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MAX819 Datasheet

Download or read online Maxim Integrated MAX819 5V µP Supervisory Circuit with Manual Reset Input pdf datasheet.



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19-0486; Rev 3; 12/05
+5V Microprocessor Supervisory Circuits
General Description
The MAX817/MAX818/MAX819 microprocessor (µP)
supervisory circuits simplify power-supply monitoring,
battery control, and chip-enable gating in µP systems
by reducing the number of components required.
These devices are designed for use in +5V-powered
systems. Low supply current (11µA typical) and small
package size make these devices ideal for portable
applications. The MAX817/MAX818/MAX819 are specif-
ically designed to ignore fast transients on V
supervisory functions include active-low reset, backup-
battery switchover, watchdog input, battery freshness
seal, and chip-enable gating. The Selector Guide below
lists the specific functions available from each device.
These devices offer two pretrimmed reset threshold volt-
ages for ±5% or ±10% power supplies: 4.65V for the L
versions and 4.40V for the M versions. The MAX817/
MAX818/MAX819 are available in space-saving µMAX
packages, as well as 8-pin DIP/SO.
_____________________Selector Guide
MAX817
FEATURE
L/M

Active-Low Reset

Backup-Battery Switchover

Power-Fail Comparator

Watchdog Input

Battery Freshness Seal
Manual Reset Input
Chip-Enable Gating
8-DIP/SO/
Pin-Package
µMAX
Low-Power, Pin-
MAX690A/
Compatible Upgrades for:
MAX692A
________________________Applications
Battery-Powered Computers and Controllers
Embedded Controllers
Intelligent Instruments
Critical µP Monitoring
Portable Equipment
Typical Operating Circuit appears at end of data sheet.
*P
________________________________________________________________ Maxim Integrated Products
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.
____________________________Features
o Precision Supply-Voltage Monitor:
4.65V (MAX81_L)
4.40V (MAX81_M)
o 11µA Quiescent Supply Current
o 200ms Reset Time Delay
o Watchdog Timer with 1.6sec Timeout
(MAX817/MAX818)
. Other
CC
o Battery-Backup Power Switching; Battery Voltage
Can Exceed V
o Battery Freshness Seal
o On-Board, 3ns Gating of Chip-Enable Signals
(MAX818)
o Uncommitted Voltage Monitor for Power-Fail or
Low-Battery Warning (MAX817/MAX819)
o Manual Reset Input (MAX819)
______________Ordering Information
PART
MAX818
MAX819
MAX817_CPA
L/M
L/M
MAX817_CSA


MAX817_CUA


Ordering Information continued on last page.

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

table below, select the suffix corresponding to the desired


threshold and insert it into the blank to complete the part number.
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.
8-DIP/SO/
8-DIP/SO/
µMAX
µMAX
MAX703/
MAX704
_________________Pin Configurations
TOP VIEW
Pin Configurations continued at end of data sheet.
CC
TEMP. RANGE
PIN-PACKAGE
0°C to +70°C
8 Plastic DIP
0°C to +70°C
8 SO
0°C to +70°C
8 µMAX
SUFFIX
RESET THRESHOLD (V)
L
4.65
M
4.40
1
8
BATT
OUT
2
RESET
V
7
CC
MAX817
3
WDI
GND
6
4
PFI
5
PFO
DIP/SO/µMAX
1

Summary of Contents

Page 1

... These devices offer two pretrimmed reset threshold volt- ages for ±5% or ±10% power supplies: 4.65V for the L versions and 4.40V for the M versions. The MAX817/ MAX818/MAX819 are available in space-saving µMAX packages, as well as 8-pin DIP/SO. ___Selector Guide MAX817 ...

Page 2

Microprocessor Supervisory Circuits ABSOLUTE MAXIMUM RATINGS Input Voltage V , BATT ...-0.3V to 6.0V CC All Other Pins (Note 1)...-0. Input Current V Peak ... Continuous ...250mA CC BATT Peak ...250mA BATT Continuous ...50mA GND ...

Page 3

... POWER-FAIL COMPARATOR (MAX817/MAX819 only) PFI Input Threshold V PFI Input Hysteresis PFI Input Current V PFO Output Voltage V PFO Short-Circuit Current MANUAL RESET INPUT (MAX819 only) MR Input Threshold MR Pulse Width MR Pulse that Would Not Cause a Reset MR to Reset Delay MR Pull-Up Resistance ___ 4.5V to 5.5V for MAX81_M, V ...

