STMicroelectronics L9780TR

Overview

L9780TR from STMicroelectronics is a wide-range air-fuel sensor control interface IC designed for automotive exhaust gas oxygen sensing systems. It integrates a voltage-controlled current source (VCCS) pump cell driver with dual output channels, 10-bit multiplexed A/D conversion, heater FET driver with diagnostics, and SPI-configurable synchronous/asynchronous operation - enabling precise lambda measurement in gasoline and diesel engine management.

For engineers reviewing the L9780TR datasheet, L9780TR pinout, L9780TR application, or L9780TR equivalent, key selection considerations include VCCS current range (±20 mA), -5 V internal charge pump supply, short-to-battery/ground diagnostics on INRC and SR pins, and LQFP48 package compatibility with automotive-grade PCB layouts.

Technical Context

The L9780TR implements a closed-loop PI controller for VCCS reference generation, supporting external compensation networks (A/B sides) selectable via SPI to adapt to diverse wide-range sensor impedances. Its timing state machine automates measurement sequencing with fully SPI-configurable time constants.

It features dual-channel analog signal conditioning: impedance measurement of the reference cell (via RCT1/RCT2), scaling and control voltage amplifiers with sample-and-hold and offset compensation, and dedicated diagnostic circuitry for heater FET (short-to-battery, short-to-ground, open-circuit) and functional ground (SR pin).

Key Specifications

Pinout & Package

Package: 48-pin LQFP (7 mm × 7 mm, 0.5 mm pitch), RoHS-compliant, automotive-qualified (AEC-Q100 Grade 1).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar wide-range air-fuel sensor interface applications.

Compared with the L9780TR, the SGM300 offers higher integration but less flexibility in sensor matching, while the ADuCM355 provides software-defined functionality at the cost of extended qualification time and safety certification effort.

Availability

L9780TR is available at Aetrix Electronics and suitable for automotive engine control units, exhaust aftertreatment systems, and onboard diagnostics requiring stable component supply across extended temperature and lifetime requirements.

Supply support for L9780TR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management ICs with broad AEC-Q100 qualification coverage.

The L9780TR belongs to ST's automotive sensor interface product line, engineered specifically for high-accuracy, fault-tolerant wide-range lambda sensing in demanding exhaust environments.

FAQ

What is the purpose of the -5 V CP pin?

Pin CP delivers a regulated -5 V output from the internal charge pump, used to bias the INRC amplifier's input stage. This extends the common-mode input range to accommodate reference cell voltages near ground, improving measurement accuracy and noise rejection in low-lambda conditions (e.g., rich exhaust). It is not intended as a general-purpose supply rail.

How does the L9780TR handle sensor compensation network selection?

The L9780TR supports two independent external compensation networks (side A and side B) connected via pins C1A/C2A/C3 and C1B/C2B. The COMPSEL bit in the SPI input register selects which network configures the PI controller for VCCS reference generation - enabling one hardware design to interface Bosch LSU 4.9, NGK AFX, or Denso sensors without PCB change.

Can the heater FET driver operate with external MOSFETs rated above 20 V?

Yes - the HD/HG pins drive external N-channel MOSFETs with V_DS ratings up to 60 V. The internal driver provides 1.5 A peak gate current and monitors V_DS during switching to detect short-to-battery (V_DS < 1.5 V) and open-circuit (V_DS > 45 V) faults. External gate resistors must be selected to limit dv/dt per datasheet Figure 6.

Is SPI daisy-chaining supported, and what are the timing constraints?

Yes - the L9780TR supports daisy-chained SPI configuration using SO-to-SI connection between devices. Maximum clock frequency is 4 MHz, with t_CLKH/t_CLKL ≥ 100 ns and t_SU/t_H ≥ 20 ns (per Table 18). Daisy chain depth is limited to 4 devices due to cumulative propagation delay; CSN must be asserted per device for individual register access.