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PDF MAX808 Data sheet ( Hoja de datos )
| Número de pieza | MAX808 | |
| Descripción | 8-Pin P Supervisory Circuits with 1.5eset Accuracy | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-1086; Rev 0; 6/96
8-Pin µP Supervisory Circuits
with ±1.5% Reset Accuracy
_______________General Description
The MAX801/MAX808 microprocessor (µP) supervisory
circuits monitor and control the activities of +5V µPs by
providing backup-battery switchover, low-line indica-
tion, and µP reset. Additional features include a watch-
dog for the MAX801 and CMOS RAM write protection
for the MAX808.
The MAX801/MAX808 offer a choice of reset-threshold
voltage (denoted by suffix letter): 4.675V (L), 4.575V
(N), and 4.425V (M). These devices are available in
8-pin DIP and SO packages.
________________________Applications
Computers
Controllers
Intelligent Instruments
Critical µP Power Monitoring
Portable/Battery-Powered Equipment
Embedded Systems
Pin Configurations appear at end of data sheet.
__________Typical Operating Circuit
+5V
0.1µF
0.1µF
VCC OUT
BATT
0.1µF
LOWLINE
RESET
MAX808
CE IN
CE OUT
GND
POWER FOR µP
CMOS RAM POWER
NMI
RESET
µP SYSTEM
FROM I/O SYSTEM OR
ADDRESS DECODER
TO CMOS RAM
____________________________Features
o Precision Voltage Monitoring, ±1.5% Reset
Accuracy
o 200ms Power-OK/Reset Time Delay
o RESET Output (MAX808)
RESET and RESET Outputs (MAX801)
o Watchdog Timer (MAX801)
o On-Board Gating of Chip-Enable Signals (MAX808):
Memory Write-Cycle Completion
3ns CE Gate Propagation Delay
o 1µA Standby Current
o Power Switching:
250mA in VCC Mode
20mA in Battery-Backup Mode
o MaxCap™/SuperCap™ Compatible
o RESET Guaranteed Valid to VCC = 1V
o Low-Line Threshold 52mV Above Reset
Threshold
MaxCap is a trademark of The Carborundum Corp.
SuperCap is a trademark of Baknor Industries.
______________Ordering Information
PART*
MAX801_CPA
MAX801_CSA
MAX801_EPA
MAX801_ESA
MAX801_MJA
MAX808_CPA
MAX808_CSA
MAX808_EPA
MAX808_ESA
MAX808_MJA
TEMP. RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
8 CERDIP**
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
8 CERDIP**
* 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.
**Contact factory for availability and processing to MIL-STD-883.
SUFFIX
L
N
M
RESET THRESHOLD (V)
MIN
TYP
MAX
4.60
4.675
4.75
4.50
4.575
4.65
4.35
4.425
4.50
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
1 page  
8-Pin µP Supervisory Circuits
with ±1.5% Reset Accuracy
____________________________Typical Operating Characteristics (continued)
(VCC = 5V, VBATT = 2.8V, no load, TA = +25°C, unless otherwise noted.)
