MAX791CSE+ Maxim Integrated Products, MAX791CSE+ Datasheet - Page 13

• Manufacturer Part Number: MAX791CSE+
• Description: IC MPU SUPERVISOR CIRCUIT 16SOIC
• Manufacturer: Maxim Integrated Products
• Type: Battery Backup Circuitr

Specifications of MAX791CSE+

• Number Of Voltages Monitored: 1
• Output: Push-Pull, Totem Pole
• Reset: Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 4.65V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Monitored Voltage: 4.65 V
• Undervoltage Threshold: 4.5 V
• Overvoltage Threshold: 4.75 V
• Manual Reset: Resettable
• Watchdog: Yes
• 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): 150 uA
• Maximum Power Dissipation: 696 mW
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 70 C
• Chip Enable Signals: Yes
• Minimum Operating Temperature: 0 C
• Output Type: Active Low or Open Drain or Push-Pull
• Power Fail Detection: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The Battery On (BATT ON) output indicates the status
of the internal V
which controls the internal V
For V
teresis effect), BATT ON typically sinks 3.2mA at 0.1V
saturation voltage. In battery-backup mode, this termi-
nal sources approximately 10µA from V
ON to indicate battery-switchover status or to supply
base drive to an external pass transistor for higher-cur-
rent applications (see Typical Operating Circuit).
The Input Supply Voltage (V
+5V. V
large PMOS switch. The switch carries the entire cur-
rent load for currents less than 250mA. The parallel
diode carries any current in excess of 250mA. Both the
switch and the diode have impedances less than 1Ω
each (Figure 10). The maximum continuous current is
250mA, but power-on transients may reach a maximum
of 1A.
The Backup-Battery Input (VBATT) is similar to V
except the PMOS switch and parallel diode are much
smaller. Accordingly, the on-resistances of the diode
and the switch are each approximately 10Ω.
Continuous current should be limited to 25mA and peak
currents (only during power-up) limited to 250mA. The
Figure 10. V
CC
CC
VBATT
V
greater than VBATT (ignoring the small hys-
CC
connects to V
CC
1
3
and VBATT-to-V
CC
______________________________________________________________________________________
/battery-switchover comparator,
MAX791
OUT
OUT
Backup-Battery Input
Input Supply Voltage
CC
via a parallel diode and a
CC
Microprocessor Supervisory Circuit
) should be a regulated
Switch
Battery On Output
and VBATT switches.
2
OUT
0.1µF
. Use BATT
V
OUT
CC
,
reverse leakage of this input is less than 1µA over tem-
perature and supply voltage.
The Output Supply Voltage (V
ed to the substrate of the IC and supplies all the current
to the external system and internal circuitry. All open-
circuit outputs will, for example, assume the V
age in their high states rather than the V
the maximum source current of 250mA, V
cally be 200mV below V
a 0.1µF capacitor.
The MAX791 low-battery voltage function monitors
VBATT. Low-battery detection of 2.0V ±0.15V is moni-
tored only during the reset-timeout period (200ms) that
occurs either after a normal power-up sequence or
after the MR reset input has been returned to its high
state. If the battery voltage is below 2.0V, the second
CE pulse is inhibited after reset timeout. If the battery
voltage is above 2.0V, all CE pulses are allowed
through the CE gate after the reset timeout period. To
use this function, after the 200ms reset delay, write 00
(HEX) to a location using the first CE pulse, and write
FF (HEX) to the same location using the second CE
pulse following RESET going inactive on power-up. The
contents of the memory then indicates a good battery
(FF) or a low battery (00) (Figure 11).
Figure 11. Backup-Battery Monitor Timing Diagram
THRESHOLD
CE OUT
RESET
CE IN
V
CC
RESET
200ms TYP
SECOND CE PULSE ABSENT WHEN VBATT < 2V
CC
Output Supply Voltage
. Decouple this terminal with
Low-Battery Monitor
OUT
) is internally connect-
CC
OUT
voltage. At
OUT
will typi-
volt-
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