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PDF SC195F Data sheet ( Hoja de datos )
| Número de pieza | SC195F | |
| Descripción | 500mA Synchronous Step Down DC-DC Regulator | |
| Fabricantes | Semtech | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SC195F (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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POWER MANAGEMENT
Features
Input Voltage — 2.9V to 5.5V
Output Voltage — 0.8V to 3.3V
Output current capability — 500mA
Efficiency up to 94%
15 Programmable output voltages
Fast transient response
Oscillator frequency — 3.5MHz
100% duty cycle capability
Quiescent current — 4.8 mA typ
Shutdown Current — 0.1µA typ
Internal soft-start
Over-voltage protection
Current limit and short circuit protection
Over-temperature protection
Input under-voltage lockout
Floating control pin protection
MLPQ-UT8 1.5 x 1.5 x 0.6 (mm) package
Pb free, halogen free, and RoHS/WEEE compliant
Applications
Smart phones and cellular phones
MP3/Personal media players
Personal navigation devices
Digital cameras
Single Li-ion cell or 3 NiMH/NiCd cell devices
Devices with 3.3V or 5V internal power rails
SC195F
3.5MHz, 500mA Synchronous
Step Down DC-DC Regulator
Description
The SC195F is a high efficiency, 500mA step down regula-
tor designed to operate with an input voltage range of
2.9V to 5.5 V. The input voltage range makes it ideal for
battery operated applications with space limitations. The
SC195F operates at a fixed 3.5MHz switching frequency in
normal PWM (Pulse-Width Modulation) mode. The
SC195F also includes fifteen programmable output
voltage settings that can be selected using the four
control pins, eliminating the need for external feedback
resistors. The output voltage can be fixed to a single
setting or dynamically switched between different levels.
Pulling all four control pins low disables the output.
The SC195F provides several protection features to safe-
guard the device under stressed conditions. These
include short circuit protection, over-temperature protec-
tion, input under-voltage lockout, and soft-start to control
in-rush current. These features, coupled with the small
1.5 x 1.5 x 0.6 (mm) package make the SC195F a versatile
device ideal for step-down regulation in products needing
high efficiency and a small PCB footprint.
Typical Application Circuit
VIN
2.9V to 5.5V
CIN
4.7µF
SC195F
IN
LX
OUT
LX
1.0µH
Control Logic
Lines
Rev 2.0
CTL3
CTL2
CTL1
CTL0
GND
© 2016 Semtech Corporation
VOUT
0.8V to 3.3V
COUT
10µF
1
1 page  
SC195F
Typical Characteristics
CIN = 4.7µF, COUT = 10µF, LX = 1µH, TA = 25°C unless otherwise noted.
Efficiency vs. IOUT Vin=5V
5555566666777778888899902468024680246802468024 Vin=5V
VID=0.8V
VID=1V
VID=1.2V
VID=1.4V
VID=1.5V
VID=1.6V
VID=1.8V
VID=2V
VID=2.3V
VID=2.35V
VID=2.4V
VID=2.45V
VID=2.8V
VID=3V
VID=3.3V
0 0.1 0.2 0.3 0.4 0.5
Load Current (A)
Efficiency vs. IOUT Vin=4.2V
55555666667777788888999555556666677777888889990246802468024680246802402468024680246802468024 Vin=4.2V
00
00..11
00..22 00..33
Load Current (A)
00..44
VID=0.8V
VID=1V
VID=1.2V
VID=1.4V
VID=1.5V
VID=1.6V
VID=1.8V
VID=2V
VID=2.3V
VID=2.35V
VID=2.4V
VID=2.45V
VID=2.8V
VID=3V
VID=3.3V
00..55
Efficiency vs. IOUT Vin=3.6V
55555666667777788888999990246802468024680246802468 Vin=3.6V
0 0.1
0.2 0.3
Load Current (A)
0.4
VID=0.8V
VID=1V
VID=1.2V
VID=1.4V
VID=1.5V
VID=1.6V
VID=1.8V
VID=2V
VID=2.3V
VID=2.35V
VID=2.4V
VID=2.45V
VID=2.8V
VID=3V
VID=3.3V
0.5
3.5 Vin=5V
Regulation vs. IOUT Vin=5V
3
2.5
2
1.5
1
0.5
0
0.1 0.2 0.3 0.4
Load Current (A)
VID=0.8V
VID=1V
VID=1.2V
VID=1.4V
VID=1.5V
VID=1.6V
VID=1.8V
VID=2V
VID=2.3V
VID=2.35V
VID=2.4V
VID=2.45V
VID=2.8V
VID=3V
VID=3.3V
0.5
3.5 Vin=4.2V
Regulation vs. IOUT Vin=4.2V
