Analog Devices Inc./Maxim Integrated MAX870EUK+T

Overview

The MAX870EUK+T from Maxim Integrated is a monolithic CMOS switched-capacitor voltage inverter that converts +1.4V to +5.5V input to a regulated negative output, operates at 125kHz, delivers 25mA with 500mV dropout, and achieves 90% power efficiency at +25°C - ideal for generating local -5V supplies from 5V logic rails in space-constrained portable systems.

For engineers reviewing the MAX870EUK+T datasheet, MAX870EUK+T pinout, MAX870EUK+T application, or MAX870EUK+T equivalent, this page provides verified technical context, confirmed pin functions, real-world load behavior (e.g., VOUT = -(VIN – IOUT × RS–)), capacitor selection guidance per oscillator frequency, and validated alternative options for inverted supply generation.

Technical Context

The MAX870EUK+T implements a two-phase charge-pump topology using four on-chip MOSFET switches to invert input voltage without inductors. Its fixed 125kHz oscillator drives C1 (flying capacitor) and C2 (reservoir capacitor) in alternating half-cycles to generate negative output.

It is not a regulated device: output voltage droop follows VOUT = –(VIN – IOUT × RS–), where RS– ≈ 20Ω at +25°C and VIN = +5V. Efficiency drops from 99% at no load to 90% at 25mA due to quiescent current (0.7mA) and switch resistance dominance.

Key Specifications

Pinout & Package

MAX870EUK+T is housed in a 5-pin SOT23-5 package (JEDEC MO-178AA), with exposed pad not electrically connected. Pin 1 is OUT (inverting charge-pump output), Pin 2 is IN (positive power-supply input), Pin 3 is C1– (flying capacitor's negative terminal), Pin 4 is GND (ground), and Pin 5 is C1+ (flying capacitor's positive terminal).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX870EUK+T, MAX871EUK+T trades lower quiescent current and relaxed capacitor sizing for higher EMI and reduced efficiency at light loads, while MAX860ESA+ offers double the output current in a larger package - making MAX870EUK+T optimal for space-constrained 25mA applications requiring lowest standby power.

Availability

MAX870EUK+T is available at Aetrix Electronics and suitable for battery-operated equipment, medical handheld instruments, and small LCD panel power supplies requiring stable component supply, long-lifecycle support, and guaranteed -40°C to +85°C operation.

Supply support for MAX870EUK+T 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

Maxim Integrated (now part of Analog Devices) is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for industrial, automotive, and communications markets.

The MAX870EUK+T belongs to Maxim's switched-capacitor voltage inverter product line, designed specifically for compact, inductorless negative rail generation in portable and space-constrained electronic systems.

FAQ

What is the maximum output current specification for the MAX870EUK+T?

The MAX870EUK+T delivers up to 25mA output current with a 500mV voltage drop at VIN = +5V and TA = +25°C. This value is confirmed in the Electrical Characteristics table under "OUT Output Current" and validated across the full -40°C to +85°C operating range. Exceeding 25mA causes excessive droop and efficiency loss, and the absolute maximum rating for continuous output current is 50mA - but sustained operation above 25mA is not recommended without thermal evaluation. The MAX870EUK+T data sheet specifies 25mA as the rated output capability.

Does the MAX870EUK+T include built-in shutdown control?

No, the MAX870EUK+T does not integrate logic-controlled shutdown. Unlike the MAX1720/MAX1721, it lacks an enable pin. However, external shutdown can be implemented using the circuit in Figure 8 of the datasheet: a logic buffer drives the IN pin, and a 0.1µF capacitor filters transients. This method adds ~20Ω output resistance per buffer stage but preserves the core functionality of the MAX870EUK+T without modifying its internal architecture.

What capacitor values are required for stable operation of the MAX870EUK+T?

The MAX870EUK+T requires two external ceramic capacitors: C1 (flying capacitor) and C2 (reservoir capacitor), both nominally 1µF per the Typical Operating Circuit and Table 2. Low-ESR X7R or NP0 ceramics are mandatory - tantalum or electrolytic types increase output resistance and ripple. A 0.1µF input bypass capacitor is also recommended when loading from IN-to-OUT. These values ensure 20Ω output resistance and <500mV droop at 25mA, as specified for the MAX870EUK+T.

How does temperature affect the performance of the MAX870EUK+T?

Over the -40°C to +85°C range, the MAX870EUK+T maintains guaranteed specifications including 25mA output, 125kHz oscillator frequency, and 500mV dropout. Output resistance rises from ~20Ω at +25°C to ~75Ω at -40°C (per Figure ROC3), increasing voltage droop under load. Efficiency remains ≥90% across temperature, and all -40°C to +85°C specs are production-tested - confirming consistent MAX870EUK+T behavior in industrial and automotive environments.

Can multiple MAX870EUK+T devices be paralleled to increase output current?

Yes, multiple MAX870EUK+T units can be paralleled to reduce effective output resistance and increase total current capacity. Each device requires its own C1 flying capacitor, but a single shared C2 reservoir capacitor suffices - sized at n×1µF for n devices (per Figure 5). The combined output resistance becomes ROUT_SINGLE / n. This configuration is documented in the Applications Information section and validated for up to four parallel MAX870EUK+T units in production designs.