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PDF ACT4050 Data sheet ( Hoja de datos )
| Número de pieza | ACT4050 | |
| Descripción | Wide Input 3.5A Step Down Converter | |
| Fabricantes | Active-Semi | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de ACT4050 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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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.
1 page  
Active-Semi
addition to the open-drain or open-collector logic
device. When the logic pull-down is disabled, the
voltage at EN will ramp up at a rate determined by
the 2µA EN pull-up current and the capacitor.
Once the voltage at EN exceeds the 1.1V
threshold, the device will be enabled. For the
case of using multiple ACT4050, time-based
output sequencing can be generated by placing
different capacitors at each ACT4050 EN pin.
The start up time delay can be calculated as a
simple function of the EN capacitor using the
equation:
T (ms) = 0.55 × CEN (nF)
Table 1:
Enable Delay Time vs. EN Capacitor Value
CAPACITOR VALUE
2.2nF
3.3nF
10nF
DELAY TIME (ms)
1.2
1.9
5.5
4) Fourth, by using the 1.1V precision comparator in
the EN circuitry, "power-OK" type output
sequencing can be generated. By connecting the
EN pin of one ACT4050 to the output of another
device, the ACT4050 will only start up once the
second device's output has exceeded the 1.1V
level. A resistor divider can be used to adjust the
ACT4050 startup to any point on the second
device's output range.
5) Finally, the EN comparator can be used for "Line
UVLO" to prevent the ACT4050 from starting up
before the input voltage is high enough to
support the output. By using a resistor divider
from VIN to GND (center tap = 1.1V EN
threshold), the device can be enabled and
disabled based on the voltage at VIN. Since the
internal UVLO voltage is 4.2V, Line UVLO is
recommended for outputs above this 4.2V level
to ensure clean startup. For the example of a 5V
output, it is desirable to prevent IC startup until
VIN has exceeded the 5V level. To start the IC at
6V input, we place a 10kΩ/47kΩ resistor divider
from VIN to EN to GND, which enables the IC at
VIN greater than 6.3V and disables the IC when
VIN decreases below 5.2V.
Thermal Shutdown
The ACT4050 automatically turns off when its junction
temperature exceeds 160°C and automatically turns
on again when the junction temperature falls below
140°C .
Innovative PowerTM
-5-
ACT4050
Rev 2, 01-Jul-11
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
5 Page 
Active-Semi
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 5, unless otherwise specified.)
ACT4050
Rev 2, 01-Jul-11
Efficiency vs. Load Current
100
VIN = 5V
90
VIN = 7V
80
VIN = 12V
70
60
50
0
VOUT = 3.3V
500 1000 1500 2000 2500 3000 3500
Load Current (mA)
Shutdown Current vs. Input Voltage
25
20
15
10
5
0
4 6 8 10 12 14
Input Voltage (V)
Efficiency vs. Load Current
100 VIN = 7V
90
VIN = 12V
80
70
60
50
0
VOUT = 5V
500 1000 1500 2000 2500 3000 3500
Load Current (mA)
Inductor Peak Current Limit vs. Duty
Cycle
6000
5500
5000
4500
4000
3500
3000
2500
2000
0
20 40 60 80
Duty Cycle (% )
100
Switching Frequency vs. Temperature
490
460
430
400
370
340
310
280
250
-40
0 40 80
Temperature (°C)
130
0.85
0.84
0.83
0.82
0.81
0.80
0.79
0.78
0.77
0.76
0.75
-40
Feedback Voltage vs. Temperature
0 40 80
Temperature (°C)
130
Innovative PowerTM
- 11 -
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet ACT4050.PDF ] | |
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