MAX792 Maxim, MAX792 Datasheet - Page 11

• Manufacturer Part Number: MAX792
• Description: Microprocessor and Non-Volatile Memory Supervisory Circuits
• Manufacturer: Maxim

The RESET output is active low and typically sinks 1.6mA
at 0.1V. When deasserted, RESET sources 1.6mA at typi-
cally V
RESET. RESET is guaranteed to be valid down to V
and an external 10kΩ pull-down resistor on RESET
ensures that it will be valid with V
(Figure 5). As V
RESET output switch reduces accordingly, increasing the
r
resistor ensures that the parallel combination of switch
plus resistor will be around 10kΩ and the saturation
voltage will be below 0.4V while sinking 40µA. When
using an external pull-down resistor of 10kΩ, the high
state for the RESET output with V
4.60V.
The overvoltage comparator is an uncommitted com-
parator that has no effect on the operation of other chip
functions. Use this input to provide overvoltage indica-
tion by connecting a voltage divider from the input sup-
ply, as in Figure 6.
Connect OVI to ground if the overvoltage function is not
used. OVO goes low when OVI goes above 1.30V. With
OVI below 1.30V, OVO is actively pulled to V
source1µA.
Figure 4c. Alternative Connection for External Programming Mode
DS(ON)
V
V
LOW LINE
RESET
R1
R2
CC
and the saturation voltage. The 10kΩ pull-down
REGULATOR
= 1.3 R3 + R4
- 1.5V. The RESET output is the inverse of
= 1.3
(
(
R4
CC
R1 + R2
R3
R4
R2
______________________________________________________________________________________
Reset Outputs (RESET and
)
goes below 1V, the gate drive to the
)
Overvoltage Comparator
RESET IN/INT
LLIN/REFOUT
MAX792
MAX820
GND
V
CC
CC
LOW LINE
= 4.75V is typically
Microprocessor and Non-Volatile
CC
RESET
RESET
down to GND
2
1
10
CC
Memory Supervisory Circuits
CC
and can
TO P
TO P
TO P NMI
RESET)
= 1V,
The watchdog monitors µP activity via the watchdog
input (WDI). If the µP becomes inactive, WDO and WDPO
are asserted. To use the watchdog function, connect
WDI to a µP bus line or I/O line. If WDI remains high or
low for longer than the watchdog timeout period
(1.6sec nominal), WDPO and WDO are asserted, indicat-
ing a software fault condition (see Watchdog-Pulse
Output and Watchdog Output sections).
If the watchdog function is unused, connect WDI to V
or GND. A change of state (high-to-low, low-to-high, or
a minimum 100ns pulse) at WDI during the watchdog
period resets the watchdog timer. The watchdog timer
Figure 5. Adding an external pull-down resistor ensures RESET
is valid with V
Figure 6. Detecting an Overvoltage Condition
VOLTAGE REGULATOR
CC
MAX792
MAX820
down to GND.
7
OVI
RESET
MAX792
MAX820
1
1.30V
GND
V
CC
12
3
Watchdog Function
10k
OVO
6
Watchdog Input
TO P RESET
OVERVOLTAGE
CC
11