|
|
PDF SC4501 Data sheet ( Hoja de datos )
| Número de pieza | SC4501 | |
| Descripción | 2MHz Step-Up Switching Regulator | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de SC4501 (archivo pdf) en la parte inferior de esta página. Total 21 Páginas | ||
|
No Preview Available !
POWER MANAGEMENT
Description
The SC4501 is a high-frequency current-mode step-up
switching regulator with an integrated 2A power transis-
tor. Its high switching frequency (programmable up to
2MHz) allows the use of tiny surface-mount external pas-
sive components. Programmable soft-start eliminates high
inrush current during start-up. The internal switch is rated
at 32V making the converter suitable for high voltage ap-
plications such as Boost, SEPIC and Flyback.
www.DataTShheeeto4pUe.croamting frequency of the SC4501 can be set with an
external resistor. The ability to set the operating frequency
gives the SC4501 design flexibilities. A dedicated COMP
pin allows optimization of the loop response. The SC4501
is available in thermally enhanced 8-Pin MSOP and 10-pin
MLPD packages.
SC4501
2Amp, 2MHz Step-Up Switching
Regulator with Soft-Start
Features
u Low saturation voltage switch: 220mV at 2A
u Constant switching frequency current-mode control
u Programmable switching frequency up to 2MHz
u Soft-Start function
u Input voltage range from 1.4V to 16V
u Output voltage up to 32V
u Low shutdown current
u Adjustable undervoltage lockout threshold
u Small low-profile thermally enhanced packages
Applications
u Flat screen LCD bias supplies
u TFT bias supplies
u XDSL power supplies
u Medical equipment
u Digital video cameras
u Portables devices
u White LED power supplies
Typical Application Circuit
VIN
5V
C1
2.2µF
L1 D1
10BQ015
65
IN
OFF ON 3 SHDN
SW
FB 2
SC4501
8
SS
COMP 1
C3
47nF
GND
4
ROSC
7
R4
R3
C6
C4
R1
174K
R2
20K
VOUT
12V, 0.7A
C2
10µF
All Capacitors are Ceramic.
MSOP-8 Pinout
f / MHz R3 / KΩ R4 / KΩ C4 / pF C6 / pF
0.7
22.1
22.1 2200
-
L1 / µH
10.5 (Falco D08019)
1.35 30.9
9.31
820
-
4.7 (Falco D08017)
2
63.4 4.75 470
22 3.3 (Coilcraft DO1813P)
Efficiency
95
10.5µH, 700KHz
90
4.7µH, 1.4MHz
85
80
3.3µH, 2MHz
75
70
65
60
55 VIN = 5V
VOUT = 12V
50
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Load Current (A)
Figure 1(a). 5V to 12V Boost Converter.
Revision: October 25, 2005
Figure 1(b). Efficiencies of 5V to 12V Boost Converters at
700KHz, 1.4MHz and 2MHz.
1 www.semtech.com
1 page  
SC4501
POWER MANAGEMENT
Pin Descriptions (MLPD - 10)
Pin Pin Name Pin Function
1
COMP
The output of the internal transconductance error amplifier. This pin is used for loop compensation.
2 FB The inverting input of the error amplifier. Tie to an external resistive divider to set the output voltage.
3 SHDN
www.DataSheet4U.com
4,5
GND
Shutdown Pin. The accurate 1.1V shutdown threshold and the 4.6uA shutdown pin current
hysteresis allow the user to set the undervoltage lockout threshold and hysteresis for the switching
regulator. Pulling this pin below 0.1V causes the converter to shut down to low quiescent current.
Tie this pin to IN if the UVLO and the shutdown features are not used. This pin should not be left
floating.
Ground. Tie both pins to the ground plane. Pins 4 and 5 are not internally connected.
6,7 SW Collector of the internal power transistor. Connect to the boost inductor and the rectifying diode.
8 IN Power Supply Pin. Bypassed with capacitors close to the pin.
9
ROSC
A resistor from this pin to the ground sets the switching frequency.
10
SS
Soft-Start Pin. A capacitor from this pin to the ground lengthens the start-up time and reduces start-
up current.
Exposed Pad The exposed pad must be soldered to the ground plane on the PCB for good thermal conduction.
Block Diagram
IN
8
4.6µA
SW SW
67
SHDN
3
1.1V
+
CMP
-
VOLTAGE
REFERENC E
THERMAL
SHUTDOWN
INTERNAL
SUPPLY
ENABL E
CLK
REG
FB
2
COM P
1
SS
10
1.242V
REG_GOOD
ENABL E
ROSC
9
© 2005 Semtech Corp.
