Renesas X9421YP18I

Overview

X9421YP18I from Intersil is a single-channel, SPI-interface digitally controlled potentiometer (XDCP™) with 64-tap resistor array, 2.5kΩ end-to-end resistance, and industrial temperature range (–40°C to +85°C). It integrates volatile wiper counter register (WCR) and four non-volatile data registers for storing multiple wiper positions, enabling programmable gain control in voltage amplifiers and DC bias trimming in sensor signal conditioning circuits.

For engineers reviewing the X9421YP18I datasheet, X9421YP18I pinout, X9421YP18I application, or X9421YP18I equivalent, key selection considerations include SPI bus compatibility, 2.5kΩ/10kΩ resistance options, TSSOP-14 vs SOIC-16 package fit, power-on recall behavior, and nonvolatile write endurance (100,000 cycles).

Technical Context

The X9421YP18I implements a 63-segment CMOS resistor ladder with switch-controlled wiper positioning driven by a 6-bit Wiper Counter Register (WCR). Its SPI interface supports full-duplex read/write operations, including direct WCR access, data register transfers, and increment/decrement commands with real-time wiper response (<10µs).

Nonvolatile storage uses on-chip EEPROM technology with 100-year data retention and hardware write protection via the WP pin. Power-up automatically loads DR0 into the volatile WCR, ensuring deterministic startup wiper position without host initialization.

Key Specifications

Pinout & Package

Package: 14-lead TSSOP (4.4mm width), RoHS-compliant, Pb-free matte tin termination.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digitally controlled potentiometer applications.

Compared with X9421YP18I, ISL22416 sacrifices flexibility (no HOLD, narrow V_CC) for cost-sensitive 5V-only designs, while ISL22419 offers superior resolution and pin compatibility at the expense of package size - both require layout revision due to different pinouts and footprints.

Availability

X9421YP18I is available at Aetrix Electronics and suitable for industrial sensor calibration, embedded audio control, and RF biasing applications requiring stable component supply, long-term calibration retention, and SPI-based digital adjustment.

Supply support for X9421YP18I 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

Intersil (now part of Renesas Electronics) is a semiconductor manufacturer specializing in precision analog, power management, and interface ICs for industrial, communications, and computing markets.

The X9421 product line delivers digitally programmable resistance for replacing mechanical potentiometers in calibration-critical systems where nonvolatile storage, SPI control, and low-noise analog performance are essential.

FAQ

What is the operating temperature range for the X9421YP18I?

The X9421YP18I is rated for industrial operation from –40°C to +85°C. This range is confirmed in the Ordering Information table on page 2 of FN8196 Rev.1.00, where "X9421YV14I" denotes the industrial-grade 14-lead TSSOP variant. The "P18I" suffix aligns with this industrial specification, ensuring reliable performance across extended thermal environments encountered in motor controls and outdoor electronics.

Does the X9421YP18I support true three-wire SPI communication?

Yes, the X9421YP18I supports standard three-wire SPI with separate SI and SO lines. Its SO pin is push-pull (not open-drain), allowing direct connection to MCU MISO without pull-up. The datasheet explicitly states SI and SO "can be connected together" for single-wire mode, confirming native three-wire capability as the default configuration - critical for deterministic timing in real-time control loops using the X9421YP18I.

How does power-on recall work in the X9421YP18I?

At power-up, once VCC reaches its final value and stabilizes, the X9421YP18I automatically loads the contents of Data Register 0 (DR0) into the volatile Wiper Counter Register (WCR). This behavior is unconditional and requires no host intervention. Page 1 of the datasheet confirms "Power-on Recall. Loads Saved Wiper Position on Power-up," and Page 5 specifies DR0 as the default source - ensuring the X9421YP18I resumes its last calibrated state immediately after reset.

What is the maximum clock frequency supported by the X9421YP18I SPI interface?

The X9421YP18I supports an SPI clock frequency (fSCK) of up to 2.0 MHz, as specified in the AC Timing table on page 14 of FN8196 Rev.1.00. This limit applies across the full industrial temperature range and VCC span (2.7V–5.5V). Exceeding 2 MHz may cause setup/hold violations on SI/SO, leading to corrupted register transfers - a constraint directly tied to internal logic propagation delays within the X9421YP18I's CMOS interface circuitry.

Can the X9421YP18I be used as a two-terminal variable resistor?

Yes, the X9421YP18I can operate as a two-terminal variable resistor by connecting either RH/VH or RL/VL to VW/RW, leaving the unused terminal open. The datasheet's Description section explicitly states it "can be used as a three-terminal potentiometer or as a two terminal variable resistor." This configuration reduces effective resistance range and increases wiper resistance contribution, but is fully supported and characterized - commonly applied in LED current-setting and filter Q-adjustment circuits using the X9421YP18I.