202060A.pdf

DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
General Description
Features
The AAT1275A SwitchReg is a 2MHz, 500mA synchronous
boost converter with an integrated current-limiting load
switch controlled output. The AAT1275A operates from a
single-cell Lithium-ion/polymer battery source and provides a regulated 5V, current limit controlled output to
support USB port VBUS applications in portable consumer
electronic products. The AAT1275A can support both USB
2.0 host port and USB on-the-go operation, as well as
general purpose applications where a 5V supply with a
user programmable current limit is needed.
• High Frequency Boost With 5V / 500mA Output
Capability From a Single-Cell Lithium-Ion/Polymer
Battery
• Input Voltage Range: 2.7V to 5V
• VOUT1 Adjustable
• >90% Efficiency
• 2MHz Switching Frequency
• True Load Disconnect
• Load Switch With Programmable Current Limit
• Over-Temperature, Over-Current Protection
• Inrush Current Limit
• Fault Report
• Low Shutdown Current < 1μA Typical
• -40°C to +85°C Temperature Range
• TSOPJW-12 and TDFN34-16 Packages
The high efficiency boost converter section of the
AAT1275A is typically set for a 5V output and can deliver
up to 500mA load current to support USB VBUS operation
from an input supply as low as 2.7V. The high boost converter switching frequency (up to 2.0MHz) provides fast
load transient and allows the use of small external components. Fully integrated control circuitry simplifies system design and reduces total solution size.
Applications
•
•
•
•
•
•
The integrated, programmable current limiting load
switch provides USB port protection for portable devices
allowing the AAT1275A to supply a 5V USB VBUS up to
500mA. The load switch provides an active low fault flag
to alert the system in the event of an over-current condition applied to the AAT1275A output.
USB On-the-Go
Cell Phones
Digital Still Cameras
PDAs and Portable Media Players
Smart Phones
Other Hand-Held Devices
The AAT1275A is available in the Pb-free, space-saving
12-pin TSOPJW and 16-pin TDFN34 packages and is
rated over the -40°C to +85°C operating temperature
range.
Typical Application
L1 2.2μH
LIN
VIN
SW
OUT1
IN
CIN
4.7μF
RFB1
432k
VCC
FB
10k
AAT1275A
Fault
COUT1
4.7μF
RFB2
59k
FLT
Enable
EN
VBUS Output
OUT2
SET
RSET
COUT2
1μF
GND
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
1
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Pin Descriptions
Pin
TSOPJW-12
TDFN34-16
Symbol
1
2
3
4
5
6
1, 16
3, 15
13, 14
11, 12
10
9
LIN
IN
PGND
SW
OUT1
OUT2
7
8
SET
8
7
FLT
9
10
11
12
6
5
4
2
FB
GND
VCC
EN
EP
Function
Switched power input. Connect an inductor between this pin and the SW pin.
Supply input. Connect to VCC for proper operation.
Power ground.
Switch pin. Boost inductor is connected between SW and LIN.
Boost converter output.
Load switch output.
Load switch current limit programming pin. Connect a set resistor between this pin
and ground.
Load switch over-current or over-temperature fault flag. Active low, open-drain output. A 10k external pull-up resistor is recommended.
Boost converter voltage feedback pin.
Ground.
Bias supply for the internal circuitry. Connect to IN for proper operation.
Enable pin, active high.
Exposed paddle (bottom); connect to ground directly beneath the package.
Pin Configuration
TSOPJW-12
(Top View)
2
TDFN34-16
(Top View)
LIN
1
16
LIN
EN
2
15
IN
IN
3
14
PGND
VCC
4
13
PGND
GND
5
12
SW
FLT
FB
6
11
SW
SET
FLT
7
10
OUT1
SET
8
9
OUT2
LIN
1
12
EN
IN
2
11
VCC
PGND
3
10
GND
SW
4
9
FB
OUT1
5
8
OUT2
6
7
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Absolute Maximum Ratings
Symbol
Description
VCC, IN, OUT
SW
LIN, FB
EN, SET, FLT
TJ
TLEAD
IN, OUTx to GND
SW to GND
LIN, FB to GND
EN, SET, FLT to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
6.0
-0.3 to VOUT + 0.3
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-40 to 150
300
V
V
V
V
°C
°C
Value
Units
Thermal Characteristics1
Symbol
Description
JA
Maximum Thermal Resistance
PD
Maximum Power Dissipation @ TA = 25°C
TSOPJW-12
TDFN34-16
TSOPJW-12
TDFN34-16
110
50
909
2.0
°C/W
mW
W
1. Mounted on an FR4 board.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
3
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Electrical Characteristics1
