ACTIVE-SEMI ACT6390MH-T

ACT6390/ACT6391
Rev0, 13-May-08
1.7A/2.5A PWM Step-Up DC/DC Converters In MSOP
FEATURES
•
•
•
•
GENERAL DESCRIPTION
Greater than 90% Efficiency
The ACT6390/ACT6391 are high-performance,
fixed-frequency, current-mode PWM step-up
DC/DC converters that incorporate internal power
MOSFETs. The ACT6390 includes an integrated
0.2Ω power MOSFET that supports peak currents
of up to 1.7A, while the ACT6391’s integrated
0.15Ω power MOSFET supports currents of up to
2.5A.
Adjustable Output Voltage Up to 12V
Internal 14V Power MOSFET
Two Peak Current Options:
− ACT6390: 1.7A, 0.2Ω
− ACT6391: 2.5A, 0.15Ω
• Selectable 700kHz/1.3MHz Frequency
•
•
•
•
•
The ACT6390 and ACT6391 both utilize simple external loop compensation and a pin-selectable
fixed-frequency of either 700kHz or 1.3MHz, allowing optimization between component size, cost, and
AC performance across a wide range of applications. Additional functions include an externally programmable soft-start function for easy inrush current control, internal over-voltage protection (OVP),
cycle-by-cycle current limit protection, and thermal
shutdown.
Integrated Over-Voltage Protection (OVP)
Programmable Soft-Start Function
Thermal Shutdown
Cycle-by-Cycle Over-Current Protection
Small MSOP-8 Package
APPLICATIONS
•
•
•
•
Both the ACT6390 and the ACT6391 are available
in the small 8-pin MSOP-8 package.
TFT LCD Monitors
Battery-Powered Equipment
Set-Top Boxes
DSL and Cable Modems and Routers
SIMPLIFIED APPLICATION CIRCUIT
VIN
2.7V to 5.5V
ON
OFF
1.3MHz
700kHz
IN
EN
ACT6390
ACT6391
SW
FREQ
VOUT
R1
SS
FB
COMP
G
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Copyright © 2008 Active-Semi, Inc.
ACT6390/ACT6391
Rev0, 13-May-08
ORDERING INFORMATION
PART
NUMBER
CURRENT
LIMIT
TEMPERATURE
RANGE
PACKAGE
PINS
PACKAGING
ACT6390MH-T
1.7A
-40°C to 85°C
MSOP-8
8
TAPE & REEL
ACT6391MH-T
2.5A
-40°C to 85°C
MSOP-8
8
TAPE & REEL
PIN CONFIGURATION
COMP
1
FB
2
EN
3
G
4
ACT6390
ACT6391
8
SS
7
FREQ
6
IN
5
SW
MSOP-8
PIN DESCRIPTIONS
PIN
NAME
1
COMP
2
FB
Feedback Input. Connect this pin a resistor divider from the output to set the output voltage. FB
is regulated to 1.24V.
3
EN
Enable Control. Connect to a logic high level to enable the IC. Connect to a logic low level to
disable the IC. When unused, connect EN pin to IN (do not leave pin floating).
4
G
5
SW
6
IN
7
FREQ
8
SS
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DESCRIPTION
Error Amplifier Compensation Node. Connect to a resistor RC and capacitor CC in series to
ground.
Ground.
Switch Output. Connect this pin to the inductor and the schottky diode. To minimize EMI, minimize the PCB trace path between this pin and the input bypass capacitor.
Supply Input. Bypass to G with a 1µF or larger capacitor.
Frequency Setting Pin. A logic low sets the switching frequency at 700kHz. A logic high sets
the switching frequency at 1.3MHz. This pin has an internal 5.5µA pull-down current.
Soft Start Control Input. Connect a capacitor from this pin to G to set soft-start timing duration
(tSS = 2.2 x 105 x CSS). SS is discharged to ground in shutdown. SS may be left unconnected if
soft start is not desired.
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Copyright © 2008 Active-Semi, Inc.
ACT6390/ACT6391
Rev0, 13-May-08
ABSOLUTE MAXIMUM RATINGSc
PARAMETER
VALUE
UNIT
SW to G
-0.3 to 14
V
IN, EN, FB, FREQ, COMP to G
-0.3 to 6
V
SS to G
-0.3 to VIN + 0.3
V
Continuous SW Current
Internally Limited
A
Junction to Ambient Thermal Resistance (θJA)
200
°C/W
Maximum Power Dissipation
0.5
W
Operating Junction Temperature
-40 to 150
°C
Storage Temperature
-55 to 150
°C
300
°C
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.
