STMicroelectronics STM819LDS6E

Overview

STM819LDS6E from STMicroelectronics is a 5 V industrial-grade microprocessor supervisor IC with integrated battery switchover, dual reset outputs (RST and RST), manual reset input (MR), and power-fail comparator (PFI/PFO). It guarantees RST assertion down to VCC = 1.0 V, provides 200 ms typical reset timeout (trec), and draws only 40 µA typical supply current. It is used in embedded systems requiring non-volatile SRAM backup and reliable power monitoring - e.g., industrial HMIs with battery-backed memory.

For engineers reviewing the STM819LDS6E datasheet, STM819LDS6E pinout, STM819LDS6E application, or STM819LDS6E equivalent, key selection criteria include guaranteed reset assertion at low VCC, push-pull RST/RST outputs, battery switchover behavior, PFI/PFO response timing, and compatibility with external LPSRAM power gating.

Technical Context

The STM819LDS6E implements a precision voltage-monitoring architecture with independent comparators for VCC (reset threshold VRST ≈ 4.63 V), power-fail detection (VPFI ≈ 2.4 V), and battery switchover (VSO = min(VBAT, VRST)). Its logic diagram (Figure 2) confirms absence of watchdog timer - unlike STM690A/802 - and presence of MR-driven reset assertion with internal 40 kΩ pull-up.

All RST and RST outputs are push-pull, ensuring fast, rail-to-rail drive capability without external pull-ups. The device operates across –40 °C to +85 °C and asserts reset within 10 µs (typ) of VCC falling below VRST, with trec = 200 ms (typ) guaranteeing sufficient MCU initialization time after power recovery.

Key Specifications

Pinout & Package

STM819LDS6E is housed in an 8-pin SO8 (Small Outline) package with 1.27 mm pitch, RoHS-compliant, and rated for industrial temperature range. Pin functions are validated per ST's DocID10522 Rev 11 (Table 3, Figure 5).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692AESA+ and TPS3823-46DBVR, STM819LDS6E uniquely integrates battery switchover, dual-polarity reset, and PFI/PFO in one SO8 package - eliminating four discrete components in SRAM-backed industrial controllers.

Availability

STM819LDS6E is available at Aetrix Electronics and suitable for industrial programmable logic controllers, smart electricity meters, factory HMIs, and building automation controllers requiring stable component supply across extended product lifecycles.

Supply support for STM819LDS6E 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, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The STM8xx supervisor family targets industrial embedded systems needing robust, low-power, battery-backed memory management and deterministic reset behavior - especially where regulatory compliance (IEC 61000-4-2/4) and long-term supply stability are critical.

FAQ

Does STM819LDS6E include a watchdog timer?

No. Unlike STM690A or STM802, the STM819LDS6E omits the watchdog timer function entirely - confirmed in Section 2.3 of DocID10522 Rev 11 ("NOT available on STM703/704/819"). Its reset supervision relies solely on VCC monitoring, MR input, and PFI-triggered PFO assertion.

What is the maximum allowable VBAT voltage relative to VCC?

VBAT may exceed VCC - explicitly permitted per Section 1.1.6 and Figure 5. When VCC is absent or below VSO, VBAT powers VOUT directly. The internal P-channel MOSFET switch isolates VCC and VBAT paths, preventing backfeed; absolute max VBAT is 5.5 V per Table 5 (Absolute Maximum Ratings).

How does the battery freshness seal operate on STM819LDS6E?

The battery freshness seal disables VBAT-to-VOUT conduction until VCC first rises above VRST (≈4.63 V), preventing battery drain during storage. As described in Section 2.12, this seal is activated once and cannot be re-engaged without power-cycling VCC - ensuring zero standby current prior to system commissioning.

Can PFI be left unconnected if power-fail detection is unused?

Yes. Per Section 1.1.9, PFI should be connected to ground if unused. Leaving it floating is not recommended due to noise susceptibility; grounding ensures PFO remains high (inactive) and avoids false power-fail assertions caused by leakage or EMI coupling.