MAX808LESA+ Maxim Integrated Products, MAX808LESA+ Datasheet - Page 11

• Manufacturer Part Number: MAX808LESA+
• Description: IC SUPERVISOR MPU 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Battery Backup Circuitr

Specifications of MAX808LESA+

• Number Of Voltages Monitored: 1
• Reset: Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 4.675V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Monitored Voltage: 0 V to 5.5 V
• Output Type: Active Low, Push-Pull
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Battery Backup Switching: Backup
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 0 V
• Supply Current (typ): 48 uA
• Maximum Power Dissipation: 471 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: No
• Undervoltage Threshold: 4.6 V
• Overvoltage Threshold: 4.75 V
• Power-up Reset Delay (typ): 280 ms
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

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 V
source turns off when the transmission gate is enabled.
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, V
capacitors to GND.
The MAX801/MAX808 operate in two distinct modes:
1) Normal Operating Mode, with all circuitry powered
2) Battery-Backup Mode, where V
BATT has the same operating voltage range as V
the battery-switchover threshold voltage is typically
V
V
SuperCap (e.g., around 0.47F) and a simple charging
Figure 7. MAX808 CE Gate Test Circuit
__________Applications Information
BATT
CC
50Ω DRIVER
up. Typical supply current from V
for the MAX808), while only leakage currents flow
from the battery.
and V
ically less than 1µA.
is increasing. This hysteresis allows use of a
when V
RST
. The supply current from the battery is typ-
Using SuperCaps™ or MaxCaps™
CC
is decreasing or V
______________________________________________________________________________________
CE IN
with the MAX801/MAX808
V
MAX808
RST
CC
GND
V
CC
(max)
, and BATT with 0.1µF
CE OUT
Chip-Enable Output
CC
BATT
CC
CC
is below V
or V
is 68µA (48µA
+ 0.05V when
50pF C
BATT
8-Pin µP Supervisory Circuits
CC
LOAD
with ±1.5% Reset Accuracy
. The
, and
BATT
circuit as a backup source (Figure 8). Since V
exceed V
special precautions are needed when using these µP
supervisors with a SuperCap.
The backup battery can be disconnected while V
above the reset threshold, provided BATT is bypassed
with a 0.1µF capacitor to ground. No precautions are
necessary to avoid spurious reset pulses.
While issuing resets to the µP during power-up, power-
down, and brownout conditions, these supervisors are
relatively immune to short-duration, negative-going V
transients (glitches). It is usually undesirable to reset
the µP when V
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 V
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 V
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 V
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 V
provides additional transient immunity.
Figure 8. Using the MAX801/MAX808 with a SuperCap
CC
+5V
1N4148
0.47F
while V
CC
Negative-Going V
Backup-Battery Replacement
experiences only small glitches.
CC
is above the reset threshold, no
BATT
MAX801
MAX808
CC
GND
V
CC
transient may typically
OUT
CC
CC
Transients
transient that
BATT
CC
CC
can
pin
CC
CC
11
is