Texas Instruments SA555PG4

Overview

SA555PG4 from Texas Instruments is a precision bipolar 555 timer IC operating in monostable or astable mode, delivering timing intervals from microseconds to hours with ±1% threshold accuracy, 200mA output sink/source capability, and –40°C to +85°C industrial temperature range. It serves as a programmable delay generator or oscillator in power supply sequencing, pulse conditioning, and industrial control circuits.

For engineers reviewing the SA555PG4 datasheet, SA555PG4 pinout, SA555PG4 application, or SA555PG4 equivalent, key selection criteria include its TTL-compatible output drive, adjustable duty cycle via dual-resistor timing network, supply voltage insensitivity (0.1%/V), and thermal stability (50 ppm/°C) across industrial temperature extremes.

Technical Context

The SA555PG4 implements a bipolar transistor-based architecture with two comparators, an SR flip-flop, and a high-current output stage. Its internal resistor divider sets precise 1/3 VCC trigger and 2/3 VCC threshold reference levels, both modifiable via the CONT pin for external voltage injection.

Timing operation relies on RC charging/discharging through external components: monostable mode uses one resistor and capacitor; astable mode uses two resistors and one capacitor to independently adjust frequency and duty cycle. The DISCH pin provides open-collector discharge path synchronized with output state.

Key Specifications

Pinout & Package

SA555PG4 is housed in an 8-pin PDIP (Plastic Dual In-line Package) with 0.3-inch body width and standard through-hole mounting footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar precision timer applications.

Compared with NE555P and LM555CN, SA555PG4 offers guaranteed industrial temperature operation without derating, tighter threshold tolerance (±1% vs ±1.5%), and lower supply sensitivity - making it optimal for mission-critical timing in harsh environments.

Availability

SA555PG4 is available at Aetrix Electronics and suitable for power supply sequencing, pulse-width modulation, missing-pulse detection, industrial timer relays, and sequential control requiring stable component supply across extended temperature ranges.

Supply support for SA555PG4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies.

The SA555PG4 belongs to TI's legacy precision timer product line, designed specifically for robust, low-cost, high-reliability timing functions in industrial automation, power systems, and instrumentation where microcontroller-based solutions add unnecessary complexity.

FAQ

What is the maximum timing interval achievable with the SA555PG4?

The SA555PG4 supports timing intervals from 10 µs to several hours, limited primarily by external RC component values and leakage. With a 10 MΩ timing resistor and 1000 µF capacitor, SA555PG4 achieves ~11.5-second monostable pulses; larger values extend duration further, though capacitor leakage and comparator input bias current become limiting factors beyond ~100 seconds.

Can the SA555PG4 operate from a 3.3 V supply?

No, the SA555PG4 requires a minimum supply voltage of 4.5 V per its Recommended Operating Conditions. At 3.3 V, internal comparators fail to switch reliably and output drive strength collapses. For 3.3 V systems, consider CMOS alternatives like TLC555CP, which maintains full functionality down to 2 V.

How does the CONT pin affect timing accuracy in the SA555PG4?

The CONT pin directly connects to the internal voltage divider node. Applying an external voltage alters both trigger (1/3 × VCONT) and threshold (2/3 × VCONT) levels, enabling precise modulation of timing windows. However, injecting noise or high-impedance sources degrades accuracy; TI recommends bypassing CONT to GND with a 10 nF ceramic capacitor for stable operation.

Is the SA555PG4 pin-compatible with other 555 variants like NE555 or LM555?

Yes, SA555PG4 uses the industry-standard 8-pin PDIP package with identical pinout to NE555P, LM555CN, and NA555P. All share identical pin functions, electrical characteristics, and timing behavior - allowing direct substitution in existing designs without PCB changes.

What is the purpose of the DISCH pin in SA555PG4 astable operation?

In astable mode, the DISCH pin provides a low-impedance path to GND when the output is low, actively discharging the external timing capacitor through RB only. This enables independent control of charge (RA + RB) and discharge (RB) paths - the core mechanism enabling adjustable duty cycle without additional components.