Precision Adjustable Current-Limited Switch Evaluation Board

General Description

The RTQ9728W is a precision adjustable current-limited power-distrilbution switches. Its input voltage range is from 2.5V to 6V and provides an adjustable current limited from 0.1A to 2.5A. This document explains the function and use of the RTQ9728W evaluation board (EVB), and provides information to enable operation, modification of the evaluation board and circuit to suit individual requirements.

Performance Specification Summary

Summary of the RTQ9728WGQW(2) Evaluation Board performance specificiaiton is provided in Table 1. The ambient temperature is 25°C.

Table 1. RTQ9728WGQW(2) Evaluation Board Performance Specification Summary

Power-up Procedure

Suggestion Required Equipments

• RTQ9728WGQW Evaluation Board
• DC power supply capable of at least 6V and 3A
• Electronic load capable of 6A
• Function Generator
• Oscilloscope

Quick Start Procedures

The Evaluation Board is fully assembled and tested. Follow the steps below to verify board operation. Do not turn on supplies until all connections are made. When measuring the output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the output voltage ripple by touching the probe tip and ground ring directly across the last output capacitor.

Proper measurement equipment setup and follow the procedure below.

1) With power off, connect the input power supply to VIN and GND pins.

2) With power off, connect the electronic load between the VOUT and nearest GND pins.

3) Turn on the power supply at the input. Make sure that the input voltage does not exceeds 5.5V on the Evaluation Board.

4) Check for the proper output voltage using a voltmeter.

5) Once the proper output voltage is established, adjust the load within the operating ranges and observe the output voltage regulation, ripple voltage, efficiency and other performance.

Detailed Description of Hardware

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. Apply a 5V nominal input power supply (2.5V < V_IN < 6V) to the VIN and GND terminals.

2. Set the jumper at JP1 to connect terminals 1 and 2, connecting EN to VIN. The Enable pin can connected to VIN directly as well to enable operation.

3. Verify the output voltage (approximately 5V) between VOUT and GND.

4. Connect an external load up to 1.9A to the VOUT and GND terminals and verify the output voltage and current.

Current Limit Setting

Set the current limit with the resistive divider (R2) between ILIM and GND. The current limit is set by the following below data:

The placement of the resistive divider should be within 5mm of the ILIM pin. For better output current limit accuracy, divider resistors (R2) should have tolerance of ±1% tolerance.

Bill of Materials

Typical Applications

EVB Schematic Diagram

V_IN 5V, V_OUT 5V/1.9A

Note:

1. Do not hot-plug a live 5V supply to the board; if hot-plugging is required, add ~100µF electrolytic capacitor at the input.

2. All the stated input and output capacitor values are the effective capacitances, including any de-rating effect, like a DC Bias. The stability of the converter may be impacted when using small size MLCC output capacitors, which may have much lower capacitance at the application DC output voltage than the rated value.

Measurement Results

Evaluation Board Layout

Figure 1. Top View

Figure 2. Bottom View