MAX808
CHIP-ENABLE PROPAGATION DELAY
vs. CE OUT LOAD CAPACITANCE
8
50Ω DRIVER
6
4
2
0
0
4.70
50
CLOAD (pF)
RESET THRESHOLD
vs. TEMPERATURE
100
4.65
MAX80_L
4.60
4.55 MAX80_N
4.50
4.45
MAX80_M
4.40
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
LOWLINE THRESHOLD
vs. TEMPERATURE (VCC RISING)
4.80
4.75 MAX80_L
4.70
4.65 MAX80_N
4.60
4.55
4.50 MAX80_M
4.45
4.40
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
BATT to OUT ON-RESISTANCE
vs. TEMPERATURE
30
VCC = 0V
IOUT = 10mA
25
20 VBATT = 2.0V
15
VBATT = 2.8V
10
VBATT = 4.5V
5
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
RESET TIMEOUT PERIOD
vs. TEMPERATURE (VCC RISING)
280
260
240
220
200
180
160
140
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
LOWLINE COMPARATOR PROPAGATION
DELAY vs. TEMPERATURE (VCC FALLING)
40
VCC FALLING AT 1mV/µs
35
30
25
20
15
10
5
0
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
VCC to OUT ON-RESISTANCE
vs. TEMPERATURE
1.6
1.5 IOUT = 250mA
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
LOWLINE to RESET THRESHOLD
vs. TEMPERATURE (VCC FALLING)
80
70
60
50
40
30
20
10
0
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
RESET COMPARATOR PROPAGATION
DELAY vs. TEMPERATURE (VCC FALLING)
40
VCC FALLING AT 1mV/µs
35
30
25
20
15
10
5
0
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
_______________________________________________________________________________________ 5
5 Page 
50Ω DRIVER
VRST(max)
VCC
MAX808
CE IN
CE OUT
GND
8-Pin µP Supervisory Circuits
with ±1.5% Reset Accuracy
50pF CLOAD
+5V
1N4148
0.47F
VCC
BATT OUT
MAX801
MAX808
GND
Figure 7. MAX808 CE Gate Test Circuit
Figure 8. Using the MAX801/MAX808 with a SuperCap
Chip-Enable Output
In enabled mode, CE OUT’s impedance is equivalent to
75Ω in series with the source driving CE IN. In disabled
mode, the 75Ω transmission gate is off and CE OUT is
actively pulled to the higher of VCC or VBATT. The
source turns off when the transmission gate is enabled.
__________Applications Information
The MAX801/MAX808 are not short-circuit protected.
Shorting OUT to ground, other than power-up transients
such as charging a decoupling capacitor, may destroy
the device. If long leads connect to the IC’s inputs,
ensure that these lines are free from ringing and other
conditions that would forward bias the IC’s protection
diodes. Bypass OUT, VCC, and BATT with 0.1µF
capacitors to GND.
The MAX801/MAX808 operate in two distinct modes:
1) Normal Operating Mode, with all circuitry powered
up. Typical supply current from VCC is 68µA (48µA
for the MAX808), while only leakage currents flow
from the battery.
2) Battery-Backup Mode, where VCC is below VBATT
and VRST. The supply current from the battery is typ-
ically less than 1µA.
Using SuperCaps™ or MaxCaps™
with the MAX801/MAX808
BATT has the same operating voltage range as VCC, and
the battery-switchover threshold voltage is typically
VBATT when VCC is decreasing or VBATT + 0.05V when
VCC is increasing. This hysteresis allows use of a
SuperCap (e.g., around 0.47F) and a simple charging
circuit as a backup source (Figure 8). Since VBATT can
exceed VCC while VCC is above the reset threshold, no
special precautions are needed when using these µP
supervisors with a SuperCap.
Backup-Battery Replacement
The backup battery can be disconnected while VCC is
above the reset threshold, provided BATT is bypassed
with a 0.1µF capacitor to ground. No precautions are
necessary to avoid spurious reset pulses.
Negative-Going VCC Transients
While issuing resets to the µP during power-up, power-
down, and brownout conditions, these supervisors are
relatively immune to short-duration, negative-going VCC
transients (glitches). It is usually undesirable to reset
the µP when VCC experiences only small glitches.
The Typical Operating Characteristics show a graph of
Maximum Transient Duration vs. Reset Threshold
Overdrive, for which reset pulses are not generated.
The graph was produced using negative-going VCC
pulses, starting at 5V and ending below the reset
threshold by the magnitude indicated (reset compara-
tor overdrive). The graph shows the maximum pulse
width that a negative-going VCC transient may typically
have without causing a reset pulse to be issued. As the
amplitude of the transient increases (i.e., goes farther
below the reset threshold), the maximum allowable
pulse width decreases. Typically, a VCC transient that
goes 40mV below the reset threshold and lasts for 3µs
or less will not cause a reset pulse to be issued. A
0.1µF bypass capacitor mounted close to the VCC pin
provides additional transient immunity.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX808.PDF ] | |
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