ACTIVE-SEMI ACT4060ASH-T

ACT4060A
Rev 0, 28-Apr-09
Wide Input 2A Step Down Converter
FEATURES
•
•
•
•
•
•
•
•
•
•
GENERAL DESCRIPTION
The ACT4060A is a current-mode step-down
DC/DC converter that provides up to 2A of output
current at 400kHz switching frequency. The device
utilizes Active-Semi’s proprietary high voltage process for operation with input voltages up to 24V.
2A Output Current
Up to 96% Efficiency
4.5V to 24V Input Range
10µA Shutdown Supply Current
The ACT4060A provides fast transient response
and eases loop stabilization while providing excellent line and load regulation. This device features a
very low ON-resistance power MOSFET which provides peak operating efficiency up to 96%. In shutdown mode, the ACT4060A consumes only 10μA of
supply current.
400kHz Switching Frequency
Adjustable Output Voltage
Cycle-by-Cycle Current Limit Protection
Thermal Shutdown Protection
Frequency FoldBack at Short Circuit
This device also integrates protection features including cycle-by-cycle current limit, thermal shutdown and frequency fold-back at short circuit.
Stability with Wide Range of Capacitors,
Including Low ESR Ceramic Capacitors
• SOP-8 Package
The ACT4060A is available in a SOP-8 package
and requires very few external devices for operation.
APPLICATIONS
•
•
•
•
•
•
•
TFT LCD Monitors
Portable DVDs
Car-Powered or Battery-Powered Equipments
Set-Top Boxes
Telecom Power Supplies
DSL and Cable Modems and Routers
Termination Supplies
TYPICAL APPLICATION CIRCUIT
BS
Up to 24V
SW
IN
2.5V/2A
ACT4060A
ENABLE
EN
G
FB
COMP
+
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-1-
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
ORDERING INFORMATION
PART NUMBER
TEMPERATURE RANGE
PACKAGE
PINS
PACKING
ACT4060ASH
-40°C to 85°C
SOP-8
8
TUBE
ACT4060ASH-T
-40°C to 85°C
SOP-8
8
TAPE & REEL
PIN CONFIGURATION
SOP-8
PIN DESCRIPTIONS
PIN
NAME
1
BS
Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver.
Connect a 10nF capacitor between BS and SW.
2
IN
Input Supply. Bypass this pin to G with a low ESR capacitor. See Input Capacitor
in the Application Information section.
3
SW
4
G
Ground.
5
FB
Feedback Input. The voltage at this pin is regulated to 1.293V. Connect to the
resistor divider between output and ground to set output voltage.
6
COMP
Compensation Pin. See Stability Compensation in the Application Information
section.
7
EN
Enable Input. When higher than 1.3V, this pin turns the IC on. When lower than
0.7V, this pin turns the IC off. Output voltage is discharged when the IC is off.
When left unconnected, EN is pulled up to 4.5V with a 2µA pull-up current.
8
N/C
Not Connected.
Innovative PowerTM
DESCRIPTION
Switch Output. Connect this pin to the switching end of the inductor.
-2-
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
ABSOLUTE MAXIMUM RATINGSc
PARAMETER
VALUE
UNIT
-0.3 to 28
V
SW Voltage
-1 to VIN + 1
V
BS Voltage
VSW - 0.3 to VSW + 8
V
EN, FB, COMP Voltage
-0.3 to 6
V
Continuous SW Current
Internally Limited
A
Junction to Ambient Thermal Resistance (θJA)
105
°C/W
Maximum Power Dissipation
0.76
W
Operating Junction Temperature
-40 to 150
°C
Storage Temperature
-55 to 150
°C
300
°C
IN Supply Voltage
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 = 12V, TA = 25°C, unless otherwise specified.)
