Datenblatt-pdf.com

ACT4072 Schematic ( PDF Datasheet ) - Active-Semi

Teilenummer ACT4072
Beschreibung Wide Input 2A Step Down Converter
Hersteller Active-Semi
Logo Active-Semi Logo 



Gesamt 10 Seiten
		
ACT4072 Datasheet, Funktion
www.DataSheet4U.com
ACT4072
Rev 1, 12/2006
Wide Input 2A Step Down Converter
FEATURES
 2A Output Current
 Up to 95% Efficiency
 Up to 30V Input Range
 6µA Shutdown Supply Current
 400kHz Switching Frequency
 Adjustable Output Voltage
 Cycle-by-Cycle Current Limit Protection
 Thermal Shutdown Protection
 Frequency FoldBack at Short Circuit
 Stability with Wide Range of Capacitors,
Including Low ESR Ceramic Capacitors
 SOP-8 Package
APPLICATIONS
GENERAL DESCRIPTION
The ACT4072 is a current-mode step-down
DC/DC converter that generates up to 2A output
current at 400kHz switching frequency. The
device utilizes Active-Semi’s proprietary
ISOBCD30 process for operation with input
voltage up to 30V.
Consuming only 6µA in shutdown mode, the
ACT4072 is highly efficient with peak efficiency at
95% when in operation. Protection features
include cycle-by-cycle current limit, thermal
shutdown, and frequency foldback at short circuit.
The ACT4072 is available in SOP-8 package and
requires very few external devices for operation.
 TFT LCD Monitors or Televisions and HDTV
 Portable DVD Players
 Car-Powered or Battery-Powered Equipment
 Set-Top Boxes
 Telecom Power Supplies
 DSL and Cable Modems and Routers
TYPICAL APPLICATION CIRCUIT
Innovative Products. Active Solutions.
-1-
www.active-semi.com
Copyright © 2006 Active-Semi, Inc.






ACT4072 Datasheet, Funktion
www.DataSheet4U.com
ACT4072
Stability compensation
Figure 2:
Stability Compensation
: CCOMP2 is needed only for high ESR output capacitors or PCB
parasitics
The feedback system of the IC is stabilized by the
components at the COMP pin, as shown in Figure
2. The DC loop gain of the system is determined by
the following equation:
AVDC
1.222V
IOUT
AVEAGCOMP
(4)
The dominant pole P1 is due to CCOMP:
fP1
GEA
2AVEACCOMP
(5)
The second pole P2 is the output pole:
fP 2
IOUT
2VOUTCOUT
(6)
The first zero Z1 is due to RCOMP and CCOMP:
fZ1
1
2RCOMPCCOMP
(7)
And finally, the third pole is due to RCOMP and
CCOMP2 (if CCOMP2 is used):
fP 3
1
2R CCOMP COMP2
(8)
Follow the following steps to compensate the IC:
STEP 1. Set the cross over frequency at 1/10 of the
switching frequency via RCOMP:
RCOMP
2VOUT COUT fSW
10GEAGCOMP 1.222V
2.3
x10
V8
OUT
COUT
(Ω) (9)
but limit RCOMP to 15kΩ maximum.
STEP 2. Set the zero fZ1 at 1/4 of the cross over
frequency. If RCOMP is less than 15kΩ, the equation
for CCOMP is:
C COMP
1.8 10 5
RCOMP
(F) (10)
If RCOMP is limited to 15kΩ, then the actual cross
over frequency is 3.4/(VOUTCOUT). Therefore:
CCOMP 1.3 x105VOUTCOUT
(F) (11)
STEP 3. If the output capacitor’s ESR is high
enough to cause a zero at lower than 4 times the
cross over frequency, an additional compensation
capacitor CCOMP2 is required. The condition for using
CCOMP2 is:
RESROUT
Min

1.1x10
COUT
6
,0.012VOUT

)
(12)
And the proper value for CCOMP2 is:
CCOMP2
C ROUT ESROUT
RCOMP
(13)
A small value CCOMP2 such as 100pF may improve
stability against PCB layout parasitic effects.
Table 2 shows some calculated results based on the
compensation method above.
Table 2:
Typical Compensation for Different Output volt-
ages and Output Capacitors
VOUT
2.5V
COUT
22μF Ceramic
RCOMP CCOMP CCOMP2
8.2kΩ 2.2nF 100pF
3.3V 22μF Ceramic 12kΩ 1.5nF 100pF
5V 22μF Ceramic 15kΩ 1.5nF 100pF
2.5V 47μF SP CAP 15kΩ 1.5nF 100pF
3.3V 47μF SP CAP 15kΩ 1.8nF 100pF
5V 47μF SP CAP 15kΩ 2.7nF 100pF
2.5V 470µF/6.3V/30mΩ 15kΩ 15nF 1nF
3.3V 470µF/6.3V/30mΩ 15kΩ 22nF 1nF
5V 470µF/6.3V/30mΩ 15kΩ 27nF 1nF
: CCOMP2 is needed for board parasitic and high ESR output
capacitor.
Figure 3 shows an example ACT4072 application
circuit generating a 5V/2A output.
Innovative Products. Active Solutions.
-6-
www.active-semi.com
Copyright © 2006 Active-Semi, Inc.

6 Page


SeitenGesamt 10 Seiten
PDF Download[ ACT4072.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
ACT4070Wide Input 3A Step Down ConverterActive-Semi
Active-Semi
ACT4070Wide Input 3A Step Down ConverterActive-Semi
Active-Semi
ACT4070BWide Input 3A Step Down ConverterActive-Semi
Active-Semi
ACT4072Wide Input 2A Step Down ConverterActive-Semi
Active-Semi
ACT4075Wide Input 2.5A 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