View ACT6305UC_4120059.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Data Sheet Rev PrA, 6/2006
ACT6305
Low Input High Efficiency Synchronous Step-Up DC-DC Converter
FEATURES
0.95V Typical Startup Voltage Up to 94% Efficiency Fully Integrated Power Stage Fixed 3.3V / 5V or Adjustable Output Voltage NanoStandbyTM Shutdown Mode Tiny SOT 23-5 Package
GENERAL DESCRIPTION
The ACT6305 is a high-efficiency synchronous step-up DC-DC converter that consumes just 17A of quiescent supply current and is capable of delivering more than 400mA output current using only three external components. This device achieves a typical startup voltage of just 0.95V, making this device ideal for applications operating from 1 or 2 alkaline cells. This device incorporates an internal synchronous rectifier, and achieves excellent peak efficiencies of up to 94% and features a proprietary control scheme that ensures high efficiency over a wide load current range. The ACT6305 voltages of 3.3V externally to any The ACT6305 is Package. features pin-selectable output or 5V, or it can also be set voltage between 2V and 5V. available in the tiny SOT23-5
APPLICATIONS
Hand-Held Devices One to Three Cell Battery Operated Devices PDAs Cellular Phones Digital Cameras GPS
4.7-6.8H
22F Ceramic
4.7- 10F Ceramic
VOUT= 5V
Figure 1. Typical Application Circuit
Active-Semi, Inc.
-1-
www.active-semi.com
ACT6305
ORDERING INFORMATION
PART NUMBER ACT6305UC TEMPERATURE RANGE -40 C to 85 C PACKAGE SOT23-5 PINS 5 TOP MARK HBCA
PIN CONFIGURATION
FB G EN 1 2 3 ACT6305 UC 4 LX 5 OUT
SOT23-5
PIN DESCRIPTION
PIN NUMBER 1 2 3 4 5 PIN NAME FB G EN LX OUT PIN DESCRIPTION Output Voltage Selected and Feedback Input. Connect to G to select VOUT = 5V. Connect to OUT to select VOUT = 3.3V. Connect to a resistor divider to set output voltage between 2V and 5V. Ground. Shutdown Input. Drive EN to IN or to a logic high for normal operation, drive to G or to a logic low to disable the regulator. Inductor Connection Output. ACT6305 regulates the voltage at this pin. OUT also provides power to the IC.
Active-Semi, Inc.
-2-
www.active-semi.com
ACT6305
ABSOLUTE MAXIMUM RATINGS
(Note: Exceeding these limits may damage the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.) PARAMETER VALUE UNIT
OUT, EN to G FB, LX to G Continuous LX Current Maximum Power Dissipation (derate 5mW/C above TA = 50C) Junction to Ambient Thermal Resistance ( JA) Operating Junction Temperature Storage Temperature Lead Temperature (Soldering, 10 sec)
-0.3 to 6 -0.3 to VOUT + 0.3 Internally Limited 0.53 190 -40 to 150 -55 to 150 300
V V A W C/W C C C
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = 1.5V, VOUT = 3.3V, TA = 25C unless otherwise specified.) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT
Minimum Operating Input Voltage Startup Voltage Output Voltage Startup to Normal Transition Voltage Threshold FB Feedback Voltage FB Input Current Power Switch Current Limit Power Switch On Resistance Synchronous Rectifier On Resistance LX Leakage Current Output Voltage Range Quiescent Current at OUT Shutdown Supply Current Maximum On Time Programming High Time Finish High Time Off Timeout Input Current VOUT FB = OUT FB = G 3.2 4.85
0.6 0.95 3.3 5 1.85
1.1 3.4 5.15
V V V V
VFB ILIM RONN RONP
VOUT = 2V to 5V FB = 1.3V ILX = 100mA ILX = 100mA SHDN = G, VLX = 0 or 3.3V External Feedback divider VFB = 1.3V SHDN = G VOUT = 2V to 5.5V
1.16 1
1.18 1.2 0.15 0.25 0.1 17 0.1 50
2
IQ ISD
tONMAX
1 500
1.2 0.1 1.4 0.3 0.5 1 5 34 1 5 75 500 1
V A A A V A A ns s s s A
tFINISH tOFF
300
Active-Semi, Inc.
-3-
www.active-semi.com
ACT6305
Figure 2. Functional Block Diagram
FUNCTIONAL DESCRIPTION
The ACT6305 comprises a reference, feedback select error comparator, control logic and timers, internal power MOSFETs and current comparators. The Functional Block Diagram is shown in Figure 2.
voltage.
LIGHT LOAD OPERATION
Under light load conditions, the IC automatically enters a power-saving mode by extending the OFF time. This reduces switching losses and allows the ACT6305 to maintain high efficiency across a very wide load range.
MAIN CONTROL LOOP
The ACT6305 control architecture utilizes a series of one-shot and current sense circuits to regulate the output voltage with very low quiescent supply current of just 17A. An ON cycle begins when FB falls below the ACT6305's internal reference voltage. During an ON cycle, the N-channel power switch is turned on to connect the LX node to ground, transferring energy from input supply to the inductor. The ON cycle persists until either the 5s maximum ON time is exceeded or the 1A current limit is reached. When either or these conditions occur, the N-channel power switch turns off and the OFF cycle begins. During the OFF cycle, the energy stored in the inductor is released into the output capacitor and load through the synchronous rectifier. Once the 1s minimum OFF time expires, another ON cycle begins when the FB voltage drops below the reference
