MAX793REPE Maxim Integrated, MAX793REPE Datasheet - Page 14
MAX793REPE
Manufacturer Part Number
MAX793REPE
Description
Supervisory Circuits
Manufacturer
Maxim Integrated
Series
MAX793, MAX793R, MAX793S, MAX793T, MAX794, MAX795, MAX795R, MAX795S, MAX795Tr
Datasheet
1.MAX793SCPE.pdf
(20 pages)
Specifications of MAX793REPE
Number Of Voltages Monitored
1
Monitored Voltage
3 V, 3.3 V
Undervoltage Threshold
Adjustable
Overvoltage Threshold
Adjustable
Output Type
Active High, Active Low, Open Drain
Manual Reset
Resettable
Watchdog
Watchdog
Battery Backup Switching
Backup
Power-up Reset Delay (typ)
280 ms
Supply Voltage - Max
5.5 V
Maximum Operating Temperature
+ 85 C
Mounting Style
Through Hole
Package / Case
PDIP N
Chip Enable Signals
Yes
Maximum Power Dissipation
842 mW
Minimum Operating Temperature
- 40 C
Power Fail Detection
Yes
Supply Current (typ)
62 uA
Supply Voltage - Min
1.1 V
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
MAX793REPE+
Manufacturer:
Maxim Integrated Products
Quantity:
135
3.0V/3.3V Adjustable Microprocessor
Supervisory Circuits
Figure 12. Using the Power-Fail Comparator to Monitor an Additional Power Supply: (a) V
The power-fail comparator turns off and PFO goes low
when V
first half of the reset timeout period (t
high, irrespective of V
ond half of t
and PFO follows PFI. If the comparator is unused, con-
nect PFI to V
be connected to MR so that a low voltage on PFI gener-
ates a reset (Figure 12b). In this configuration, when
the monitored voltage causes PFI to fall below V
PFO pulls MR low, causing a reset to be asserted.
Reset remains asserted as long as PFO holds MR low,
and for 200ms after PFO pulls MR high when the moni-
tored supply is above the programmed threshold.
In the event of a brownout or power failure, it may be
necessary to preserve the contents of RAM. With a
backup battery installed at BATT, the devices automati-
cally switch RAM to backup power when V
order to allow the backup battery (e.g., a 3.6V lithium
cell) to have a higher voltage than V
supervisors (designed for 3.3V and 3V systems) does
not always connect BATT to OUT when V
greater than V
140Ω switch) either when V
14
(a)
______________________________________________________________________________________
PFO
V
V
TRIP
CC
CC
V
L
= R2
= R2
falls below V
R1
R2
RP
CC
V
(V
(V
IN
PFT
PFT
CC
, the power-fail comparator is enabled
and leave PFO unconnected. PFO can
)
+ V
(
. BATT connects to OUT (through a
PFH
1
R1
Backup-Battery Switchover
+
)
(
PFI
R2
1
R1
1
SW
)
. At the beginning of the sec-
+
–
PFI
R2
1
V
on power-down. During the
R1
CC
V
L
)
CC
–
MAX793
MAX794
V
CC
R1
V
V
GND
TRIP
falls below V
CC
CC
3.0V OR 3.3V
RP
WHERE
, this family of µP
NOTE: V
), PFO is forced
PFO
0V
TRIP,
V
V
CC
PFT
PFH
V
= 1.237V
= 10mV
L
falls. In
SW
BATT
ARE NEGATIVE
V
IN
PFT
and
is
,
V
1.75V (typ) regardless of the BATT voltage.
Switchover at V
entered before V
mum required to reliably retain data in most CMOS
RAM, (switchover at higher V
decrease backup-battery life). When V
switchover is deferred either until V
V
reset threshold (V
power-up switchover technique prevents V
charging the backup battery through OUT when using
an external transistor driven by BATT ON. OUT con-
nects to V
when V
BATT ON is high when OUT is connected to BATT.
Although BATT ON can be used as a logic output to
indicate the battery switchover status, it is most often
used as a gate or base drive for an external pass tran-
sistor for high-current applications (see Driving an
External Switch with BATT ON in the Applications
Information section). When V
power-up, BATT ON sinks 3.2mA at 0.4V. In battery-
backup mode, this terminal sources 100µA from BATT.
(b)
BATT
BATT
PFO
V
CC
is greater than V
CC
is below V
V
V
H
TRIP
= (V
CC
R1
R2
crosses the reset threshold (Figure 13).
=
PFT
V
V
PFT
IN
through a 4Ω (max) PMOS power switch
+ V
SW
(
PFH
R1
OUT
IN
R2
+ R2
)
RST
ensures that battery-backup mode is
BATT ON (MAX793/MAX794)
RST
(
Is Negative, (b) V
R1
)
R2
, or when V
+ R2
gets too close to the 2.0V mini-
) if V
V
CC
PFI
TRIP
)
, or when V
BATT
V
MAX793
MAX794
H
V
GND
CC
CC
CC
is above V
CC
IN
3.0V OR 3.3V
CC
exceeds V
Is Positive
voltages would
rises above the
crosses V
PFO
CC
MR
CC
falls below
recovers,
RST
CC
RST
BATT
V
. This
IN
from
on
if