ACTIVE-SEMI ACT6305 Low input high efficiency synchronous step-up dc/dc converter Datasheet

ACT6305
Rev 2, 22-Feb-11
Low Input High Efficiency
Synchronous Step-Up DC/DC Converter
FEATURES
GENERAL DESCRIPTION
•
•
•
•
•
•
The ACT6305 is a high efficiency synchronous
step-up DC/DC converter that consumes just 17µA
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 1V, making it ideal for
applications operating from 1 or 2 alkaline cells.
1V Typical Startup Voltage
Up to 94% Efficiency
Fully Integrated Power Stage
Fixed 3.3V/5V or Adjustable Output Voltage
NanoStandbyTM Shutdown Mode
This device incorporates an internal synchronous
rectifier, and achieves excellent peak efficiency of
up to 94% and features a proprietary control
scheme that ensures high efficiency over a wide
load current range.
Tiny SOT23-5 Package
− RoHS Compliant Package
APPLICATIONS
•
•
•
•
•
•
The ACT6305 features pin-selectable output voltages of 3.3V or 5V, or it can also be set externally
to any voltage between 2V and 5V. The ACT6305 is
available in a tiny SOT23-5 package.
Hand-Held Devices
One to Three Cell Battery Operated Devices
PDAs
Cellular Phones
Digital Cameras
GPS
TYPICAL APPLICATION CIRCUIT
Efficiency vs. Output Current
Efficiency (%)
90
80
VIN = 2.4V
VIN = 5V
ACT6305-001
100
70
VIN = 3.5V
VIN = 1.2V
60
Pb-free
50
40
VOUT = 5V
30
0.1
1.0
10
100
1000
Output Current (mA)
Innovative PowerTM
-1-
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
ORDERING INFORMATION
PART NUMBER
TEMPERATURE RANGE
ACT6305UC-T
-40°C to 85°C
PACKAGE PINS
SOT23-5
PACKING METHOD
TOP MARK
TAPE & REEL
HBCA
5
All Active-Semi components are RoHS Compliant and with Pb-free plating unless specified differently. The term “Pb-free” means semiconductor products that are in compliance with current RoHS (Restriction of Hazardous Substances) standards.
PIN CONFIGURATION
FB
1
G
2
EN
3
5
OUT
4
LX
ACT6305
UC
SOT23-5
PIN DESCRIPTIONS
PIN NUMBER PIN NAME
PIN DESCRIPTION
1
FB
Output Voltage Selection and Feedback Input. Connect this pin to G for VOUT = 5V, to
OUT for VOUT = 3.3V. Connect FB to a resistor divider to set the output voltage between 2V and 5V. See the Output Voltage Selection section for more information.
2
G
Ground.
3
EN
Shutdown Input. Drive EN to OUT or to a logic high for normal operation, drive EN to
G or to a logic low to disable the regulator.
4
LX
Inductor Connection.
5
OUT
Innovative PowerTM
Output. ACT6305 regulates voltage at this pin. OUT also provides power to the IC.
-2-
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
ABSOLUTE MAXIMUM RATINGSc
PARAMETER
VALUE
UNIT
-0.3 to 6
V
FB, LX to G
-0.3 to VOUT + 0.3
V
Continuous LX Current
Internally Limited
A
Maximum Power Dissipation (derate 5mV/°C above TA = 50°C)
0.53
W
Junction to Ambient Thermal Resistance ( θJA )
190
°C/W
Operating Junction Temperature
-40 to 150
°C
Storage Temperature
-55 to 150
°C
300
°C
OUT, EN to G
Lead Temperature (Soldering, 10 sec)
c: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may
affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = 1.5V, VOUT = 3.3V, TA = 25°C, unless otherwise specified.)
PARAMETER
SYMBOL
Minimum Operating Input Voltage
VIN
Maximum Operating Input Voltage
VIN
Startup Voltage
VIN
Output Voltage
VOUT
Output Voltage Range
TEST CONDITIONS
MIN
TYP
MAX
0.6
ILOAD = 1mA
V
5
V
1
1.18
V
FB = OUT; 60mVPP Ripple
3.2
3.3
3.4
FB = G; 40mVPP Ripple
4.85
5
5.15
External Feedback Divider
UNIT
2
V
5
V
Quiescent Current at OUT
IQ
VFB = 1.3V
17
34
µA
Shutdown Supply Current
ISD
EN = G
0.1
1
µA
Startup to Normal Transition Threshold
FB Feedback Voltage
1.85
VFB
FB Input Current
Power Switch Current Limit
VOUT = 2V to 5V
1.15
FB = 1.3V
ILIM
1.180
V
1.21
50
0.7
V
nA
1
1.25
A
Power Switch On Resistance
RONN
ILX = 100mA
0.19
0.4
Ω
Synchronous Rectifier On Resistance
RONP
ILX = -100mA
0.21
0.4
Ω
EN = G, VLX = 0V or 3.3V
0.1
1
µA
LX Leakage Current
Maximum Switch On-Time
tONMAX
3.75
5
6.25
µs
Minimum Switch Off-Time
tOFFMIN
0.75
1
1.25
µs
EN Logic Low Threshold
VIL
0.3
V
EN Logic High Threshold
VIH
0.6
1
EN Input Current
Innovative PowerTM
V
-3-
µA
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
TYPICAL PERFORMANCE CHARACTERISTICS
(Typical Application Circuit, L = 6.8µH, C1 = 22µF ceramic, C2 = 22µF ceramic, unless otherwise specified.)
