IC STEP-DWN SW REG 3A 28V 8-SOIC

SC4525ASETRT

Manufacturer Part NumberSC4525ASETRT
DescriptionIC STEP-DWN SW REG 3A 28V 8-SOIC
ManufacturerSemtech
TypeStep-Down (Buck)
SC4525ASETRT datasheet
 


Specifications of SC4525ASETRT

Internal Switch(s)YesSynchronous RectifierNo
Number Of Outputs1Current - Output3A
Frequency - Switching300kHz ~ 1.3MHzVoltage - Input8 ~ 28 V
Operating Temperature-40°C ~ 125°CMounting TypeSurface Mount
Package / Case8-SOICLead Free Status / RoHS StatusLead free / RoHS Compliant
Voltage - Output-Power - Output-
Other namesSC4525ASETR  
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POWER MANAGEMENT
Features
Wide input range: 8V to 28V
3A Output Current
200kHz to 2MHz Programmable Frequency
Precision V Feedback Voltage
Peak Current-Mode Control
Cycle-by-Cycle Current Limiting
Hiccup Overload Protection with Frequency Foldback
Soft-Start and Enable
Thermal Shutdown
Thermally Enhanced 8-pin SOIC Package
Fully RoHS and WEEE compliant
Applications
XDSL and Cable Modems
Set Top Boxes
Point of Load Applications
CPE Equipment
DSP Power Supplies
LCD and Plasma TVs
Typical Application Circuit
10V – 28V
V
IN
C4
4.7mF
BST
IN
SW
SC4525A
SS/EN
FB
COMP
ROSC
GND
C7
R7
R5
10nF
18.2k
C8
24.3k
10pF
C5
1nF
L1: Coiltronics CD1-5R2
C2: Murata GRM31CR60J106K
C4: Murata GRM32ER71H475K
Figure 1. 1MHz 10V -28V to 5V/3A Step-down Converter
November 8, 2007
28V 3A Step-Down Switching Regulator
Description
The SC4525A is a constant frequency peak current-mode
step-down switching regulator capable of producing 3A
output current from an input ranging from 8V to 28V. The
switching frequency of the SC4525A is programmable
up to 2MHz, allowing the use of small inductors and
ceramic capacitors for miniaturization, and high input/
output conversion ratio. The SC4525A is suitable for
next generation XDSL modems, high-definition TVs and
various point of load applications.
Peak current-mode PWM control employed in the
SC4525A achieves fast transient response with simple loop
compensation. Cycle-by-cycle current limiting and hiccup
overload protection reduces power dissipation during
output overload. Soft-start function reduces input start-
up current and prevents the output from overshooting
during power-up.
The SC4525A is available in SOIC-8 EDP package.
SC4525A
90
D1
1N4148
80
C1
0.1mF
L1
OUT
70
5.2mH
5V/3A
R4
33.2k
60
D2
R6
C2
50
20BQ030
8.25k
10mFX3
40
Efficiency of the 1MHz 10V-28V to 5V/3A Step-Down Conve
SC4525A
Efficiency
V
= 24V
IN
V
= 12V
IN
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Load Current (A)


SC4525ASETRT Summary of contents

  • Page 1

    POWER MANAGEMENT Features Wide input range 28V  3A Output Current  200kHz to 2MHz Programmable Frequency  Precision V Feedback Voltage  Peak Current-Mode Control  Cycle-by-Cycle Current Limiting  Hiccup Overload Protection with Frequency Foldback  ...

  • Page 2

    ... GND Pin SOIC - EDP) Marking Information yyww=Date code (Example: 0752) xxxxx=Semtech Lot No. (Example: E900) Ordering Information Device SC4525ASETRT BST SC4525AEVB FB Notes: COMP () Available in tape and reel only. A reel contains 2,500 devices. (2) Available in lead-free package only. Device is fully WEEE and RoHS SS/EN compliant ...

  • Page 3

    Absolute Maximum Ratings V Supply Voltage ……………………………… -0.3 to 32V IN BST Voltage ……………………………………………… 42V BST Voltage above SW …………………………………… 34V SS Voltage ……………………………………………-0 Voltage …………………………………………… -0 Voltage ………………………………………… -0 Transient ...

