datasheet for ACT4070BYH-T by Active-Semi

datasheet for ACT4070BYH-T by Active-Semi
ACT4070B
Rev 1, 01-Feb-13
Wide Input 3A Step Down Converter
FEATURES
GENERAL DESCRIPTION
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•
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ACT4070B is a wide input voltage step-down
DC/DC converter that provides up to 3A output current at 300kHz switching frequency. ACT4070B is a
replacement part for ACT4070 with advanced features such as lower standby current and higher light
load efficiency. ACT4070B can be dropped into
ACT4070 socket with only feedback resistance
value changed.
3A Output Current
Up to 95% Efficiency
6V to 30V Input Range
100µA Shutdown Supply Current
4mA Standby Input Current
300kHz Switching Frequency
ACT4070B’s protection features include Cycle-byCycle current limit, thermal shutdown, and frequency foldback at over current and short circuit.
The devices are available in a SOP-8EP package
and require very few external devices for operation.
Output Voltage Up to 12V
Cycle-by-Cycle Current Limit Protection
Thermal Shutdown Protection
Internal Soft Start Function
Frequency Fold Back at Short Circuit
NOTE:
Stability with Wide Range of Capacitors
∗
Including Low ESR Ceramic Capacitors
ACT4070B
ACT4070.
is
the
replacement
part
for
SOP-8/EP (Exposed Pad) Package
APPLICATIONS
•
•
•
•
•
•
TFT LCD Monitors or Televisions and HDTV
Portable DVD Players
Car-Powered or Battery-Powered Equipment
Set-Top Boxes
Telecom Power Supplies
DSL and Cable Modems and Routers
TYPICAL APPLICATION CIRCUIT
Efficiency vs. Load Current
ACT4070B-001
100
VIN = 12V
Efficiency (%)
80
60
VIN = 24V
40
20
VOUT = 5V
0
1
10
100
1000
10000
Load Current (mA)
Innovative PowerTM
-1-
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
ORDERING INFORMATION
PART NUMBER
TEMPERATURE RANGE
PACKAGE
PINS
PACKING
ACT4070BYH
-40°C to 85°C
SOP-8/EP
8
TUBE
ACT4070BYH-T
-40°C to 85°C
SOP-8/EP
8
TAPE & REEL
PIN CONFIGURATION
SOP-8/EP
PIN DESCRIPTION
PIN NUMBER
PIN NAME
1
BS
Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver.
Connect a 10nF between this pin and SW.
2
IN
Input Supply. Bypass this pin to GND with a low ESR capacitor. See Input Capacitor in Application Information section.
3
SW
4
GND
5
FB
6
COMP
Compensation Pin. See Compensation Technique in Application Information section.
7
EN
Enable Input. When higher than 1.6V, this pin turns the IC on. When lower than
1.5V, this pin turns the IC off. This pin has a small internal pull up current to a high
level voltage when pin is not connected.
8
N/C
Not Connected.
EP
Exposed Pad shown as dashed box. The exposed thermal pad should be connected to board ground plane and pin 4. The ground plane should include a large
exposed copper pad under the package for thermal dissipation (see package outline). The leads and exposed pad should be flush with the board, without offset
from the board surface.
EP
Innovative PowerTM
PIN DESCRIPTION
Switch Output. Connect this pin to the switching end of the inductor.
Ground.
Feedback Input. The voltage at this pin is regulated to 0.808V. Connect to the
resistor divider between output and ground to set output voltage.
-2-
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
ABSOLUTE MAXIMUM RATINGS¦
PARAMETER
VALUE
UNIT
IN to GND
-0.3 to + 34
V
EN to GND
-0.3 to VIN + 0.3
V
SW to GND
-1 to VIN + 1
V
BS to SW
-0.3 to + 7
V
FB, COMP to GND
-0.3 to 6
V
Internally limited
A
46
°C/W
1.8
W
Operating Junction Temperature
-40 to 150
°C
Storage Temperature
-55 to 150
°C
300
°C
Continuous SW Current
Junction to Ambient Thermal Resistance (
JA)
Maximum Power Dissipation
Lead Temperature (Soldering, 10 sec)
¦: 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 = 12V, TA= 25°C, unless otherwise specified.)
