General Description
The Evaluation Board demonstrates the RT8525DGQW’s capability to be designed for a 19V/1A output from a 5V input at 200kHz switching frequency. The RT8525DGQW provides complete protection functions such as input undervoltage lockout, output undervoltage protection, output overvoltage protection, overcurrent 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 RT8525DGQW Evaluation Board performance specificiaiton. The ambient temperature is 25°C.
Table 1. RT8525DGQW Evaluation Board Performance Specification Summary
|
Specification
|
Test Conditions
|
Min
|
Typ
|
Max
|
Unit
|
|
Input Voltage Range
|
|
4.5
|
--
|
5
|
V
|
|
Output Current
|
|
0
|
--
|
1
|
A
|
|
Default Output Voltage
|
|
--
|
19
|
--
|
V
|
|
Operation Frequency
|
|
--
|
200
|
--
|
kHz
|
|
Maximum Efficiency
|
VIN = 5V, VOUT = 12V, IOUT = 0.5A
|
--
|
92
|
--
|
%
|
Power-up Procedure
Suggestion Required Equipments
- RT8525DGQW Evaluation Board
- DC power supply capable of at least 10V and 5A
- Electronic load capable of 2A
- 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 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.
|
Test Point/
Pin Name
|
Function
|
|
VIN
|
Input voltage.
|
|
VOUT
|
Output voltage.
|
|
GND
|
Ground.
|
|
EN/J1
|
Enable test point and EN jumper. Connect EN to ground to disable or enable.
|
|
LX
|
Switch node test point.
|
|
COMP
|
Compensation pin for error amplifier.
|
|
FLT_B
|
Test point for pullup voltage of the Open-drain power-good indication output.
|
|
VDC
|
Test point for uutput of internal pre-regulator.
|
|
FB
|
Feedback test point.
|
|
OVP
|
Test point for overvoltage protection and undervoltage protection.
|
|
ISW
|
Test point for external MOSFET switch current sens.
|
|
DRV
|
Drive output for the N-MOSFET.
|
Bill of Materials
|
VIN = 12V, VOUT = 5V, IOUT = 0.5A, fSW = 500kHz
|
|
Reference
|
Count
|
Part Number
|
Value
|
Description
|
Package
|
Manufacturer
|
|
U1
|
1
|
RT8525DGQW
|
RT8525DGQW
|
Step-Up Controller
|
WDFN-12L 3x3
|
RICHTEK
|
|
C1
|
1
|
GJ821BR71H105KA12
|
1µF
|
Capacitor, Ceramic, 50V, X7R
|
0805
|
MURATA
|
|
C2
|
1
|
GRM188R61H105KAALD
|
1µF
|
Capacitor, Ceramic, 50V, X7R
|
0603
|
MURATA
|
|
C3
|
1
|
0603B273K500CT
|
27nF
|
Capacitor, Ceramic, 50V, X7R
|
0603
|
WALSIN
|
|
C5
|
1
|
C1608X7R1C334K080AC
|
0.33µF
|
Capacitor, Ceramic, 16V, X7R
|
0603
|
TDK
|
|
C7, C8, C10, C11, C12
|
5
|
TMK325B7226KM-TR
|
22µF
|
Capacitor, Ceramic, 25V, X5R
|
1210
|
TAIYO YUDEN
|
|
D1
|
1
|
SK34
|
Schottky Diode, 40V/3A
|
Schottky Diode, 40V/3A
|
SMC
|
PANJIT
|
|
L1
|
1
|
NRS8040T100MJGJ
|
10µH
|
Inductor, Isat = 3.4A, 34mΩ
|
8x8
|
TAIYO YUDEN
|
|
Q1
|
1
|
IPD20N03L
|
AOD2810
|
AOD2810
|
TO-252-3
|
AOS
|
|
R1, R10, R13
|
3
|
WR06X000 PTL
|
0
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R2
|
1
|
WR06X5601FTL
|
5.6k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R3
|
1
|
WR06X5602FTL
|
56k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R4
|
1
|
WR06X1003FTL
|
100k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R5
|
1
|
RTT033001FTP
|
3k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
RALEC
|
|
R6
|
1
|
CR0603F6K04P05
|
6.04k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
EVER OHMS
|
|
R7
|
1
|
WR06X6202FTL
|
62k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R8
|
1
|
WR06X4302FTL
|
43k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R12
|
1
|
WR06X2401FTL
|
2.4k
|
Resistor, Chip, 1/10W, 1%
|
0603
|
WALSIN
|
|
R14
|
1
|
CR2512FR050E04Z
|
0.05
|
Resistor, Chip,
3W, 1%
|
2512
|
EVER OHMS
|
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
|
Boost Efficiency vs. Load Current
|
Switching Frequency vs. Temperature
|
|
|
|
Note: When measuring the input or 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 directly across the output capacitor.
Evaluation Board Layout
Figure 1 and Figure 2 are RT8525DGQW Evaluation Board layout. This board size is 100mm x 72mm and is constructed on two-layer PCB, top layers and bottom layers with 1 oz.
Figure 1. Top View (1st layer)
Figure 2. Bottom View (2nd Layer)