MCP2122 Microchip Technology, MCP2122 Datasheet - Page 6

• Manufacturer Part Number: MCP2122
• Description: Converts serial data from UART bitstreams to IrDA standard bitstreams (encodes) and from IrDA standard bitstreams to UART bitstreams ...
• Manufacturer: Microchip Technology

MCP2122
2.3.1
Some applications may subject the MCP2122 to a
brown-out condition. Good design practice requires
that when a system is in brown-out, the system should
be in reset to ensure that the system is in a known
state when the system exits the brown-out. This
brown-out circuitry is external to the MCP2122.
2.3.1.1
Figure 2-2 shows a circuit for external brown-out
protection using the TCM809 device.
Figure 2-3 and Figure 2-4 illustrate two examples of
external circuitry that may be implemented. Each
option needs to be evaluated to determine if they
satisfy the requirements of the application.
FIGURE 2-2:
FIGURE 2-3:
DS21894B-page 6
V
Note 1: Resistors should be adjusted for the
DD
33 k
TCM809
2: This circuit will activate reset when
BROWN-OUTS
V
External Brown-Out Reset Circuits
DD
RST
characteristics of the transistor.
V
where Vz = Zener voltage.
DD
V
SS
10 k
goes below (Vz + 0.7V),
40 k
EXTERNAL BROWN-OUT
PROTECTION USING THE
TCM809
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 1
Q1
MCP2122
RESET
V
DD
V
MCP2122
RESET
DD
Preliminary
FIGURE 2-4:
Note 1: This circuit is less expensive, but
R1
R2
V
2: Resistors should be adjusted for the
DD
less accurate. Transistor Q1 turns
off when V
such that:
characteristics of the transistor.
V
40 k
DD
PROTECTION CIRCUIT 2
•
EXTERNAL BROWN-OUT
 2004 Microchip Technology Inc.
DD
R1 + R2
Q1
is below a certain level
R1
RESET
MCP2122
V
DD
= 0.7V