PARAMETER
SYMBOL
TEST CONDITIONS
Input Voltage
VIN
VOUT = 3.3V, ILOAD = 0A to 1A
Feedback Voltage
VFB
4.5V ≤ VIN ≤ 24V, VCOMP = 1.5V
MIN
TYP
4.5
1.267
1.293
MAX
UNIT
24
V
1.319
V
High-Side Switch On Resistance
RONH
0.18
Ω
Low-Side Switch On Resistance
RONL
4.5
Ω
SW Leakage
Current Limit
COMP to Current Limit
Transconductance
VEN = 0
ILIM
GCOMP
Error Amplifier Transconductance
GEA
Error Amplifier DC Gain
AVEA
Switching Frequency
2.4
DMAX
10
µA
2.85
A
VIN = 12V, VOUT = 5V
1.8
A/V
ΔICOMP = ±10µA
650
µA/V
4000
V/V
fSW
Short Circuit Switching Frequency
Maximum Duty Cycle
0
350
400
450
kHz
VFB = 0
60
kHz
VFB = 1.1V
95
%
Minimum Duty Cycle
VFB = 1.4V
Enable Threshold Voltage
Hysteresis = 0.1V
Enable Pull-Up Current
Pin pulled up to 4.5V typically
when left unconnected
2
Supply Current in Shutdown
VEN = 0
10
IC Supply Current in Operation
VEN = 3V, VFB = 1.4V
0.55
mA
Thermal Shutdown Temperature
Hysteresis = 10°C
160
°C
Innovative PowerTM
-3-
0.7
1
0
%
1.3
V
µA
20
µA
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
FUNCTIONAL BLOCK DIAGRAM
IN
ENABLE
EN
COMP
1.293V
REGULATOR
&
REFERENCE
BS
CURRENT SENSE
AMPLIFIER
+
-
ERROR
AMPLIFIER
+
+
-
-
-
+
PWM
COMP
0.18Ω
HIGH-SIDE
POWER
SWITCH
FB
FOLDBACK
CONTROL
OSCILLATOR
&
RAMP
SW
LOGIC
4.5Ω LOW-SIDE
POWER SWITCH
THERMAL
SHUTDOWN
G
The COMP voltage is the integration of the error
between FB input and the internal 1.293V reference. If FB is lower than the reference voltage,
COMP tends to go higher to increase current to the
output. Current limit happens when COMP reaches
its maximum clamp value of 2.55V.
FUNCTIONAL DESCRIPTION
As seen in Functional Block Diagram, the ACT4060A 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 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 Oscillator normally switches at 400kHz. However, if FB voltage is less than 0.7V, then the
switching frequency decreases until it reaches a
typical value of 60kHz at VFB = 0.5V.
Shutdown Control
The ACT4060A has an enable input EN for turning
the IC on or off. When EN is less than 0.7V, the IC
is in 10μA low current shutdown mode and output is
discharged through the Low-Side Power Switch.
When EN is higher than 1.3V, the IC is in normal
operation mode. EN is internally pulled up with a
2μA current source and can be left unconnected for
always-on operation. Note that EN is a low voltage
input with a maximum voltage of 6V, it should never
be directly connected to IN.
Thermal Shutdown
The High-Side Power Switch is driven by logic using
BS as the positive rail. This pin is charged to VSW +
6V when the Low-Side Power Switch turns on.
Innovative PowerTM
The ACT4060A automatically turns off when its
junction temperature exceeds 160°C.
-4-
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
APPLICATIONS INFORMATION
Input Capacitor
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.
Output Voltage Setting
Figure 1:
Output Voltage Setting
VOUT
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 the 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.
RFB1
ACT4060A
FB
RFB2
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. Typically, use RFB2 ≈ 10kΩ and determine
RFB1 from the following equation:
⎞
⎛ V
R FB1 = R FB 2 ⎜ OUT − 1 ⎟
⎠
⎝ 1.293V
Output Capacitor
(1)
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 IOUTMAX K RIPPLE
VRIPPLE = IOUTMAX K RIPPLE RESR
+
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 = 30% to correspond to the peak-to-peak ripple current being 30%
of the maximum output current.
Rectifier Diode
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 a reverse voltage
rating higher than the maximum input voltage.
