SS8037 SSC [Silicon Standard Corp.], SS8037 Datasheet - Page 8

• Manufacturer Part Number: SS8037
• Description: Microprocessor Reset IC
• Manufacturer: SSC [Silicon Standard Corp.]

10/6/2004 Rev.2.20
Figure 3. Interfacing to µPs with bidirectional
Figure 4. SS8038L open-drain
V
V
CC
CC
8038
8038
reset I/O
allows use with multiple supplies
+3.3V
+3.3V
GND
GND
GND
GND
V
V
V
V
CC
CC
CC
CC
RESET
RESET
RESET
RESET
R
R
PULL-UP
PULL-UP
R
R
PULL-UP
PULL-UP
RESET
RESET
RESET
INPUT
INPUT
RESET
RESET
INPUT
INPUT
5V SYSTEM
5V SYSTEM
www.SiliconStandard.com
+5.0V
+5.0V
GND
GND
µP
µP
MOTOROLA
MOTOROLA
V
V
output
GND
GND
V
V
CC
CC
CC
CC
68HCXX
68HCXX
Interfacing to µPs with Bidirectional Reset Pins
Since the RESET output on the SS8038L is open drain,
this device interfaces easily with µPs that have bidirec-
tional reset pins, such as the Motorola 68HC11. Con-
necting the µP supervisor’s RESET output directly to
the microcontroller’s (µC’s) RESET pin with a single
pull-up resistor allows either device to assert reset (Fig-
ure 3).
8038L Open-Drain
Multiple Supplies
Generally, the pull-up connected to the SS8038L will
connect to the supply voltage that is being monitored at
the IC’s V
open-drain output to level-shift from the monitored supply
to reset circuitry powered by some other supply (Figure
4). Note that as the SS8038L’s V
so does the IC’s ability to sink current at RESET . Also,
with any pull-up, RESET will be pulled high as
cays toward 0. The voltage where this occurs depends
on the pull-up resistor value and the voltage to which it is
connected.
Benefits of Highly Accurate Reset Threshold
Most µP supervisor ICs have reset threshold voltages
between 5% and 10% below the value of nominal supply
voltages. This ensures a reset will not occur within 5% of
the nominal supply, but will occur when the supply is 10%
below nominal.
When using ICs rated at only the nominal supply ±5%,
this leaves a zone of uncertainty where the supply is be-
tween 5% and 10% low, and where the reset may or
may not be asserted.
The SS803xx463/803xx308 use highly accurate circuitry
to ensure that reset is asserted close to the 5% limit, and
long before the supply has declined to 10% below nomi-
nal.
CC
pin. However, some systems may use the
RESET
Output Allows Use with
CC
SS8037/8(G)
decreases below 1V,
VCC
8 of 9
de-