SC4521

Manufacturer Part NumberSC4521
Description3A Step-Down Switching Regulator
ManufacturerSemtech Corporation
SC4521 datasheet
 
1
Page 1
2
Page 2
3
Page 3
4
Page 4
5
Page 5
6
Page 6
7
Page 7
8
Page 8
9
Page 9
10
Page 10
11
12
13
14
15
16
17
18
Page 1/18

Download datasheet (368Kb)Embed
Next
POWER MANAGEMENT
Description
The SC4521 is a current mode switching regulator with
an integrated switch, operating at 600kHz with
programmable soft start and enable functions. The
integrated switch allows for cost effective low power
solutions (peak switch current 3 amps). High frequency
operation allows for very small passive components.
Current mode operation allows for fast dynamic response
and instantaneous duty cycle adjustment as the input
varies (ideal for CPE applications where the input is a
www.DataSheet4U.com
wall plug power).
The low shutdown current makes it ideal for portable
applications where battery life is important.
The SC4521 is an 600kHz switching regulator with a low
pin count.
The SC4521 allows customers to use large capacitive
loads because its programmable soft start limits the dv/
dt of the output at start up.
Typical Application Circuit
V
V
IN
IN
Enable
Enable
C3
C3
Revision: October 5, 2007
3A Step-Down Switching Regulator
with Programmable Soft Start
Features
Wide operating voltage range: 4.4V to 24V
Integrated 3 Amp switch
600kHz frequency of operation
Programmable soft start funchion
Current mode control
Precision enable threshold
SO-8 EDP Lead-free package, fully WEEE and RoHS
compliant
Applications
XDSL modems
CPE equipment
DC-DC point of load applications
Portable equipment
Digtial consumer electronics
C1
C1
1
1
BST
BST
2
2
3
3
IN
IN
SW
SW
5
5
6
6
SC4521
SC4521
EN
EN
FB
FB
8
8
7
7
SS
SS
COMP
COMP
GND
GND
4
4
C6
C6
C4
C4
R3
R3
1
SC4521
D1
D1
L1
L1
V
V
OUT
OUT
R1
R1
C2
C2
D2
D2
R2
R2
www.semtech.com

SC4521 Summary of contents

  • Page 1

    ... The low shutdown current makes it ideal for portable applications where battery life is important. The SC4521 is an 600kHz switching regulator with a low pin count. The SC4521 allows customers to use large capacitive loads because its programmable soft start limits the dv the output at start up ...

  • Page 2

    ... ° ° SC4521 ° ° C ° C ° ...

  • Page 3

    ... SC4521 µ µ µ µ ...

  • Page 4

    ... SC4521 ...

  • Page 5

    ... OSCILLATOR FREQUENCY FREQUENCY SC4519H OCP Limit vs Duty Cycle Duty Cycle (%) ISEN ISEN 40m 40m BST BST Q Q POWER POWER TRANSISTOR TRANSISTOR GND GND HICCUP HICCUP ILIM @-40C ILIM @25C ILIM @125C 80 100 SC4521 www.semtech.com ...

  • Page 6

    ... Pulling and holding the EN pin below 0.4V activates the shut down mode of the SC4521 which reduces the input supply current to 250µA. During the shut down mode, the switch is turned off. The SC4521 is turned on if the EN pin is pulled high. Oscillator Its internal free running oscillator sets the PWM frequency at 600kHz for the SC4521 without any external components to program the frequency ...

  • Page 7

    ... The first one is the required ESR (Equivalent Series Resistance) which should be low enough to reduce the output voltage deviation during load changes. The second one is the required capacitance, which should be high enough to hold up the output voltage. Before the SC4521 regulates the inductor current to a new value during ...

  • Page 8

    ... Its maximum repetitive reverse block voltage has to be higher than the input voltage of the SC4521. A low forward conduction drop is also required to increase the overall efficiency. The freewheeling diode should be ...

  • Page 9

    ... V I diode F Loop Compensation Design The SC4521 has an internal error amplifier and requires a compensation network to connect between the COMP pin and GND pin as shown in Figure 3. The compensation network includes C4, C5 and R3. R1 and R2 are used to program the output voltage according to: ...

  • Page 10

    ... Connect the ground of the feedback divider and the compensation components directly to the GND pin of the SC4521 by using a separate ground trace. 8. Connect Pin large copper area to remove the IC heat and increase the power capability of the SC4521. A few feedthrough holes are required to ...

  • Page 11

    ... SC4521 =1V @2A =1V @ ...

  • Page 12

    ... SC4521 =1. www.semtech.com ...

  • Page 13

    ... SC4521 V V =3.3V =3. 10u 10u / . ...

  • Page 14

    ... SC4521 V V =5V = ...

  • Page 15

    ... POWER MANAGEMENT Application Information (Cont.) www.DataSheet4U.com 2007 Semtech Corp. (PCB - TOP) (PCB - BOTTOM) 15 SC4521 www.semtech.com ...

  • Page 16

    ... POWER MANAGEMENT Application Information (Cont.) www.DataSheet4U.com 2007 Semtech Corp. (Componet Side - TOP) (Componet Side - TOP) 16 SC4521 www.semtech.com ...

  • Page 17

    ... BSC 6.00 BSC e .050 BSC 1.27 BSC F .116 .120 .130 2.95 3.05 3.30 H .085 .095 .099 2.15 2.41 2. .010 .020 0.25 0.50 L .016 .028 .041 0.40 0.72 1.04 (.041) (1.05 0° 8° 0° 8° aaa .004 0.10 bbb .010 0.25 ccc .008 0. GAGE PLANE 0. (L1) A DETAIL A -H- SC4521 www.semtech.com ...

  • Page 18

    ... FAILURE MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804 18 DIMENSIONS DIM INCHES MILLIMETERS (.205) (5.20 .134 3.40 E .201 5.10 F .101 2.56 G .118 3.00 P .050 1.27 X .024 0.60 Y .087 2.20 Z .291 7.40 SC4521 www.semtech.com ...