Table 1:
Typical Inductor Values
1.8V
2.5V
3.3V
5V
L
6.8μH
6.8μH
10μH
15μH
22μH
Innovative PowerTM
(3)
For ceramic output capacitor, typically choose a
capacitance of about 22µF. For tantalum or electrolytic capacitors, choose a capacitor with less than
50mΩ ESR.
With this inductor value, the peak inductor current is
IOUT × (1 + KRIPPLE/2). Make sure that this peak inductor current is less that the 3A current limit. Finally, select the inductor core size so that it does
not saturate at 3A. Typical inductor values for various output voltages are shown in Table 1.
1.5V
2
28 × fSW LC OUT
where IOUTMAX is the maximum output current, KRIPPLE is the ripple factor, RESR is the ESR of the output
capacitor, fSW is the switching frequency, L is the
inductor value, and 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 capacitors, 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
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
STABILITY COMPENSATION
STEP 2. Set the zero fZ1 at 1/4 of the cross over
frequency. If RCOMP is less than 15kΩ, the equation
for CCOMP is:
Figure 2:
Stability Compensation
C COMP =
1 .8 × 10 −5
R COMP
(F)
(10)
If RCOMP is limited to 15kΩ, then the actual cross
over frequency is 3.4 / (VOUTCOUT). Therefore:
CCOMP = 1.2 ×10 −5 VOUTCOUT
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:
c: CCOMP2 is needed only for high ESR output capacitor
The feedback loop of the IC is stabilized by the
components at the COMP pin, as shown in Figure 2.
The DC loop gain of the system is determined by
the following equation:
1 .3V
AVDC =
AVEA GCOMP
(4)
I OUT
The dominant pole P1 is due to CCOMP:
G EA
fP1 =
2 π A VEA C COMP
⎛ 1.1 × 10 −6
⎞
RESRCOUT ≥ Min⎜⎜
,0.012 × VOUT ⎟⎟ (Ω)
⎝ COUT
⎠
I OUT
2 π V OUT C OUT
CCOMP2 =
Table 2:
Typical Compensation for Different Output
Voltages and Output Capacitors
(7)
2 π R COMP C COMP
And finally, the third pole is due to RCOMP and
CCOMP2 (if CCOMP2 is used):
fP 3 =
1
(8)
2π R COMP C COMP2
(13)
Table 2 shows some calculated results based on
the compensation method above.
(6)
1
COUT RESRCOUT
RCOMP
Though CCOMP2 is unnecessary when the output capacitor has sufficiently low ESR, a small value
CCOMP2 such as 100pF may improve stability against
PCB layout parasitic effects.
(5)
The first zero Z1 is due to RCOMP and CCOMP:
fZ1 =
(12)
And the proper value for CCOMP2 is:
The second pole P2 is the output pole:
fP 2 =
(11)
(F)
VOUT
COUT
RCOMP
CCOMP CCOMP2c
2.5V
22μF Ceramic
8.2kΩ
2.2nF
None
3.3V
22μF Ceramic
12kΩ
1.5nF
None
5V
22μF Ceramic
15kΩ
1.5nF
None
2.5V
47μF SP CAP
15kΩ
1.5nF
None
The following steps should be used to compensate
the IC:
3.3V
47μF SP CAP
15kΩ
1.8nF
None
5V
47μF SP CAP
15kΩ
2.7nF
None
STEP 1. Set the cross over frequency at 1/10 of the
switching frequency via RCOMP:
2.5V
470μF/6.3V/30mΩ
15kΩ
15nF
1nF
3.3V
470μF/6.3V/30mΩ
15kΩ
22nF
1nF
5V
470μF/6.3V/30mΩ
15kΩ
27nF
None
R COMP =
2π VOUT C OUT f SW
10 G EA GCOMP × 1 .3V
= 1.7 × 10 8 VOUT C OUT
c: CCOMP2 is needed for high ESR output capacitor.
(Ω)
Figure 3 shows an example ACT4060A application circuit generating a 2.5V/2A output.
(9)
but limit RCOMP to 15kΩ maximum.
