Datenblatt-pdf.com


ACT4050 Schematic ( PDF Datasheet ) - Active-Semi

Teilenummer ACT4050
Beschreibung Wide Input 3.5A Step Down Converter
Hersteller Active-Semi
Logo Active-Semi Logo 




Gesamt 13 Seiten
ACT4050 Datasheet, Funktion
Active-Semi
ACT4050
Rev 2, 01-Jul-11
Wide Input 3.5A Step Down Converter
FEATURES
3.5A Output Current
Up to 96% Efficiency
4.5V to 15V Input Range
12µA Shutdown Supply Current
400kHz Switching Frequency
Adjustable Output Voltage From 0.817V
Cycle-by-Cycle Current Limit Protection
Thermal Shutdown Protection
Frequency Fold-Back at Short Circuit
Stability with Wide Range of Capacitors,
Including Low ESR Ceramic Capacitors
SOP-8/EP (Exposed Pad) Package
APPLICATIONS
Digital TV
Portable DVDs
Car-Powered or Battery-Powered Equipments
Set-Top Boxes
Telecom Power Supplies
Consumer Electronics
GENERAL DESCRIPTION
The ACT4050 is a current-mode step-down DC/DC
converter that provides up to 3.5A of output current
at 400kHz switching frequency. The device utilizes
Active-Semi’s proprietary high voltage process for
operation with input voltages up to 15V.
The ACT4050 provides fast transient response and
eases loop stabilization while providing excellent
line and load regulation. This device features a very
low ON-resistance power MOSFET which provides
peak operating efficiency up to 96%. In shutdown
mode, the ACT4050 consumes only 12μA of supply
current.
This device also integrates protection features
including cycle-by-cycle current limit, thermal
shutdown and frequency fold-back at short circuit.
The ACT4050 is available in a SOP-8/EP (Exposed
Pad) package and requires very few external
devices for operation.
TYPICAL APPLICATION CIRCUIT
Efficiency vs. Load Current
100
VIN = 7V
90
VIN = 12V
80
70
60
50 VOUT = 5V
0 500 1000 1500 2000 2500 3000 3500
Load Current (mA)
Innovative PowerTM
- 1 - www.active-semi.com
Copyright © 2011 Active-Semi, Inc.






