Active-Semi
ACT4523
Rev 4, 21-Jul-11
Wide-Input Sensorless CC/CV Step-Down DC/DC Converter
FEATURES
• 40V Input Voltage Surge
• 38V Steady State Operation
• Up to 3A output current
• Output Voltage up to 12V
• Patent Pending Active CC Sensorless Constant
Current Control
− Integrated Current Control Improves
Efficiency, Lowers Cost, and Reduces
Component Count
• Resistor Programmable
− Current Limit from 1.5A to 3A
− Patented Cable Compensation from 0Ω to
0.3Ω
• ±7.5% CC Accuracy
− Compensation of Input /Output Voltage Change
− Temperature Compensation
− Independent of inductance and Inductor DCR
• 2% Feedback Voltage Accuracy
• Up to 94% Efficiency
• 225kHz 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-8EP Package
APPLICATIONS
• Car Charger/ Adaptor
• Rechargeable Portable Devices
• General-Purpose CC/CV Supply
GENERAL DESCRIPTION
ACT4523 is a wide input voltage, high efficiency
Active CC step-down DC/DC converter that
operates in either CV (Constant Output Voltage)
mode or CC (Constant Output Current) mode.
ACT4523 provides up to 3A output current at
225kHz switching frequency.
Active CC is a patent-pending control scheme to
achieve highest accuracy sensorless constant
current control. Active CC eliminates the expensive,
high accuracy current sense resistor, making it ideal
for battery charging applications and adaptors with
accurate current limit. The ACT4523 achieves
higher efficiency than traditional constant current
switching regulators by eliminating 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-
8EP package and require very few external devices
for operation.
Input 10V to 40V
ENABLE
HSB
IN
SW
ACT4523
EN
FB
ISET GND COMP
C3
22nF
50V
5V
L1 30µH
R2 52k
C1
47µF
R1 C2
R4
11.5k 2.2nF
10k
R3
8.2k
D1
SK34
C4
220µF
Innovative PowerTM
-1-
CC/CV Curve
6.0
VIN = 24V
5.0
4.0
VIN = 12V
3.0
2.0
1.0
0.0
0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2
Output Current (A)
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