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ACT6390/ACT6391
Rev0, 13-May-08
ELECTRICAL CHARACTERISTICS
(VIN = VEN = 3V, VFREQ = 0V, TA = 25°C, unless otherwise specified.)
PARAMETER
TEST CONDITIONS
MIN
TYP
Switch Voltage Rating
Input Voltage
Under Voltage Lockout Threshold
2.7
VIN Rising
2.2
Under Voltage Lockout Hysteresis
Supply Current in Shutdown
Switching Frequency
Maximum Duty Cycle
VFB = 1.0V, Switching
5.5
V
2.5
V
mV
ACT6390
1
4
ACT6391
1.4
4
0.1
10
µA
EN = G
mA
FREQ = G
490
700
910
kHz
FREQ = IN
900
1300
1700
kHz
FREQ = G
80
86
92
FREQ = IN
86
1.22
VFB = 1.27V
FB Voltage Line Regulation
VFB from 2.6V to 5.5V
Error Amplifier Trans-conductance
∆I = 5µA
Error Amplifier Output Current
VFB = 1.15V and 1.35V, VCOMP = 1.1V
Switch Current Limit
VFB = 1V, Duty Cycle = 65%
Current Sense Trans-resistance
V
0.35
FB Input Current
Switch Leakage Current
12
0.2
FB Feedback Voltage
Switch On Resistance
UNIT
65
VFB = 1.3V, Not Switching
Quiescent Supply Current
2.35
MAX
70
1.24
1.26
V
0
80
nA
0.05
0.15
%/V
150
240
µs
11
µA
ACT6390
1.2
1.7
2.3
ACT6391
1.8
2.5
3.4
ACT6390
0.2
0.4
ACT6391
0.15
0.3
VSW = 12V, EN = G
15
ACT6390
0.45
ACT6391
0.3
Soft Start Pin Bias Current
VSS = 1.2V
Soft Start Reset Resistance
VSS = 1.2V, VEN = 0V
Logic High Threshold
EN, FREQ
Logic Low Threshold
EN, FREQ
EN Input Current
VEN = 0V or 5V
FREQ Pull-down Current
VFREQ = 3V
2
A
Ω
µA
V/A
4.5
7
µA
110
220
Ω
1.4
2.5
%
V
0.4
V
0
1
µA
5.5
8.5
µA
Thermal Shutdown Temperature
160
°C
Thermal Shutdown Hysteresis
20
°C
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ACT6390/ACT6391
Rev0, 13-May-08
FUNCTIONAL BLOCK DIAGRAM
IN
EN
4.5µA
SOFT
START
COMP
ERROR
AMPLIFIER
ERROR
COMPARATOR
+
SW
CONTROL
AND
DRIVE
LOGIC
+
1.24V
-
FB
SS
CLOCK
SLOPE
COMPENSATION
+
CURRENT SENSE
AMPLIFIER
5.5µA
FUNCTIONAL DESCRIPTION
G
(1)
t SS = 2 . 2 × 10 5 × C SS
The ACT6390 and ACT6391 are highly efficient
step-up DC/DC converters that employ a currentmode, fixed frequency pulse-width modulation
(PWM) architecture with excellent line and load
regulation.
Frequency Selection
The ACT6390 and ACT6391 include a pinselectable operating frequency drive FREQ to a
logic high for 1.3MHz operation, drive FREQ to a
logic low for 700kHz operation.
The ACT6390 and ACT6391 operate at constant
switching frequency under medium to high load current conditions. At light loads, these devices operate in a pulse-skipping mode in order to improve
light-load efficiency.
Selectable operating frequency, in combination with
the external compensation network, allows a wide
range of flexibility in optimizing total solution size
and cost.
FREQ is internally pulled down by 5.5µA, this pin
may be left unconnected to achieve a 700kHz operating frequency.
Soft-Start
The ACT6390 and ACT6391 both offer a programmable soft-start function which minimizes inrush
current during startup. The soft-start period is programmed by connecting a capacitor (CSS) between
SS and G. Operation of the soft-start function is as
follows: when the IC is disabled, SS is actively discharged to G. Upon enabling the IC, CSS is charged
with a 4.5µA current so that the voltage at SS increases in a controlled manner. The peak inductor
current is limited by the voltage at SS, so that the
input current is limited until the soft-start period expires, and the regulator can achieve its full output
current rating.
Setting the Output Voltage
The ACT6390 and ACT6391 both feature external
adjustable output voltages of up to 12V. To program
the output voltage, simply connect a resistive voltage divider between the output, FB, and G, with
resistors set according to the following equation:
⎡⎛ V
R1 = R 2 × ⎢⎜⎜ OUT
⎣⎝ VFB
⎞ ⎤
⎟⎟ − 1⎥
⎠ ⎦
(2)
Where VFB is 1.24V.