Efficiency vs. Output Current
Efficiency vs. Constant Current
VIN = 2.4V
90
Efficiency (%)
Efficiency (%)
80
70
VIN = 3.5V
VIN = 1.2V
60
50
40
80
VIN = 1.2V
70
VIN = 1.8V
50
VOUT = 3.3V
FB = OUT
30
0.1
1.0
10
0.1
1000
100
Efficiency vs. Constant Current
Efficiency (%)
VIN = 2.4V
VOUT = 5V
FB = G
L = 4.7µH
C1 = 10µF
40
ACT6305-004
VIN = 5V
60
50
1000
90
70
VIN = 1.2V
100
100
ACT6305-003
90
VIN = 3.5V
10
Efficiency vs. Constant Current
100
80
1
Constant Current (mA)
Output Current (mA)
Efficiency (%)
VIN = 2.4V
60
40
VOUT = 5V
FB = G
30
80
VIN = 2.4V
70
VIN = 1.2V
VIN = 1.8V
60
50
VOUT = 3.3V
FB = OUT
L = 4.7µH
C1 = 10µF
40
30
30
0.1
1
10
100
0.1
1000
1
10
100
1000
Constant Current (mA)
Constant Current (mA)
Startup Voltage vs. Constant Resistance Load
Startup Voltage vs. Constant Resistance Load
1.50
1.75
Startup Voltage (V)
1.75
1.25
1.00
0.75
0
50
100
150
1.25
1.00
VOUT = 3.3V
FB = OUT
0.5
0
200
50
100
150
200
Current Load at 3.3V (mA)
Current Load at 5V (mA)
Innovative PowerTM
1.50
0.75
VOUT = 5V
FB = G
0.5
ACT6305-006
2.00
ACT6305-005
2.00
Startup Voltage (V)
ACT6305-002
90
VIN = 5V
100
ACT6305-001
100
-4-
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
TYPICAL PERFORMANCE CHARACTERISTICS CONT’D
(Typical Application Circuit, L = 6.8µH, C1 = 22µF ceramic, C2 = 22µF ceramic, unless otherwise specified.)
Startup Voltage vs. Temperature
Maximum On-Time (µS)
6.5
1.0
0.5
5.5
4.5
-40
-20
0
20
40
60
80
100
120
-40
0
20
40
60
80
100
120
Temperature (°C)
Minimum Off-Time vs. Temperature
Quiescent Supply Current vs. Temperature
Quiescent Supply Current (µA)
1.3
1.2
1.1
1.0
-20
0
20
40
60
80
100
120
20
15
10
5
0
-40
Temperature (°C)
Innovative PowerTM
25
ACT6305-010
ACT6305-009
1.4
-40
-20
Temperature (°C)
1.5
Minimum Off-Time (µS)
ACT6305-008
Startup Voltage (V)
ACT6305-007
1.5
Maximum On-Time vs. Temperature
-20
0
20
40
60
80
100
120
Temperature (°C)
-5-
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
TYPICAL PERFORMANCE CHARACTERISTICS CONT’D
(Typical Application Circuit, L = 6.8µH, C1 = 22µF ceramic, C2 = 22µF ceramic, unless otherwise specified.)
