STMicroelectronics TL7705AID1/A

Overview

TL7705AID1/A from STMicroelectronics is a precision supply voltage supervisor IC designed for microprocessor reset control, featuring a 4.5 V ±1.5% threshold voltage, true and complement reset outputs (RESET and RESET), 3.6–18 V operating supply range, -25°C to 85°C temperature rating, and externally adjustable reset pulse width via capacitor on CT pin. It ensures reliable power-on and brownout reset in embedded controllers.

For engineers reviewing the TL7705AID1/A datasheet, TL7705AID1/A pinout, TL7705AID1/A application, or TL7705AID1/A equivalent, key selection criteria include its fixed 4.5 V sense threshold, dual active-high/active-low reset outputs, CT-based timing flexibility, REF output stability with 0.1 µF bypass, and SO-8 package compatibility with legacy board layouts.

Technical Context

The TL7705AID1/A integrates a temperature-compensated bandgap reference and precision comparator to monitor the SENSE input against a 4.5 V nominal threshold with ±50 mV hysteresis. Its internal state machine asserts RESET (high) and RESET (low) during power-up until VS exceeds VT and the CT-timed delay expires.

Reset assertion is re-triggered on supply droop below VT, and RESIN pin provides manual override. The REF output delivers a stable 2.53 V reference (±50 mV) for external monitoring or biasing, requiring a 0.1 µF capacitor to ground per datasheet recommendation.

Key Specifications

Pinout & Package

TL7705AID1/A is housed in an SO-8 (Small Outline, 8-pin) surface-mount package with standard 1.27 mm pitch, 5.0 mm × 4.0 mm body, and gull-wing leads. Thermal resistance is 120°C/W (junction-to-ambient).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage supervisor applications.

Compared with TL7705AID1/A, TPS3808G33DBVR offers tighter delay accuracy but sacrifices adjustability and reference functionality, while MAX6326UT45D3+ reduces pin count and power but removes design flexibility in timing and signal polarity.

Availability

TL7705AID1/A is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, medical infusion pumps, and point-of-sale terminals requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for TL7705AID1/A 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, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The TL7700A series belongs to ST's legacy voltage supervisor product line, engineered specifically for deterministic microprocessor reset control in cost-sensitive, thermally demanding embedded systems where external timing components and dual-polarity outputs add design value.

FAQ

What is the exact threshold voltage of TL7705AID1/A and how does it vary with temperature?

The TL7705AID1/A has a nominal SENSE threshold of 4.5 V, with a typical variation of ±1.5% over the full -25°C to +85°C operating range. Electrical characteristics tables confirm VT = 4.50 V (min), 4.55 V (typ), 4.60 V (max) at 25°C, and VT = 4.45 V (min), 4.55 V (typ), 4.60 V (max) across temperature. Hysteresis remains stable at 15 mV.

Can TL7705AID1/A be used with a 3.3 V microcontroller supply rail?

No - TL7705AID1/A is not rated for direct supervision of 3.3 V rails. Its minimum supply voltage is 3.6 V, and its 4.5 V threshold exceeds 3.3 V by >1 V. Using it on a 3.3 V rail would prevent proper reset assertion. For 3.3 V systems, ST recommends TL7703A or alternatives like TPS3808G33.

Is the REF output intended for precision analog use or only decoupling?

The REF output delivers a 2.53 V bandgap reference with ±50 mV tolerance over temperature and load, making it suitable for moderate-precision tasks such as biasing external comparators or feeding low-resolution ADC references. It is not specified for <0.1% accuracy or high-current loads, and requires the mandatory 0.1 µF capacitor to GND for stability.

How do I calculate the reset pulse width for a custom CT capacitor value?

Use the formula tpo = 1.3 × 10⁴ × CT, where CT is in farads and tpo is in seconds. For example, a 0.047 µF (4.7×10⁻⁸ F) capacitor yields tpo ≈ 0.611 ms. Datasheet Figure 1 confirms this linear relationship, and measured values fall within 0.65–2.6 ms for CT = 0.1 µF, validating the scaling factor.