SBVS157B
–
APRIL 2011
–
REVISED AUGUST 2011
MONITORING MULTIPLE SUPPLIES
Because the TLV803 has an open-drain output, multiple TLV803 outputs can be directly tied together to form a
logical OR-ing function for the RESET line. Only one pull-up resistor is required for this configuration.
shows two TLV803s connected together to provide monitoring of a 3.3-V power rail and a 5.0-V power rail. A
reset is generated if either power rail falls below the threshold voltage of its corresponding TLV803.
5.0 V
3.3 V
0.1
mF
V
DD
TLV803M
RESET
GND
3.3 V
100 kW
V
IO
V
CORE
Microprocessor
RST
0.1
mF
V
DD
TLV803S
RESET
GND
Figure 9. Multiple Voltage Rail Monitoring
BIDIRECTIONAL RESET PINS
Some microcontrollers have bidirectional reset pins that act as both inputs and outputs. In a situation where the
TLV803 is pulling the RESET line low while the microcontroller is trying the force the RESET line high, a series
resistor should be placed between the output of the TLV803 and the RESET pin of the microcontroller to protect
against excessive current flow.
shows the connection of the TLV803 to a microcontroller using a series
resistor to drive a bidirectional RESET line.
3.3 V
V
CC
V
DD
TLV803S
RESET
100 kW
47 kW RST
Microprocessor
GND
Figure 10. Connection to Bidirectional Reset Pin
Copyright
©
2011, Texas Instruments Incorporated
7
TI [ TEXAS INSTRUMENTS ]
