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RT8555WSC Evaluation Board

EVB_RT8555WSC

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The RT8555 is a high efficiency driver for white LEDs. It is suitable for single/two cell battery input to drive LED light bars which contains six strings in parallel and up to 10 WLEDs per string. The internal current sinks support a maximum of ±2% current mismatching for excellent brightness uniformity in each string of LEDs. To provide enough headroom for current sink operation, the Boost controller monitors the minimum voltage of the feedback pins and regulates an optimized output voltage for power efficiency.

Purpose

The RT8555 is a 36V High Efficiency Boost Converter with I2C Controlled 6-CH LED Driver. This document explains the function and use of the RT8555 evaluation board (EVB) and provides information to enable operation and modification of the evaluation board and circuit to suit individual requirements.


Introduction

General Product Information

The RT8555 is a high efficiency driver for white LEDs. It is suitable for single/two cell battery input to drive LED light bars which contains six strings in parallel and up to 10 WLEDs per string. The internal current sinks support a maximum of ±2% current mismatching for excellent brightness uniformity in each string of LEDs. To provide enough headroom for current sink operation, the Boost controller monitors the minimum voltage of the feedback pins and regulates an optimized output voltage for power efficiency.

The RT8555 has a wide input voltage operating range from 2.7V to 24V and contains I2C interface for controlling the dimming mode, operating frequency and the LED current. The internal 100mΩ, 36V power switch with current-mode control provides over-current protection. The switching frequency of the RT8555 is adjustable from 300kHz to 2MHz, which allows flexibility between efficiency and component size.

The RT8555 is available in the WL-CSP-20B 1.65 x 2.05 (BSC), with pitch 0.4mm package.


Product Feature

  • Wide Operating Input Voltage : 2.7V to 24V
  • High Output Voltage : Up to 36V
  • Programmable Channel Current : 10mA to 35mA
  • Channel Current Regulation with Accuracy ±3% and Matching ±2%
  • Dimming Controls
  • ► Direct PWM Dimming up to 20kHz and Minimum On-Time to 400ns
    ► PWM to Analog Dimming up to 20kHz with 8-bit
  • I2C Programs LED Current, Switching Frequency, Dimming Mode
  • Switching Frequency : 300kHz to 2MHz
  • Current Limit, Over-Temperature Protection and Over-Voltage Protection
  • Input Under-Voltage Lockout
  • RoHS Compliant and Halogen Free

 

Key Performance Summary Table

Key Features

Evaluation Board Number : PCB025_V1

Default Input Voltage

3.8V

Default OVP

36V

Default Per Channel Output Current

20mA

Default Marking & Package Type

RT8555WSC, WL-CSP-20B 1.65 x 2.05 (BSC)

Operation Frequency

900kHz

Other Key Features

2.7V to 24V Input Voltage Range

Programmable LED Current, Switching Frequency, Dimming Mode

Output Over-Voltage Protection, Current Limit, Thermal Shutdown

20-Ball WL-CSP, with pitch 0.4mm Package


Bench Test Setup Conditions

Headers Description and Placement

Technical Document Image Preview

Please carefully inspect the EVB IC and external components, comparing them to the following Bill of Materials, to ensure that all components are installed and undamaged. If any components are missing or damaged during transportation, please contact the distributor or send e-mail to evb_service@richtek.com


Test Points

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

Test point/

Pin name

Signal

Comment (expected waveforms or voltage levels on test points)

VIN

Input voltage

Boost conveter input voltage.

VIN_1

Input voltage

RT8555 VIN input voltage. Connected to VIN through R1.

VOUT

Output voltage

Output voltage up to 36V. Drive LED light bars by VOUT connect to FB1 ~ FB6.

LX

Switching node test point

LX waveform

EN

Enable input

Enable signal. Connecting this pin to pull high enable operation; floating this EN pin or connecting this pin to GND can disable the device.

PWM

PWM input

PWM Dimming Control Input.

FB1 ~ FB6

FB pin

Current Sink for LED1 ~ LED6. Drive LED light bars by VOUT connect to FB1 ~ FB6.

VCP

Internal regulator

LDO Output of Internal Regulator.

GND

Ground

Ground.

SDA

Data signal

Data Signal Input of I2C Interface.

SCL

Clock signal

Clock Signal Input of I2C Interface.

JP2

Chip enable control

Install jumper or drive EN directly to enable or disable operation.

JP5

PWM control

Install jumper or drive PWM signal directly to operation.


Power-up & Measurement Procedure

1. Connect input power and input ground to VIN and GND test pins respectively.

2. Connect LED ligh bars to VOUT and FB1 ~ FB6 test pins respectively.

3. There is a 3- pin header “EN” for enable control. To use a jumper at “H” option to tie EN test pin to input power VIN for enabling the device. Inversely, to use a jumper at “L” option to tie EN test pin and ground GND for disabling the device.

4. There is a 3- pin header “PWM” for PWM dimming control. To use a jumper at “H” option to tie PWM test pin to input power VIN for PWM = 100% dimming the device. Inversely, to use a jumper at “L” option to tie PWM test pin and ground GND for PWM = 0% dimming the device.

5. Usually use Function Generator to produce PWM signal to PWM dimming RT8555 ILED current.

6. Input PWM frequency about 200Hz ~ 20kHz.

7. For detailed RT8555 function operation, please reference RT8555 datasheet.


Schematic, Bill of Materials & Board Layout

EVB Schematic Diagram

Technical Document Image Preview


Bill of Materials

Reference

Qty

Part number

Description

Package

Manufacture

U2

1

RT8555

LED Driver

WL-CSP-20B 1.65 x 2.05 (BSC)

RICHTEK

C1, CCP

1

C2012X7R1E105KT

1µF/50V/X7R

Ceramic Capacitor

0805

TDK

CIN3

1

GRM31CR71H475KA12L

4.7µF/50V/X7R

Ceramic Capacitor

1210

Murata

COUT2, COUT3, COUT4

3

UMK316BJ225KD-T

2.2µF/50V/X5R

Ceramic Capacitor

1206

TAIYO

D2

1

SR26

Schottky diodes

SMB/DO-214

PANJIT

L1

1

NR8040T6R8N

6.8μH/3.4A

DCR = 25mΩ, Inductor

L-NR8040

TAIYO

R1

1

10Ω/±1%, Resistor

0603

R2, R3, R4, R5, R6,

R7, R8, R9, R11, R12

10

0Ω, Resistor

0603

COUT1, CIN1,

CIN2, COUT5,

C2, C3, C4, C5, C6, L2, R14, R15

0

Not Installed

J1

1

4 x 2 Pin Header

J2, J5

2

3- Pin Header

TP1, TP2, TP3, Z3,

Z5, Z7, Z8

7

PWM, EN, LX, SDA,

SCL, VCP, VIN_1

Test Pin

GP1, GP2, GP3, GP4, GP5, GP6, GP7, GP8, GP9, GP10, GP11, GP12

12

VOUT, VIN, GND, LED1, LED2, LED3, LED4, LED5, LED6

Golden Pin


EVB Layout

Technical Document Image Preview

Top View (1st layer)

Technical Document Image Preview

PCB Layout—Inner Side (2nd Layer)

Technical Document Image Preview

PCB Layout—Inner Side (3rd Layer)

Technical Document Image Preview

Bottom View (4th Layer)

Title Last Update Share Download
Evaluation Board User Guide 2015/09/21
Bill of Materials 2015/09/21
Gerber File 2015/09/21
Schematic 2015/09/21
Part NumberFree SampleBuy From Authorized Distributor
EVB_RT8555WSC Not available Buy from Distributor
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