NA556, NE556, SA556, SE556
DUAL PRECISION TIMERS
SLFS023G – APRIL 1978 – REVISED JUNE 2006
Two Precision Timing Circuits Per Package
Astable or Monostable Operation
TTL-Compatible Output Can Sink or Source
up to 150 mA
Active Pullup or Pulldown
Designed to Be Interchangeable With
Signetics NE556, SA556, and SE556
NA556...D OR N PACKAGE
NE556...D, N, OR NS PACKAGE
SA556...D OR N PACKAGE
Precision Timers From Microseconds to
These devices provide two independent timing circuits of the NA555, NE555, SA555, or SE555 type in each
package. These circuits can be operated in the astable or the monostable mode with external resistor-capacitor
(RC) timing control. The basic timing provided by the RC time constant can be controlled actively by modulating
the bias of the control-voltage input.
The threshold (THRES) and trigger (TRIG) levels normally are two-thirds and one-third, respectively, of V
These levels can be altered by using the control voltage (CONT) terminal. When the trigger input falls below
trigger level, the flip-flop is set and the output goes high. If the trigger input is above the trigger level and the
threshold input is above the threshold level, the flip-flop is reset, and the output is low. The reset (RESET) input
can override all other inputs and can be used to initiate a new timing cycle. When RESET goes low, the flip-flop
is reset and the output goes low. When the output is low, a low-impedance path is provided between the
discharge (DISCH) terminal and ground (GND).
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1978–2006, Texas Instruments Incorporated
On products compliant to MIL-PRF-38535, all parameters are
tested unless otherwise noted. On all other products, production
processing does not necessarily include testing of all parameters.