PARAMETER
Input Voltage
SYMBOL
VIN
VIN UVLO Turn-on Voltage
TEST CONDITIONS
MIN
VOUT = 2.5V, ILOAD = 0A to 3A
TYP
6
30
V
5.5
V
VFB
0.792 0.808 0.824
V
High-Side Switch On Resistance
RONH
130
mΩ
Low-Side Switch On Resistance
RONL
7.9
Feedback Voltage
Input Voltage Rising
MAX UNIT
SW Leakage
High-Side Switch Peak Current
Limit
VEN = 0, VIN = 12V, VSW = 0V
ILIM
COMP to Current Limit Transconductance
GCOMP
Error Amplifier Transconductance
GEA
Error Amplifier DC Gain
AVEA
Switching Frequency
Duty Cycle = 50%
10
µA
3.7
A
ILOAD/ ICOMP
5.25
A/V
ICOMP = ±10µA
650
µA/V
4000
V/V
fSW
Short Circuit Switching Frequency
Maximum Duty Cycle
1
250
VFB = 0V
DMAX
Minimum on Time
330
kHz
44
kHz
88
%
200
ns
Enable Threshold Voltage
Hysteresis = 0.1V
Enable Pull Up Current
Pin pulled up to VIN when left unconnected
4
Supply Current in Shutdown
VEN = 0
75
115
µA
IC Supply Current in Operation
VFB = 1.2V, not switching
0.675
1
mA
Thermal Shutdown Temperature
Hysteresis = 20°C
Innovative PowerTM
-3-
1.47
300
1.6
150
1.73
V
µA
°C
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
FUNCTIONAL BLOCK DIAGRAM
FUNCTIONAL DESCRIPTION
As seen in the Functional Block Diagram, the
ACT4070B is a current mode pulse width modulation (PWM) 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 its 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. At this point, the
SW side of the inductor swings to a diode voltage
below ground, 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
BS bootstrap pin as the positive rail. This pin is
charged to VSW + 6V when the Low-Side Power
Switch turns on.
Innovative PowerTM
-4-
The COMP voltage is the integration of the error
between FB input and the internal 0.808V reference. If FB is lower than the reference voltage,
COMP tends to go higher to increase current to the
output.
The Oscillator normally switches at 300kHz. However, if FB voltage is less than 0.6V, then the
switching frequency decreases until it reaches a
typical value of 36kHz at VFB = 0V.
Shutdown Control
The ACT4070B has an enable input EN for turning
the IC on or off. When EN is less than 1.5V, the IC
is in 100 A low current shutdown mode and output
is discharged through the Low-Side Power Switch.
When EN is higher than 1.6V, the IC is in normal
operation mode. EN is internally pulled up with a
4 A current source and can be left unconnected for
always-on operation.
Thermal Shutdown
The ACT4070B automatically turns off when its
junction temperature exceeds 160°C and then restarts once the temperature falls to 150°C.
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
APPLICATIONS INFORMATION
Output Voltage Setting
Input Capacitor
Figure 1 shows the connections for setting the output voltage. Select the proper ratio of the two feedback resistors RFB1 and RFB2 based on the output
voltage. Adding a capacitor in parallel with RFB1
helps the system stability. Typically, RFB2 ≈ 10k
and determine RFB1 from the output voltage:
The input capacitor needs to be carefully selected to
maintain sufficiently low ripple at the supply input of
the converter. A low ESR capacitor is highly recommended. Since large current flows in and out of this
capacitor during switching, its ESR also affects efficiency.
⎞
⎛ V OUT
-1 ⎟
R FB 1 = R FB2 ⎜
⎠
⎝ 0 . 808 V
The input capacitance needs to be higher than
10µF. The best choice is the ceramic type; however,
low ESR tantalum or electrolytic types may also be
used provided that the RMS ripple current rating is
higher than 50% of the output current. The input
capacitor should be placed close to the IN and G
pins of the IC, with shortest traces possible. In the
case of tantalum or electrolytic types, they can be
further away if a small parallel 0.1µF ceramic capacitor is placed right next to the IC.