  • Page 4

    Electrical Characteristics (Cont.) Unless otherwise noted 2V 5V BST Parameter Minimum Switch On-time Minimum Switch Off-time Switch Leakage Current Minimum Bootstrap Voltage BST Pin Current Oscillator Switching Frequency Foldback Frequency Soft Start and Overload ...

  • Page 5

    Pin Descriptions SO-8 Pin Name Pin Function Emitter of the internal NPN power transistor. Connect this pin to the inductor, the freewheeling diode and the  SW bootstrap capacitor. Power supply to the regulator also the collector of ...

  • Page 6

    Block Diagram COMP COMP FREQUENCY FREQUENCY FOLDBACK FOLDBACK ROSC ROSC SS/EN SS/ REFERENCE REFERENCE ...

  • Page 7

    Eff Typical Characteristics Efficiency =3. =2. =1. (5) V =12V IN 50 1MHz 0.5 1 1.5 2 Load ...

  • Page 8

    Typical Characteristics (Cont.) SS270 REV 6-7 V Thresholds vs Temperature IN 3.0 2.9 Start 2.8 2.7 2.6 (14) UVLO 2.5 2.4 -50 - Temperature ( SS270 REV 6-7 V Quiescent Current 2.5 ...

  • Page 9

    Applications Information Operation The SC4525A is a constant-frequency, peak current- mode, step-down switching regulator with an integrated 28V, 3.6A power NPN transistor. Programmable switching frequency makes the regulator design more flexible. With the peak current-mode control, the double reactive poles ...

  • Page 10

    Applications Information (Cont.) As the load draws more current from the regulator, the current-limit comparator ILIM (Figure 2) will eventually limit the switch current on a cycle-by-cycle basis. The over-current signal OC goes high, setting the latch B soft-start capacitor ...

  • Page 11

    Applications Information (Cont.) Minimum Off Time Limitation The PWM latch in Figure 2 is reset every cycle by the clock. The clock also turns off the power transistor to refresh the bootstrap capacitor. This minimum off time limits the attainable ...

  • Page 12

    Applications Information (Cont.) diodes should have an average forward current rating at least 3A and a reverse blocking voltage of at least a few volts higher than the input voltage. For switching regulators operating at low duty cycles (i.e. low ...

  • Page 13

    Applications Information (Cont.) CONTROLLER AND SCHOTTKY DIODE CONTROLLER AND SCHOTTKY DIODE REF REF + + Vc Vc PWM PWM EA EA MODULATOR MODULATOR Vramp Vramp COMP COMP ...

  • Page 14

    ⋅ π ⋅ π ...

  • Page 15

    Applications Information (Cont.) PCB Layout Considerations In a step-down switching regulator, the input bypass capacitor, the main power switch and the freewheeling diode carry pulse current (Figure 9). For jitter-free operation, the size of the loop formed by these components ...

  • Page 16

    Recommended Component Parameters in Typical Applications Table 5 lists the recommended inductance (L voltages. The inductance is determined by assuming that the ripple current is 35% of load current I parameters are calculated by assuming a 47mF low ESR ceramic ...

  • Page 17

    Typical Application Schematics V IN Figure 10. 300kHz 24V to 1.5V/3A Step-down Converter V IN Figure 11. 1MHz 10V-26V to 3.3V/3A Step-down Converter D1 D3 24V 18V Zener 1N4148 C4 4.7mF IN BST SW SC4525A SS/EN FB COMP ROSC GND ...

  • Page 18

    Typical Performance Characteristics (For A 12V to 5V/3A Step-down Converter with 1MHz Switching Frequency) SS270 REV 6-7 Load Characteristic 0.5 1 1.5 2 2.5 Load Current (A) Figure 12(a). Load Characteristic 5V ...

  • Page 19

    ... THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. Semtech Corporation Power Mangement Products Division 200 Flynn Road, Camarillo, CA 9302 Phone: (805) 498-2 Fax: (805) 498-3804 ...