Programmable Timers and Oscillators

The TLC556IDRG4 from Texas Instruments is a dual 555-type timer/oscillator Integrated Circuit at 2.1 MHz in a 14-SOIC package.

The IDT3CP0C02-18.432NSGE from Renesas Electronics America Inc is a programmable timer Integrated Circuit rated 18.432 MHz, in a 4-VFQFPN (5x3.2) package.

The DS4250D+ from Analog Devices Inc./Maxim Integrated is a 250 MHz clock oscillator Integrated Circuit in a 10-LCCC (5x3.2) package.

The DS4425BN+ from Analog Devices Inc./Maxim Integrated is a 425 MHz clock oscillator Integrated Circuit in a 10-LCCC (5x3.2) package.

The DS1073M-80 from Analog Devices Inc./Maxim Integrated is a dual fixed-frequency oscillator Integrated Circuit rated 80 MHz, in an 8-PDIP package.

The DS1075M-60 from Analog Devices Inc./Maxim Integrated is a dual fixed-frequency oscillator Integrated Circuit rated 60 MHz, in an 8-DIP package.

The DS1050Z-1/T&R from Analog Devices Inc./Maxim Integrated is a programmable timer and oscillator Integrated Circuit rated at 1 kHz, in an 8-SOIC package.

CD4536BEE4 from Texas Instruments is a CMOS Programmable Timer - Specialty logic ICs. CD4536B is a programmable timer consisting of 24 ripple-binary counter stages. The salient feature of this device is its flexibility. The device can count from 1 to 2 24 or the first 8 stages can be bypassed to allow an output, selectable by a 4-bit code, from any one of the remaining 16 stages. It can be driven by an external clock or an RC oscillator that can be constructed using on-chip components. Input IN1 serves as either the external clock input or the input to the on-chip RC oscillator. OUT1 and OUT2 are connection terminals for the external RC components. In addition, an on-chip monostable circuit is provided to allow a variable pulse width output. Various timing functions can be achieved using combinations of these capabilities. A logic 1 on the 8-BYPASS input enables a bypass of the first 8 stages and makes stage 9 the first counter stage of the last 16 stages. Selection of 1 of 16 outputs is accomplished by the decoder and the BCD inputs A, B, C and D. MONO IN is the timing input for the on-chip monostable oscillator. Grounding of the MONO IN terminal through a resistor of 10K ohms or higher, disables the one-shot circuit and connects the decoder directly to the DECODE OUT terminal. A resistor to V DD and a capacitor to ground from the MONO IN terminal enables the one-shot circuit and control its pulse width. A fast test mode is enabled by a logic 1 on 8-BYPASS, SET, and RESET. This mode divides the 24-stage counter into three 8-stage sections to facilitate a fast test sequence. The CD4536B types are supplied in 16-lead hermetic dual-in-line ceramic packages (F3A suffix), 16-lead dual-in-line plastic packages (E suffix), 16-lead small-outline packages (DW, DWR, and NSR suffixes), and 16-lead thin shrink small-outline packages (PW and PWR suffixes).

CD4541BEE4 from Texas Instruments is a CMOS Programmable Timer - High Voltage Type (20V Rating) - Specialty logic ICs. CD4541B programmable timer consists of a 16-stage binary counter, an oscillator that is controlled by external R-C components (2 resistors and a capacitor), an automatic power-on reset circuit, and output control logic. The counter increments on positive-edge clock transitions and can also be reset via the MASTER RESET input. The output from this timer is the Q or Q output from the 8th, 10th, 13th, or 16th counter stage. The desired stage is chosen using time-select inputs A and B (see Frequency Select Table). The output is available in either of two modes selectable via the MODE input, pin 10 (see Truth Table). When this MODE input is a logic "1", the output will be a continuous square wave having a frequency equal to the oscillator frequency divided by 2 N. With the MODE input set to logic "0" and after a MASTER RESET is initiated, the output (assuming Q output has been selected) changes from a low to a high state after 2 N-1 counts and remains in that state until another MASTER RESET pulse is applied or the MODE input is set to a logic "1". Timing is initialized by setting the AUTO RESET input (pin 5) to logic "0" and turning power on. If pin 5 is set to logic "1", the AUTO RESET circuit is disabled and counting will not start until after a positive MASTER RESET pulse is applied and returns to a low level. The AUTO RESET consumes an appreciable amount of power and should not be used if low-power operation is desired. For reliable automatic power-on reset, V DD should be greater than 5V. The RC oscillator, shown in Figure 2, oscillates with a frequency determined by the RC network and is calculated using: Where f is between 1kHz and 100kHz and R S and 2R TC.