+
EA
-
REG
1.5µA
-
PWM
+
R
Q
S
+
ILIM
-
I-LIM IT
CLK
+
Σ
+
OSCILLATOR
SLOPE COMP
+
ISEN
-
Figure 3. SC4501 (MLPD-10) Block Diagram.
5
RSENSE
45
GND GND
www.semtech.com
5 Page 
SC4501
POWER MANAGEMENT
Application Information
small sizes. However these types of capacitors have high
temperature and high voltage coefficients. For example,
the capacitance of a Z5U capacitor can drop below 60%
of its room temperature value at –25°C and 90°C. X5R
ceramic capacitors, which have stable temperature and
voltage coefficients, are the preferred type.
The diode current waveform in Figure 5 is discontinuous
with high ripple-content. In a buck converter the inductor
www.DatarTSihhpeepeltoe4Uuc.tcpuourmrternipt p∆leIL
determines
voltage of a
the output ripple
boost regulator is
voltage.
however
much higher and is determined by the absolute inductor
current. Decreasing the inductor ripple current does not
appreciably reduce the output ripple voltage. The current
flowing in the output filter capacitor is the difference
between the diode current and the output current. This
capacitor current has a RMS value of:
IOUT
VOUT
VIN
−1
(8)
If a tantalum capacitor is used, then its ripple current rating
in addition to its ESR will need to be considered.
When the switch is turned on, the output capacitor supplies
the load current IOUT (Figure 5). The output ripple voltage
due to charging and discharging of the output capacitor is
therefore:
forward voltages). This is because the diode conduction
interval is much longer than that of the transistor.
Converter efficiency will be improved if the voltage drop
across the diode is lower.
The rectifying diodes should be placed close to the SW
pins of the SC4501 to minimize ringing due to trace
inductance. Surface-mount equivalents of 1N5817,
1N5818, MBRM120 (ON Semi) and 10BQ015 (IRF) are
all suitable.
Soft-Start
Soft-start prevents a DC-DC converter from drawing
excessive current (equal to the switch current limit) from
the power source during start up. If the soft-start time is
made sufficiently long, then the output will enter regulation
without overshoot. An external capacitor from the SS pin
to the ground and an internal 1.5µA charging current
source set the soft-start time. The soft-start voltage ramp
at the SS pin clamps the error amplifier output. During
regulator start-up, COMP voltage follows the SS voltage.
The converter starts to switch when its COMP voltage
exceeds 0.7V. The peak inductor current is gradually
increased until the converter output comes into regulation.
If the shutdown pin is forced below 1.1V or if fault is
detected, then the soft-start capacitor will be discharged
to ground immediately.
The SS pin can be left open if soft-start is not required.
∆VOUT
=
IOUTDT
COUT
(9)
For most applications, a 10-22µF ceramic capacitor is
sufficient for output filtering. It is worth noting that the
output ripple voltage due to discharging of a 10µF ceramic
capacitor (9) is higher than that due to its ESR.
Rectifying Diode
For high efficiency, Schottky barrier diodes should be used
as rectifying diodes for the SC4501. These diodes should
have a RMS current rating of at least 1A and a reverse
blocking voltage of at least a few Volts higher than the
output voltage. For switching regulators operating at low
duty cycles (i.e. low output voltage to input voltage
conversion ratios), it is beneficial to use rectifying diodes
with somewhat higher RMS current ratings (thus lower
Shutdown
The input voltage and shutdown pin voltage must be greater
than 1.4V and 1.1V respectively to enable the SC4501.
Forcing the shutdown pin below 1.1V stops switching.
Pulling this pin below 0.1V completely shuts off the SC4501.
The total VIN current decreases to 10µA at 2V. Figure 6
shows several ways of interfacing the control logic to the
shutdown pin. Beware that the shutdown pin is a high
impedance pin. It should always be driven from a low-
impedance source or tied to a resistive divider. Floating
the shutdown pin will result in undefined voltage. In Figure
6(c) the shutdown pin is driven from a logic gate whose
VOH is higher than the supply voltage of the SC4501. The
diode clamps the maximum shutdown pin voltage to one
diode voltage above the input power supply.
© 2005 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet SC4501.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| SC450 | Dual Phase Power Supply Controller | Semtech Corporation |
| SC4501 | 2MHz Step-Up Switching Regulator | Semtech Corporation |
| SC4502 | 2MHz Step-Up Switching Regulator | Semtech Corporation |
| SC4502H | 2MHz Step-Up Switching Regulator | Semtech Corporation |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |