Texas Instruments LM3881MMX/NOPB

Overview

LM3881MMX/NOPB from Texas Instruments is a simple power sequencer IC that controls startup and shutdown sequencing of up to three independent power rails using three open-drain flag outputs, precision enable threshold (1.22 V), adjustable timing via external capacitor (e.g., 10 nF yields ~9.6 ms delays), and logic-invertable output polarity. It operates across 2.7 V–5.5 V supply and targets FPGA, microprocessor, and multi-rail server power systems.

For engineers reviewing the LM3881MMX/NOPB datasheet, LM3881MMX/NOPB pinout, LM3881MMX/NOPB application, or LM3881MMX/NOPB equivalent, key selection considerations include its VSSOP-8 package, 80 µA quiescent current, EN-controlled staggered power-up (FLAG1→FLAG2→FLAG3) and reverse-order power-down, TADJ-based timing adjustability, and compatibility with both active-high and active-low regulator enable inputs via INV pin.

Technical Context

The LM3881MMX/NOPB implements a clock-based sequencing engine driven by a linearly charged/discharged TADJ pin (12 µA source/sink between 0.5 V and 1.22 V thresholds), generating a programmable clock period (e.g., 1.2 ms with 10 nF). Its internal counter triggers FLAG1 after 9–10 clock cycles, then FLAG2 and FLAG3 each after exactly 8 additional cycles - enabling precise, repeatable delay intervals without external timers.

Power sequencing is fully controlled by the EN pin: assertion initiates power-up in forward order; deassertion triggers power-down in reverse order (FLAG3→FLAG2→FLAG1). The INV pin selects active-high or active-low flag logic, while all flags tolerate short-circuit-to-VCC conditions and require external pullups (typically 100 kΩ).

Key Specifications

Pinout & Package

VSSOP-8 (DGK) package, 3.00 mm × 3.00 mm body size, 0.65 mm lead pitch, thermally enhanced exposed pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3881MMX/NOPB, TPS3808G33DBVR offers simpler supervision but no sequencing capability, while ADM1085AKSZ-REEL7 provides integrated triple outputs without timing adjustability - making LM3881MMX/NOPB the only option among the three supporting user-defined, capacitor-programmable delays across all three flags.

Availability

LM3881MMX/NOPB is available at Aetrix Electronics and suitable for FPGA sequencing, microprocessor power management, and multi-rail server applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LM3881MMX/NOPB 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 for industrial, automotive, and communications markets.

The LM3881MMX/NOPB belongs to TI's Simple Power Sequencer product line, designed specifically to replace complex discrete or programmable solutions with minimal-component, capacitor-timed sequencing for cost-sensitive and space-constrained multi-rail systems.

FAQ

What is the function of the INV pin on the LM3881MMX/NOPB?

The INV pin on the LM3881MMX/NOPB selects the logic polarity of all three FLAG outputs. When INV is low, FLAG1–FLAG3 are active-high (open-drain, pulled up externally); when INV is high, they become active-low. This allows direct interface with both active-high enable inputs (e.g., most LDOs) and active-low shutdown pins (e.g., certain DC-DC controllers), eliminating level-shifting circuitry. The pin must be driven - floating is not permitted.

How does the LM3881MMX/NOPB generate its timing delays?

The LM3881MMX/NOPB generates timing delays using an internal current source/sink (12 µA typical) that linearly charges and discharges an external capacitor connected to the TADJ pin between two precision thresholds (0.5 V and 1.22 V). This creates a sawtooth waveform whose period determines the base clock (e.g., 1.2 ms with 10 nF). Flag delays are integer multiples of this clock - 9 cycles for FLAG1, 8 for FLAG2 and FLAG3 - enabling predictable, capacitor-scaled sequencing intervals.

Can the LM3881MMX/NOPB be used for power-down sequencing only?

Yes, the LM3881MMX/NOPB inherently supports controlled power-down sequencing: when the EN pin is deasserted, it automatically reverses the power-up order - FLAG3 pulls low first, followed by FLAG2 then FLAG1 - with identical time delays (TD4 = TD1, TD5 = TD2, TD6 = TD3). This ensures safe, staggered shutdown even if EN is toggled mid-sequence, preventing backfeeding or latch-up in downstream regulators.

What is the recommended pullup resistor value for the LM3881MMX/NOPB FLAG outputs?

Texas Instruments recommends 100 kΩ pullup resistors for the LM3881MMX/NOPB FLAG outputs, as validated in the datasheet's typical application circuit and layout guidelines. This value balances low static current (≤33 µA per flag at 3.3 V), sufficient drive strength for standard CMOS inputs, and noise immunity. Lower values (e.g., 10 kΩ) increase current draw unnecessarily; higher values (>1 MΩ) risk slow edges and noise susceptibility in noisy environments.

Does the LM3881MMX/NOPB require an input bypass capacitor on VCC?

While not strictly required, Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC pin of the LM3881MMX/NOPB to suppress high-frequency noise on the supply rail. This improves stability of the internal bandgap reference and timing circuitry, especially in systems with switching regulators or shared power planes. The capacitor should be X7R or better dielectric and mounted with minimal trace length and loop area.