SN6505BEVM

EVAL BOARD FOR SN6505B DRIVER

Thisdocument describes theSN6505AandSN6505Bevaluationmodule(EVM). It allowsdesigners to analyzeandevaluatetheSN6505AandSN6505Boscillator/powerdriverfromTI.

Inaddition to theSN6505AandSN6505B, theEVMcontainsasmall form-factor transformer, simple rectifier circuit, and voltage regulator. This combination simulates a complete isolated power supply systemsuitableformanydifferentapplications.

1 Introduction

1.1 Overview

This SN6505A and SN6505B evaluation module allows the user to evaluate the performance and features of the SN6505A and SN6505B in an actual isolated power application. This includes the transformer, rectifier, and low-dropout (LDO) voltage regulator shown in Figure 1.

The complementary output signals (D1 and D2) from the SN6505x are ground-referenced, N-channel, power switches that drive the primary side of the center-tapped transformer. The secondary of the transformer has its center-tap referenced to an isolated ground, and the complementary outputs are rectified through a simple two-diode bridge. The make-before-break feature of the two driver outputs from the SN6505x ensures that only one side of the transformer is driven at a time. After being rectified, the dc voltage is smoothed and routed to the TPS76701QD voltage regulator. The regulator outputs a stable, regulated +5-Vdc output that is used to drive downstream circuitry.

The EVM is the SN6505x EVM which is configured for +5-Vdc/ input and +5-Vdc output.

1.2 SN6505xEVM Kit Contents

• SN6505xEVM Printed-Circuit Board

• SN6505xEVM Evaluation Module User’s Guide

• SN6505x data sheet

2 Printed-Circuit Board

The SN6505xEVM printed-circuit board (PCB) contains an SN6505x, transformer, and voltage regulator. The board has separate and isolated grounds across the isolation transformer allowing evaluation of the isolated power supply system contained on the EVM. Although the transformer secondary can be wound to provide any isolated voltage, the EVM uses a transformer with a 1:1.1 turns ratio, ideal for generating the rectified voltage required by the TPS76701QD regulator.

Refer to the SN6505xEVM schematic and bill of materials (BOM) to become familiar with the PCB components and layout. The PCB files (Gerber/ODB) are available from TI on request.

2.1 SN6505xEVM Operation

2.1.1 Left-Side Operation: SN6505x and Transformer Primary

DC Power– The SN6505x (installed on the left-side of the isolation transformer) is operated using either a single +5-V (±10%), or single +5-V (±10%) dc power supply. On this EVM, the turns-ratio of the transformer is 1:1.1, providing a slight step-up voltage function. This allows evaluation of the system performance using a supply voltage anywhere within the range of +5-Vdc to 5.5-Vdc. The small amount of dc current required also allows operation of the EVM from a battery. The input dc power supply must be connected to the J1 terminal block on the left side of the EVM. No other controls are required to operate the EVM. The SN6505X oscillates and drives the transformer when dc voltage is applied.

2.1.2 Right-Side Operation

DC Output Power– The right side of the isolation transformer contains a two-diode rectifier, filter capacitors, and a voltage regulator. Because the purpose of the EVM is to generate isolated power across the transformer, a separate power supply on the right side of the EVM is unnecessary. The rectified, unregulated output voltage is observed at TP5. Monitor the output from the transformer while varying the input voltage to the SN6505X. The regulated output is available at TP7. Connect external circuitry and/or loading to evaluate the operating range, line regulation, load regulation, and efficiency of the EVM. Note that the ground reference on the right side of the transformer (GND2) is not connected to the ground of the SN6505X (GND1). This demonstrates the isolation feature of the EVM.

2.1.3 Functional Test Procedure

Please find the functional test procedure for the SN6505x EVM board.

1. Insert Shunt J5.

2. Connect 5-V , 200 mA Voltage source between TP1 (VIN) and TP2 (GND1)

3. Measure voltage with a DMM at TP5 (VOUT) w.r.t TP8 (GND2) should be greater than 5.5-V

4. Measure voltage with DMM at TP7 (VLDO) w.r.t. TP6 (GND2) should be between 4.9-V and 5.1-V.

2.2 Bill of Materials and Schematic

2.2.1 Bill of Materials

The bill of materials for the SN6505xEVM is shown in Table 1.

2.2.2 Schematic

Figure 2 shows the electrical schematic for the SN6505xEVM.

3 SN6505xEVM Printed Circuit Board

Figure 3 through Figure 6 contain the PCB layout views.