MAX793REPE Maxim Integrated, MAX793REPE Datasheet - Page 15
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
These µP supervisory circuits are not short-circuit pro-
tected. Shorting V
transients such as charging a decoupling capacitor,
destroys the device. Decouple both V
pins to ground by placing 0.1µF ceramic capacitors as
close to the device as possible.
BATT ON can be directly connected to the base of a
PNP transistor or the gate of a PMOS transistor. The
PNP connection is straightforward: connect the emitter
Figure 13. Battery Switchover Timing
Table 1. Input and Output Status in
Battery-Backup Mode
__________Applications Information
V
Driving an External Switch with BATT ON
V
V
CC
OUT
BATT
PIN NAME
LOWLINE
BATT ON
BATT OK
CE OUT
= 3.6V
RESET
RESET
CE IN
WDO
BATT
OUT
PFO
V
WDI
PFI
MR
CC
V
RST
3.6V
______________________________________________________________________________________
OUT
Connected to BATT through an internal
140Ω switch
Disconnected from OUT
Pulled up to BATT
Logic low
Disabled
Logic low
Disabled, but still pulled up to V
Logic low
Disabled
Logic low
Pulled up to V
Connected to OUT
Logic low
High impedance
Pulled to BATT
to ground, excluding power-up
3.0V/3.3V Adjustable Microprocessor
3.3V
CC
STATUS
3.6V
V
SW
CC
3.3V
and BATT
CC
to V
(Figure 14a). No current-limiting resistor is required, but
a resistor connecting the base of the PNP to BATT ON
can be used to limit the current drawn from V
longing battery life in portable equipment.
If you are using a PMOS transistor, however, it must be
connected backwards from the traditional method.
Connect the gate to BATT ON, the drain to V
the source to OUT (Figure 14b). This method orients
the body diode from V
backup battery from discharging through the FET when
its gate is high. Two PMOS transistors in the Siliconix
LITTLE FOOT
-2.7V. The Si9433DY has a maximum 100mΩ drain-
source on-resistance with 2.7V of gate drive and a 2A
drain-source current. The Si9434DY specifies a 60mΩ
drain-source on-resistance with 2.7V of gate drive and
a 5.1A drain-source current.
Super caps are capacitors with extremely high capaci-
tance values (e.g., order of 0.47F) for their size. Figure
15 shows two ways to use a super cap as a backup
power source. The super cap can be connected
through a diode to the 3V input (Figure 15a); or, if a 5V
supply is also available, the super cap can be charged
up to the 5V supply (Figure 15b), allowing a longer
backup period. Since V
V
precautions when using these µP supervisors with a
super cap.
These µP supervisors were designed for battery-
backed applications. If a backup battery is not used,
connect BATT, OUT, and V
ent µP supervisor.
The backup power source can be removed while V
remains valid, without danger of triggering a reset
pulse, provided that BATT is decoupled with a 0.1µF
capacitor to ground. As long as V
reset threshold, battery-backup mode cannot be
entered.
LITTLE FOOT is a registered trademark of Siliconix Inc.
CC
CC
is above the reset threshold, there are no special
Supervisory Circuits
, the collector to OUT, and the base to BATT ON
®
Using a Super Cap as a Backup
series are specified with V
Replacing the Backup Battery
CC
BATT
Backup Power Source
CC
to OUT and prevents the
Operation without a
together, or use a differ-
can exceed V
CC
Power Source
stays above the
GS
CC
CC
CC
down to
, pro-
, and
while
CC
15