NXP Semiconductors PCF1175CT/S420/2:1

Overview

PCF1175CT/S420/2:1 from Philips Semiconductors is a CMOS 4-digit duplex LCD car clock IC with integrated 4.19 MHz oscillator, electrically programmable voltage regulator (adjustable 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 PCF1175CT/S420/2:1 datasheet, PCF1175CT/S420/2:1 pinout, PCF1175CT/S420/2:1 application, or PCF1175CT/S420/2:1 equivalent, key selection considerations include its SO28 package, LCD segment/backplane drive architecture, temperature-compensated VDD regulation, EEPROM-programmable calibration, and dual-switch time-setting interface.

Technical Context

The PCF1175CT/S420/2:1 implements a 1:2 multiplexed duplex LCD driver with three-level backplane signals (BP1/BP2) generating VON(RMS) = 0.79 VDD and VOFF(RMS) = 0.35 VDD. Its internal 4.194304 MHz oscillator feeds a programmable divider chain for seconds/minutes/hours counting, with EEPROM-stored calibration pulses (0–31) to correct crystal frequency deviation up to +117.8 × 10⁻⁶.

Time setting uses two debounced SPST switch inputs (S1/S2) with auto-increment logic and enable control (ENABLE), while mode selection (12/24-hour) is determined by MODE pin level. LCD contrast is maintained via temperature-dependent VDD regulation-e.g., 4.5 V at 25 °C shifts to 3–4 V at +85 °C and 5–6 V at −40 °C.

Key Specifications

Pinout & Package

PCF1175CT/S420/2:1 is housed in a plastic small outline package (SO28, SOT136-1) with 28 leads, 7.5 mm body width, and 1.27 mm lead pitch. Pin 1 index is marked on the package per JEDEC MS-013AE.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCF1175CT/S420/2:1, PCF1174CT trades EEPROM programmability for simpler analog biasing, while PCF1176CT extends functionality with alarm output - both retain identical timing accuracy, temperature range, and 4-digit duplex LCD drive capability.

Availability

PCF1175CT/S420/2:1 is available at Aetrix Electronics and suitable for automotive dashboard systems, aftermarket infotainment displays, and commercial vehicle telematics requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.

Supply support for PCF1175CT/S420/2:1 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, emphasizing reliability, qualification rigor, and system-level integration.

The PCF1175CT/S420/2:1 belongs to Philips' car clock IC product line, designed specifically for cost-sensitive, high-volume automotive LCD time displays requiring zero-trim operation, wide temperature resilience, and minimal external components.

FAQ

What is the primary function of the PCF1175CT/S420/2:1 in automotive systems?

The PCF1175CT/S420/2:1 serves as a fully integrated 4-digit duplex LCD car clock IC, providing real-time hours/minutes/seconds counting, 12- or 24-hour mode selection, colon blink control, and direct segment/backplane drive. Its internal 4.194304 MHz oscillator, EEPROM-programmable calibration, and temperature-compensated voltage regulator eliminate external timing and contrast components - making PCF1175CT/S420/2:1 ideal for automotive dashboard and infotainment displays.

How does the PCF1175CT/S420/2:1 achieve temperature-stable LCD contrast?

The PCF1175CT/S420/2:1 achieves temperature-stable LCD contrast through an internal adjustable voltage regulator whose output varies with ambient temperature: e.g., programmed to 4.5 V at 25 °C, it delivers 3–4 V at +85 °C and 5–6 V at −40 °C. This automatic scaling maintains optimal RMS segment voltages (VON = 0.79 VDD, VOFF = 0.35 VDD) across the full −40 to +85 °C operating range - ensuring consistent contrast without user or system intervention in PCF1175CT/S420/2:1-based designs.

Can the PCF1175CT/S420/2:1 be used without an external crystal?

No - the PCF1175CT/S420/2:1 requires an external 4.194304 MHz quartz crystal connected between OSC IN and OSC OUT pins. The IC includes an internal feedback resistor (300–3000 kΩ) and oscillator circuitry but no built-in resonator; crystal load capacitance is set by internal design and does not require external capacitors. Omitting the crystal prevents oscillator startup and halts all timekeeping functions in the PCF1175CT/S420/2:1.

What are the time-setting interface requirements for the PCF1175CT/S420/2:1?

The PCF1175CT/S420/2:1 uses two SPST switch inputs (S1 for hours, S2 for minutes) with internal pull-up resistors (45–180 kΩ) and hardware debounce (30–100 ms). Time setting is enabled by connecting ENABLE to VDD; S1/S2 pulled to VSS initiate auto-increment (1 sec initial delay, then 1/sec). Both switches pressed simultaneously activates segment test mode. No microcontroller or external logic is needed - the complete time-setting interface for PCF1175CT/S420/2:1 consists of two switches, one enable line, and debounced inputs.

Is the PCF1175CT/S420/2:1 pin-compatible with other members of the PCF117x family?

Yes - the PCF1175CT/S420/2:1 shares identical SO28 (SOT136-1) packaging, pinout, and core functionality with PCF1174CT and PCF1176CT. Differences lie in feature set: PCF1174CT omits EEPROM voltage programming, while PCF1176CT adds ALARM output. All three support the same 4-digit duplex LCD drive, 4.19 MHz oscillator, and switch-based time setting - enabling drop-in substitution where feature alignment permits, as confirmed in Philips' official ordering information and package outline documentation for PCF1175CT/S420/2:1.