MAX704CSA+ Maxim Integrated Products, MAX704CSA+ Datasheet - Page 6

• Manufacturer Part Number: MAX704CSA+
• Description: IC MPU SUPERVISORY CIRCUIT 8SOIC
• Manufacturer: Maxim Integrated Products
• Type: Battery Backup Circuitr

Specifications of MAX704CSA+

• Number Of Voltages Monitored: 1
• Output: Push-Pull, Totem Pole
• Reset: Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 4.4V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Monitored Voltage: 4.4 V
• Undervoltage Threshold: 4.25 V
• Overvoltage Threshold: 4.5 V
• Manual Reset: Resettable
• Watchdog: No
• Battery Backup Switching: Yes
• Power-up Reset Delay (typ): 280 ms
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 0 V
• Supply Current (typ): 350 uA
• Maximum Power Dissipation: 471 mW
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 70 C
• Chip Enable Signals: No
• Minimum Operating Temperature: 0 C
• Output Type: Active Low or Push-Pull
• Power Fail Detection: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

drops to more than 1V below V
switchover comparator shuts off and the supply current
falls to less than 1µA.
The manual reset input (MR) allows RESET to be acti-
vated by a pushbutton switch. The switch is effectively
debounced by the 140ms minimum reset pulse width.
Because it is TTL/CMOS compatible, MR can be driven
by an external logic line.
SuperCaps are capacitors with extremely high capaci-
tance values (on the order of 0.1 Farad). When using
SuperCaps, if V
thresholds (4.65V and 4.40V, respectively), V
not exceed V
erance on V
+ 0.6V = 5.35V. Similarly, with a 10% tolerance on V
V
Figure 4’s SuperCap circuit uses the MAX703 with a
±5% tolerance voltage supply. In this circuit, the
SuperCap rapidly charges to within a diode drop of
V
charge the SuperCap voltage to V
and the power is suddenly removed and then reapplied
with V
allowable 0.6V difference voltage.
Figure 5’s circuit uses the MAX704 with a ±10% tole-
rance voltage supply. Note that if V
V
and reapplied with V
not exceed the allowable 0.6V voltage difference.
Low-Cost Microprocessor Supervisory
Circuits with Battery Backup
Figure 4. Using a SuperCap as a Backup Power Source with a
MAX703 and a +5V ±5% Supply
SuperCap is a registered trademark of Bankor Industries.
6
BATT
CC
BATT
_______________________________________________________________________________________
. However, the diode leakage current with trickle-
CC
0.1F
should not exceed 5.1V.
≤ 5.1V, the power can be suddenly removed
= 4.75V, V
+5V
CC
CC
Applications Information
CC
, V
by more than 0.6V. Thus, with a 5% tol-
BATT
V
V
exceeds the MAX703/MAX704 reset
BATT
CC
BATT
CC
MAX703
GND
should not exceed V
Using a SuperCap
= 4.5V, and V
Backup Power Source
- V
RESET
V
CC
OUT
does not exceed the
CC
BATT
. If V
Manual Reset
TO STATIC RAM
TO µP
CC
BATT
, the internal
BATT
= 5.5V and
- V
BATT
CC
= 5.25V
®
CC
as a
(min)
may
CC
will
,
Lithium batteries work well as backup batteries
because they have very low self-discharge rates and
high-energy density. Single lithium batteries with open-
circuit voltages of 3.0V to 3.6V are ideal for use with the
MAX703/MAX704. Batteries with an open-circuit volt-
age less than the minimum reset threshold plus 0.3V
can be directly connected to the MAX703/MAX704
V
Operating Circuit ).
However, batteries with open-circuit voltages greater
than the reset threshold plus 0.3V CANNOT be used as
backup batteries, since they source current into the
substrate through diode D1 (Figure 3) when V
close to the reset threshold.
If a backup power source is not used, ground V
and connect V
eliminates any voltage drop across the internal switch,
which would otherwise appear at V
use the MAX705–MAX708, which do not have battery-
backup capabilities.
Figure 5. Using a SuperCap as a Backup Power Source with
the MAX704 and a +5V ±10% Supply
Table 2. Allowable Backup-Battery Voltages
MAX703
MAX704
BATT
PART
100kΩ
input with no additional circuitry (see the Typical
Using the MAX703/MAX704 without a
+5V
MAXIMUM BACKUP-BATTERY VOLTAGE (V)
CC
Batteries and Power Supplies
to V
0.1F
as Backup Power Sources
OUT
V
V
BATT
CC
. A direct connection to V
Backup Power Source
MAX704
GND
4.80
4.55
RESET
V
OUT
OUT
. Alternatively,
TO STATIC RAM
TO µP
CC
BATT
CC
is