SC4524B

Manufacturer Part NumberSC4524B
Description16V 2A Step-Down Switching Regulator
ManufacturerSemtech Corporation
SC4524B datasheet
 


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POWER MANAGEMENT
Features
Wide input range: 3V to 16V
2A Output Current
200kHz to 2MHz Programmable Frequency
Precision 1V Feedback Voltage
Peak Current-Mode Control
Cycle-by-Cycle Current Limiting
Hiccup Overload Protection with Frequency Foldback
www.DataSheet4U.com
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 – 16V
V
IN
C4
2.2mF
IN
SC4524B
SS/EN
COMP
ROSC
C7
R7
10nF
C8
30.1k
10pF
C5
1nF
L1: Wurth 744 778 9006
November 1, 2007
16V 2A Step-Down Switching Regulator
Description
The SC4524B is a constant frequency peak current-mode
step-down switching regulator capable of producing 2A
output current from an input ranging from 3V to 16V. The
switching frequency of the SC4524B is programmable
up to 2MHz, allowing the use of small inductors and
ceramic capacitors for miniaturization, and high input/
output conversion ratio. The SC4524B is suitable for
next generation XDSL modems, high-definition TVs and
various point of load applications.
Peak current-mode PWM control employed in the
SC4524B 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 SC4524B is available in SOIC-8 EDP package.
SS270 REV 4
D1
1N4148
C1
0.1mF
BST
L1
OUT
SW
6.8mH
5V/2A
R4
102k
FB
GND
D2
R6
C2
R5
20BQ030
25.5k
22mF
18.2k
C2: Murata GRM31CR60J226K
C4: Murata GRM31CR61E225K
Figure 1. 1MHz 10V-16V to 5V/2A Step-down Converter
SC4524B
Efficiency
90
85
80
V
= 12V
IN
75
70
65
60
55
50
45
40
0
0.5
1
1.5
Load Current (A)
2
1

SC4524B Summary of contents

  • Page 1

    ... SC4524B 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 SC4524B is available in SOIC-8 EDP package. SS270 REV 4 D1 1N4148 C1 0.1mF ...

  • Page 2

    ... Lot No. (Example: E9010) Ordering Information 8 BST 7 FB Notes COMP (1) 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 5 SS/EN compliant. Device Package SC4524BSETRT SOIC-8 EDP (1)(2) SC4524BEVB Evaluation Board SC4524B 2 ...

  • Page 3

    ... OSC Min Typ 3 2.70 2.82 225 2 40 0.980 1.000 0.005 -170 280 60 8 2 0.8V 25 2.6 3.3 250 SC4524B 5.5°C/W Max Units µA V 1.020 %/V nA -340 µ Ω A/V V µA 4.3 A ...

  • Page 4

    ... OSC R = 93.1kΩ, V OSC SS/ 1.5 V SS/EN V Rising SS/EN V Falling SS/EN V Falling SS/EN Min Typ 135 100 1.8 60 1.04 1.3 240 300 = 0 110 230 100 FB 0.2 0.3 1.0 1.13 1.7 1.2 2.0 1.5 2.15 1.9 0.6 1.0 165 10 SC4524B Max Units ns 150 ns 10 µA 2 1.56 MHz 360 kHz 350 kHz 170 0.4 V 1.3 V µA 2.8 µ 1.2 V °C °C 4 ...

  • Page 5

    ... V The exposed pad serves as a thermal contact to the circuit board soldered to the ground plane of the 9 Exposed Pad PC board. falls below 0.8V, then the switching frequency will be reduced order to fully enhance the internal NPN power transistor. IN SC4524B 5 ...

  • Page 6

    ... SOFT-START AND AND 1V 1V 1.9V 1.9V OVERLOAD OVERLOAD HICCUP HICCUP REFERENCE REFERENCE FAULT FAULT CONTROL CONTROL & THERMAL & THERMAL SHUTDOWN SHUTDOWN Figure 2. SC4524B Block Diagram - - 1.9V 1. 2mA 2mA B1 B1 1V/2.15V 1V/2.15V 3.5mA 3.5mA Figure 3. Soft-start and Overload Hiccup Control Circuit ...