(1)
Figure 1:
Output Voltage Setting
Output Capacitor
The output capacitor also needs to have low ESR to
keep low output voltage ripple. The output ripple
voltage is:
Inductor Selection
The inductor maintains a continuous current to the
output load. This inductor current has a ripple that is
dependent on the inductance value: higher inductance reduces the peak-to-peak ripple current. The
trade off for high inductance value is the increase in
inductor core size and series resistance, and the
reduction in current handling capability. In general,
select an inductance value L based on ripple current
requirement:
L=
VOUT × (VIN - VOUT )
VIN fSW IOUTMAXK RIPPLE
VRIPPLE = IOUTMAX K RIPPLE RRIPPLE
+
where VIN is the input voltage, VOUT is the output
voltage, fSW is the switching frequency, IOUTMAX is the
maximum output current, and KRIPPLE is the ripple
factor. Typically, choose KRIPPLE = between 20% and
30% to correspond to the peak-to-peak ripple current
being a percentage of the maximum output current.
Use a Schottky diode as the rectifier to conduct current when the High-Side Power Switch is off. The
Schottky diode must have current rating higher than
the maximum output current and the reverse voltage rating higher than the maximum input voltage.
Typical Inductor Values
2.5V
3.3V
5V
L
6.8 H
6.8 H
8.5 H
15 H
15 H
Innovative PowerTM
(3)
Rectifier Diode
Table 1:
1.8V
2
For ceramic output type, typically choose a capacitance of about 22µF. For tantalum or electrolytic type,
choose a capacitor with less than 50m ESR.
With this inductor value (Table 1), the peak inductor
current is IOUT (1 + KRIPPLE / 2). Make sure that this
peak inductor current is less that the 5A current
limit. Finally, select the inductor core size so that it
does not saturate at 5A.
1.5V
28 × fSW LCOUT
where IOUTMAX is the maximum output current, KRIPPLE
is the ripple factor, RESR is the ESR resistance of the
output capacitor, fSW is the switching frequency, L in
the inductor value, COUT is the output capacitance. In
the case of ceramic output capacitors, RESR is very
small and does not contribute to the ripple. Therefore, a lower capacitance value can be used for ceramic type. In the case of tantalum or electrolytic
type, the ripple is dominated by RESR multiplied by the
ripple current. In that case, the output capacitor is
chosen to have sufficiently low ESR.
(2)
VOUT
VIN
-5-
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
Stability compensation
STEP 2. Set the zero fZ1 at 1/4 of the cross over
frequency. If RCOMP is less than 15k , the equation
for CCOMP is:
Figure 2:
Stability Compensation
C COMP
=
2 . 83 x 10
R COMP
C COMP = 6 . 45 x10
The feedback system of the IC is stabilized by the
components at COMP pin, as shown in Figure 2.
The DC loop gain of the system is determined by
the following equation:
⎛ 1 . 77 x 10
≥ Min ⎜⎜
C OUT
⎝
(4)
G EA
2 π A VEA C COMP
CCOMP =
(5)
I OUT
2 π VOUT C OUT
(6)
1
⎞
,0 . 006 V OUT ⎟⎟
⎠
( )
(12)
COUT R ESROUT
RCOMP
(13)
Table 2 shows some calculated results based on
the compensation method above.
(7)
2 πRCOMP CCOMP
−6
Though CCOMP2 is unnecessary when the output
capacitor has sufficiently low ESR, a small value
CCOMP2 such as 220pF may improve stability
against PCB layout parasitic effects.
The first zero Z1 is due to RCOMP and CCOMP:
fZ1 =
(11)
And the proper value for CCOMP2 is:
The second pole P2 is the output pole:
fP 2 =
(F)
V OUT C OUT
R ESROUT
The dominant pole P1 is due to CCOMP:
fP 1 =
−6
STEP 3. If the output capacitor’s ESR is high
enough to cause a zero at lower than 4 times the
cross over frequency, an additional compensation
capacitor CCOMP2 is required. The condition for using CCOMP2 is:
¦: CCOMP2 is needed only for high ESR output capacitor
AVDC
(10)
(F)
If RCOMP is limited to 15k , then the actual cross
over frequency is 4.8/(VOUTCOUT). Therefore:
¦
0 . 808 V
=
AVEA G COMP
I OUT
5
Table 2:
Typical Compensation for Different Output
Voltages and Output Capacitors
And finally, the third pole is due to RCOMP and
CCOMP2 (if CCOMP2 is used):
COUT
1.8V
22 F Ceramic
4k
3.3nF
220pF
2.5V
22 F Ceramic
5.6k
3.3nF
220pF
Follow the following steps to compensate the IC:
5V
22 F Ceramic
12k
1.5nF
220pF
STEP 1. Set the cross over frequency at 1/10 of
the switching frequency via RCOMP:
1.8V
100 F SP CAP
15k
1.5nF
220pF
2.5V
100 F SP CAP
15k
2.2nF
220pF
5V
100 F SP CAP
15k
4.7nF
220pF
fP 3 =
R COMP
1
(8)
2 πRCOMP CCOMP2
=
2 π V OUT C OUT f SW
10 G EA G COMP 0 . 808 V
= 5 . 12 x 10 7 V OUT C OUT
but limit RCOMP to 15k
Innovative PowerTM
( )
(9)
RCOMP
CCOMP CCOMP2¦
VOUT
¦: CCOMP2 is needed for board parasitic and high ESR output
capacitor.
