HT7555CRZ

The HT7555C and HT7556C are CMOS RC timers providing significantly improved performance over the standard SE/NE 555/556 and 355 timers, while at the same time being direct replacements for those devices in most applications. Improved parameters include low supply current, wide operating supply voltage range, low Threshold, Trigger and Reset currents, no crowbarring of the supply current during output transitions, higher frequency performance and no requirement to decouple Control Voltage for stable operation. Specifically, the HT7555C and HT7556C are stable controllers capable of producing accurate time delays or frequencies. The HT7556C is a dual HT7555C, with the two timers operating independently of each other, sharing only V+ and GND. In the one shot mode, the pulse width of each circuit is precisely controlled by one external resistor and capacitor. For astable operation as an oscillator, the free running frequency and the duty cycle are both accurately controlled by two external resistors and one capacitor. Unlike the regular bipolar SE/NE 555/556 devices, the Control Voltage terminal need not be decoupled with a capacitor. The circuits are triggered and reset on falling (negative) waveforms, and the output inverter can source or sink currents large enough to drive TTL loads, or provide minimal offsets to drive CMOS loads.

Applications

• Precision timing
• Pulse generation
• Sequential timing
• Time delay generation
• Pulse width modulation
• Pulse position modulation
• Missing pulse detector

Key features

• Exact equivalent in most cases for SE/NE 555/556 or TLC555/556
• Low supply current - HT7555C ... 60μA - HT7556C ... 120μA
• Extremely low input currents ... 20pA
• High speed operation ... 1MHz
• Guaranteed supply voltage range ... 2V to 18V
• Temperature stability ... 0.005%/°C at ±25°C
• Normal reset function - no crowbarring of supply during output transition
• Can be used with higher impedance timing elements than regular 555/556 for longer RC time constants
• Timing from microseconds through hours
• Operates in both astable and monostable modes
• Adjustable duty cycle
• High output source/sink driver can drive TTL/CMOS
• Outputs have very low offsets, HIGH and LOW
• Pb-free (RoHS Compliant)