Page 4

Microprocessor Supervisory Circuits ELECTRICAL CHARACTERISTICS (continued 4.75V to 5.5V for MAX81_L noted. Typical values are 25°C.) A PARAMETER SYMBOL CHIP-ENABLE GATING (MAX818 only Leakage Current OUT ...

Page 5

Microprocessor Supervisory Circuits ___Typical Operating Characteristics (V 5V 3.0V 25°C, unless otherwise noted.) CC BATT A SUPPLY CURRENT vs. TEMPERATURE (NO LOAD -40 - ...

Page 6

... TEMPERATURE (°C) BATTERY SUPPLY CURRENT vs. SUPPLY VOLTAGE (V) CC MAX817/MAX819 PFI TO PFO PROPAGATION DELAY vs. TEMPERATURE -40 - 100 TEMPERATURE (°C) ...

Page 7

... Microprocessor Supervisory Circuits ___Pin Description PIN MAX817 MAX818 MAX819 4 4 5 5 5 — — ___ NAME Supply Output for CMOS RAM. When V OUT or above V , OUT is connected to V BATT MOSFET switch ...

Page 8

... Microprocessor Supervisory Circuits BATT V CC THIS PIN FOR MAX819 MR ONLY. WDI THIS SECTION FOR MAX817/ MAX818 ONLY. PFI THIS SECTION FOR MAX817/ MAX819 ONLY. THIS SECTION FOR MAX818 ONLY Figure 1. Functional Diagram 8 ___ BATTERY SWITCHOVER CIRCUITRY RESET GENERATOR 1.25V ...

Page 9

... Manual Reset Input (MAX819) Many µP-based products require manual reset capabil- ity, allowing the operator, a test technician, or external logic circuitry to initiate a reset. On the MAX819, a logic low on MR asserts reset. Reset remains asserted while MR is low, and for t (200ms) after it returns high. ...

Page 10

... Microprocessor Supervisory Circuits On the MAX819, MR must be high or open to enable the battery freshness seal. Once the battery freshness seal is enabled its operation is unaffected by MR. Watchdog Input (MAX817/MAX818) In the MAX817/MAX818, the watchdog circuit monitors the µPs activity. If the µP does not toggle the watchdog input (WDI) within t (1 ...

Page 11

... PFI parator is unused, connect PFI to ground and leave PFO unconnected. PFO can be connected the MAX819 so that a low voltage on PFI will generate a reset (Figure 9). In this configuration, when the monitored voltage causes PFI to fall below V causing a reset to be asserted. Reset remains asserted ...

Page 12

... BATT off and the supply current falls to less than 1µA. ___Applications Information BATT The MAX817/MAX818/MAX819 are protected for typical falls CC short-circuit conditions of 10sec or less. Shorting OUT to ground for longer than 10sec destroys the device. Decouple V 0.1µF capacitors as close to the device as possible. ...

Page 13

... SuperCap on BATT discharges through V CC until V BATT mode is then initiated and the current through V goes to zero. The MAX817/MAX818/MAX819 were designed for bat- tery-backed applications backup battery is not used, connect V ground. The backup power source can be removed while V remains valid, without danger of triggering a reset pulse, if BATT is decoupled with a 0.1µ ...

Page 14

... Bidirectional Reset Pins µPs with bidirectional reset pins, such as the Motorola 68HC11 series, can contend with the MAX817/MAX818/ MAX819 RESET output. If, for example, the RESET out- put is driven high and the µP wants to pull it low, inde- terminate logic levels may result. To correct this, connect a 4.7kΩ ...

Page 15

... ADDRESS DECODE START SET WDI LOW SUBROUTINE OR PROGRAM LOOP, SET WDI HIGH RETURN END OUT 1 8 BATT 2 RESET MAX818 3 WDI GND OUT DIP/SO/µMAX OUT 1 8 BATT 2 RESET MAX819 3 MR GND PFO PFI DIP/SO/µMAX 15 ...

Page 16

... MAX819_CUA 0°C to 70°C MAX819_EPA -40°C to 85°C MAX819_ESA -40°C to 85°C These parts offer a choice of reset threshold voltage. From the table below, select the suffix corresponding to the desired threshold and insert it into the blank to complete the part number. ...

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