Microchip Technology MCP1257-E/UN

Overview

MCP1257-E/UN from Microchip Technology is a 10-pin DFN-packaged, inductorless charge-pump DC/DC converter generating a regulated 3.3V output from 1.8V–3.6V input. It delivers up to 100 mA output current, maintains ±3.0% output voltage accuracy, operates at 650 kHz switching frequency, and features low-power SLEEP mode with 10 µA typical quiescent current-designed for PIC® MCU bias and portable measurement instruments.

For engineers reviewing the MCP1257-E/UN datasheet, MCP1257-E/UN pinout, MCP1257-E/UN application, or MCP1257-E/UN equivalent, key selection criteria include its SLEEP-mode operation (not BYPASS), LBO low-battery indication, thermal shutdown at 160°C, -40°C to +125°C operating range, and compatibility with ceramic flying capacitors (1 µF) and output capacitors (10 µF).

Technical Context

The MCP1257-E/UN uses switched-capacitor topology with automatic 1.5x/2x mode selection based on input voltage and load to maximize efficiency. Its regulation employs bang-bang control with hysteresis, enabling stable 3.3V output while minimizing external components-only four ceramic capacitors required.

It integrates dedicated LBO open-drain output asserting logic low when VIN drops below 1.95 V (with 240 mV hysteresis), and supports soft-start (175 µs wake-up time), short-circuit protection (150 mA typical limit), and thermal shutdown with 15°C hysteresis-ensuring robust operation in battery-powered systems.

Key Specifications

Pinout & Package

Package: 10-lead 3 mm × 3 mm DFN (exposed pad), RoHS-compliant, thermal resistance θ_JA = 57°C/W on 4-layer board.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar charge-pump DC/DC converter applications.

Compared with MCP1256-E/UN, the MCP1257-E/UN substitutes LBO for PGOOD-making it optimal for battery telemetry-but shares identical SLEEP mode, efficiency, and thermal protection. Versus MCP1257T-E/UN, only packaging differs; both deliver identical performance in circuit.

Availability

MCP1257-E/UN is available at Aetrix Electronics and suitable for portable measurement instruments, home automation sensor nodes, and PIC® MCU bias applications requiring stable component supply, extended temperature support, and long-term obsolescence management.

Supply support for MCP1257-E/UN 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

Microchip Technology Inc. is a leading provider of microcontroller, mixed-signal, analog, and Flash-IP solutions, serving automotive, industrial, consumer, and communications markets.

The MCP125x family was designed specifically for low-noise, inductorless step-up conversion in space-constrained, battery-powered systems-emphasizing simplicity, reliability, and minimal external component count.

FAQ

What is the primary function of the MCP1257-E/UN?

The MCP1257-E/UN is an inductorless, regulated charge-pump DC/DC converter that generates a precise 3.3V output from a 1.8V–3.6V input. Its core function is to provide efficient, low-EMI bias voltage for microcontrollers and analog circuits in portable systems-leveraging SLEEP mode and LBO to optimize battery life and system health monitoring. The MCP1257-E/UN achieves this with only four external ceramic capacitors and no inductors.

How does the LBO pin on the MCP1257-E/UN operate?

The LBO pin on the MCP1257-E/UN is an open-drain output that asserts logic low when the input voltage falls below 1.95 V (typical), with 240 mV hysteresis to prevent oscillation during threshold crossing. It remains high-impedance during shutdown or when disabled. A pull-up resistor (10 kΩ to 1 MΩ) to VOUT is required for digital interfacing. This feature is exclusive to the MCP1257-E/UN and MCP1259 variants-not present on MCP1256-E/UN or MCP1258-E/UN.

What is the maximum output current capability of the MCP1257-E/UN?

The MCP1257-E/UN delivers up to 100 mA of continuous output current when the input voltage is ≥2.2 V. At lower inputs (1.8V–2.0V), max output drops to 30 mA; at 2.0V–2.2V, it is 70 mA. These limits are defined by internal charge-pump strength and efficiency curves-verified across -40°C to +125°C. Exceeding these currents risks regulation loss or thermal shutdown. The MCP1257-E/UN sustains this performance using two 1 µF flying capacitors and a 10 µF output capacitor.

Does the MCP1257-E/UN support automatic mode switching between 1.5x and 2x boost?

Yes, the MCP1257-E/UN automatically selects between 1.5x and 2x charge-pump modes based on input voltage and load conditions to maximize efficiency-without external control. At higher VIN (e.g., 2.8V), it favors 1.5x mode; at lower VIN (e.g., 1.8V), it defaults to 2x. This dynamic switching is handled entirely by internal comparator logic and gate drive sequencing, as confirmed in the functional block diagram and Table 1 switch logic of the DS21989B datasheet for MCP1257-E/UN.

What package type is used for the MCP1257-E/UN?

The MCP1257-E/UN is supplied in a 10-lead, 3 mm × 3 mm DFN package with exposed thermal pad. This RoHS-compliant package offers θ_JA = 57°C/W on a standard 4-layer board-significantly better thermal performance than the MSOP variant (θ_JA = 200°C/W). Pinout matches the MSOP version, enabling footprint interchangeability where board space allows. The DFN package is explicitly listed for MCP1257-E/UN in Microchip's packaging documentation and ordering codes.