The soft-start period can be calculated as a simple
function of the soft-start capacitor using the equation:
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-
OSCILLATOR
+
FREQ
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ACT6390/ACT6391
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Inductor Selection
As a step-up converter, the switch duty cycle (D) is
determined by the input voltage (VIN) and output
voltage (VOUT), as given by the following formula:
D=
VOUT − VIN
VOUT
∆IL
(3)
For example: VIN = 3.3V, VOUT = 12V, fSW = 700kHz
IOUT = 250mA, η = 85%, FREQ = G, K = 0.4
⎛V ⎞
L = ⎜⎜ IN ⎟⎟
⎝ VOUT ⎠
(4)
I L (DC )
VIN
V ×D
DT = IN
L
L × fSW
VOUT × IOUT
VIN × η
Assuming the minimum input voltage is 3V and low
cost external components are used, yielding a low
efficiency of just 80%.
(6)
IL (DC ,MAX ) =
∆IL (MAX ) =
Solving equations (3),(4),(5) and (6) for the inductor
value,
⎞ (VOUT − VIN ) η
⎟⎟
×
⎠ IOUT × fSW K
(11)
Select L = 10µH
(5)
Where η is typical efficiency.
⎛V
L = ⎜⎜ IN
⎝VOUT
⎛ VOUT − VIN ⎞ η
⎜⎜
⎟⎟ ×
⎝ IOUT × fSW ⎠ K
0.85 ⎞
⎛ 3.3V ⎞ ⎛ 12V − 3.3V
=⎜
×
⎟ ⎜
⎟ ≈ 7.99µH
⎝ 12V ⎠ ⎝ 250mA ×700kHz 0.4 ⎠
IL(DC) is the inductor DC current, given by:
IL (DC ) =
2
2
Where: ∆IL is the inductor ripple current in steady
state, typically chosen to be about 0.3, and
∆ IL =
(10)
1.75 × fSW
Where RCS is the current sense trans-resistance,
RCS is 0.45Ω for ACT6390, and RCS = 0.3Ω for
ACT6391.
Define
K=
(VOUT − VIN ) × RCS
L > LMIN =
250 mA ×12V
= 1.25 A
3V × 0.8
3V × (12V − 3V )
= 0.32 A
12V ×10 µH × 700 kHz
IPEAK (MAX ) = 1.25 A +
2
(7)
(12)
1
0.32 A = 1.41A
2
(13)
(14)
For stability,
This equation can be used to determine the correct
trade-off between efficiency, current ripple, size and
cost.
LMIN =
(12V − 3.3V ) × 0.45 Ω = 3.2 µH
(15)
1.75 × 700kHz
Which meets the slope compensation requirement.
When selecting an inductor make sure that the inductors maximum DC current and saturation current
exceed the maximum operation point, calculated
by:
I
×V
IL (DC ,MAX ) = OUT (MAX ) OUT
(8)
VIN (MIN ) × η
Loop Compensation
REF
FB 2
+
-
EA
GM
COMP
3
RCOMP
CCOMP2
and
CCOMP
1
IL(PEAK ,MAX ) = IL(DC,MAX ) + ∆IL(MAX )
2
IOUT (MAX ) ×VOUT 1 VIN (MIN ) [VOUT −VIN (MIN ) ]
=
+ ×
(9)
VIN (MIN ) × η
2
VOUT × L × fSW
The ACT6390 and ACT6391 feature a simple loop
compensation scheme. Simple follow the procedure
detailed below to determine suitable compensation
components. For best results be sure to prototype
to confirm the values, and adjust the compensation
network (by inspecting the transient response, for
example) as needed to optimize results for your
particular application.
If the output voltage is greater than two times of
input voltage, that means the duty cycle is greater
than 50%, the slope compensation is required for
stability. When operating in this condition ensure
that the inductor value is greater than LMIN:
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When the converter operates with continuous inductor current, a right-half-plane zero exits in the
loop’s gain-frequency response. To ensure stability,
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ACT6390/ACT6391
Rev0, 13-May-08
CCOMP2,
the cross-over frequency (unity gain-frequency)
should be less than one-fifth of the right-half-plane
zero fZ(RHP), and lower than one-fifteenth of switching frequency fsw.