ACT4050 Datasheet, Funktion
Active-Semi
ACT4050
Rev 2, 01-Jul-11
APPLICATIONS INFORMATION
Output Voltage Setting
Figure 1:
Output Voltage Setting
VOUT
ACT4050
FB
RFB1
RFB2
Figure 1 shows the connections for setting the
output voltage. Select the proper ratio of the two
feedback resistors RFB1 and RFB2 based on the
output voltage. Typically, use RFB2 10kand
determine RFB1 from the following equation:
R FB 1
=
R FB
2
⎜⎛
VOUT
0 .817
V
1 ⎟⎞
(1)
Note: To achieve best performance with 12V input application,
we recommend to use output voltage greater than 1.4V.
LLIM is the internal current limit, as shown in
Electrical Characteristics Table.
Input Capacitor
The input capacitor needs to be carefully selected to
maintain sufficiently low ripple at the supply input of
the converter. A low ESR capacitor is highly
recommended. Since large current flows in and out
of this capacitor during switching, its ESR also
affects efficiency.
The input capacitance needs to be higher than
10µF. The best choice is the ceramic type,
however, low ESR tantalum or electrolytic types
may also be used provided that the RMS ripple
current rating is higher than 50% of the output
current. The input capacitor should be placed close
to the IN and G pins of the IC, with the shortest
traces possible. In the case of tantalum or
electrolytic types, they can be further away if a small
parallel 0.1µF ceramic capacitor is placed right next
to the IC.
Inductor Selection
The inductor maintains a continuous current to the
output load. This inductor current has a ripple that is
dependent on the inductance value: higher
inductance reduces the peak-to-peak ripple current.
The trade off for high inductance value is the
increase in inductor core size and series resistance,
and the reduction in current handling capability. In
general, select an inductance value L based on
ripple current requirement:
( )L
=
VOUT × VIN VOUT
V f I KIN SW OUTMAX RIPPLE
(2)
where VIN is the input voltage, VOUT is the output
voltage, fSW is the switching frequency, IOUTMAX is the
maximum output current, and KRIPPLE is the ripple
factor. Typically, choose KRIPPLE = 30% to
correspond to the peak-to-peak ripple current being
30% of the maximum output current.
With a selected inductor value the peak-to-peak
inductor current is estimated as:
( )ILPK -PK
=
VOUT × VIN
L × VIN ×
- VOUT
fSW
(3)
The peak inductor current is estimated as:
ILPK
= ILOADMAX
+
1
2
ILPK
- PK
(4)
The selected inductor should not saturate at ILPK.
The maximum output current is calculated as:
I OUTMAX
= I LIM
-
1
2
I LPK
- PK
(5)
Output Capacitor
The output capacitor also needs to have low ESR to
keep low output voltage ripple. The output ripple
voltage is:
VRIPPLE
= IOUTMAX K RRIPPLE ESR
+
28
VIN
× fSW 2 LCOUT
(6)
where IOUTMAX is the maximum output current, KRIPPLE
is the ripple factor, RESR is the ESR of the output
capacitor, fSW is the switching frequency, L is the
inductor value, and COUT is the output capacitance. In
the case of ceramic output capacitors, RESR is very
small and does not contribute to the ripple.
Therefore, a lower capacitance value can be used for
ceramic type. In the case of tantalum or electrolytic
capacitors, the ripple is dominated by RESR multiplied
by the ripple current. In that case, the output
capacitor is chosen to have sufficiently low ESR.
For ceramic output capacitor, typically choose a
capacitance of about 22µF. For tantalum or
electrolytic capacitors, choose a capacitor with less
than 50mESR.
Rectifier Diode
Use a Schottky diode as the rectifier to conduct
current when the High-Side Power Switch is off. The
Schottky diode must have current rating higher than
the maximum output current and a reverse voltage
rating higher than the maximum input voltage.
Innovative PowerTM
- 6 - www.active-semi.com
Copyright © 2011 Active-Semi, Inc.

6 Page









ACT4050 pdf, datenblatt
Active-Semi
ACT4050
Rev 2, 01-Jul-11
TYPICAL PERFORMANCE CHARACTERISTICS CONT’D
(Circuit of Figure 5, unless otherwise specified.)
Start-up/Shutdown by VIN Pin
Start-up/Shutdown by VIN Pin
CH1
CH2
VIN = 12V
VOUT = 5V
No Load
CH1: VIN, 5.0V/div
CH2: VOUT, 2V/div
TIME: 100µs/div
VIN = 12V
VOUT = 5V
ILOAD = 1A
Start-up/Shutdown by EN Pin
CH1
CH1
CH2
VIN = 12V
VOUT = 5V
1Load
CH1: VIN, 5.0V/div
CH2: VOUT, 2V/div
TIME: 100µs/div
Start-up/Shutdown by EN Pin
CH1
CH2
VIN = 12V
VOUT = 5V
No Load
CH1: VEN, 2.0V/div
CH2: VOUT, 2.0V/div
TIME: 400µs/div
Switching Waveform
CH1
CH2
VIN = 12V
VOUT = 3.3V
ILOAD = 1A
CH1: VOUT, 20mV/div (AC COUPLED)
CH2: VSW, 5.0V/div
TIME: 1µs/div
Innovative PowerTM
CH2
VIN = 12V
VOUT = 5V
2Load
CH1: VEN, 2.0V/div
CH2: VOUT, 2.0V/div
TIME: 200µs/div
Switching Waveform
CH1
CH2
VIN = 12V
VOUT = 5V
ILOAD = 1A
CH1: VOUT, 20mV/div (AC COUPLED)
CH2: VSW, 5.0V/div
TIME: 1µs/div
- 12 -
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.

12 Page





SeitenGesamt 13 Seiten
PDF Download[ ACT4050 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
ACT4050Wide Input 3.5A Step Down ConverterActive-Semi
Active-Semi

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche