NXP Semiconductors PCF1178CT,118

Overview

PCF1178CT,118 from Philips Semiconductors is a single-chip 4-digit duplex LCD car clock IC with integrated 4.19 MHz oscillator, programmable internal voltage regulator (3–6 V), and EEPROM-based time calibration. It drives automotive dashboard displays in 12- or 24-hour mode across −40 to +85 °C, supporting battery-powered operation via external resistor and 47 µF capacitor.

For engineers reviewing the PCF1178CT,118 datasheet, PCF1178CT,118 pinout, PCF1178CT,118 application, or PCF1178CT,118 equivalent, key selection considerations include its SO28 package, LCD backplane multiplexing (BP1/BP2), EEPROM-programmable contrast compensation, colon pulse control (FLASH), and dual-switch time setting (S1/S2) with debounce.

Technical Context

The PCF1178CT,118 implements a 1:2 multiplexed duplex LCD driver architecture with three-level backplane signals (BP1, BP2) generating VON(RMS) = 0.79 VDD and VOFF(RMS) = 0.35 VDD for segment contrast control. Its timekeeping core uses a 4.194304 MHz crystal oscillator with ±30 × 10⁻⁶ frequency tolerance and EEPROM-stored calibration pulses (0–31) to correct quartz deviation up to +117.8 × 10⁻⁶.

Operation is governed by CMOS logic with pull-up resistors on S1, S2, TS, SEL, and DATA (45–180 kΩ), enabling direct SPST switch interfacing. Voltage regulation adapts LCD supply (VDD) across temperature: e.g., 4.0–4.5 V at 25 °C, 3–4 V at +85 °C, and 5–6 V at −40 °C - ensuring stable contrast without external trimming components.

Key Specifications

Pinout & Package

PCF1178CT,118 is housed in a plastic small outline package (SO28) per SOT136-1: 28 leads, body width 7.5 mm, lead pitch 1.27 mm, maximum height 2.65 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LCD car clock applications.

Compared with PCF1177CT, PCF1178CT,118 delivers autonomous contrast control across temperature without external components; versus PCF1187CT, it omits alarm circuitry to reduce cost and layout overhead for non-alert applications.

Availability

PCF1178CT,118 is available at Aetrix Electronics and suitable for automotive dashboard systems, aftermarket infotainment displays, and industrial HMI panels requiring stable component supply with long lifecycle assurance.

Supply support for PCF1178CT,118 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

Philips Semiconductors (now NXP Semiconductors) is a global semiconductor innovator with leadership in automotive, consumer, and industrial ICs since the 1950s.

The PCF1178CT,118 belongs to Philips' dedicated car clock IC family designed specifically for cost-sensitive, high-reliability automotive LCD time displays - emphasizing EEPROM programmability, wide temperature operation, and minimal external component count.

FAQ

What is the primary function of the PCF1178CT,118 in automotive electronics?

The PCF1178CT,118 serves as a fully integrated 4-digit duplex LCD car clock IC, providing hours, minutes, and seconds timekeeping with built-in 4.19 MHz oscillator, programmable voltage regulation, and EEPROM-based time calibration. It directly drives automotive dashboard LCDs in 12- or 24-hour mode without external trimmers or regulators - making PCF1178CT,118 ideal for space-constrained, battery-backed vehicle instrumentation.

How does the PCF1178CT,118 achieve temperature-stable LCD contrast?

The PCF1178CT,118 achieves temperature-stable LCD contrast through its electrically programmable internal voltage regulator, which adjusts VDD output based on ambient temperature - e.g., 4.5 V at 25 °C, 3–4 V at +85 °C, and 5–6 V at −40 °C. This dynamic regulation maintains optimal RMS segment voltages (VON = 0.79 VDD, VOFF = 0.35 VDD) across the full −40 to +85 °C range, eliminating manual contrast tuning. The PCF1178CT,118 stores the base voltage setting in EEPROM for consistent behavior after power cycles.

Can the PCF1178CT,118 be used with a standard 32.768 kHz watch crystal?

No, the PCF1178CT,118 requires a 4.194304 MHz crystal oscillator - not a 32.768 kHz watch crystal. Its internal counter chain divides this frequency to generate 1 Hz for seconds counting and derives all timekeeping functions from that base. Using a 32.768 kHz crystal would result in incorrect timing; the PCF1178CT,118 oscillator circuit is optimized for 4.194304 MHz with specified load capacitance (12 pF) and feedback resistance (300–3000 kΩ). Substituting crystals invalidates PCF1178CT,118 timing accuracy.

What are the requirements for programming the EEPROM in the PCF1178CT,118?

Programming the EEPROM in the PCF1178CT,118 requires applying VDD −5 V to VPP (e.g., 0 V when VDD = 5 V), leaving SEL open-circuit, and delivering precise pulses to the DATA pin: a 4–6 ms erase pulse (t_E) clears the register, followed by 1–1.5 µs increment pulses (t_L) to step voltage or calibration values, and a final 4–6 ms store pulse (t_W) to lock the setting. All pulses must meet timing tolerances in Figure 6 of the datasheet; improper sequencing may corrupt PCF1178CT,118 EEPROM contents.

Does the PCF1178CT,118 support both 12-hour and 24-hour display formats?

Yes, the PCF1178CT,118 supports both 12-hour and 24-hour display formats via the MODE pin: connecting MODE to VDD selects 12-hour mode with AM/PM indicator, while connecting MODE to VSS selects 24-hour mode. If MODE is left open-circuit, the device defaults to 24-hour mode on power-up. The PCF1178CT,118 automatically configures segment drivers (e.g., AM/PM pin activation) and display logic accordingly - no software or external logic is needed to switch formats.