EVB RT8555WSC-00 EN

RT8555WSC
Evaluation Board
your power partner.
RT8555WSC Evaluation Board
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.
Table of Contents
Purpose ................................................................................................................................................................. 1
Introduction............................................................................................................................................................ 2
Key Performance Summary Table .......................................................................................................................... 2
Bench Test Setup Conditions ................................................................................................................................. 2
Schematic, Bill of Materials & Board Layout ........................................................................................................... 4
More Information.................................................................................................................................................... 8
Important Notice for Richtek Evaluation Board ....................................................................................................... 8
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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
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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
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Bench Test Setup Conditions
Headers Description and Placement
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
[email protected]
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.
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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
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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
0805
TDK
CIN3
1
GRM31CR71H475KA12L
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
R2, R3, R4, R5, R6,
R7, R8, R9, R11,
R12
COUT1, CIN1,
CIN2, COUT5,
C2, C3, C4, C5, C6,
L2, R14, R15
J1
1
10Ω/±1%, Resistor
0603
10
0Ω, Resistor
0603
0
Not Installed
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
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1µF/50V/X7R
Ceramic Capacitor
4.7µF/50V/X7R
Ceramic Capacitor
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EVB Layout
Top View (1st layer)
PCB Layout—Inner Side (2nd Layer)
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PCB Layout—Inner Side (3rd Layer)
Bottom View (4th Layer)
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More Information
For more information, please find the related datasheet or application notes from Richtek website
http://www.richtek.com.
Important Notice for Richtek Evaluation Board
THIS DOCUMENT IS FOR REFERENCE ONLY, NOTHING CONTAINED IN THIS DOCUMENT SHALL BE CONSTRUED AS RICHTEK’S WARRANTY, EXPRESS
OR IMPLIED, UNDER CONTRACT, TORT OR STATUTORY, WITH RESPECT TO THE PRESENTATION HEREIN. IN NO EVENT SHALL RICHTEK BE LIABLE T O
BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL
DAMAGES.
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