CAT803_14 Datasheet, PDF (7/11 Pages) ON Semiconductor – 3-Pin Microprocessor Power Supply Supervisors

CAT803, CAT809, CAT810
Valid RESET with V_CC Under 1.0 V
To ensure that the CAT809 RESET pin is in a known state when V_CC is under 1.0 V, a >10 kW pull−down resistor between
RESET pin and GND is recommended. For the CAT810, a pull−up resistor from RESET pin to V_CC is needed.
Power
Supply
Power
Supply
V_CC
CAT809
RESET
GND
10 kW
V_CC
CAT810
RESET
GND
10 kW
Figure 8. RESET Valid with V_CC Under 1.0 V
Figure 9. RESET Valid with V_CC Under 1.1 V
Bi−directional Reset Pin Interfacing
The CAT809/810 can interface with mP/mC bi−directional reset pins by connecting a 4.7 kW resistor in series with the
CAT809/810 reset output and the mP/mC bi−directional reset pin.
Power
Supply
BUF
Buffered
RESET
V_CC
CAT809
RESET
4.7 kW
GND
Bi−directional
I/O Pin
V_CC
mP
RESET
INPUT
GND
(For example:
68HC11)
Figure 10. Bi−directional Reset Pin Interfacing
CAT803 Open−Drain RESET Application
The CAT803 features an open−drain RESET output and
therefore needs a pull−up resistor on the output for proper
operation, as shown on Figure 11. An advantage of the
open−drain output includes the ability to “wire AND”
several outputs together to form an inexpensive logic circuit.
It is also possible to have the pull−up resistor connected to
a different supply which can be higher than the CAT803 V_CC
pin. The value of the pull−up resistor is not critical in most
applications, typical values being between 5 kW and 10 kW.
Power
Supply
V_CC
CAT803
RESET
GND
5 kW
V_CC
mP
RESET
INPUT
GND
Figure 11. Typical CAT803 Open−Drain
Circuit Configuration
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