Microchip Technology MCP73855T-I/MF

Overview

MCP73855T-I/MF from Microchip Technology is a linear lithium-ion/lithium-polymer battery charge management controller with integrated P-channel MOSFET pass transistor, current sensing, and reverse blocking protection. It delivers ±0.5% voltage regulation accuracy at 4.1V or 4.2V, supports USB-compliant charge currents up to 400 mA, and operates across –40°C to +85°C for portable USB-powered devices.

For engineers reviewing the MCP73855T-I/MF datasheet, MCP73855T-I/MF pinout, MCP73855T-I/MF application, or MCP73855T-I/MF equivalent, this page provides verified technical context, real-world design meaning of key specs, validated 10-lead DFN package mapping, confirmed pin functions, and two rigorously cross-checked alternative parts for Li-ion charging systems requiring compact, thermally regulated, single-cell solutions.

Technical Context

The MCP73855T-I/MF implements a complete linear charge algorithm: preconditioning (trickle charge) below 2.8 V, constant-current fast charge (programmable 85–400 mA), then constant-voltage regulation (4.1V/4.2V ±0.5%) with automatic termination at ~7% I_REG. It uses an internal P-channel MOSFET with thermal regulation that scales charge current above 125°C and full thermal shutdown at 155°C.

All safety timers-preconditioning (60 min), fast charge (1.5 hr), and elapsed time (3 hr)-are scaled by a single external capacitor on the TIMER pin. Unlike the MCP73853, it omits THERM, THREF, STAT2, VBAT3, and VDD2 pins, confirming its role as the reduced-feature, 10-lead DFN variant optimized for cost-sensitive USB chargers without temperature monitoring.

Key Specifications

Pinout & Package

Package: 10-lead, 3 mm × 3 mm DFN (exposed pad at VSS potential). Thermal resistance θ_JA = 51°C/W on standard 4-layer board.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear Li-ion charge management applications.

Compared with MCP73853T-I/MF, the MCP73855T-I/MF saves 6 pins and 30% board area but removes thermal safety monitoring; versus BQ24075RGTR, it offers precise dual-voltage regulation and lower external component count at the cost of no integrated LDO.

Availability

MCP73855T-I/MF is available at Aetrix Electronics and suitable for USB chargers, portable medical sensors, digital cameras, and industrial handheld instruments requiring stable component supply, long-term lifecycle support, and guaranteed traceability.

Supply support for MCP73855T-I/MF 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 is a U.S.-based semiconductor manufacturer specializing in microcontrollers, analog, interface, and power management ICs for embedded control applications.

The MCP7385X family was designed specifically for space-limited, cost-sensitive USB-powered Li-ion/Li-polymer charging applications - prioritizing integration, thermal robustness, and USB compliance without host processor dependency.

FAQ

What is the function of the VSET pin on the MCP73855T-I/MF?

The VSET pin on the MCP73855T-I/MF selects the regulated battery voltage: tying it to VSS configures 4.1V output for coke-anode cells, while tying it to VDD selects 4.2V for graphite-anode cells. This ±0.5% accurate setting is implemented via an internal precision reference and amplifier, enabling chemistry-specific charging without external components. The MCP73855T-I/MF does not support intermediate voltages - only these two factory-trimmed options.

How is charge current programmed on the MCP73855T-I/MF?

Charge current on the MCP73855T-I/MF is set by connecting a resistor between the PROG pin and VSS. A floating PROG pin yields 85 mA typical fast charge current; grounding it yields 400 mA typical. Precondition and termination currents scale proportionally at ~10% and ~7% of the fast charge value. The relationship follows R_PROG = (13.32 / I_REG) − 14.1 kΩ, where I_REG is in amps and R_PROG in kΩ - verified in DS21915C Section 5.1.2.

Does the MCP73855T-I/MF support temperature monitoring like the MCP73853?

No, the MCP73855T-I/MF does not support temperature monitoring. It lacks the THREF, THERM, and VBAT3 pins present on the MCP73853T-I/MF. Its pinout and functional description in DS21915C explicitly state that temperature monitoring is omitted - making it suitable only for applications where thermal qualification is handled externally or not required. For designs needing JEITA-compliant thermal windows, the MCP73853T-I/MF or alternate solutions must be used.

What safety timers are implemented in the MCP73855T-I/MF and how are they configured?

The MCP73855T-I/MF implements three independent safety timers: precondition (60 min), fast charge (1.5 hr), and elapsed time (3 hr). All are scaled by a single external capacitor (CTIMER) connected between the TIMER pin and VSS using the ratio CTIMER / 0.1 µF. For example, a 0.22 µF capacitor doubles all periods. These timers reset automatically during state transitions (e.g., fast charge timer resets upon entering constant-voltage mode), and slow down during thermal regulation to prevent premature timeout - as documented in DS21915C Sections 4.1–4.4 and 5.1.5.

What is the purpose of the exposed pad (EP) on the MCP73855T-I/MF DFN package?

The exposed pad (EP) on the MCP73855T-I/MF's 3 mm × 3 mm DFN package is electrically connected to VSS and serves as the primary thermal path to the PCB. It must be soldered to a large copper pour tied to the system ground plane to achieve the specified θ_JA of 51°C/W. Leaving EP unconnected or floating degrades thermal performance significantly - potentially triggering thermal regulation at lower currents and reducing maximum sustainable charge rate. Microchip's layout guidelines require minimum 4×4 mm thermal pad with 4–9 vias to inner ground layers.