CCOMP2 =
VIN × R LOAD
2
2VOUT × π × L
Choose fC =
CCOMP
(16)
For example:
(3.3V )2 × ⎛⎜
1
fZ (RHP ) , then calculate CCOMP:
5
fZ (RHP)
R
V
G
= FB × LOAD × M (1 − D )
VOUT
RCS
2πfC
=
VIN × VFB RLOAD × GM
×
2
RCS × 2πfC
VOUT
RCOMP
K⎞
⎛
RCS × VOUT × IOUT ⎜1 + ⎟
2⎠
⎝
=
α × VFB × GM × VIN × η
(17)
CCOMP =
α=
(19)
(20)
The output capacitor is chosen to set the output
pole for canceling the RCOMP, CCOMP zero.
RLOAD × COUT 48Ω × 33µF
=
= 233kΩ
CCOMP
6.8nF
(29)
If a ceramic capacitor is used with an assumed
ESR of 20mΩ,
(21)
fZ (ESR ) =
CCOMP2 is optional and can be used when the output
capacitor has significant ESR. The ESR will form a
zero as follows:
1
= 241kHz
2π × 33 µF × 20 mΩ
(30)
fZ(ESR) > fC
Since the zero frequency is greater than the pole
frequency ,CCOMP2 can be omitted.
(22)
If a tantalum capacitor is used, whose ESR is about
0.5Ω,
If this zero occurs at a higher frequency than the
cross-over frequency, it can be ignored. Otherwise,
it should be canceled with the pole set by capacitor
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RCOMP × CCOMP 180kΩ × 6.8nF
=
= 25.5 µF (28)
RLOAD
⎛ 12V ⎞
⎜
⎟
⎝ 0.25 A ⎠
RCOMP =
GM: is the trans-conductance of the error amplifier.
1
2π × RESR × COUT
(26)
COUT can be chosen to be either 22µF or 33µF,
choose 33µF to reduce droop.
VFB: is the feedback voltage, 1.24V
fZ (ESR ) =
200 mV
1
=
60
12V
COUT =
η: is the typical efficiency.
RCOMP × CCOMP
RLOAD
3.3V ×1.24V 48Ω
150µS
×
×
= 6.26nF (25)
2
0.45Ω 2π ×11.56kHz
(12V )
⎛ 0.4 ⎞
0.45Ω ×12V × 250mA⎜1 +
⎟
2 ⎠
⎝
RCOMP =
= 186.3kΩ (27)
1
×1.24V ×150µS × 3.3V × 0.85
60
Choose RCOMP = 180kΩ
K: is defined in equation (4)
COUT =
1
fZ (RHP ) = 11.56 kHz
5
Assume that 200mV of transient droop can be
accepted:
(18)
α is the transient droop percentage which can be
accepted, calculated by:
∆VOUT
VOUT
(24)
Choose CCOMP = 6.8nF
Where:
α=
12V ⎞
⎟
⎝ 250mA ⎠ ≈ 57.8kHz
=
2
2 × (12V ) × π ×10 µH
Choose fC =
Select RCOMP to meet the transient-droop requirements.
V ×I
⎛ K⎞
α ×VFB × GM × RCOMP = RCS × OUT OUT × ⎜1 + ⎟
VIN × η
⎝ 2⎠
(23)
If the value of CCOMP2 calculated by (23) is smaller
than 10pF, CCOMP2 can be omitted.
2
fZ (RHP ) =
COUT × RESR
RCOMP
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ACT6390/ACT6391
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fZ (ESR) =
1
= 9.64kHz
2π × 33µF × 0.5 Ω
(31)
fZ(ESR) < fC
RESR × COUT 0.5 Ω × 33µF
=
= 70.8 pF
RCOMP
233kΩ
Choose CCOMP2 = 82pF
CCOMP2 =
(32)
Rectifier Selection
For optimal performance, the rectifier should be a
Schottky rectifier that is rated to handle both the
output voltage as well as the peak switch current.
Over Voltage Protection
The ACT6390 and ACT6391 both feature internal
automatic over-voltage protection (OVP). Once the
outputs achieve regulation, if the voltage at FB falls
below 0.125V the controller will automatically disable and latch off, preventing the controller from
running open-loop and potentially damaging the IC
and load.
To re-enable the converters, simply cycle the EN
pin or remove and reapply power to the input.
Shutdown
Drive EN low to disable the IC and reduce the supply current to just 0.1µA. As with all nonsynchronous step-up DC/DC converters, the external Schottky diode provides a DC path from the input to the output in shutdown. As a result, the output drops to one diode voltage drop below the input
in shutdown.
Thermal Shutdown
The ACT6390 and ACT6391 both feature integrated
thermal overload protection. Both devices are automatically disabled when their junction temperatures
exceed 160°C, and automatically re-enable when
the die temperature decreases by 20°C.
