Texas Instruments FX1077

Overview

FX1077 from Texas Instruments is a low-quiescent-current, programmable-delay supervisory circuit designed to monitor system supply voltages and assert an open-drain RESET signal when the SENSE input falls below a precision threshold (e.g., 1.12 V for 1.2-V rail) or upon manual reset assertion. It delivers 0.5% threshold accuracy, 2.4 μA typical supply current, and user-adjustable reset delay from 1.25 ms to 10 s-enabling reliable power-on reset in battery-powered microcontroller systems.

For engineers reviewing the FX1077 datasheet, FX1077 pinout, FX1077 application, or FX1077 equivalent, this page provides verified technical context, exact pin functions, real-world timing behavior, package-specific thermal data, and validated alternative options for voltage monitoring and reset generation in embedded and portable electronics.

Technical Context

The FX1077 implements a precision voltage comparator with built-in hysteresis and an on-chip 220-nA current source that charges an external capacitor on the CT pin to control reset timeout. Its SENSE input monitors rails from 0.4 V to 5 V, while MR provides asynchronous reset initiation with internal 90-kΩ pull-up.

RESET output is open-drain, requiring an external pull-up resistor (10 kΩ–1 MΩ), and remains asserted for the full delay period after both SENSE exceeds VIT + VHYS and MR returns high. The device operates across –40°C to 125°C and supports fixed delays (20 ms or 300 ms) or fully programmable delays via CT capacitor selection.

Key Specifications

Pinout & Package

FX1077 is available in two RoHS-compliant packages: 6-pin SOT-23 (DBV, 2.90 mm × 1.60 mm) and 6-pin WSON (DRV, 2.00 mm × 2.00 mm with thermal pad). Both packages support identical pin mapping and electrical performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar supervisory circuit applications.

Compared with FX1077, TPS3809K33 trades programmability and ultra-low power for smaller footprint and lower unit cost, while MAX6326UT29D offers lower IQ but sacrifices MR interface and delay flexibility-making FX1077 optimal for designs needing configurable timing, manual reset, and extended battery runtime.

Availability

FX1077 is available at Aetrix Electronics and suitable for microcontroller power-on reset, battery-powered portable devices, FPGA configuration monitoring, and industrial PLC I/O modules requiring stable component supply across automotive, medical, and industrial production cycles.

Supply support for FX1077 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 company delivering analog and embedded processing solutions, with leadership in power management, signal chain, and high-reliability ICs.

The TPS3808 product line was engineered specifically for precision voltage supervision in resource-constrained embedded systems-emphasizing ultra-low quiescent current, factory-trimmed threshold accuracy, and flexible reset timing without external timing resistors.

FAQ

What is the minimum supply voltage required for FX1077 to assert a valid RESET signal?

FX1077 requires VDD ≥ 1.7 V to guarantee proper RESET assertion and de-assertion behavior. Below 1.7 V, the device enters undefined operation per absolute maximum ratings. The power-on reset voltage (VPOR) is specified at 0.8 V, but functional reset timing and threshold accuracy are only guaranteed above 1.7 V. FX1077 must be powered within its recommended operating range to ensure reliable supervision of downstream logic.

Can FX1077 monitor a 0.8-V core rail, and if so, how?

Yes, FX1077 can monitor a 0.8-V rail using the adjustable-threshold TPS3808G01 variant with an external resistor divider on the SENSE pin. The G01 version has a base threshold of 0.405 V, and scaling via R1/R2 allows setting VIT to 0.8 V precisely. FX1077 itself is a generic part number referencing the TPS3808 family; actual threshold capability depends on the specific suffix (e.g., G01, G12). Confirm the exact orderable part matches the required threshold.

How does the CT pin determine reset delay time in FX1077?

The CT pin connects to an internal 220-nA current source that charges an external capacitor to 1.23 V; RESET de-asserts when that voltage is reached. With CT open, internal circuitry yields 20 ms; tying CT to VDD through 40–200 kΩ gives 300 ms; connecting CT to GND via ≥100-pF capacitor enables delay calculation as tD = CT(nF) × 10⁻³ + 0.5 ms. FX1077's CT behavior is defined in Section 8.3.2 of its datasheet and validated across temperature.

Is FX1077 pin-compatible with other TPS3808 variants like TPS3808G33?

Yes, all TPS3808 variants-including FX1077, TPS3808G33, and TPS3808G12-share identical 6-pin SOT-23 (DBV) and WSON (DRV) packages and pinout. Pin functions (RESET, GND, MR, CT, SENSE, VDD) are electrically and physically identical across the family. FX1077 refers to the base family; specific threshold and ordering codes (e.g., G33) do not affect pin compatibility or PCB layout.

What is the maximum allowable voltage on the RESET pin of FX1077?

The RESET pin of FX1077 supports voltages up to 6.5 V, independent of VDD, due to its open-drain architecture and internal clamp structure. This allows interfacing with higher-voltage logic families (e.g., 5-V MCUs) while powered from a 3.3-V supply. The datasheet specifies absolute maximum rating of 7 V, but recommended operating condition is 0–6.5 V. FX1077's RESET pin must be pulled up externally to the target logic voltage.