Chip-Enable Output

In enabled mode, CE OUT’s impedance is equivalent to

75

Ω in series with the source driving CE IN. In disabled

mode, the 75

Ω transmission gate is off and CE OUT is

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

capacitors to GND.

The MAX801/MAX808 operate in two distinct modes:

1) Normal Operating Mode, with all circuitry powered

for the MAX808), while only leakage currents flow

from the battery.

ically less than 1µA.

Using SuperCaps™ or MaxCaps™

with the MAX801/MAX808

the battery-switchover threshold voltage is typically

SuperCap (e.g., around 0.47F) and a simple charging

special precautions are needed when using these µP

supervisors with a SuperCap.

Backup-Battery Replacement

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

transients (glitches). It is usually undesirable to reset

The Typical Operating Characteristics show a graph of

Maximum Transient Duration vs. Reset Threshold

Overdrive, for which reset pulses are not generated.

pulses, starting at 5V and ending below the reset

threshold by the magnitude indicated (reset compara-

tor overdrive). The graph shows the maximum pulse

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

goes 40mV below the reset threshold and lasts for 3µs

or less will not cause a reset pulse to be issued. A

provides additional transient immunity.

8-Pin µP Supervisory Circuits

with ±1.5% Reset Accuracy

______________________________________________________________________________________

11

MAX808

CE IN

CE OUT

GND

50

Ω DRIVER

Figure 7. MAX808 CE Gate Test Circuit

MAX801

MAX808

0.47F

1N4148

+5V

GND

BATT

OUT

Figure 8. Using the MAX801/MAX808 with a SuperCap