SNJ54S124J from Texas Instruments is a Dual Voltage-Controlled Oscillators - Specialty logic ICs. The 'S124 features two independent voltage-controlled oscillators (VCO) in a single monolithic chip. The output frequency of each VCO is established by an external capacitor in combination with two voltage-sensitive inputs, one for frequency range and one for frequency control. These inputs can be used to vary the output frequency as shown under typical characteristics. These highly stable oscillators can be set to operate at any frequency typically between 0.12 hertz and 85 megahertz. While the enable input is low, the output is enabled. While the enable input is high, the output is high. These devices can operate from a single 5-volt supply. However, one set of supply-voltage and ground pins (V CC and GND) is provided for the enable, synchronization-gating, and output sections, and a separate set (GND) and is provided for the oscillator and associated frequency-control circuits so that effective isolation can be accomplished in the system. The enable input of these devices starts or stops the output pulses when it is low or high, respectively. The internal oscillator of the 'S124 is started and stopped by the enable input. The enable input is one standard load; it and the buffered output operate at standard Schottky-clamped TTL levels. The pulse synchronization-gating section ensures that the first output pulse is neither clipped nor extended. Duty cycle of the square-wave output is fixed at approximately 50 percent. The SN54S124 is characterized for operation over the full military temperature range of -55°C to 125°C; the SN74S124 is characterized for operation from 0°C to 70°C.

SE555FKB from Texas Instruments is a Precision Timer - Real-time clocks (RTCs) & timers. The Nx555 and Sx555 devices are precision timing circuits capable of producing accurate time delays or oscillation. In time-delay or monostable operating modes, the timed interval is controlled by a single external resistor and capacitor network. In the astable mode of operation, the frequency and duty cycle are controlled independently with two external resistors and a single external capacitor. Each timer has a trigger level equal to approximately one-third of the supply voltage and a threshold level equal to approximately two-thirds of the supply voltage. These levels can be altered by use of the control voltage pin (CONT). When the trigger input (TRIG) is less than the trigger level, the flip-flop is set and the output goes high. If TRIG is greater than the trigger level and the threshold input (THRES) is greater than the threshold level, the flip-flop is reset and the output is low. The reset input (RESET) overrides all other inputs and is used to initiate a new timing cycle. If RESET is low, the flip-flop is reset and the output is low. Whenever the output is low, a low-impedance path is provided between the discharge pin (DISCH) and the ground pin (GND). Tie all unused inputs to an appropriate logic level to prevent false triggering The output circuit is capable of sinking or sourcing current up to 200mA. Operation is specified for supplies of 5V to 15V. With a 5V supply, output levels are compatible with TTL inputs.

TLC555MJGB from Texas Instruments is a Low Power LinCMOS™ Timer - Real-time clocks (RTCs) & timers. The TLC555 is a CMOS monolithic timing circuit. The timer is fully compatible with CMOS, TTL, and MOS logic and operates at frequencies up to 2MHz. Because of a high input impedance, this device supports smaller timing capacitors than those supported by the NE555 or LM555. As a result, more accurate time delays and oscillations are possible. Power consumption is low across the full range of power-supply voltage. Like the NE555, the TLC555 has a trigger level equal to approximately one-third of the supply voltage and a threshold level equal to approximately two-thirds of the supply voltage. These levels can be altered by use of the control voltage terminal (CONT). When the trigger input (TRIG) falls below the trigger level, the flip-flop is set and the output goes high. If TRIG is above the trigger level and the threshold input (THRES) is above the threshold level, the flip-flop is reset and the output is low. The reset input (RESET) can override all other inputs and can be used to initiate a new timing cycle. If RESET is low, the flip-flop is reset and the output is low. Whenever the output is low, a low-impedance path is provided between the discharge terminal (DISCH) and GND. All unused inputs must be tied to an appropriate logic level to prevent false triggering.

The JM38510/10902BCA from Texas Instruments is a dual 555-type precision timer/oscillator Integrated Circuit in a 14-CDIP package with a -55 value.