General Description
The Evaluation Board demonstrates the RT8575GQW’s capability to be designed for a wide input range from a 12V to 24V and provide 120mA LED current at 280kHz switching frequency. The dimming range makes it suitable from 120Hz to 1kHz of intput PWM signal for LED systems. The RT8575GQW provides complete protection functions such as input undervoltage lockout, Boost output overvoltage protection, Boost overcurrent protection, opened LED protection, shorted LED protection and thermal shutdown. Cycle-by-cycle current limit provides protection against shorted outputs, and soft-start eliminates input current surge during start-up.
Performance Specification Summary
Table 1 shows the summary of the RT8575GQW Evaluation Board performance specificiaiton. The ambient temperature is 25°C.
Table 1. RT8575GQW Evaluation Board Performance Specification Summary
|
Specification
|
Test Conditions
|
Min
|
Typ
|
Max
|
Unit
|
|
Input Voltage Range
|
|
12
|
--
|
24
|
V
|
|
Maximum ILED Current
|
RISET = 7.5kΩ
|
--
|
120
|
--
|
mA
|
|
Boost Output Overvoltage
|
|
--
|
51
|
--
|
V
|
|
Boost Operation Frequency
|
|
--
|
280
|
--
|
kHz
|
|
LED Current Accuracy
|
ILED = 120mA, VIN = 12V to 24V
|
--
|
±3
|
--
|
%
|
|
LED Current Matching
|
ILED = 120mA, VIN = 12V to 24V
|
--
|
±1
|
±3
|
%
|
Power-up Procedure
Suggestion Required Equipments
- RT8575GQW Evaluation Board
- DC power supply capable of at least 30V and 5A
- LED Load Board
- 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, use jumper to pull high EN pin of J1.
3) With power off, connect the Function Generator to PWM pin, set up frequency range from 120Hz to 1kHz, 100% duty and amplitude does not exceed 5V
4) With power off, connect the LED Load Board to VOUT and LEDx pins.
5) Turn on the power supply at the input. Make sure that the input voltage does not exceeds 24V on the Evaluation Board.
6) Turn on the Function Genetator at the PWM pin.
7) Check LED Load Board brightness.
8) Once the proper output voltage is established, adjust the PWM duty within the operating ranges and observe the output LED brightness, ICHx, 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.
|
Test Point/
Pin Name
|
Function
|
|
VIN
|
Input voltage.
|
|
VOUT
|
Output voltage.
|
|
GND
|
Ground.
|
|
EN
|
Enable test point.
|
|
J1
|
EN jumper. Connect EN to L to disable and H to enable.
|
|
LX
|
Switch node test point.
|
|
PWM
|
Dimming control input.
|
|
COMP
|
Compensation pin for error amplifer.
|
|
ISET
|
LED current is set by the value of the resistor RISET connected from the ISET pin to ground. Do not short the ISET pin. VISET is typically 1V.
|
|
OVP
|
Overvoltage protection for boost converter. The detecting threshold is 1.2V.
|
|
LEDx
|
Current Sink for LED. (Connect to GND, if not used.)
|
Bill of Materials
|
VIN = 12V, ILED = 120mA, fSW = 280kHz
|
|
Reference
|
Count
|
Part Number
|
Value
|
Description
|
Package
|
Manufacturer
|
|
U2
|
1
|
RT8575GQW
|
RT8575GQW
|
LED Drver
|
WDFN-16L 5x5
|
RICHTEK
|
|
C1
|
1
|
0603B104K500CT
|
100nF
|
Capacitor, Ceramic
50V/X7R
|
0603
|
WALSIN
|
|
C16
|
1
|
0603N101J500CT
|
100pF
|
Capacitor, Ceramic
50V/X7R
|
0603
|
WALSIN
|
|
CIN1
|
1
|
0603X105K250CT
|
1µF
|
Capacitor, Ceramic
25V/X5R
|
0603
|
WALSIN
|
|
C25, C35, COUT1, COUT2, COUT3, COUT4, COUT5, COUT6,
|
8
|
GRM32ER71H106KA12L
|
10µF
|
Capacitor, Ceramic
50V/X7R
|
1210
|
MURATA
|
|
D1
|
1
|
SR26
|
Schottky Diode 60V/2A
|
Schottky Diode 60V/2A
|
SMA/DO-214AC
|
PANJIT
|
|
L1
|
1
|
NRS8040T220MJGJ
|
22µH
|
Inductor, Isat = 2.4A, 66mΩ
|
8x8
|
TAIYO YUDEN
|
|
R1, R9
|
2
|
WR06X000 PTL
|
0
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R2
|
1
|
WR06X7501FTL
|
7.5k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R4
|
1
|
RTT032263FTP
|
226k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
RALEC
|
|
R5
|
1
|
WR06X5601FTL
|
5.6k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R6
|
1
|
WR06X5102FTL
|
51k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R7
|
1
|
WR06X10R0FTL
|
10
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R8, R10
|
2
|
WR06X1001FTL
|
1k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
Typical Applications
EVB Schematic Diagram
1. The capacitance values of the input and output capacitors will influence the input and output voltage ripple.
2. MLCC capacitors have degrading capacitance at DC bias voltage, and especially smaller size MLCC capacitors will have much lower capacitance.
Measurement Result
|
Efficiency vs. Input Voltage
|
LED Current vs. Input Voltage
|
|
|
|
|
LED Current vs. Temperature
|
LED Current vs. Dimming Duty
|
|
|
|
|
Power On from PWM
|
Power Off from PWM
|
|
|
|
|
Power On from EN
|
Power Off from EN
|
|
|
|
|
Power On from VIN
|
Power Off from EN
|
|
|
|
Evaluation Board Layout
Figure 1 and Figure 2 are RT8575GQW Evaluation Board layout. This board size is 100mm x 72mm and is constructed on two-layer PCB, top and bottom layers with 1 oz.
Figure 1. Top View (1st layer)
Figure 2. Bottom View (2th Layer)