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
Figure 3:
ACT4060A 3.3V/2A Output Applicationc
VIN
C3
BS
Up to 24V
IN
ENABLE
L1
SW
VOUT
IC1
ACT4060A
EN
G
COMP
R1
FB
C2
+
R2
C1
C4
D1
C5
(OPTIONAL)
R3
c: D1 is a 40V, 3A Schottky diode with low forward voltage, an IR 30BQ040 or SK34 equivalent. C4 can be either a ceramic capacitor
(Panasonic ECJ-3YB1C226M) or SP-CAP (Specialty Polymer) Aluminum Electrolytic Capacitor such as Panasonic EEFCD0J470XR.
The SP-Cap is based on aluminum electrolytic capacitor technology, but uses a solid polymer electrolyte and has very stable capacitance characteristics in both operating temperature and frequency compared to ceramic, polymer, and low ESR tantalum capacitors.
Table 3:
ACT4060A Bill of Materials (Apply for 3.3V Output Application)
ITEM
1
DESCRIPTION
MANUFACTURER
QTY
REFERENCE
IC, ACT4060A
Active-Semi
15µH ± 20%, ISAT = 2.7A, IDC = 2.4A@ ΔT = 40°C
Taiyo Yuden NR 8040T 150M
15µH ± 10%, ISAT = 2.88A, IDC = 2.47A@ ΔT = 40°C
Wurth Electronik 744776115
10µH ± 20%, ISAT = 3.4A, IDC = [email protected] = 40°C
Taiyo Yuden NR 6045T 100M
10µH ± 10%, ISAT = 2.95A, IDC = 2.3A@ ΔT = 40°C
Wurth Electronik 74477510
Schottky Diode SK34/40V, 3A, SMB
Transys electronics
1
Schottky Diode B340C/40V, 3A, SMB
Diodes Inc
1
4
Ceramic cap 10µF/35V, X7R, 1210
Murata, TDK,Taiyo Yuden
1
C1
5
Ceramic cap 2.2nF/6.3V, X7R, 0603
Murata, TDK,Taiyo Yuden
1
C2
6
Ceramic cap 10nF/50V, X7R, 0603
Murata, TDK,Taiyo Yuden
1
C3
1
C4
1
C5 (OPTIONAL)
2
3
Ceramic cap 22µF/10V, X7R, 1210
Murata, TDK,Taiyo Yuden
SP cap 47µF/6.3V, 50mΩ
Kemet, Panasonic
8
Ceramic cap 220pF/6.3V, X7R, 0603
Murata, TDK,Taiyo Yuden
9
Resistor, 15.5kΩ, 1/16W, 1%, 0603
10
Resistor, 10kΩ, 1/16W, 1%, 0603
11
Resistor, 12kΩ, 1/16W, 5%, 0603
7
Innovative PowerTM
1
U1
1
L1
D1
R1
FengHua, Neohm, Yageo
1
R2
R3
-7-
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
Figure 4:
ACT4060A 5V/2A Output Applicationc
VIN
C3
BS
Up to 24V
IN
ENABLE
L1
SW
VOUT
IC1
ACT4060A
EN
G
COMP
R1
FB
C2
+
C1
R3
R2
C4
D1
C5
(OPTIONAL)
c: D1 is a 40V, 3A Schottky diode with low forward voltage, an IR 30BQ040 or SK34 equivalent. C4 can be either a ceramic capacitor
(Panasonic ECJ-3YB1C226M) or SP-CAP (Specialty Polymer) Aluminum Electrolytic Capacitor such as Panasonic EEFCD0J470XR.
The SP-Cap is based on aluminum electrolytic capacitor technology, but uses a solid polymer electrolyte and has very stable capacitance characteristics in both operating temperature and frequency compared to ceramic, polymer, and low ESR tantalum capacitors.