3
2.5
2
1.5
1
0.5
0
0.1 0.2 0.3 0.4 0.5
Load Current (A)
VID=0.8V
VID=1V
VID=1.2V
VID=1.4V
VID=1.5V
VID=1.6V
VID=1.8V
VID=2V
VID=2.3V
VID=2.35V
VID=2.4V
VID=2.45V
VID=2.8V
VID=3V
VID=3.3V
Regulation vs. IOUT Vin=3.6V
3.5 Vin=3.6V
3
2.5
2
1.5
1
0.5
0
0.1 0.2 0.3 0.4 0.5
Load Current (A)
VID=0.8V
VID=1V
VID=1.2V
VID=1.4V
VID=1.5V
VID=1.6V
VID=1.8V
VID=2V
VID=2.3V
VID=2.35V
VID=2.4V
VID=2.45V
VID=2.8V
VID=3V
VID=3.3V
5
5 Page 
SC195F
Applications Information (continued)
VIN
CIN
Enable
SC195F
IN LX
CTL3
CTL2
CTL1
CTL0
OUT
GND
LX
CFF
RFB1
RFB2
VOUT
COUT
Figure 1 — Application Circuit with External Resistors
To simplify the design, it is recommended to program the
output setting to 1.0V, use resistor values smaller than
10kΩ, and include a feed-forward capacitance calculated
with the equation above. If the output voltage is set to
1.0V, the previous equation reduces to
CFF
8 u106 u VOUT 0.5 2
RFB1 VOUT 1
Example:
An output voltage of 1.3V is desired, but this is not a pro-
grammable option. What external component values for
Figure 1 are needed?
Solution: To keep the circuit simple, set RFB2 to 10kΩ so
current into the OUT pin can be neglected and set the
CTL3-0 pins to 0010 (1.0V setting). The necessary compo-
nent values for this situation are
RFB1
RFB2
u
VOUT VSET
VSET
3k:
CFF
8 u 106 u VOUT 0.5 2
RFB1 VOUT 1
5.69nF
PWM and 100% Duty Cycle Operation
In order to start up from pre-charged output voltage,
SC195F does not allow inductor current to go negative in
soft start stage, refer to the soft start waveforms in the
Typical Characteristics page. When the output voltage
exceeds 90% of the set point, determined by the CTLx
combinations, the device will enter fixed 3.5MHz PWM
mode operation. An internal synchronous NMOS rectifier
turns on complementary to the top PMOSFET.
The duty cycle (percentage of time PMOS is active)
increases as VIN decreases to maintain output voltage
regulation. As the input voltage approaches the pro-
grammed output voltage, the duty cycle approaches
100% (PMOS always on) and the device enters a pass-
through mode until the input voltage increases or the
load decreases enough to allow PWM switching to
resume.
Protection Features
The SC195F provides the following protection features:
•• Current Limited Soft-Start Operation
•• Over-Voltage Protection
•• Current Limit
•• Thermal Shutdown
•• Input Voltage Under-Voltage Lockout
Soft-Start with Current Limit
The soft-start sequence is activated after a CTL code tran-
sition from an all zeros code to a non-zero code enables
the start up process. From the beginning of a start-up
process, the internal reference start-up takes typically
50μs, then PMOS current limit is stepped through four
levels: 25%, 40%, 60%, and 100%. Each step is maintained
for typically 75μs. A complete 4 steps start-up period
could take 350μs. Before VOUT reaches 90%, the inductor
current is not allowed to go negative. The inductor
current is confined between different current limit levels,
25%, 40%, 60%, or 100% to zero.
As VOUT reaches 90% of the target value, the device will
transition into a fixed 3.5MHz operation allowing induc-
tor current in both directions.
Due to current limit operation, if the load is heavy or the
output capacitor is large, the soft start process may expe-
rience all 4 current limit steps before reaching 90% target
voltage. This will make the soft start time long. If the load
is light and output capacitor is small, the device may only
need the first current limit step, reaching 90% of target,
and transition into PWM operation. This makes the soft
start time shorter.
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet SC195F.PDF ] | |
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