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PDF SC4612 Data sheet ( Hoja de datos )
| Número de pieza | SC4612 | |
| Descripción | Wide Input Range High Performance Synchronous Buck Switching Regulator | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
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SC4612
Wide Input Range High Performance
Synchronous Buck Switching Controller
POWER MANAGEMENT
Description
Features
SC4612 is a high performance synchronous buck controller
that can be configured for a wide range of applications.
The SC4612 utilizes synchronous rectified buck topology
where high efficiency is the primary consideration. SC4612
is optimized for applications requiring wide input supply
range and low output voltages down to 500mV.
SC4612 implements an asynchronous soft-start mode,
which keeps the lower side MOSFET off during soft-start, a
www.DatadSeheseirt4eUd.cfoemature when a converter turns on into a preset
external voltage or pre-biased output voltage. With the lower
MOSFET off, the external bus is not discharged, preventing
any disturbances in the start up slope and any latch-up of
modern day ASIC circuits.
Wide voltage range, VDD = 28V, VPWRIN = 40V
Internally regulated DRV
Output voltage as low as 0.5V
1.7A gate drive capability
Asynchronous start up mode
Low side RDS-ON sensing with hiccup mode current
limit
Programmable current limit
Programmable frequency up to 1.2 MHz
Available in MLPD-12 and SOIC-14 Lead-free
packages. This product is fully WEEE and RoHS
compliant
Applications
SC4612 comes with a rich set of features such as regulated
DRV supply, programmable soft-start, high current gate
drivers, internal bootstrapping for driving high side
N-channel MOSFET, shoot through protection, RDS-ON sensing
with hiccup over current protection, and asynchronous start
up with over current protection.
Distributed power architectures
Telecommunication equipment
Servers/work stations
Mixed signal applications
Base station power management
Point of use low voltage high current applications
Typical Application Circuit
R1 R2
1
C1
2
C2
3
U1
S C4 61 2M LP
ILIM PHASE
OSC DH
SS/EN
BST
12
11
10
R3 4 EAO
C3 C4
5 FB
DRV 9
DL 8
6 VDD
C5
GND 7
R5
R4
C6 R6
C7
D1
Q1
Q2
C8
L1
+
C9 Vin
_
+
C10 Vout
_
Revision: January 31, 2007
1
www.semtech.com
1 page  
POWER MANAGEMENT
Timing Diagrams
Vcc
UVLO
4.58V
2.75V
1.3V
www.DataSheet4U.com
0.8V
0.5V
No fault start up sequence
SC4612
VCC
SS/EN
EAO
Vcc
UVLO
4.58V
2.75V
1.3V
0.8V
0.5V
Soft Start Duration
Asynchronous
Operation
Over current fault at Asynchronous start up sequence
Fault
occur
Fault removed,
normal operation resumed
EOA<FB+0.7V
DH
DL
VCC
SS/EN
EAO
DH
2007 Semtech Corp.
Fault
present for
10 cycles
Soft Start Duration
Asynchronous
Operation
5
DL
www.semtech.com
5 Page 
POWER MANAGEMENT
Applications Information (Cont.)
Below are examples of calculating the OCP trip voltages.
Low Side RDS_ON Current Limit
SC4612
2.75V
SC4612
www.DataSheet4U.com
Vin Ra
DRV pin
ILIM pin
R3 R4
130k 260k
R1
2k
COMP
Rb
L
R2 +100mV
10k
PHASE pin
R
load
Iloa d @T off
C1 R5
2pF 10k
C2
5pF
OCP
1. Ra, Rb - Not installed:
2.75V − 100mV
R3
=
100mV − Vphase
R2
solving for: VPHASE = -100mV, therefore the circuit will trip @ RDS_ON x ILOAD = 100mV
2. To lower trip voltage - install Rb. For example: Rb = 13k
2.75V − 100mV
R3
=
100mV − Vphase
R2 || (Rb + R1)
solving for: VPHASE = -20mV, obviously more sensitive! RDS_ON x ILOAD = 20mV
3. To increase trip voltage - install Ra. For example: Ra = 800k; VDRIVE = 7.8V typ.
2.75V − 100mV
R3
+
Vdrive
Ra + R1
=
100mV − Vphase
R2
solving for: VPHASE = -200mV. Current limit has doubled compared to original conditions.
NOTE! Allow for tempco and RDS_ON variation of the MOSFET - see “overcurrent protection” information on page 11 in the
datasheet.
2007 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet SC4612.PDF ] | |
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