Table 4:
ACT4060A Bill of Materials (Apply for 5V Output Application)
ITEM
1
2
3
DESCRIPTION
MANUFACTURER
IC, ACT4060A
Active-Semi
15µH ± 20%, ISAT =2.7A, IDC = 2.4A@ ΔT = 40°C
Taiyo Yuden NR 8040T 150M
15µH ± 10%, ISAT = 2.88A, IDC = 2.47A@ ΔT = 40°C Wurth Electronik 744776115
Schottky Diode SK34/40V, 3A, SMB
Transys electronics
Schottky Diode B340C/40V, 3A, SMB
Diodes Inc
QTY
REFERENCE
1
U1
1
L1
1
D1
4
Ceramic cap 10µF/35V, X7R, 1210
Murata, TDK, Taiyo Yuden
1
C1
5
Ceramic cap 2.2nF/6.3V, X7R, 0603
Murata, TDK, Taiyo Yuden
1
C2
6
Ceramic cap 10nF/50V, X7R, 0603
Murata, TDK, Taiyo Yuden
1
C3
Ceramic cap 22µF/10V, X7R, 1210
Murata, TDK, Taiyo Yuden
SP cap 47µF/6.3V, 50mΩ
Kemet, Panasonic
1
C4
8
Ceramic cap 220pF/6.3V, X7R, 0603
Murata, TDK, Taiyo Yuden
1
C5 (OPTIONAL)
9
Resistor, 28.7kΩ, 1/16W, 1%, 0603
10
Resistor, 10kΩ, 1/16W, 1%, 0603
11
Resistor, 15kΩ, 1/16W, 5%, 0603
7
Innovative PowerTM
R1
FengHua, Neohm, Yageo
1
R2
R3
-8-
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 3, unless otherwise specified.)
Efficiency vs. Output Current
Efficiency vs. Output Current
Efficiency (%)
80
70
80
VIN = 12V
60
50
40
30
VIN = 7V
70
VIN = 12V
60
50
40
30
20
20
10
10
0
0
10
100
1000
10
10000
100
Efficiency vs. Output Current
Maximum Output Current vs. Duty Cycle
Maximum Output Current (mA)
40
20
VOUT = 3.3V
0
10
100
1000
ACT4060A-004
VIN = 12V
60
5000
ACT4060A-003
VIN = 5V
4000
3000
2000
1000
0
10000
0
20
40
60
80
100
Duty Cycle (% )
Output Current (mA)
Switching Frequency vs. Input Voltage
Feedback Voltage vs. Temperature
400
Feedback Voltage (V)
405
395
390
ACT4060A-006
1.33
ACT4060A-005
410
Switching Frequency (kHz)
10000
Output Current (mA)
80
385
1000
Output Current (mA)
100
Efficiency (%)
VOUT = 5V
90
Efficiency (%)
VIN = 7V
ACT4060A-002
VOUT = 2.5V
90
100
ACT4060A-001
100
1.31
1.29
1.27
VOUT = 2.5V
IOUT = 1A
380
1.25
4
6
8
10
12
14
16
18
-50
20
Innovative PowerTM
0
100
50
150
Temperature (°C)
Input Voltage (V)
-9-
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
TYPICAL PERFORMANCE CHARACTERISTICS CONT’D
(Circuit of Figure 3, unless otherwise specified.)
Shutdown Current vs. Input Voltage
Shutdown Current (µA)
ACT4060A-007
25
20
15
10
5
0
5
10
15
20
25
Input Voltage (V)
Innovative PowerTM
- 10 -
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Copyright © 2009 Active-Semi, Inc.
ACT4060A
Rev 0, 28-Apr-09
PACKAGE OUTLINE
SOP-8 PACKAGE OUTLINE AND DIMENSIONS
D
C
SYMBOL
θ
e
B
DIMENSION IN
MILLIMETERS
DIMENSION IN
INCHES
MIN
MAX
MIN
MAX
A
1.350
1.750
0.053
0.069
A1
0.100
0.250
0.004
0.010
A2
1.350
1.550
0.053
0.061
B
0.330
0.510
0.013
0.020
C
0.190
0.250
0.007
0.010
D
4.700
5.100
0.185
0.201
E
3.800
4.000
0.150
0.157
E1
5.800
6.300
0.228
0.248
e
1.270 TYP
0.050 TYP
L
0.400
1.270
0.016
0.050
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 lifesupport 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. For other inquiries, please send to:
2728 Orchard Parkway, San Jose, CA 95134-2012, USA
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