Light Load Operation for Low ESR COUT
ACT6305-012
CH2
ACT6305-011
VOUT = 5V
VIN = 1.2V
ILOAD = 5mA
Medium Load Operation for Low ESR COUT
VOUT = 5V
VIN = 1.2V
ILOAD = 150mA
CH2
CH1
CH1
CH1: VLX, 2.00V/div
CH2: VOUT, 100mV/div
TIME: 100µs/div
CH1: VLX, 2.00V/div
CH2: VOUT, 100mV/div
TIME: 2.50µs/div
Medium Load Operation for Low ESR COUT
ACT6305-014
CH2
ACT6305-013
VOUT = 5V
VIN = 2.4V
ILOAD = 300mA
Heavy Load Operation for Low ESR COUT
VOUT = 5V
VIN = 3.6V
ILOAD = 500mA
CH2
CH1
CH1
CH1: VLX, 2.00V/div
CH2: VOUT, 50mV/div
TIME: 2.50µs/div
CH1: VLX, 2.00V/div
CH2: VOUT, 100mV/div
TIME: 2.50µs/div
Light Load Operation for Low ESR COUT
ACT6305-016
CH2
ACT6305-015
VOUT = 3.3V
VIN = 1.2V
ILOAD = 50mA
Medium Load Operation for Low ESR COUT
VOUT = 3.3V
VIN = 1.8V
ILOAD = 400mA
CH2
CH1
CH1
CH1: VLX, 2.00V/div
CH2: VOUT, 50mV/div
TIME: 25.0µs/div
Innovative PowerTM
CH1: VLX, 2.00V/div
CH2: VOUT, 100mV/div
TIME: 2.50µs/div
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
FUNCTIONAL BLOCK DIAGRAM
OUT
EN
REFERENCE
LOW INPUT
START UP
VREF
1µs
ONE -SHOT
SET
LATCH Q
RESET
5µs
ONE -SHOT
DRIVER
LX
–
ERROR
COMPARATOR
–
+
+
FB
–
FEEDBACK
SELECT
+
VREF
CURRENT LIMIT
COMPARATOR
G
FUNCTIONAL DESCRIPTION
Light Load Operation
As seen in the Functional Block Diagram, the
ACT6305 comprises a reference, low input startup
circuitry, feedback select, error comparator, control
logic and timers, internal power MOSFETs and current comparators.
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
Low Voltage Startup
The ACT6305 control architecture utilizes a series
of one-shot and current sense circuits to regulate
the output voltage with a very low quiescent supply
current of just 17µA. 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 or the 1A current
limit is reached. When either of these conditions
occurs, 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 1µs minimum OFF time expires,
another ON cycle begins when the FB voltage
drops below the reference voltage.
The ACT6305 uses proprietary start-up circuitry that
allows it to achieve very low voltage startup down to
1V. The ACT6305 remains in low voltage startup
mode until VOUT exceeds 1.85V. The ACT6305 cannot support its full rated load current when operating in low-voltage startup mode. Care should be
taken to minimize load current during startup.
Innovative PowerTM
Shutdown
In shutdown mode, all internal circuits including the
power switch and the synchronous rectifier are disabled, reducing quiescent supply current to less
than 1µA. 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.
-7-
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
APPLICATIONS INFORMATION
Board Layout
Output Voltage Selection
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.
The ACT6305 provides fixed output voltage options
of 3.3V or 5V, or the output voltage may be adjusted over a 2V to 5V range by connecting an
external resistive voltage divider. When Output Voltage is set by external resistive voltage divider, add
a 47pF to 150pFcapacitor as feedforward capacitor
(CFF) as shown in Figure 1.
If an 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.
Table 1:
Output Voltage Programming
FB = OUT
VOUT = 3.3V
FB = G
VOUT = 5V
FB connect to resistive
divider
VOUT = 1.18V (1 + RFB1/RFB2)
Figure 1:
Output Voltage Setting
VOUT
OUT
ACT6305
CFF
RFB1
FB
RFB2
Output Capacitor Selection
A minimum value of output capacitance is required
to maintain loop stability and normal operation of
the IC. The output capacitor value should be in the
range of 22µF to 100µF. 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 1µF can be connected in parallel to filter high
frequency noise.
Inductor Selection
For most applications, the inductor value should be
in the range of 4.7µH to 22µH. 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.
Innovative PowerTM
-8-
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Copyright © 2011 Active-Semi, Inc.
ACT6305
Rev 2, 22-Feb-11
PACKAGE OUTLINE
SOT23-5 PACKAGE OUTLINE AND DIMENSIONS
D
θ
0.2
SYMBOL
L
E
E1
c
e
A
A1
A2
e1
DIMENSION IN
MILLIMETERS
DIMENSION IN
INCHES
MIN
MAX
MIN
MAX
A
-
1.450
-
0.057
A1
0.000
0.150
0.000
0.006
A2
0.900
1.300
0.035
0.051
b
0.300
0.500
0.012
0.020
c
0.080
0.220
0.003
0.009
L1
b
D
2.900 BSC
0.114 BSC
E
1.600 BSC
0.063 BSC
E1
2.800 BSC
0.110 BSC
e
0.950 BSC
0.037 BSC
e1
1.900 BSC
0.075 BSC
L
0.60REF
0.024REF
L1
0.300
0.600
0.012
0.024
θ
0°
8°
0°
8°
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 datasheet, 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
[email protected] or visit http://www.active-semi.com.
®
is a registered trademark of Active-Semi.
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