MAX793SCSE+C48 Maxim Integrated, MAX793SCSE+C48 Datasheet - Page 12

• Manufacturer Part Number: MAX793SCSE+C48
• Description: Supervisory Circuits 3.0V/3.3V Adjustable Microprocessor Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX793, MAX793R, MAX793S, MAX793T, MAX794, MAX795, MAX795R, MAX795S, MAX795Tr

Specifications of MAX793SCSE+C48

• Number Of Voltages Monitored: 1
• Monitored Voltage: 3 V, 3.3 V
• Output Type: Active High, Active Low, Open Drain
• Manual Reset: Resettable
• Watchdog: Watchdog
• Battery Backup Switching: Backup
• Supply Voltage - Max: 5.5 V
• Chip Enable Signals: Yes
• Maximum Power Dissipation: 842 mW
• Power Fail Detection: Yes
• Supply Current (typ): 62 uA
• Supply Voltage - Min: 1 V

The CE transmission gate remains disabled and CE IN
remains high impedance (regardless of CE IN activity)
for the first half of the reset timeout period (t
time a reset is generated. While disabled, CE IN is high
impedance. When the CE transmission gate is enabled,
the impedance of CE IN appears as a 46Ω resistor in
series with the load at CE OUT.
3.0V/3.3V Adjustable Microprocessor
Supervisory Circuits
Figure 7. Chip-Enable Transmission Gate
Figure 8. Chip-Enable Timing
12
CE IN
V
RESET PULLED UP TO V
V
CE OUT
RESET
(PULLED TO V
CE IN
______________________________________________________________________________________
BATT
CC
= 3.6V
CHIP-ENABLE
GENERATOR
V
MAX793
MAX794
MAX795
CONTROL
BATT
OUTPUT
RESET
CC
)
t
V
RP
RST
/
CC
2
t
RP
P
N
OUT
RP
P
/ 2), any
CE OUT
V
RST
V
10µs
SW
V
BATT
The propagation delay through the CE transmission
gate depends on V
drive connected to CE IN, and the loading on CE OUT.
The CE propagation delay is production tested from the
50% point on CE IN to the 50% point on CE OUT using
a 50Ω driver and 50pF of load capacitance (Figure 9).
For minimum propagation delay, minimize the capaci-
tive load at CE OUT and use a low-output-impedance
driver.
When the CE transmission gate is enabled, the imped-
ance of CE OUT is equivalent to a 46Ω resistor in series
with the source driving CE IN. In the disabled mode,
the transmission gate is off and an active pullup con-
nects CE OUT to OUT (Figure 8). This pullup turns off
when the transmission gate is enabled.
Critical systems often require an early warning indicat-
ing that power is failing. This warning provides time for
the µP to store vital data and take care of any additional
“housekeeping” functions, before the power supply
gets too far out of tolerance for the µP to operate reli-
ably. The MAX793/MAX794 offer two methods of
achieving this early warning. If access to the unregulat-
ed supply is feasible, the power-fail comparator input
(PFI) can be connected to the unregulated supply
through a voltage divider, with the power-fail compara-
tor output (PFO) providing the NMI to the µP (Figure
V
RST
V
CC
CC
Early Power-Fail Warning
, the source impedance of the
(MAX793/MAX794)
Chip-Enable Output
V
RST
V
SW