Figure 3 shows a sample ACT4070B application
circuit generating a 2.5V/3A output.
maximum.
-6-
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
Figure 3:
ACT4070B 5V/3A Output Application¦
Table 3:
BOM List for 5V/3A Car Charger
ITEM REFERENCE
DESCRIPTION
MANUFACTURER
QTY
1
U1
IC, ACT4070B, SOP-8EP
Active-Semi
1
2
C1
Capacitor, Ceramic, 10µF/50V, 1206, SMD
Murata, TDK
1
3
C2
Capacitor, Ceramic, 4.7nF/25V, 0603, SMD
Murata, TDK
1
4
C3
Capacitor, Ceramic, 10nF/25V, 0603, SMD
Murata, TDK
1
5
C4
Capacitor, Ceramic, 22µF/10V, 0805, SMD
Murata, TDK
1
6
C5
Capacitor, Ceramic, 1nF/16V, 0603, SMD
Murata, TDK
1
7
L1
Inductor, 15µH, 4A, 20%, SMD
Sunlord
1
8
D1
Diode, Schottky, 40V/3A, SK34
Diodes
1
9
R1
Chip Resistor, 51k , 0603, 1%
Murata, TDK
1
10
R2
Chip Resistor, 9.76k , 0603, 1%
Murata, TDK
1
11
R3
Chip Resistor, 12k , 0603, 5%
Murata, TDK
1
Innovative PowerTM
-7-
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 3, unless otherwise specified.)
Efficiency vs. Load Current
Shutdown Current vs. Input Voltage
Shutdown Current (µA)
Efficiency (%)
VIN = 24V
40
20
ACT4070B-003
VIN = 12V
80
60
120
ACT4070B-002
100
100
80
60
40
20
VOUT = 5V
0
1
10
100
1000
0
10000
Load Current (mA)
5
10
15
25
20
30
Input Voltage (V)
Load Transient Response
Load Transient Response
VIN = 24V
V0UT = 5V
ACT4070B-005
CH1
ACT4070B-004
VIN = 12V
V0UT = 5V
CH1
CH2
CH2
CH1: IOUT, 1A/div
CH2: VOUT, 200mV/div
TIME: 400µs/div
CH1: IOUT, 1A/div
CH2: VOUT, 200mV/div
TIME: 400µs/div
Maximum Peak Current vs. Duty Cycle
Maximum CC Current (A)
ACT4070B-006
4.5
4.2
3.9
3.6
3.3
3
20
30
40
50
60
70
Duty Cycle
Innovative PowerTM
-8-
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Copyright © 2013 Active-Semi, Inc.
ACT4070B
Rev 1, 01-Feb-13
PACKAGE OUTLINE
SOP-8/EP PACKAGE OUTLINE AND DIMENSIONS
SYMBOL
DIMENSION IN
MILLIMETERS
DIMENSION IN
INCHES
MIN
MAX
MIN
MAX
A
1.350
1.700
0.053
0.067
A1
0.000
0.100
0.000
0.004
A2
1.350
1.550
0.053
0.061
b
0.330
0.510
0.013
0.020
c
0.170
0.250
0.007
0.010
D
4.700
5.100
0.185
0.200
D1
3.202
3.402
0.126
0.134
E
3.800
4.000
0.150
0.157
E1
5.800
6.200
0.228
0.244
E2
2.313
2.513
0.091
0.099
e
L
1.270 TYP
0.050 TYP
0.400
1.270
0.016
0.050
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
sales@active-semi.com or visit http://www.active-semi.com.
is a registered trademark of Active-Semi.
Innovative PowerTM
-9-
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Copyright © 2013 Active-Semi, Inc.
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