  • Page 7

    ... Foldback Frequency =93.1k OSC 0.75 0.5 0.25 R =12.1k OSC 0 75 100 125 0.0 0.2 0 SS270 REV 6-7 BST Pin Current vs Switch Current 100.0 V =12V IN V =15V BST 75.0 50.0 o -40 C 25.0 0.0 75 100 125 0 0 Switch Current (A) C) SC4524B 50 75 100 125 = 0.6 0.8 1.0 (V) o 125 C 1 ...

  • Page 8

    ... Temperature ( SS270 REV 6-7 V Shutdown Current - 1 (V) IN SS270 REV 6-7 Soft-Start Charging Current vs Soft-Start Voltage 0.0 -0.5 -1.0 o 125 C -1.5 -2.0 -2.5 -3.0 75 100 125 SC4524B IN o 125 - ...

  • Page 9

    ... When the SS/EN pin is released, the soft-start capacitor is charged with an internal 1.6µA current source (not shown in Figure 3). As the SS/EN voltage exceeds 0.4V, the internal bias circuit of the SC4524B turns on and the SC4524B draws 2mA from V turns off and the 2µA current source I charges the soft-start capacitor. ...

  • Page 10

    ... V Setting the Switching Frequency = = − − CESAT CESAT The switching frequency of the SC4524B is set with an external resistor from the ROSC pin to ground ⋅ ⋅ − − ...

  • Page 11

    ... ⋅ D ⋅ ⋅ ⋅ CESAT CESAT The peak current limit of SC4524B power transistor least 2.6A. The maximum deliverable load current for the       ⋅ ...

  • Page 12

    ... B220A (Diodes Inc.), SS13, SS22 (Vishay), CMSH1-20M, CMSH1-20ML and CMSH2-20M (Central-Semi.) are all suitable. The freewheeling diode should be placed close to the SW pin of the SC4524B on the PCB to minimize ringing due to trace inductance. Bootstrapping the Power Transistor The minimum BST-SW voltage required to fully saturate the power transistor is shown in Figure 5, which is about 1 ...

  • Page 13

    ...     buck converter with the SC4524B. The inner loop (current loop) consists of a current sensing resistor (R     and a current amplifier (CA) with gain ( − − ⋅ ⋅ A ...

  • Page 14

    ... where g =0.28mA/V is the EA gain of the SC4524B. m Example: Determine the voltage compensator for an 800kHz, 12V to 3.3V/2A converter with 22uF ceramic output capacitor. Choose a loop gain crossover frequency of 80kHz, and place voltage compensator zero and pole at F    ...

  • Page 15

    ... SC4524B , for common input and output The compensator Recommended Parameters R7(k) C5(nF) C8(pF) 6.65 2.2 12.4 0.68 6.65 2.2 12.4 0.68 22.1 0.68 35.7 0.47 18.2 0.68 35.7 0.47 6.65 2.2 12.7 0.68 6.65 2.2 12.7 0.68 11.3 1.5 23.7 0.47 11 ...

  • Page 16

    ... Figure 11. 500kHz 10V-16V to 1.5V/2A Step-down Converter D1 D1 1N4148 1N4148 C1 C1 0.1mF 0.1mF L1 L1 OUT OUT 2.2mH 2.2mH 3.3V/2A 3.3V/ 33.2k 33. 20BQ030 20BQ030 14.3k 14.3k 22mF 22mF C1 C1 0.33mF 0.33mF L1 L1 OUT OUT EVB #a EVB #a 4.7mH 4.7mH 1.5V/2A 1.5V/ 33.2k 33. 20BQ030 20BQ030 66.5k 66.5k 22mF 22mF EVB #b EVB #b SC4524B 16 ...

  • Page 17

    ... Inductor Current (1A/DIV) 40us/DIV Figure 12(c). Load Transient Response (I = 0. 1.5 2 2.5 3 OCP 12V Input (5V/DIV) 5V Output (2V/DIV) SS Voltage (1V/DIV) 10ms/DIV Figure 12(b). V Start up Transient ( Output Short (5V/DIV) Retry Inductor Current (2A/DIV) SS Voltage (2V/DIV) 20ms/DIV Figure 12(d). Output Short Circuit (Hiccup) SC4524B =2A ...

  • Page 18

    ... 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 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 SC4524B DIMENSIONS INCHES MILLIMETERS DIM MIN NOM ...