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ACT6390/ACT6391
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TYPICAL PERFORMANCE CHARACTERISTICS
(VIN = VEN = 3.3V, FREQ = G, TA = 25°C, unless otherwise specified.)
ACT6390 Efficiency vs. Output Current
FREQ = IN
L = 2.7µH
80
85
FREQ = G
L = 5.4µH
75
VIN = 5V
VOUT = 12V
90
Efficiency (%)
85
70
65
FREQ = G
L = 10µH
80
FREQ = IN
L = 5.4µH
75
70
65
60
60
55
55
50
50
0
10
100
0
1000
10
ACT6390 Efficiency vs. Output Current
ACT6390 No Load Supply Current vs. VIN
80
Supply Current (mA)
85
FREQ = G
L = 10µH
75
FREQ = IN
L = 5.4µH
70
65
60
0.36
FREQ = IN
L = 5.4µH
ACT6390-004
VIN = 3.3V
VOUT = 12V
90
1000
0.40
ACT6390-003
95
100
Output Current (mA)
Output Current (mA)
Efficiency (%)
ACT6390-002
VIN = 3.3V
VOUT = 5V
90
Efficiency (%)
ACT6390 Efficiency vs. Output Current
95
ACT6390-001
95
0.32
0.28
FREQ = G
L = 10µH
0.24
55
0.20
50
0
10
100
1000
2.5
3
3.5
Output Current (mA)
4
4.5
5
5.5
VIN (V)
2200
ACT6390-005
Maximum Output Current (mA)
ACT6390 Maximum Output Current vs. Input Voltage
FREQ = G
1800
1400
VOUT = 5V
VOUT = 9V
1000
600
VOUT = 12V
200
0
2.5
3.1
3.7
4.3
4.9
5.5
Input Voltage (V)
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Rev0, 13-May-08
TYPICAL PERFORMANCE CHARACTERISTICS
(VIN = VEN = 3.3V, FREQ = G, TA = 25°C, unless otherwise specified.)
ACT6391 Efficiency vs. Output Current
Efficiency (%)
85
80
85
FREQ = IN
L = 4.7µH
75
VIN = 5V
VOUT = 12V
90
Efficiency (%)
FREQ = G
L = 5.4µH
70
65
FREQ = IN
L = 4.7µH
80
75
FREQ = G
L = 10µH
70
65
60
60
55
55
50
50
0
10
100
0
1000
10
ACT6391 Efficiency vs. Output Current
85
80
75
Supply Current (mA)
FREQ = G
L = 10µH
0.40
FREQ = IN
L = 4.7µH
70
65
60
ACT6391-009
VIN = 3.3V
VOUT = 12V
90
1000
ACT6391 No Load Supply Current vs. VIN
ACT6391-008
95
100
Output Current (mA)
Output Current (mA)
Efficiency (%)
ACT6391-007
VIN = 3.3V
VOUT = 9V
90
ACT6391 Efficiency vs. Output Current
95
ACT6391-006
95
VOUT = 12V
0.36
FREQ = IN
L = 4.7µH
0.32
FREQ = G
L = 10µH
0.28
0.24
55
0.20
50
0
10
100
1000
2.5
3
3.5
Output Current (mA)
4
4.5
5
5.5
VIN (V)
2400
ACT6391-010
Maximum Output Current (mA)
ACT6391 Maximum Output Current vs. Input Voltage
FREQ = G
2000
VOUT = 5V
1600
VOUT = 9V
1200
800
400
VOUT = 12V
0
2.5
3
3.5
4
4.5
5
Input Voltage (V)
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PACKAGE OUTLINE
MSOP-8 PACKAGE OUTLINE AND DIMENSIONS
e
C
DIMENSION IN
SYMBOL MILLIMETERS
MIN
MAX
DIMENSION
IN INCHES
MIN
MAX
A
0.820
1.100
0.032
0.043
A1
0.020
0.150
0.001
0.006
A2
0.750
0.950
0.030
0.037
b
0.250
0.380
0.010
0.015
C
0.090
0.230
0.004
0.009
D
2.900
3.100
0.114
0.122
E
2.900
3.100
0.114
0.122
E1
4.750
5.050
0.187
0.199
E
E1
L
b
A2
D
e
A
A1
θ
0.650 TYP
0.026 TYP
L
0.400
0.800
0.016
0.031
θ
0°
6°
0°
6°
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 sales@activesemi.com or visit http://www.active-semi.com. For other inquiries, please send to:
1270 Oakmead Parkway, Suite 310, Sunnyvale, California 94085-4044, USA
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