PIC17C752-08/CL MICROCHIP [Microchip Technology], PIC17C752-08/CL Datasheet - Page 29

• Manufacturer Part Number: PIC17C752-08/CL
• Description: High-Performance 8-Bit CMOS EPROM Microcontrollers with 10-bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

5.1.5
PIC17C7XX devices have on-chip Brown-out Reset cir-
cuitry. This circuitry places the device into a reset when
the device voltage falls below a trip point (BV
ensures that the device does not continue program
execution outside the valid operation range of the
device. Brown-out resets are typically used in AC line
applications or large battery applications where large
loads may be switched in (such as automotive).
The BODEN configuration bit can disable (if clear/pro-
grammed) or enable (if set) the Brown-out Reset cir-
cuitry. If V
parameter #D005
greater than
reset the chip. A reset is not guaranteed to occur if V
falls below BV
will remain in Brown-out Reset until V
BV
Timer will then be invoked. This will keep the chip in
reset the greater of 96 ms and 1024 T
below BV
Start-up Timer is running, the chip will go back into a
Brown-out Reset. The Power-up Timer/Oscillator
Start-up Timer will be initialized. Once V
BV
will start their time delays.
Brown-out situations.
In some applications, the Brown-out reset trip point of
the device may not be at the desired level.
and
that may be implemented. Each needs to be evaluated
to determine if they match the requirements of the
application.
FIGURE 5-10: BROWN-OUT SITUATIONS
1998 Microchip Technology Inc.
Note:
DD
DD
Figure 5-9
. The Power-up Timer and Oscillator Start-up
, the Power-up Timer/Oscillator Start-up Timer
BROWN-OUT RESET (BOR)
DD
Before using the on-chip brown-out for a
voltage
review the electrical specifications to
ensure that they meet your requirements.
DD
parameter
DD
Internal
Internal
Internal
while the Power-up Timer/Oscillator
are two examples of external circuitry
Reset
Reset
Reset
falls below BV
for less than
in electrical specification section), for
V
V
V
DD
DD
DD
supervisory
#35, the brown-out situation will
Figure 5-10
parameter
DD
function,
OSC
(Typically 4.0V,
DD
DD
#35. The chip
shows typical
. If V
rises above
rises above
Figure 5-8
DD
DD
please
). This
drops
DD
< 96 ms
Greater of 96 ms
FIGURE 5-8:
FIGURE 5-9:
and 1024 Tosc
Greater of 96 ms
Greater of 96 ms
This brown-out circuit is less expensive, albeit less
accurate. Transistor Q1 turns off when V
certain level such that:
This circuit will activate reset when V
(Vz + 0.7V) where Vz = Zener voltage.
and 1024 Tosc
and 1024 Tosc
33k
R1
R2
V
V
DD
DD
V
DD
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 1
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 2
10k
•
40 k
40 k
R1 + R2
PIC17C7XX
R1
Q1
BV
BV
BV
BV
BV
BV
DD
DD
DD
DD
DD
DD
Max.
Min.
Max.
Min.
Max.
Min.
PIC17CXXX
PIC17CXXX
MCLR
= 0.7V
V
MCLR
V
DD
DD
DS30289A-page 29
DD
goes below
DD
is below a