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PDF ACT4060B Data sheet ( Hoja de datos )
| Número de pieza | ACT4060B | |
| Descripción | 18V/2A Step-Down DC/DC Converter | |
| Fabricantes | Active-Semi | |
| Logotipo |  |
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® ACT4060B
Rev 1, 23-May-12
18V/2A Step-Down DC/DC Converter
FEATURES
• 2A Output Current
• Wide 4.5V to 18V Operating Input Range
• Synchronous Buck Topology
• Integrated 130mΩ Power MOSFET Switches
• Output Adjustable from 0.923V to 12V
• Up to 96% Efficiency
• Stable with Low ESR Ceramic Output
Capacitors
• Internal Soft Start
• 1.5mA Low Standby Input Current
• High Light Load Efficiency
• Cycle-by-Cycle Over Current Limit
• Input Under Voltage Lockout
• Hiccup Protection at Short Circuit and Over
Current
• Low Power Loss at Output Short
• Frequency Fold Back Protection
• Low Power Dissipation at Over Current and
Short Circuit
APPLICATIONS
• LCD-TV
• Set-top Box
• Distributed Power Systems
• Networking Systems
GENERAL DESCRIPTION
ACT4060B is a monolithic synchronous buck
regulator. The device integrates two 130mΩ
MOSFETs, and provides 2A of continuous load
current over a wide input voltage of 4.5V to 18V.
Current mode control provides fast transient
response and cycle-by-cycle current limit. Hiccup at
short circuit reduces IC temperatures.
An internal soft-start prevents inrush current at turn-
on, and in shutdown mode the supply current drops
to 10μA. Pulse-skipping mode at light load reduces
standby power down to 1.5mA.
This device, available in an 8-pin SOP package,
provides a very compact solution with minimal
external components.
Innovative PowerTM
Efficiency vs. Load Current
100
95 VIN = 7V
90
85 VIN = 18V
80
75 VIN = 12V
70
65
60
55
10
VOUT = 5V
100
1000
10000
Load Current (mA)
- 1 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
1 page  
®
FUNCTIONAL BLOCK DIAGRAM
ACT4060B
Rev 1, 23-May-12
FUNCTIONAL DESCRIPTION
As seen in Function Block Diagram, the ACT4060B
is peak current mode controlled synchronous Buck
converter. 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 and the Low-Side Power Switch turns on. 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 0.923V
reference. If FB is lower than the reference voltage,
COMP tends to go higher to increase current to the
output to keep the output voltage regulated. The
Oscillator normally switches at 350kHz.
Pulse Skipping Mode
To decrease the power recycling at very light load,
the low-side FET current is sensed to emulate a
diode. When the low-side FET current decreases to
zero, the FET is turned off to avoid negative
inductor current. At no load and very light load,
ACT4060B skips pulse automatically and thus
achieve very high light load efficiency. With load
increasing, ACT4060B goes into Discontinuous
Current Mode (DCM) and then Continuous Current
Mode (CCM).
Soft Startup
The ACT4060B builds in internal soft startup
function. The internal FB reference voltage rises to
steady state of 0.923V in 2ms to avoid inrush input
current during startup.
Under Voltage Protection (UVP)
At output short circuit or over current, the FB
voltage is usually pulled low. To protect the IC at
over current and short circuit, the ACT4060B builds
in Under Voltage Protection (UVP) function. When
ACT4060B detects the FB voltage below 80% of
the 0.923V reference, it pulls low COMP voltage
and discharges internal soft-start capacitor and
goes into hiccup mode. The IC restarts in 32ms
after going into hiccup mode. If the short circuit or
over current is clear, the IC restarts back to
normal mode. The UVP is disabled for 6ms
starting from startup. If the output is short at
startup, the output voltage never rises to nominal
voltage. During the 6ms period of time, the output
current is limited by cycle-by-cycle current limit.
With 32ms shutdown period, the average input and
output current at short circuit is significantly reduced
and the IC is more reliable.
Innovative PowerTM
- 5 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
5 Page 
®
Figure 5:
Typical Application Circuit for 5V/2A DC-DC Converter
ACT4060B
Rev 1, 23-May-12
Table 4:
BOM List for 5V/2A DC-DC Converter
ITEM REFERENCE
DESCRIPTION
1 U1 IC, ACT4060BSH, SOP-8
2 C1 Capacitor, Ceramic, 10µF/50V, 1210, SMD
3 C2 Capacitor, Ceramic, 6.8nF/6.3V, 0603, SMD
4 C3 Capacitor, Ceramic, 10nF/50V, 0603, SMD
5
C4,C5
Capacitor, Ceramic, 22µF/10V, 1206, SMD
6 L1 Inductor, 22µH, 3A, 20%
7 D1 Diode, 75V/150mA, LL4148
8 R1 Chip Resistor, 47kΩ, 0603, 1%
9 R2 Chip Resistor, 10.5kΩ, 0603, 1%
10 R3 Chip Resistor, 8.2kΩ, 0603, 5%
MANUFACTURER
Active-Semi
Murata, TDK
Murata, TDK
Murata, TDK
Murata, TDK
Sumida
Good-ARK
Murata, TDK
Murata, TDK
Murata, TDK
QTY
1
1
1
1
2
1
1
1
1
1
Innovative PowerTM
- 11 -
www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ACT4060B.PDF ] | |
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