DESCRIPTION
The M54HC191 is an high speed CMOS 4-BIT SYNCHRONOUS UP/DOWN COUNTER fabricated with silicon gate C2MOS technology. State changes of the counter are synchronous with the LOW-to-HIGH transition of the Clock Pulse Input.
An asynchronous parallel load input overrides counting and loads the data present on the DATA inputs into the flip-flops, which makes it possible to use the circuits as programmable counters. A count enable input serves as the carry/borrow input in multi-stage counters. Control input, Down/ Up, determines whether a circuit counts up or down. A MAX/MIN output and a Ripple Clock output provide overflow/underflow indication and make possible a variety of methods for generating carry/borrow signals in multi-stage counter applications.
All inputs are equipped with protection circuits against static discharge and transient excess voltage.

■ HIGH SPEED: fMAX = 61 MHz (TYP.) at VCC = 6V
■ LOW POWER DISSIPATION: ICC =4µA(MAX.) at TA=25°C
■ HIGH NOISE IMMUNITY: VNIH = VNIL = 28% VCC (MIN.)
■ SYMMETRICAL OUTPUT IMPEDANCE: |IOH| = IOL = 4mA (MIN)
■ BALANCED PROPAGATION DELAYS: tPLH ≅ tPHL
■ WIDE OPERATING VOLTAGE RANGE: VCC (OPR) = 2V to 6V
■ PIN AND FUNCTION COMPATIBLE WITH 54 SERIES 191
■ SPACE GRADE-1: ESA SCC QUALIFIED
■ 50 krad QUALIFIED, 100 krad AVAILABLE ON REQUEST
■ NO SEL UNDER HIGH LET HEAVY IONS IRRADIATION
■ DEVICE FULLY COMPLIANT WITH SCC-9204-066