VCC = VIN = 3.6V, VOUT1 = 5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol
VIN, VCC
VOUTx
VUVLO
IQ
Description
Operating Input Voltage Range
Maximum Output Voltage Range
Under-Voltage Lockout
Quiescent Supply Current
ISHDN
Shutdown Current
Boost Converter
Continuous Output Current
IO
ILIMIT
Input Switch Current Limit
VFB
FB Pin Regulation
VOUT
Output Voltage Tolerance
VOUT
Load Regulation
(VOUT*VIN)
VOUT/VOUT Line Regulation
RDS(ON)H
High Side Switch On Resistance
RDS(ON)L
Low Side Switch On Resistance
RDS(ON)_IN
Input Disconnect Switch
TSS
Soft-Start Time

FOSC
Conditions
Efficiency
Switching Frequency
Load Switch
RDS(ON)
Current Limit Switch On Resistance
Current Limit
ILIM
ILIM(MIN)
Minimum Current Limit
TRESP
Current Limit Response Time
TON
Turn-On Delay Time
TOFF
Turn-Off Delay Time
VFLT_LOW
FLT Logic Output Low
IFLT
FLT Logic Output High Leakage Current
Fault Blanking Time
TBLANK
Control
VTH-L
EN Threshold Low
VTH-H
EN Threshold High
IEN
EN Input Leakage
TJ-TH
TJ Thermal Shutdown Threshold
TJ-HYS
TJ Thermal Shutdown Hysteresis
Min
Typ
3.0
No Load, Switching
No Load, Not Switching, VFB = 1.5V
EN = GND
100
45
3V < VIN < 5V, VO = 5V
No Load, TA = 25°C
ILOAD = 0 to 500mA, VIN = 2.7V to 5V
Max
Units
5.0
5.5
2.9
V
V
V
90
1.0
500
0.591
-3
ILOAD = 0 to 500mA
VIN = 2.7V to 5V
VOUT1 = 5V, IOUT1 = 500mA
VOUT1 = 5V, IOUT1 = 500mA
VOUT1 = 5V, IOUT1 = 500mA
From Enable to Output Regulation
IOUT1 = 250mA, L = 2.2μH, VIN = 3.6V,
VOUT1 = 5V
TA = 25°C, IOUT1 = 500mA, VIN = 3.6V,
VOUT1 = 5V
VOUT1 = 5V, TA = 25°C
RSET = 16.9k
RSET = 40k
VOUT1 = 5V
VOUT1 = 5V, RL = 10
VOUT1 = 5V, RL = 10
ISINK = 1mA
VFAULT = 5V
Rising and Falling Edge
2.5
0.6
0.609
3
μA
mA
A
V
%
0.005
%/mA
0.2
200
170
170
300
%/V
m
m
m
μs
90
%
2.0
MHz
500
100
0.4
4
10
0.5
4
0.25
625
0.4
1
0.4
VEN = 5V, VIN = 5V
μA
1.4
-1
1
140
15

mA
mA
μs
ms
μs
V
μA
ms
V
V
μA
°C
°C
1. The AAT1275A is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Typical Characteristics
Efficiency vs. Output Current
Load Regulation
(VOUT = 5V)
(VOUT = 5.0V)
1.5
100
80
70
60
50
40
30
VIN = 4.2V
VIN = 3.6V
VIN = 2.7V
20
10
0
0.1
1
10
100
Output Error (%)
Efficiency (%)
90
VIN = 4.2V
VIN = 3.6V
VIN = 2.7V
1.0
0.5
0.0
-0.5
-1.0
-1.5
0.1
1000
1
10
Output Current (mA)
Line Regulation
(VIN = 3.6V; VOUT = 5V; IOUT = 100mA)
1.5
Output Voltage Error (%)
Line Regulation (%)
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
2.7
3.0
3.3
3.6
3.9
4.2
4.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-50
-25
0
Quiescent Current vs. Input Voltage
No Load Current (µA)
20
15
10
5
3.6
3.9
Input Voltage (V)
100
140
85°C
25°C
-40°C
3.3
75
(VIN = 3.6V; VOUT = 5.0V)
25
3.0
50
No Load Current vs. Temperature
(VOUT = 5V; No Load)
2.7
25
Temperature (°°C)
Input Voltage (V)
Input Current (mA)
1000
Output Voltage vs. Temperature
(VOUT = 5V; IOUT = 300mA)
0
100
Output Current (mA)
4.2
4.5
120
100
80
60
40
20
0
-50
0
50
100
150
Temperature (°°C)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
5
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Typical Characteristics
Load Transient
Load Transient
(VOUT = 5V; VIN = 3.6V; IOUT = 1mA to 500mA)
(VOUT = 5V; VIN = 3.6V; IOUT = 250mA to 500mA)
4.90
4.80
0.8
0.4
0.0
1.6
5.05
1.4
5.00
1.2
4.95
1.0
4.90
0.8
4.85
0.6
4.80
0.4
4.75
0.2
4.70
0.0
Output Current (bottom)
(200mA/div)
5.00
Output Voltage (top)
(50mV/div)
5.10
5.10
Output Current (bottom)
(400mA/div)
Output Voltage (top)
(100mV/div)
5.20
-0.4
Time (20µs/div)
Time (20µs/div)
Line Transient
Load Switch RDS(ON) vs. Input Voltage
6.2
4.0
6.0
3.5
5.8
3.0
5.6
2.5
5.4
2.0
5.2
1.5
5.0
1.0
4.8
0.5
4.6
250
85°C
150
100
-40°C
25°C
50
0
2.5
2.7
2.9
Time (20µs/div)
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
Supply Voltage (V)
P-Channel RDS(ON) vs. Supply Voltage
N-Channel RDS(ON) vs. Supply Voltage
350
320
100°C
260
85°C
240
220
25°C
200
100°C
300
125°C
280
RDS(ON) (mΩ
Ω)
300
RDS(ON) (mΩ
Ω)
120°C
200
RDS(ON) (mΩ
Ω)
4.5
Output Voltage (bottom)
(200mV/div)
Input Voltage (top)
(500mV/div)
(VOUT = 5V; VIN = 3.6V to 4.2V; IOUT = 400mA)
125°C
250
85°C
200
25°C
150
180
100
160
2.5
2.7
2.9
3.1
3.3
3.5
3.7
3.9
Supply Voltage (V)
6
4.1
4.3
4.5
2.5
2.7
2.9
3.1
3.3
3.5
3.7
3.9
Supply Voltage (V)
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4.1
