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PDF SC1548 Data sheet ( Hoja de datos )
| Número de pieza | SC1548 | |
| Descripción | Linear Fet Controller | |
| Fabricantes | Semtech Corporation | |
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SC1548
Linear Fet Controller
POWER MANAGEMENT
Description
Features
The SC1548 is a power supply controller designed to
provide a simple single regulated power supply with over
current protection. It is part of Semtechs SmartLDO
family of products. The SC1548 can provide a 1.818V
power supply for the I/O plane or 1.515V for GTL+ / AGP
from either 3.3V or 2.5V. An adjustable option allows
generation and control of any voltage from 1.263V up to
5V.
SC1548 features include tight output voltage regulation,
an enable control and over current protection. Over
current protection is provided by feedback to the sense
pin. If the output drops below 50% of the nominal
output voltage (typical) for greater than 4ms (typical), the
output will be shut down.
u ± 2.5% output accuracy over line, load and
temperature
u 1.515V, 1.818V and adjustable output voltage
options available
u Enable control
u Over current protection
u 5-pin SOT-23 package
Applications
u Motherboards
u Graphics cards
u Microcontrollers
u Simple power supplies
The SC1548 is available in a tiny 5-pin SOT-23 surface
mount package.
Typical Application Circuit
Fixed Output Voltage Versions
1.818V OUT
Q1
IRL530N
+ C1
100uF
+ C2
100uF
+ C3
22uF
3.3V IN
12V IN
U1
1 SNS EN 5
2 GND
34
DRV IN
SC1548CSK-1.8
ENABLE
C4
0.1uF
Adjustable Output Voltage Version
2.5V OUT
R1
97.6
+ C1
100uF
Q1
IRL530N
+ C2
100uF
+ C3
22uF
R2
100
3.3V IN
12V IN
U1
1 ADJ EN 5
2
GND
3 DRV IN 4
SC1548CSK
ENABLE
C4
0.1uF
Revision 1, January 2001
1
www.semtech.com
1 page  
POWER MANAGEMENT
Pin Configuration
Top View
SOT-23-5L
Block Diagram
SC1548
Ordering Information
Part Number(1)(2)
Package
SC1548CSK-X.X.TR
SOT-23-5
Notes:
(1) Where -X.X denotes voltage options. Available
voltages are: 1.515V (-1.5) and 1.818V (-1.8). Leave blank
for adjustable version.
(2) Only available in tape and reel packaging. A reel
contains 3000 units.
Pin Descriptions
Pin Pin Name Pin Function
1 SNS Regulator sense input for fixed output voltage options. Use as a remote sense to the source of the
N-channel MOSFET.
ADJ Regulator sense input for adjustable output voltage version. Set output voltage as follows (refer to
application circuit on page 1):
VO = 1.263 • 1 + R1
R2
2 GND Ground.
3 DRV Outp ut o f re g ula to r. D ri ve s the g a te o f a n N-c ha nne l M OS F E T to ma i nta i n the o utp ut
voltage desired.
4 IN +12V supply.
5 EN Active high enable control with internal pullup. Output of regulator turns off when EN is
taken low.
ã 2001 Semtech Corp.
5
www.semtech.com
5 Page 
POWER MANAGEMENT
Typical Characteristics (Cont.)(1)
Output Short Circuit Glitch Immunity
SC1548
Note:
(1) See Applications Circuit on page 1.
Trace 1: VDRV, 5V/div.
Trace 2: VOUT, 1V/div.
Timebase: 1ms/div
SC1548 enabled, then shorted, therefore
VOUT < VTH(OC) immediately the short is applied. This
device shuts down after 5ms.
Applications Infomation
Theory Of Operation
The SC1548 linear FET controller provides a simple way
to drive an N-channel MOSFET to produce a tightly
regulated output voltage from an available, higher,
supply voltage. It takes its power from a 12V supply,
drawing typically 2mA while operating.
Also included is an overcurrent protection circuit that
monitors the output voltage. If the output voltage drops
below 50% of nominal, as would occur during an
overcurrent or short condition, the device will pull the
drive pin low and latch off.
It contains an internal bandgap reference which is
compared to the output voltage via a resistor divider.
This resistor divider is internal on the fixed output
voltage options, and user selectable on the adjustable
option. Since the drive pin can pull up to a 9V
guaranteed minimum, the device can be used to
regulate a large range of output voltages by careful
selection of the external MOSFET (see component
selection, below).
The SC1548 includes an active high enable control with
an internal pullup resistor. If this pin is pulled low, the
drive pin is pulled low, turning off the N-channel MOSFET.
If the pin is left open or pulled up to 2.5V, 3.3V or 5V,
then the drive pin will be enabled.
Fixed Output Voltage Options
Please refer to the Application Circuit on Page 1. The
fixed output voltage parts have an internal resistor
divider that draws a nominal 100µA from the output.
The voltage at the common node of the resistor divider
is then compared to the bandgap reference voltage of
1.263V. The drive pin voltage is then adjusted to
maintain the output voltage set by the resistor divider.
Referring to the block diagram on page 5, the nominal
resistor values are:
Output Voltage
1.515V
1.818V
R1 (kW)
2.52
5.55
R1 (kW)
12.63
12.63
ã 2001 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet SC1548.PDF ] | |
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