdog (see the Selector Guide below). The backup-battery voltage can exceed VCC, permitting the use of 3.6V lithium batteries in systems using 3.0V to 3.3V for VCC.
The MAX793/MAX795 offer a choice of reset threshold voltage range (denoted by suffix letter): 3.00V to 3.15V (T), 2.85V to 3.00V (S), and 2.55V to 2.70V (R). The MAX794’s reset threshold is set externally with a resistor divider. The MAX793/MAX794 are available in 16-pin DIP and narrow SO packages, and the MAX795 comes in 8-pin DIP and SO packages.
_____________________Selector Guide
FEATURE Active-Low Reset Active-High Reset
Programmable Reset Threshold
Low-Line Early Warning Output
Backup-Battery Switchover
External Switch Driver Power-Fail Comparator Battery OK Output Watchdog Input Battery Freshness Seal Manual Reset Input Chip-Enable Gating Pin-Package
MAX793
MAX794
MAX795
16-DIP/SO 16-DIP/SO
8-DIP/SO
________________________Applications
Battery-Powered Computers and Controllers Embedded Controllers Intelligent Controllers Critical µP Power Monitoring Portable Equipment
Pin Configurations appear at end of data sheet.
____________________________Features
MAX793/MAX794/MAX795
o Precision Supply-Voltage Monitor: Fixed Reset Trip Voltage (MAX793/MAX795) Adjustable Reset Trip Voltage (MAX794)
o Guaranteed Reset Assertion to VCC = 1V o Backup-Battery Power Switching—Battery
Voltage Can Exceed VCC o On-Board Gating of Chip-Enable Signals—7ns
Max Propagation Delay
MAX793/MAX794 Only
o Battery Freshness Seal
o Battery OK Output (MAX793)
o Uncommitted Voltage Monitor for Power-Fail or Low-Battery Warning
o Independent Watchdog Timer (1.6s timeout)
o Manual Reset Input
Ordering Information
PART*
TEMP RANGE
PINPACKAGE
MAX793_CPE MAX793_CSE
0°C to +70°C 0°C to +70°C
16 Plastic DIP 16 Narrow SO
Ordering Information continued at end of data sheet.
*The MAX793/MAX795 offer a choice of reset threshold voltage. Select the letter corresponding to the desired reset threshold voltage range (T = 3.00V to 3.15V, S = 2.85V to 3.00V, R = 2.55V to 2.70V) and insert it into the blank to complete the part number. The MAX794’s reset threshold is adjustable.
Devices 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.
__________Typical Operating Circuit
3.0V OR 3.3V 0.1µF
3.6V 0.1µF
+5V SUPPLY +5V FAILURE
(OPTIONAL) Si9433DY SILICONIX
PMOS VCC BATT ON OUT BATT CE OUT
0.1µF
CMOS RAM
MAX793 WDO CE IN
MR WDI PFO LOWLINE
ADDRESS DECODER
VCC
VCC A0-A15
I/O NMI
µP
PFI RESET
BATT OK GND
RESET
________________________________________________________________ Maxim Integrated Products 1
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.
3.0V/3.3V Adjustable Microprocessor Supervisory Circuits
MAX793/MAX794/MAX795
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND) VCC ......................................................................-0.3V to +6.0V VBATT...................................................................-0.3V to +6.0V All Other Inputs ..................-0.3V to the higher of VCC or VBATT
Continuous Input Current VCC .................................................................................200mA VBATT ................................................................................50mA GND ..................................................................................20mA
Output Current VOUT................................................................................200mA All Other Outputs ..............................................................20mA
Continuous Power Dissipation (TA = +70°C) 8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) .....727mW 8-Pin SO (derate 5.88mW/°C above +70°C)..................471mW 16-Pin Plastic DIP (derate 10.53mW/°C above +70°C) .842mW 16-Pin Narrow SO (derate 9.52mW/°C above +70°C) ...696mW
Operating Temperature Ranges MAX793_C_ _/MAX794C_ _/MAX795_C_ _ ......... 0°C to +70°C MAX793_E_ _/MAX794E_ _/MAX795_E_ _ ........-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10s) .................................+300°C Soldering Temperature (reflow) .......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these o.