RT4805A 2.5MHz, Synchronous Boost Regulator with Bypass Mode

Purpose

The RT4805A is a Boost converter with the input voltage range from 1.8V to 5V and provides 2A output current. This document explains the function and use of the RT4805A evaluation board (EVB), and provides information to enable operation, output voltage setting of the evaluation board.

Introduction

General Product Information

The RT4805A allows systems to take advantage of new battery chemistries that can supply significant energy when the battery voltage is lower than the required voltage for system power ICs. By combining built-in power transistors, synchronous rectification, and low supply current; this IC provides a compact solution for systems using advanced Li-Ion battery chemistries.

The RT4805A is a boost regulator designed to provide a minimum output voltage from a single-cell Li-Ion battery, even when the battery voltage is below system minimum. In boost mode, output voltage regulation is guaranteed to a maximum load current of 2A. Quiescent current in Shutdown Mode is less than 1µA, which maximizes battery life. The regulator transitions smoothly between Bypass and normal Boost Mode. The device can be forced into Bypass Mode to reduce quiescent current. The RT4805A is available in the WL-CSP-16B 1.67x1.67 (BSC) package.

Product Feature

• 4 Few External Components : 0.47μH Inductor and 0603 Case Size Input and Output Capacitors
• Input Voltage Range : 1.8V to 5V
• Output Range from 2.85V to 4.4V
• VSEL = L 3.6V
• VSEL = H 3.7V
• Maximum Continuous Load Current : 2A at V_IN > 2.65V Boosting V_OUT to 3.35V
• Up to 96% Efficient
• True Bypass Operation when V_IN > Target V_OUT
• Internal Synchronous Rectifier
• True Load Disconnectwhen Shut Down
• Forced Bypass Mode
• V_SEL Control to Optimize Target V_OUT
• Short-Circuit Protection
• I²C Controlled Interface
• Ultra low Operating Quiescent Current
• Small WL-CSP 16B Package

Key Performance Summary Table

Bench Test Setup Conditions

Headers Description and Placement

Carefully inspect all the components used in the EVB according to the following Bill of Materials table, and then make sure all the components are undamaged and correctly installed. If there is any missing or damaged component, which may occur during transportation, please contact our distributors or e-mail us at evb_service@richtek.com.

Test Points

The EVB is provided with the test points and pin names listed in the table below.

Power-up & Measurement Procedure

1. Connect input voltage (1.8V < V_IN < 5.0V).

2. To use a switch at “H” option to tie EN pin to input voltage VIN via SW1 or external voltage for enabling the device. Inversely, to use a jumper at “L” option to tie EN pin to ground GND for disabling the device.

3. To verify the output voltage V_OUT via the I2C interface.

4. To connect an external load up to 1A and verify the output voltage and current.

I2C Register Setting

The register as the table shown can be programmed by a MCU through the dedicated I2C interface. The device slave address is 0x39.

Schematic, Bill of Materials & Board Layout

EVB Schematic Diagram

Bill of Materials

PCB Layout

Top View (1^st layer)

PCB Layout—Inner Side (2^nd Layer)

PCB Layout—Inner Side (3^rd Layer)

Bottom View (4^th Layer)