SS811 SSC [Silicon Standard Corp.], SS811 Datasheet - Page 7

• Manufacturer Part Number: SS811
• Description: Reset Circuits with Manual Reset Input
• Manufacturer: SSC [Silicon Standard Corp.]

APPLICATION INFORMATION
Rev.1.01 4/06/2004
MANUAL RESET INPUT
Many microprocessor-based products require manual
reset capability, allowing operators, test technicians, or
external logic circuitry to initiate a reset. Logic low on
Reset Active Timeout Period (t
high. This input has an internal 20KO pull-up resistor,
so it can be floating if it is not used. MR can be driven
with
open-drain/collector outputs. Another alternative is to
connect a normal switch from MR to GND to create a
manual reset function. Connecting a 0.1µF capacitor
from MR to ground can provide noise immunity to
NEGATIVE-GOING VCC TRANSIENTS
In addition to issuing a reset to the microprocessor
during
conditions, the SS811 series are relatively resistant to
short-duration negative-going VCC transient.
ENSURING A VALID RESET OUTPUT DOWN TO
VCC=0
When VCC falls below 0.9V, the SS811 RESET
output no longer sinks current; it becomes an open
circuit. In this case, high-impedance CMOS logic
inputs connected to RESET can drift to undetermined
voltages. Therefore, the SS811/2 is perfect for most
CMOS applications with VCC down to 0.9V. However
in applications where RESET must be valid down to
MR asserts reset. Reset will remain asserted for the
TTL
power-up,
or
CMOS-logic
power-down,
RP
) after MR returns
levels,
www.SiliconStandard.com
and
brownout
or
with
prevent noise caused by long cables of MR or noisy
environment.
BENEFITS
THRESHOLD
The SS811/812 with specified voltage as 5V±10% or 3V
±10% are ideal for systems using a 5V±5% or 3V±5%
power supply. The reset is guaranteed to assert after
the power supply falls out of regulation, but before
power drops below the minimum specified operating
voltage range of the system ICs. The pre-trimmed
thresholds reduce the range over which an undesirable
reset may occur.
0V, adding a pull-down resistor to RESET causes
any leakage currents to flow to ground, holding
INTERFACING TO MICROPROCESSORS WITH
BIDIRECTIONAL RESET PINS
Microprocessors with bidirectional res et pins may
have contention with the SS811/812 reset outputs. If
the SS811 RESET output is asserted high and the
microprocessor wants to pull it low, indeterminate
logic levels may occur. To correct such cases,
connect a resistor between the SS811 RESET (or
SS812 RESET) output and the microprocessor reset
I/O. Buffer the reset output to other system
components.
RESET low.
OF
HIGHLY
SS811, SS812
ACCURATE
7 of 8
RESET