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PDF SC221 Data sheet ( Hoja de datos )
| Número de pieza | SC221 | |
| Descripción | Synchronous Step-Down Regulator | |
| Fabricantes | Semtech | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SC221 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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SC221 x
POWER MANAGEMENT
20MHz, 650mA, X-EMI™-Enabled
Synchronous Step-Down Regulator
Features
Description
Patented X-EMITM Inductor Technology
Enables Trace Inductors in PC Board Material
Excellent EMI Performance
Efficiency up to 90%
17.5µA Quiescent Current under Very Light Loads
Wide Input Voltage Range — 2.7V to 5.5V
Adjustable Output Voltage Down to 1.0V
Output DC Current — up to 650mA
High Light-load Efficiency via Automatic PSAVE Mode
Ultra-fast Transient Response — <1µs
Temperature Range — -40 to +85°C
Shutdown Current — 0.1µA (typical)
Requires Tiny 220nH Inductor
Requires Only 1μF of Output Capacitance
External Switching Frequency Synchronization
Protection Features Including
Over-Current Protection
Output Short-Circuit Protection
Thermal Shutdown Protection
Offered in MLPD-UT 8 Lead Packages
Lead-free, Halogen-free, and RoHS/WEEE Compliant
Applications
HDTV, Set Top Boxes, Gaming Consoles
POL Applications
White Goods
The SC221 is a 20MHz X-EMI™(1)-enabled step-down regu-
lator optimized for power low voltage rails from 2.7 to
5.5V input voltage. X-EMI™ inductor technology enables
inductors to be drawn directly on the PC board. This tech-
nology meets or exceeds the EMI performance of chip
inductors and eliminates the need for discrete inductors.
The SC221 uses a unique constant frequency, self-oscil-
lating control loop architecture to provide excellent
transient performance. Under light loads, the device
operates in Power Save mode(PSAVE) maintaining a
typical quiescent current of 17.5µA. At moderate to heavy
loads, this part operates in PWM mode with a constant
switching frequency of 20MHz. This high switching fre-
quency offers the advantages of using small and low cost
external components like a 1µF external capacitor and a
small 220nH inductor (including X-EMITM PCB trace
inductors).
The device provides adjustable output voltages down to
1.0V and an output current up to 650mA. An EN pin can
be used to synchronize to an external source and includes
de-glitching to reduce noise sensitivity.
The SC221 is available in MLPD-UT 8 Lead package.
Note 1: Purchase of SC221 includes royalty-free right to use X-EMITM inductor technology with no addi-
tional cost.
Typical Application Circuit
VIN
2.7~5.5V
CIN
1 µF
PVIN
SW
AVIN
VOUT
SC221
L, 220nH
VOUT=1.8V
up to 650mA
R1
COUT
1 µF
Enable
EN
PGND
AGND
FB
R2
Revision 2.0
© 2016 Semtech Corporation
1
1 page  
SC221 x
Pin Descriptions
Pin # Pin Name Pin Function
1 SW Switching output node — connect to the output LC filter.
2 PVIN Power input supply voltage (2.7 to 5.5V).
3 VOUT Input for sensing the output of LC filter.
4
FB
Input for regulation of output LC filter — Using R1 and R2 to set the output voltage, VOUT = VFB x (1+ R1/R2). (Please refer
to the typical application circuit diagram on page 1).
5
EN
Enable Input — when low, circuit draws <1µA. Apply a square wave clock at EN to synchronize the switching frequency
with an external clock. It is recommended that the externally applied clock frequency should not be above 20MHz.
6 AVIN Input supply voltage
7 AGND Analog ground
8 PGND Power ground
Block Diagram
5
5 Page 
SC221 x
Applications Information (Cont.)
PCB Layout Considerations
Fundamental layout rules must be followed since the
layout is critical for achieving the desirable performance.
Poor layout can degrade the performance of the DC-DC
converter and can contribute to EMI problems, ground
bounce, and resistive voltage losses, and possibly poor
regulation and instability.
The following guidelines are recommended when devel-
oping a PCB layout:
1. The input capacitor, CIN should be placed as close to
the PVIN and PGND pins as possible. This capacitor
provides a low impedance loop for the pulsed
currents present at the buck converter’s input. Use
short wide traces to connect this capacitor as close
to the IC as possible. This will minimize EMI and input
voltage ripple by localizing the high frequency current
pulses.
2. Keep the SW pin traces as short as possible to minimize
pickup of high frequency switching edges to other
parts of the circuit. COUT and L should be connected as
close as possible between the SW and GND pins, with
a direct return to the GND pin from COUT.
3. Route the output voltage feedback/sense path away
from the inductor and SW node to minimize noise
and magnetic interference to the output feedback/
sense path.
4. Use a ground plane referenced to the PGND pin,
and the ground connection of the input and output
capacitors should be put on this plane and close to
each other if possible, and as close to the PGND pin as
possible. Use several vias to connect to the component
side ground to further reduce noise and interference
on sensitive circuit nodes.
5. If possible, minimize the resistance from the VOUT
and AGND pin to the load. This will reduce the
voltage drop on the ground plane and improve the
load regulation. And it will also improve the overall
efficiency by reducing the copper losses on the output
and ground planes.
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet SC221.PDF ] | |
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