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PDF ACT4501 Data sheet ( Hoja de datos )
| Número de pieza | ACT4501 | |
| Descripción | 1.25A CC/CV Step-Down DC/DC Converter | |
| Fabricantes | Active-Semi | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de ACT4501 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
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ACT4501
Rev 2, 14-Nov-12
1.25A CC/CV Step-Down DC/DC Converter
FEATURES
• 10V-30V Input Voltage
• 40V Transparent Input Voltage Surge
• Up to 1.25A Constant Output Current
• Output Voltage up to 12V
• Good EMC Performance on Single Layer PCB
• Patent Pending ActiveCC Constant Current
Control
− Integrated Current Control Improves
Efficiency, Lowers Cost, and Reduces
Component Count
• Resistor Programmable Outputs
− Current Limit from 500mA to 1250mA
Patented cable compensation from DC Cable
Compensation from 0Ω to 0.5Ω
• 2% Feedback Voltage Accuracy
• Up to 90% Efficiency
• 125kHz Switching Frequency Eases EMI Design
• Advanced Feature Set
− Integrated Soft Start
− Thermal Shutdown
− Secondary Cycle-by-Cycle Current Limit
− Protection Against Shorted ISET Pin
• SOP-8 Package
APPLICATIONS
• Car Charger
• Rechargeable Portable Devices
• General-Purpose CC/CV Power Supply
GENERAL DESCRIPTION
ACT4501 is a dedicated cost-effective DC-DC
converter for 5V/1A car charger applications with a
wide input voltage and high efficiency. The
converter operates in either CV (Constant Output
Voltage) mode or CC (Constant Output Current)
mode. ACT4501 provides up to 1.25A output
current at 125kHz switching frequency.
ActiveCC is a patent-pending control scheme to
achieve high accuracy sensorless constant current
control. ActiveCC eliminates the expensive, high
accuracy current sense resistor, making it ideal for
battery charging applications and high-brightness
LED drive for architectural lighting. The ACT4501
achieves higher efficiency than traditional constant
current switching regulators by eliminating the
sense resistor and its associated power loss.
Protection features include cycle-by-cycle current
limit, thermal shutdown, and frequency foldback at
short circuit. The devices are available in a SOP-8
package and require very few external devices for
operation.
Innovative PowerTM
100
90
80
70
60
50
40
1
Efficiency vs. Load Current
VIN = 12V
VIN = 16V
VIN = 24V
VOUT = 5V
10
100
1000
10000
Load Current (mA)
- 1 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
1 page  
ACT4501
Rev 2, 14-Nov-12
FUNCTIONAL BLOCK DIAGRAM
AVIN
IN
BANDGAP,
REGULATOR,
EN &
OSCILLATOR
SHUTDOWN
CONTROL
VREF = 0.808V
VREF = 0.808V
FB
+
-
CC
CONTROL
COMP
ISET
PVIN
EMI
CONTROL
PWM
CONTROLLER
HSB
SW
FUNCTIONAL DESCRIPTION
CV/CC Loop Regulation
As seen in Functional Block Diagram, the ACT4501
is a peak current mode pulse width modulation
(PWM) converter with CC and CV control. The
converter operates as follows:
A switching cycle starts when the rising edge of the
Oscillator clock output causes the High-Side Power
Switch to turn on and the Low-Side Power Switch to
turn off. With the SW side of the inductor now
connected to IN, the inductor current ramps up to
store energy in the magnetic field. The inductor
current level is measured by the Current Sense
Amplifier and added to the Oscillator ramp signal. If
the resulting summation is higher than the COMP
voltage, the output of the PWM Comparator goes
high. When this happens or when Oscillator clock
output goes low, the High-Side Power Switch turns
off.
At this point, the SW side of the inductor swings to
a diode voltage below ground, causing the inductor
current to decrease and magnetic energy to be
transferred to output. This state continues until the
cycle starts again. The High-Side Power Switch is
driven by logic using HSB as the positive rail. This
pin is charged to VSW + 5V when the Low-Side
Power Switch turns on. The COMP voltage is the
integration of the error between FB input and the
internal 0.808V reference. If FB is lower than the
reference voltage, COMP tends to go higher to
increase current to the output. Output current will
increase until it reaches the CC limit set by the ISET
resistor. At this point, the device will transition from
regulating output voltage to regulating output
current, and the output voltage will drop with
increasing load.
The Oscillator normally switches at 125kHz.
However, if FB voltage is less than 0.6V, then the
switching frequency decreases until it reaches a
typical value of 20kHz at VFB = 0.15V.
Enable Pin
The ACT4501 has an enable input EN for turning
the IC on or off. The EN pin contains a precision
0.8V comparator with 75mV hysteresis and a 4µA
pull-up current source. The comparator can be used
with a resistor divider from VIN to program a startup
voltage higher than the normal UVLO value. It can
be used with a resistor divider from VOUT to disable
charging of a deeply discharged battery, or it can be
used with a resistor divider containing a thermistor
to provide a temperature-dependent shutoff
protection for over temperature battery. The
thermistor should be thermally coupled to the
battery pack for this usage.
If left floating, the EN pin will be pulled up to roughly
5V by the internal 4µA current source. It can be
driven from standard logic signals greater than
0.8V, or driven with open-drain logic to provide
digital on/off control.
Thermal Shutdown
The ACT4501 disables switching when its junction
temperature exceeds 155°C and resumes when the
temperature has dropped by 20°C.
Innovative PowerTM
- 5 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
5 Page 
ACT4501
Rev 2, 14-Nov-12
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 7, IISET = 1A, L = 82µH, CIN = 10µF, COUT = 22µF, TA = 25°C, unless otherwise specified.)
100
90
80
70
60
50
40
1
Efficiency vs. Load Current
VIN = 12V
VIN = 16V
VIN = 24V
VOUT = 5V
10
100
1000
10000
Load Current (mA)
Switching Frequency vs. Feedback Voltage
140
120
100
80
60
40
20
0
0 0.2 0.4 0.6 0.8 1
Feedback Voltage (V)
Switching Frequency vs. Input Voltage
130
125
120
115
110
105
5
100
10 15 20 25 30 35
Input Voltage (V)
1000
900
CC Current vs. Temperature
VIN = 12V
RISET = 33kΩ
800
700
600
500
400
-40 -25 0 25 50 75
Temperature (°C)
80
CC Current vs. Input Voltage
1000
RISET = 33kΩ
900
800
700
600
500
400
10
12 18 24
Input Voltage (V)
30
2500
2250
2000
1750
1500
1250
1000
750
500
250
0
0
Peak Current Limit vs. Duty Cycle
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Duty Cycle
Innovative PowerTM
- 11 -
www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ACT4501.PDF ] | |
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