LOW VOLTAGE START UP
The ACT6305 uses proprietary start-up circuitry that allows it to achieve very low voltage startup down to 0.95V. The ACT6305 remains in low-voltage startup mode until VOUT exceeds 1.85V. The ACT6305 cannot support it's full rated load current when operating in low-voltage startup mode, care should be taken to minimize load current during startup.
SHUTDOWN
In shutdown mode, all internal circuits including the power switch and the synchronous rectifier are disabled, reducing quiescent supply current to less than 1A. Note that in shutdown mode a DC path from the input supply to the output still exists due to the body diode of the synchronous rectifier.
Active-Semi, Inc.
-4-
www.active-semi.com
ACT6305
APPLICATION INFORMATION
OUTPUT VOLTAGE SELECTION
The ACT6305 uses proprietary circuitry that enables it to provide an one of three different output voltage options; the ATC6305 provides fixed output voltage options of 3.3V or 5V, or may be adjusted over a 1.2V to 5V range by connecting an external resistive voltage divider. (as shown Figure 3). FB = OUT FB = G FB connected to resistive divider VOUT = 3.3V VOUT = 5V VOUT = 1.18V (1+R1/R2) the IC. The output capacitor value should be in the range of 22F to 100F. To obtain small output ripple, use a large capacitor with low ESR; ceramic capacitors should be used for highest performance. If a tantalum capacitor is used, choose only low ESR types and a smaller low-ESR capacitor of about 1F can be connected in parallel to filter high frequency noise.
INDUCTOR SELECTION
For most applications, the inductor value should be in the range of 10H to 47H. Smaller inductors provide faster load transient response and have a smaller physical size, but they also result in higher ripple current and reduce the maximum available output current. Choose inductors with low series resistance to obtain the highest efficiency.
BOARD LAYOUT
To reduce noise and increase efficiency, high current traces should be wide and direct, and an extended ground plane should be used. Switching current paths should be laid out as tightly as possible, with the inductor and input and output capacitors located close to the IC, in order to reduce electromagnetic radiation.
Figure 3.
OUTPUT CAPACITOR SELECTION
A minimum value of capacitance is required to maintain loop stability and normal operation of
If the external resistor divider is used, place the resistors very close to the FB and G pins, and keep them away from the high switching current paths.
Active-Semi, Inc.
-5-
www.active-semi.com
ACT6305
TYPICAL PERFORMANCE CHARACTERISTICS
Active-Semi, Inc.
-6-
www.active-semi.com
ACT6305
TYPICAL PERFORMANCE CHARACTERISTICS CONT'D
Title
Active-Semi, Inc.
-7-
www.active-semi.com
ACT6305
TYPICAL PERFORMANCE CHARACTERISTICS CONT'D
DCM Mode Connection Low ESR Output Capacitor VOUT(50mV/Div)
VOUT VVOUT = 3.3V = 3.3V OUT VVIN = 1.2V = 1.2V IN I ILOAD = 10mA = 10mA
LOAD
Current Limit Condition Low ESR Output Capacitor VOUT (100mV/Div)
VOUT VOUTOUT 3.3V V = = 3.3V VINVIN 2.4V = = 2.4V ILOAD = 408mA ILOAD = 408mA
V(LX)
V(LX)
V(LX) (2V/Div) Time: 5s/Div
V(LX) (2V/Div) Time: 2.5s/Div
Heavy Load Condition Low ESR Output Capacitor VOUT(100mV/Div)
VOUT VOUT = 5.2V VIN = 3.6V ILOAD = 400mA V(LX)
DCM Mode Connection High ESR Output Capacitor VOUT(100mV/Div)
VOUT
VOUT = 3.3V VIN = 2.4V ILOAD = 112mA
V(LX)
V(LX) (2V/Div) Time: 2.5s/Div
V(LX) (2V/Div) Time: 25s/Div
Heavy Load Condition High ESR Output Capacitor VOUT(100mV/Div)
VOUT VOUT = 3.3V VIN = 2.4V ILOAD = 340mA
V(LX)
V(LX) (2V/Div) Time: 5s/Div
Active-Semi, Inc.
-8-
www.active-semi.com
ACT6305
SOT23-5 PACKAGE OUTLINE AND DIMENSIONS
DIMENSION IN MILLIMETERS MIN MAX 1.050 1.250 0.000 0.100 1.050 1.150 0.300 0.400 0.100 0.200 2.820 3.020 1.500 1.700 2.650 2.950 0.950 TYP 1.800 2.000 0.700 REF 0.300 0.600 0 8 DIMENSION IN INCHES MIN MAX 0.041 0.049 0.000 0.004 0.041 0.045 0.012 0.016 0.004 0.008 0.111 0.119 0.059 0.067 0.104 0.116 0.037 TYP 0.071 0.079 0.028 REF 0.012 0.024 0 8
SYMBOL A A1 A2 b c D E E1 e e1 L L1
Active-Semi, Inc. reserves the right to modify the circuitry or specifications without notice. Users should evaluate each product to make sure that it is suitable for their applications. Active-Semi products are not intended or authorized for use as critical components in life-support devices or systems. Active-Semi, Inc. does not assume any liability arising out of the use of any product or circuit described in this data sheet, nor does it convey any patent license. Active-Semi and its logo are trademarks of Active-Semi, Inc. For more information on this and other products, contact sales@active-semi.com or visit www.active-semi.com. For other inquiries, please send to: 1270 Oakmead Parkway, Suite 310, Sunnyvale, California 94085-4044, USA
Active-Semi, Inc.
-9-
www.active-semi.com

▲Up To Search▲

Price & Availability of ACT6305UC

	To Download ACT6305UC Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .