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PDF ACT4455YH-T Data sheet ( Hoja de datos )
| Número de pieza | ACT4455YH-T | |
| Descripción | 36V/5A Step Down DC/DC Converter | |
| Fabricantes | Active-Semo | |
| Logotipo |  |
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ACT4455
Rev 2, 21-Nov-12
36V/5A Step Down DC/DC Converter
FEATURES
• 7.5V to 36V Input Voltage
• 40V Input Voltage Surge
• Up to 5A Output Current
• Up to 12V Output Voltage
• Dual Outputs with Independent Over Current
Protection
• 7.5% Accurate Over Current Protection (OCP)
• Integrated 45mΩ High Side Power FET
• 90% Efficiency at Heavy Load
• Internal 3ms Soft Startup
• Low Standby Input Current
• Sleeping Mode at OCP, OTP and SCP
• Zero Input and Output Currents at Over Current
and Short Circuit Protection
• Auto Recovery into Full Load after Faults
• Output Cord Voltage Drop Compensation
• Stable with Low ESR Ceramic Output Capacitors
• Internal Cycle-by-Cycle Current Control
• Programmable Over Current Setting
• SOP-8EP Package
APPLICATIONS
• Automotive Industry
• Dual-Output Car Charger
• LCD-TV
GENERAL DESCRIPTION
ACT4455 is a wide input voltage step-down DC/DC
converter with high-side MOSFET integrated. It
provides up to 5A continuous output current at
200kHz switching frequency. The converter can be
configured as single output or dual outputs with
independent over current protection. The converter
achieves high efficiency and excellent load and line
regulation. The converter enters into hiccup and
sleeping mode and the converter power
consumption is nearly zero when output is
overloaded or shorted to ground. Other protection
features includes cycle-by-cycle current limit, under
voltage protection and thermal shutdown. The
device is available in SOP8-EP package.
100
90
80
70
60
50
0
Efficiency vs. Load current
VIN = 12V
VIN = 32V
VIN = 24V
1000
2000
3000
4000 5000
Efficiency (%)
Innovative PowerTM
- 1 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
1 page  
FUNCTIONAL BLOCK DIAGRAM
ACT4455
Rev 2, 21-Nov-12
FUNCTIONAL DESCRIPTION
Operation
As seen in Functional Block Diagram, the ACT4455
is a current mode controlled regulator. The EA
output voltage (COMP voltage) is proportional to
the peak inductor current.
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. 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
inductor freewheels through the schottky diode
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 internal 0.808V reference. If
FB is lower than the reference voltage, COMP
tends to go higher to increase current to the output.
Over Current and Short Circuit
Protection
CS pins are connected to the high side of current
sensing resistors to prevent output over current.
With independent CS1 and CS2 pins, two output
currents are detected. If the voltage at either CS
pins exceeds 116mV for more than 750µs. The
converter shuts down and goes into sleeping mode.
A new soft startup is triggered after 2.5s. If the fault
condition is un-cleared, the converter shuts down
again until over current condition is cleared. With
this long-waiting-time hiccup mode, the power
consumption at over loading or outputs short is
reduced to nearly zero.
Thermal Shutdown
The ACT4455 shuts down when its junction
temperature exceeds 150°C. The converter triggers
a soft-start when the temperature has dropped by
10°C. The soft-restart avoids output over voltage at
thermal hiccup.
Innovative PowerTM
- 5 - www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
5 Page 
ACT4455
Rev 2, 21-Nov-12
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 7, RCS1 = RCS2 = 50mΩ, L = 18µH, CIN = 150µF, COUT = 680µF, TA = 25°C, unless otherwise specified.)
100
90
80
70
60
50
0
Efficiency vs. Load current
VIN = 12V
VIN = 32V
VIN = 24V
1000
2000
3000
Efficiency (%)
4000 5000
Switching Frequency vs. Feedback Voltage
250
200
150
100
50
0
0 0.2 0.4 0.6 0.8 1
Feedback Voltage (mV)
Switching Frequency vs. Input Voltage
250
200
150
100
50
0
5 10 15 20 25 30 35 40
Input Voltage (V)
Maximum Peak Current vs. Duty Cycle
9
8.5
8
7.5
7
6.5
6
0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85
Duty cycle
Standby Current vs. Input Voltage
940
920
900
880
860
840
820
800
5
10 15 20 25 30 35 40
Input Voltage (V)
Input Current vs. Input Voltage at No Load
14
12
10
8
6
4
2
0
5 10 15 20 25 30 35 40
Input Voltage (V)
Innovative PowerTM
- 11 -
www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet ACT4455YH-T.PDF ] | |
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