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부품번호 | SC196 기능 |
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기능 | 1.5A Synchronous Buck Converter | ||
제조업체 | Semtech | ||
로고 | |||
전체 18 페이지수
POWER MANAGEMENT
Description
The SC196 is a synchronous step-down converter with
integrated power devices designed for use in applications
using a single-cell Li-ion battery. Its wide input voltage
range also makes it suitable for use in systems with fixed
3.3V or 5V supply rails available. The switching frequency is
nominally set to 1MHz, allowing the use of small inductors
and capacitors. The current rating of the internal MOSFET
switches allows a DC output current of 1.5A.
The output voltage is set by connecting a resistor divider
from the filter inductor to the feedback pin. See the
SC196A for pin-programmable output voltages.
The SC196 has a flexible clocking methodology that
allows it to be synchronized to an external oscillator or
controlled by the internal oscillator. The device operates
in either forced PWM mode or in PSAVE mode. If PSAVE
mode is enabled, the part will automatically enter PFM at
light loads to maintain maximum efficiency across the full
load range.
For noise sensitive applications, PSAVE mode can be
disabled by synchronizing to an external oscillator or
pulling the SYNC/PWM pin high. Shutdown turns off all
the control circuitry to achieve a typical shutdown current
of 0.1μA.
SC196
1.5A Synchronous Buck Converter
with Integrated Power Deviceswww.DataSheet4U.com
Features
Up to 95% efficiency
VOUT adjustable from less than 0.8V to VIN
Output current — 1.5A
Input range — 2.5V to 5.5V
Quiescent current — 17μA
Fixed 1MHz frequency or 750kHz to 1.25MHz
synchronized operation
PSAVE operation to maximize efficiency at light loads
Shutdown current <1μA
Fast transient response
100% duty cycle in dropout
Soft-start
Over-temperature and short-circuit protection
Lead-free package — MLPD10-UT, 3 x 3 x 0.6 mm
Applications
Cell phones
Wireless communication chipset power
Personal media players
Microprocessor/DSP core/IO power
PDAs and handheld computers
WLAN peripherals
USB powered modems
1 Li-Ion or 3 NiMH/NiCd powered devices
Typical Application Circuit
VIN
2.5V to 5.5V
CIN
10μF
VIN SC196
LX
PVIN
VOUT
MODE
ADJ
EN
SYNC/PWM
PGND
GND
L1
4.7μH
RFB1
RFB2
VOUT
<0.8V to VIN
1.5A
CFB1
10pF
COUT
22μF
February 8, 2007
1 www.semtech.com
POWER MANAGEMENT
Pin Configuration
PVIN 1
VIN 2
SYNC/PWM 3
EN 4
VOUT 5
TOP VIEW
T
10 LX
9 PGND
8 GND
7 MODE
6 ADJ
MLPD-UT: 3X3X0.6, 10 LEAD
SC196
Ordering Information
www.DPatRaSEheLeItM4U.IcNomARY
DEVICE
PACKAGE
SC196ULTRT(1)(2)
MLPD-UT10 3x3x0.6
OrderiSnCg19In6EfoVrBmation
Evaluation Board
Notes:
1) Lead-free packaging only. This product is fully WEEE and RoHS compliant.
2) Available in tape and reel only. A reel contains 3000 devices.
Marking Information
196
yyww
xxxx
yy = two digit year of manufacture
ww = two digit week of manufacture
xxxx = lot number
© 2007 Semtech Corp.
4
www.semtech.com
4페이지 SC196
POWER MANAGEMENT
Applications Information
SC196 Detailed Description
The SC196 is a synchronous step-down Pulse Width
Modulated (PWM), DC-DC converter utilizing a 1MHz
fixed-frequency current mode architecture. The device
is designed to operate in a fixed-frequency PWM mode
across the full load range and can enter Power Save Mode
(PSAVE), utilizing Pulse Frequency Modulation (PFM) at
light loads to maximize efficiency.
Operation
During normal operation, the PMOS MOSFET is activated
on each rising edge of the internal oscillator. Current
feedback for the switching regulator uses the PMOS
current path, and it is amplified and summed with
the internal slope compensation network. The voltage
feedback loop uses an external feedback divider. The on-
time is determined by comparing the summed current
feedback and the output of the error amplifier. The period
is set by the onboard oscillator or by an external clock
attached to the SYNC/PWM pin.
The SC196 has an internal synchronous NMOS rectifier
and does not require a Schottky diode on the LX pin.
www.DPatRaSEheLeItM4U.IcNomARY
Table 1 — Recommended ADJ Resistor Combinations
VOUT(V)
1
RFB2(kΩ)
200
RFB1(kΩ)
200
1.1 200 240
1.2 200 280
1.3 200 320
1.5 178 357
1.6 200 442
1.7 178 432
1.8 178 464
1.875
178
487
2.5 200 806
2.8 178 820
3 178 887
3.3 100 560
3.6 100 620
3.8 100 665
Output Voltage Selection
The output voltage can be programmed using a resistor
network connected from VOUT to ADJ to GND. The
combined resistance of the divider chain should be
greater than 10KΩ and less than 1MΩ. Table 1 lists
appropriate resistors which limit the bias current required
of the external feedback resistor chain and ensuring good
noise immunity.
The output voltage can be adjusted between less than
0.8V and VIN. The output voltage formula is:
VOUT
0.5
u
¨¨©§
RFB1
RFB2
1¸¸¹·
VOUT = output voltage (V)
RFB1 = feedback resistor from VOUT to ADJ (Ω)
RFB2 = feedback resistor from ADJ to GND (Ω)
Resistors with 1% or better tolerance are recommended
to ensure voltage accuracy.
Continuous Conduction & Oscillator Synchronization
The SC196 is designed to operate in continuous
conduction, fixed-frequency mode. When the SYNC/PWM
pin is tied high the part runs in PWM mode using the
internal oscillator. The part can be synchronized to an
external clock by driving a clock signal into the SYNC/
PWM pin. The part synchronizes to the rising edge of the
clock.
Protection Features
The SC196 provides the following protection features:
• Thermal Shutdown
• Current Limit
• Over-Voltage Protection
• Soft-Start
Thermal Shutdown
The device has a thermal shutdown feature to protect the
SC196 if the junction temperature exceeds 145°C. In
thermal shutdown, the on-chip power devices are disabled,
effectively tri-stating the LX output. Switching will resume
when the temperature drops by 10°C. During this time,
© 2007 Semtech Corp.
7
www.semtech.com
7페이지 | |||
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