MAX792SC/D Maxim Integrated, MAX792SC/D Datasheet - Page 14

• Manufacturer Part Number: MAX792SC/D
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX792, MAX792L, MAX792M, MAX792R, MAX792S, MAX792T, MAX820, MAX820L, MAX820M, MAX820R, MAX820S, MAX820Tr

Specifications of MAX792SC/D

• Number Of Voltages Monitored: 1
• Monitored Voltage: 2.75 V to 5.5 V
• Undervoltage Threshold: 2.85 V
• Overvoltage Threshold: 3 V
• Output Type: Active High, Active Low, Push-Pull
• Manual Reset: Resettable
• Watchdog: Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 280 ms
• Supply Voltage - Max: 5.5 V
• Maximum Operating Temperature: + 70 C
• Package / Case: Die
• Chip Enable Signals: Yes
• Minimum Operating Temperature: 0 C
• Power Fail Detection: Yes
• Supply Current (typ): 150 uA
• Supply Voltage - Min: 2.75 V

Microprocessor and Nonvolatile
Memory Supervisory Circuits
Figure 11. Alternate CE Gating
Using memory devices with both CE and CE inputs
allows the MAX792/MAX820 CE propagation delay
to be bypassed. To do this, connect CE IN to ground,
pull up CE OUT to V
input of each memory device (Figure 11). The CE input
of each memory device then connects directly to the
chip-select logic, which does not have to be gated by
the MAX792/MAX820.
µPs with bidirectional reset pins, such as the Motorola
68HC11 series, can contend with the MAX792/MAX820
RESET output. If, for example, the MAX792/MAX820 RESET
output is asserted high and the µP wants to pull it low,
indeterminate logic levels may result. To avoid this,
connect a 4.7kΩ resistor between the MAX792/MAX820
RESET output and the µP reset I/O, as in Figure 12.
Buffer the MAX792/MAX820 RESET output to other sys-
tem components.
While issuing resets to the µP during power-up, power-
down, and brownout conditions, these supervisors are
relatively immune to short-duration negative-going V
transients (glitches). It is usually undesirable to reset
the µP when V
Figure 13 shows maximum transient duration vs. reset-
comparator overdrive, for which reset pulses are not
generated. The graph was produced using negative-
14
*
MAXIMUM R
THE NUMBER OF RAMS.
MINIMUM R
______________________________________________________________________________________
Interfacing to µPs with Bidirectional
P
P
14
VALUE IS 1kΩ
VALUE DEPENDS ON
CE IN
CC
Negative-Going V
Alternative Chip-Enable Gating
MAX792
MAX820
experiences only small glitches.
GND
+5V
V
CC
3
CC
12
CE OUT
, and connect CE OUT to the CE
R
P
*
13
LINES FROM LOGIC
ACTIVE-HIGH CE
CE
CE
CE
CE
CE
CE
CE
CE
CC
Reset Inputs
Transients
RAM 1
RAM 2
RAM 3
RAM 4
CC
going V
reset threshold by the magnitude indicated (reset-
comparator overdrive). The graph shows the maximum
pulse width a negative-going V
cally have without causing a reset pulse to be issued.
As the amplitude of the transient increases (i.e., goes
farther below the reset threshold), the maximum allow-
able pulse width decreases. Typically, a V
that goes 100mV below the reset threshold and lasts for
30µs or less will not cause a reset pulse to be issued.
A 100nF bypass capacitor mounted close to the V
pin provides additional transient immunity.
Figure 12. Interfacing to µPs with Bidirectional RESET Pins
Figure 13. Maximum Transient Duration Without Causing a
Reset Pulse vs. Reset-Comparator Overdrive
V
CC
CC
MAX792
MAX820
100
GND
80
60
40
20
V
pulses, starting at 5V and ending below the
0
CC
RESET COMPARATOR OVERDRIVE, (V
3
12
RESET
10
1
100
4.7k
RESET
CC
1000
BUFFER
T
transient may typi-
GND
V
A
V
µP
CC
CC
= +25°C
TH
= 5V
- V
10,000
CC
CC
) (mV)
TO OTHER
SYSTEM RESET
INPUTS
transient
CC