Analog Devices Inc./Maxim Integrated MAX8504ETC

Overview

The MAX8504ETC from Maxim Integrated is a fixed-output PWM buck converter with integrated high-power bypass PFET, designed specifically for power amplifier (PA) supply in W-CDMA/N-CDMA handsets. It delivers 600mA guaranteed output current, operates from 2.6V to 5.5V input, provides externally set 1.25V–2.5V output via FB pin, and achieves 150mV dropout at 600mA load using its 0.25Ωtyp bypass FET.

For engineers reviewing the MAX8504ETC datasheet, MAX8504ETC pinout, MAX8504ETC application, or MAX8504ETC equivalent, this device is selected for fast-settling, low-noise, high-efficiency PA biasing where digitally controlled high-power bypass mode and 1MHz fixed-frequency PWM operation are required in space-constrained mobile RF power stages.

Technical Context

The MAX8504ETC implements a current-mode PWM controller with 100% duty-cycle capability and integrated synchronous rectification, enabling seamless transition into dropout and stable regulation under dynamic PA load transients. Its feedback loop uses an external resistive divider on FB (regulated to 1.25V), while HP pin enables direct battery-to-output connection via internal PFET for peak-power transmission bursts.

Unlike the MAX8500–MAX8503 variants, the MAX8504ETC lacks REFIN and instead relies on FB-based voltage setting and HP-controlled bypass activation. It features dedicated overcurrent protection comparators for both PWM and bypass paths, and supports forced-PWM (SKIP = BATT) or pulse-skipping (SKIP = GND) modes to optimize efficiency across load ranges.

Key Specifications

Pinout & Package

MAX8504ETC is housed in a 12-pin thin QFN package (4mm × 4mm, 0.8mm max height) with exposed thermal paddle (PGND-connected). Pin 1 is located at the bottom-left corner adjacent to the marking notch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck converter with bypass FET applications.

Compared with MAX8503ETC and TPS62361BDSKR, the MAX8504ETC uniquely combines fixed 1.25V–2.5V programmability, integrated 0.25Ω bypass FET, and 150mV dropout at 600mA - making it the only option optimized for W-CDMA PA VCC with burst-mode battery-direct capability.

Availability

MAX8504ETC is available at Aetrix Electronics and suitable for W-CDMA handset design, wireless modem development, and portable RF front-end power management requiring stable component supply and long-term production continuity.

Supply support for MAX8504ETC 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 semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for communications, computing, and consumer applications.

The MAX8500–MAX8504 family was engineered specifically for battery-powered CDMA/W-CDMA handset PA power stages, emphasizing ultra-low dropout, fast transient response, and integrated bypass capability to maximize RF efficiency and battery life.

FAQ

What is the primary function of the HP pin on the MAX8504ETC?

The HP (High-Power) pin on the MAX8504ETC controls activation of the internal bypass PFET. When driven logic-high, it connects the OUT pin directly to the BATT rail through a 0.25Ωtyp PFET, bypassing the buck converter entirely. This mode is used during PA peak-power transmission to eliminate conversion losses and ensure maximum efficiency. The MAX8504ETC remains fully functional in this state, with the PWM stage forced to 100% duty cycle.

How is the output voltage set on the MAX8504ETC?

The MAX8504ETC uses the FB (feedback) pin to set output voltage via an external resistive divider between OUT and GND. The internal reference regulates the FB node to 1.25V, so VOUT = 1.25V × (1 + R1/R2). Resistor R2 should be selected between 5kΩ and 50kΩ for optimal noise immunity and bias current balance. Unlike MAX8500–MAX8503, the MAX8504ETC does not support dynamic REFIN-based voltage adjustment.

What is the guaranteed output current rating for the MAX8504ETC?

The MAX8504ETC guarantees 600mA of continuous output current across the full operating temperature range (–40°C to +85°C) and input voltage range (2.6V to 5.5V). This rating applies in both PWM and bypass modes, with thermal derating applied above +70°C ambient per the 1349mW power dissipation limit in the 12-pin thin QFN package.

Does the MAX8504ETC support forced-PWM operation, and how is it enabled?

Yes, the MAX8504ETC supports forced-PWM operation to maintain constant 1MHz switching regardless of load. This mode is enabled by connecting the SKIP pin to BATT (logic-high), which disables pulse-skipping and ensures predictable EMI spectrum - essential for RF-sensitive applications like W-CDMA transceivers. In forced-PWM mode, quiescent current rises to 3.3mA typical, versus 280µA in skip mode.

What package type and dimensions does the MAX8504ETC use?

The MAX8504ETC is packaged in a 12-pin thin QFN (Quad Flat No-lead) measuring 4mm × 4mm with a maximum height of 0.8mm. It features an exposed thermal paddle on the underside, electrically connected to PGND, which must be soldered to a large PCB copper pour for thermal and electrical performance. The top marking is "AABS", and pin 1 is identified by a dot or notch near the bottom-left corner.