1. General description
The 74LVC161 is a synchronous presettable binary counter with an internal look-head carry.
Synchronous operation is provided by having all flip-flops clocked simultaneously on the
positive-going edge of the clock (CP). The outputs (Q0 to Q3) of the counters may be preset HIGH
or LOW. A LOW at the parallel enable input (PE) disables the counting action and causes the
data at the data inputs (D0 to D3) to be loaded into the counter on the positive-going edge of the
clock. Preset takes place regardless of the levels at count enable inputs (CEP and CET). A LOW
at the master reset input (MR) sets Q0 to Q3 LOW regardless of the levels at input pins CP, PE,
CET and CEP (thus providing an asynchronous clear function). The look-ahead carry simplifies
serial cascading of the counters. Both CEP and CET must be HIGH to count. The CET input is fed
forward to enable the terminal count output (TC). The TC output thus enabled will produce a HIGH
output pulse of a duration approximately equal to a HIGH output of Q0. This pulse can be used to
enable the next cascaded stage.
Inputs can be driven from either 3.3 V or 5 V devices. This feature allows the use of these devices
as translators in mixed 3.3 V and 5 V environments.
Schmitt-trigger action at all inputs makes the circuit tolerant of slower input rise and fall times.
2. Features and benefits
• Overvoltage tolerant inputs to 5.5 V
• Wide supply voltage range from 1.2 V to 3.6 V
• CMOS low power dissipation
• Direct interface with TTL levels
• Asynchronous reset
• Synchronous counting and loading
• Two count enable inputs for n-bit cascading
• Positive edge-triggered clock
• Complies with JEDEC standard:
• JESD8-7A (1.65 V to 1.95 V)
• JESD8-5A (2.3 V to 2.7 V)
• JESD8-C/JESD36 (2.7 V to 3.6 V)
• ESD protection:
• HBM JESD22-A114F exceeds 2000 V
• MM JESD22-A115-B exceeds 200 V
• CDM JESD22-C101E exceeds 1000 V
• Specified from -40 °C to +85 °C and -40 °C to +125 °C