MAX793SESE Maxim Integrated Products, MAX793SESE Datasheet - Page 13

• Manufacturer Part Number: MAX793SESE
• Description: IC MPU SUPERVISORY CIRC 16SOIC
• Manufacturer: Maxim Integrated Products
• Type: Battery Backup Circuitr

Specifications of MAX793SESE

• Number Of Voltages Monitored: 1
• Output: Open Drain, Push-Pull
• Reset: Active High/Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 2.925V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

10). If there is no easy access to the unregulated sup-
ply, the LOWLINE output can be used to generate an
NMI to the µP (see LOWLINE Output section).
The low-line comparator monitors V
voltage typically 45mV above the reset threshold (10mV
of hysteresis) for the MAX793, and 15mV above RESET
IN (4mV of hysteresis) for the MAX794. For normal
operation (V
pulled to V
µP when power begins to fall.
Figure 9. CE Propagation Delay Test Circuit
Figure 10. Using the Power-Fail Comparator to Generate
Power-Fail Warning
UNREGULATED
SUPPLY
*C
L
INCLUDES LOAD CAPACITANCE AND SCOPE PROBE CAPACITANCE.
50Ω
R1
R2
CC
CC
REGULATOR
. Use LOWLINE to provide an NMI to the
50Ω CABLE
above the reset threshold), LOWLINE is
25Ω EQUIVALENT
SOURCE IMPEDANCE
L L O O W W L L I I N N E E Output (MAX793/MAX794)
______________________________________________________________________________________
3.6V
50Ω
3.0V OR 3.3V
PFI
3.0V/3.3V Adjustable Microprocessor
MAX793
MAX794
GND
V
CC
BATT
CE IN
PFO
MAX793
MAX794
MAX795
CC
GND
V
V
CC
CC
CE OUT
with a threshold
TO µP NMI
50pF
C
L
*
In most battery-operated portable systems, reserve
energy in the battery provides ample time to complete
the shutdown routine once the low-line warning is
encountered and before reset asserts. If the system
must also contend with a more rapid V
as when the main battery is disconnected or a high-
side switch is opened during normal operation, use
capacitance on the V
the shutdown routine (Figure 11).
First, calculate the worst-case time required for the sys-
tem to perform its shutdown routine. Then, with the worst-
case shutdown time, the worst-case load current, and the
minimum low-line to reset threshold (V
the amount of capacitance required to allow the shut-
down routine to complete before reset is asserted:
where I
capacitor, V
ence (V
the system to complete an orderly shutdown routine.
The MAX793/MAX794’s PFI input is compared to an
internal reference. If PFI is less than the power-fail
threshold (V
parator is intended for use as an undervoltage detector
to signal a failing power supply (Figure 12). However,
the comparator does not need to be dedicated to this
function because it is completely separate from the rest
of the circuitry.
Figure 11. Using LOWLINE to Provide Power-Fail Warning
to the µP
Supervisory Circuits
REGULATOR
C
LL
HOLD
LOAD
C
Power-Fail Comparator (MAX793/MAX794)
- V
> I
HOLD
LR
PFT
LOAD
RST
C
is the current being drained from the
HOLD
3.0V OR 3.3V
is the low-line to reset threshold differ-
V
), PFO goes low. The power-fail com-
x t
LR
SHDN
> I
), and t
LOAD
CC
line to provide time to execute
SHDN
V
x t
CC
SHDN
MAX793
MAX794
GND
is the time required for
LOWLINE
/ V
LR
LR
CC
min), calculate
fall time, such
TO µP NMI
13