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PDF SC195B Data sheet ( Hoja de datos )
| Número de pieza | SC195B | |
| 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 SC195B (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
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POWER MANAGEMENT
Features
Input Voltage — 2.9V to 5.5V
Output Voltage — 0.8V to 3.6V
Output current capability — 500mA
Efficiency up to 94%
15 Programmable output voltages
High light-load efficiency via automatic PSAVE mode
Fast transient response
Temperature range — -40 to +85°C
Oscillator frequency — 3.5MHz
100% duty cycle capability
Quiescent current — 38µA typ
Shutdown Current — 0.1µA typ
Internal soft-start
Over-voltage protection
Current limit and short circuit protection
Over-temperature protection
Under-voltage lockout
Floating control pin protection
WLCSP8-0.80 X 0.80 X 0.375 (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
SC195B
3.5MHz, 500mA Synchronous
Step Down DC-DC Regulator
Description
The SC195B is a high efficiency, 500mA step down regula-
tor designed to operate with an input voltage range of
2.9V to 5.5V. The input voltage range makes it ideal for
battery operated applications with space limitations. The
SC195B 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 and
puts the device into a low current shutdown state.
The SC195B operates at a fixed 3.5MHz switching fre-
quency in normal PWM (Pulse-Width Modulation) mode.
A variable frequency PSAVE (power-save) mode is used to
optimize efficiency at light loads for each output setting.
Built-in hysteresis prevents chattering between the two
modes.
The SC195B provides several protection features to safe-
guard the device under stressed conditions. These
include short circuit protection, over-temperature protec-
tion, over-voltage protection, under-voltage lockout, and
soft-start to control in-rush current. These features
coupled with the small 8-bump 0.80 X 0.80 X 0.375 (mm)
package make it 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
Control Logic
(May also be
hard wired to
VIN/ GND)
CIN
4.7µF
SC195B
VIN LX
CTL3
CTL2
CTL1
CTL0
OUT
GND
L1
1µH
VOUT
0.8V to 3.6V
COUT
10µF
Rev 2.1
Semtech Corporation
1 page  
SC195B
Typical Characteristics
VIN = 4.0V for VOUT = 3.3V, VIN = 3.6V for all others. CIN = 4.7µF, COUT = 10µF, LX = 1µH, TA = 25°C unless otherwise noted.
Efficiency vs. IOUT (TA = -40°C)
Load Regulation, Vout=1.8V
100
90 3.3V
80 2.8V
1.8V
70
1V
60
50
40
30
20
10
0
0.1 1
10
Load Current (mA)
100
1000
1.88
1.86
1.84
1.82
1.8
1.78
1.76
0
0.1 0.2 0.3 0.4
Load (A)
85 °C
25 °C
-40 °C
0.5 0.6
Efficiency vs. IOUT (TA = 25°C)
100
90
80
70
60
50
40
30
20
10
0
0.1
3.3V
2.8V
1.8V
1V
1
10
Load Current (mA)
100
1000
Line Regulation, Vout=1.8V/400mA
1.88
1.86
1.84
1.82
1.80
85 °C
25 °C
-4 0 °C
1.78
1.76
2.5 3.0 3.5 4.0 4.5 5.0 5.5
Vin (V)
Efficiency vs. IOUT (TA = 85°C)
100
90
80
70
60
50
40
30
20
10
0
0.1
3.3V
2.8V
1.8V
1V
1
10
Load Current (mA)
100
1000
Efficiency vs. Vin, 1.8V/400mA
90
89
88
8 7 -40 °C
86
2 5 °C
85
8 4 85 °C
83
82
2.5 3.0 3.5 4.0 4.5 5.0
Vin (V)
5.5
5 Page 
SC195B
Applications Information
General Description
The SC195B is a synchronous step-down Pulse Width
Modulated (PWM) DC-DC regulator utilizing a 3.5MHz
fixed-frequency voltage mode architecture. The device is
designed to operate in fixed-frequency PWM mode and
enter power save (PSAVE) mode utilizing pulse frequency
modulation under light load conditions to maximize effi-
ciency. The device requires only two capacitors and a
single inductor to be implemented in most systems. The
switching frequency has been chosen to minimize the size
of the inductor and capacitors while maintaining high
efficiency. The output voltage is programmable, eliminat-
ing the need for external programming resistors. Loop
compensation is also internal, eliminating the need for
external components to control stability.
Programmable Output Voltage
The SC195B has 15 fixed output voltage levels which can
be individually selected by programming the CTL control
pins (CTL3-0 — see Table 1 on page 2 for settings). The
device is disabled whenever all four CTL pins are pulled
low and enabled whenever at least one of the CTL pins is
pulled high. This configuration eliminates the need for a
dedicated enable pin.
CTL Input Resistance
Each CTL pin is internally pulled down via 1MΩ at power
up if VIN is below 1.5V or if the voltage on the control pin is
below the input high voltage. This ensures that the output
is disabled when power is applied if there are no inputs to
the CTL pins. Each 1MΩ pull-down is disabled whenever
its pin is pulled high and remains disabled until all CTL
pins are pulled low.
Output Voltage Setting
The output voltage can be set using different approaches.
If a static output voltage is required, the CTL pins can be
tied to either IN or GND to set the desired voltage when-
ever power is applied at IN. If enable control is required,
each CTL pin can be tied to either GND or to a micropro-
cessor I/O line to create the desired control code whenever
the control signal is forced high. This approach is equiva-
lent to using the CTL pins collectively as a single enable
pin. A third option is to connect each of the four CTL pins
to individual microprocessor I/O lines. Any of the 15
output voltages can be programmed using this approach.
If only two output voltages are needed, the CTL pins can
be combined in a way that will reduce the number of I/O
lines to 1, 2, or 3, depending on the control code for each
desired voltage. Other CTL pins could be hard wired to
GND or IN. This option allows dynamic voltage adjust-
ment for systems that reduce the supply voltage when
entering sleep states. Note that applying all zeros to the
CTL pins when changing the output voltages will tempo-
rarily disable the device, so it is important to avoid this
combination when dynamically changing levels.
Dynamic Output Voltage Adjustment
Dynamically changing the CTL pins allows dynamic
voltage adjustment for systems that reduce the supply
voltage when entering sleep states. This should be done
using specific procedures. Attention is required since
applying all zeros in a very short period to the CTL pins
when changing the output voltage will temporarily
disable the device. Therefore it is important to avoid the
combination of all zeros when dynamically changing the
CTL levels. For example, when the CTLs change from
0001 to 0010 (0.8V to 1.0V), a transitional state of 0000
(shut down) state might occur for a very short period of
time, which could result the device being disabled unin-
tentionally. In order to achieve such operation, the correct
logic transition stages can be arranged in this way: 0001-
-0011--0010 (0.8V--1.1V--1V). The very short transition
state 0011 would keep the part in operation but not
affect the voltage transition waveform.
When the CTL pins are changed to raise the output
voltage, the regulator increases the inductor current to
force the output voltage to slew up. A large change in
the voltage setting could result in over-current due to
charging the output capacitor. For large voltage steps it
is recommended to use minimal output capacitors and to
raise the voltage in smaller steps to reduce the transient
inductor current.
When the CTL pins are changed to decrease the output
voltage, the output response will vary depending on the
operating mode. If the device is operating in PWM mode,
the regulator will continue active switching and will bring
the output capacitors down to match the new CTL
setting. If the device is operating in PSAVE mode, the
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet SC195B.PDF ] | |
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