RT8258 RICHTEK [Richtek Technology Corporation], RT8258 Datasheet

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RT8258

Manufacturer Part Number
RT8258
Description
1.2A, 24V, 700kHz Step-Down Converter
Manufacturer
RICHTEK [Richtek Technology Corporation]
Datasheet

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1.2A, 24V, 700kHz Step-Down Converter
General Description
The RT8258 is a high voltage buck converter that can support
the input voltage range from 4.5V to 24V and the output
current can be up to 1.2A. Current Mode operation provides
fast transient response and eases loop stabilization.
The chip also provides protection functions such as cycle-
by-cycle current limiting and thermal shutdown protection.
The RT8258 is available in a SOT-23-6 and TSOT-23-6
packages.
Ordering Information
RT8258
Note :
Richtek products are :
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
Typical Application Circuit
DS8258-02 March 2011
RoHS compliant and compatible with the current require-
Suitable for use in SnPb or Pb-free soldering processes.
ments of IPC/JEDEC J-STD-020.
Package Type
E : SOT-23-6
J6 : TSOT-23-6
Lead Plating System
G : Green (Halogen Free and Pb Free)
4.5V to 24V
Chip Enable
V
IN
C
10µF
IN
5
4
VIN
EN
RT8258
GND
PHASE
2
BOOT
FB
1
6
3
Features
Applications
Pin Configurations
Wide Operating Input Voltage Range : 4.5V to 24V
Adjustable Output Voltage Range : 0.8V to 15V
1.2A Output Current
0.3Ω Ω Ω Ω Ω Internal Power MOSFET Switch
High Efficiency up to 92%
700kHz Fixed Switching Frequency
Stable with Low ESR Output Ceramic Capacitors
Thermal Shutdown
Cycle-By-Cycle Over Current Protection
RoHS Compliant and Halogen Free
Distributed Power Systems
Battery Charger
Pre-Regulator for Linear Regulators
WLED Drivers
C
10nF
D1
B230A
BOOT
10µH
L
100k
R2
32.4k
R1
SOT-23-6/TSOT-23-6
PHASE VIN EN
V
3.3V
BOOT GND FB
OUT
(TOP VIEW)
6
22µF
C
OUT
5
2
4
3
RT8258
www.richtek.com
1

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RT8258 Summary of contents

Page 1

... Step-Down Converter General Description The RT8258 is a high voltage buck converter that can support the input voltage range from 4.5V to 24V and the output current can 1.2A. Current Mode operation provides fast transient response and eases loop stabilization. The chip also provides protection functions such as cycle- by-cycle current limiting and thermal shutdown protection ...

Page 2

... R1 (kΩ) 200 100 R2 (kΩ) 3.6 3.6 L (μ (μF) OUT Note : The value related to the loop bandwidth of the RT8258 strongly recommended to follow the parameters in above table for the specific output voltage. Function Block Diagram VIN 1µA 1.1V 10k + EN Shutdown 3V Comparator ...

Page 3

... PHASE − 4.8V LIM BOOT PHASE Rising SHDN 2V (No Switching RT8258 + 0.3V PHASE − 40°C to 125°C − 40°C to 85°C Min Typ Max Unit 0.784 0.8 0.816 V μA -- 0.1 0.3 Ω -- 0.3 -- μ 1.6 2 ...

Page 4

... RT8258 Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2. θ ...

Page 5

... IN 3.300 3.278 3.256 3.234 -50 - Temperature (°C) Quiescent Current vs. Temperature 600 575 550 525 500 475 450 425 400 -50 - Temperature (°C) RT8258 V = 12V 24V 3.3V OUT 0 OUT 75 100 125 V = 24V 12V 2V ...

Page 6

... RT8258 Power On from (2V/Div) V OUT (1V/Div 12V Time (100μs/Div) Output Ripple Voltage V OUT (10mV/Div) V PHASE (10V/Div (1A/Div 12V Time (500ns/Div) Load Transient Response V OUT (0.1V/Div) I OUT (0.5A/Div 12V OUT Time (50μs/Div) www.richtek.com 6 = 3.3V 1.2A ...

Page 7

... Application Information The RT8258 is an asynchronous high voltage buck converter that can support the input voltage range from 4.5V to 24V and the output current can 1.2A. Output Voltage Setting The resistive voltage divider allows the FB pin to sense a fraction of the output voltage as shown in Figure 1. ...

Page 8

... RT8258 Do not allow the core to saturate! Different core materials and shapes will change the size/ current and price/current relationship of an inductor. Toroid or shielded pot cores in ferrite or permalloy materials are small and do not radiate energy. However, they are usually more expensive than the similar powdered iron inductors ...

Page 9

... P D(MAX) T/SOT-23-6 package The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) θ . For RT8258 package, the Figure 3 of derating curve JA allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. 0.50 0.45 0.40 0.35 ...

Page 10

... RT8258 Table 2. Suggested Inductors for L Component Supplier Series SLF12555T TDK NR8040 TAIYO YUDEN SLF12565T TDK Table 3. Suggested Capacitors for C Location Component Supplier C MURATA IN C TDK IN C TAIYO YUDEN IN C MURATA OUT C TDK OUT C TAIYO YUDEN OUT Table 4. Suggested Diode for D1 Component Supplier ...

Page 11

... SOT-23-6 Surface Mount Package RT8258 H L Dimensions In Inches Min Max 0.031 0.051 0.000 0.006 0.055 0.071 0.010 0.022 0.102 0.118 0.106 0.122 0.033 ...

Page 12

... RT8258 Symbol Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time ...

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