4.3
4.5
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Typical Characteristics
Enable Soft Start
Current Limit vs. RSET
(VIN = 3.6V; VOUT = 5V; IOUT = 500mA)
100
VEN
(2V/div)
RSET (kΩ
Ω)
Boost
Converter
VOUT (2V/div)
Load Switch
VOUT (2V/div)
IIN
(500mA/div)
10
100
Time (1ms/div)
1000
Current Limit (mA)
Current Limit vs. Temperature
(RSET = 20.3kΩ
Ω)
Current Limit (%)
6.0
4.0
2.0
0.0
-2.0
-4.0
-6.0
-50
-25
0
25
50
75
100
Temperature (°C)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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7
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Functional Block Diagram
LIN
SW
IN
OUT1
VCC
FB
Boost Regulator
Control
EN
OUT2
SET
Load Switch
Control
FLT
Functional Description
The AAT1275A is a 500mA synchronous boost converter
with a current-limited load switch targeted for single-cell
Lithium-ion/polymer devices acting as a portable host
for USB power.
The AAT1275A has integrated control and synchronous
MOSFETs, minimizing the cost and the number of external components. Additional features include a soft-start
function which allows the load voltage to ramp up in a
controlled manner, eliminating output voltage overshoot
and minimizing inrush current. Typical soft-start time for
the boost converter is approximately 300μs.
The AAT1275A also has a load switch with user-programmable current limiting. The load switch reports
8
GND
over-current and over-temperature conditions through
an open-drain fault reporting signal (FLT). The fault
reporting signal has a 4ms turn-on delay.
Control Scheme
The control circuit uses hysteretic current mode control
with internal inductor current sensing for very high efficiency over a wide output current range. The boost converter operates in continuous conduction mode (CCM).
This minimizes the RMS current and optimizes the efficiency at load conditions where the losses are dominated
by the power MOSFET RDS(ON). This also keeps the ripple
current to a minimum and minimizes the output voltage
ripple and the output capacitor size.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Step-Up Converter
Application Information
The AAT1275A step-up converter provides the benefits of
current mode control with a simple hysteretic feedback
loop. The device maintains exceptional DC regulation,
transient response, and cycle-by-cycle current limit without additional compensation components. The AAT1275A
modulates the power MOSFET switching current in
response to changes in output voltage. The voltage loop
programs the required inductor current in response to
changes in the output load and input voltage.
The switching cycle initiates when the N-channel MOSFET
is turned ON and the inductor current ramps up. The ON
interval is terminated when the inductor current reaches
the programmed peak current level. During the OFF
interval, the input current decays until the lower threshold is reached. The lower current is equal to the peak
current minus a preset hysteresis threshold, which
determines the inductor ripple current. The peak current
is adjusted by the controller until the output current
requirement is met.
The magnitude of the feedback error signal determines
the average input current. Therefore, the AAT1275A boost
controller implements a programmed current source connected to the output capacitor and load resistor. There is
no right-half plane zero, and loop stability is achieved with
no additional external compensation components.
The operating frequency varies with changes in the input
voltage, output voltage, and inductor size. A small 2.2μH
(± 20%) inductor is selected to maintain high frequency
operation for the 5V USB output voltage.
Output Voltage Programming
The output voltage is programmed through a resistor
divider network located from the OUT1 output capacitor
to the FB pin to ground.
Soft Start / Enable
The input disconnect switch is activated when a valid
input voltage is present and the EN pin is pulled high. The
slew rate control on the P-channel MOSFET ensures minimal inrush current as the output voltage is charged to the
input voltage prior to switching of the N-channel power
MOSFET. The soft-start circuitry guarantees monotonic
turn-on and eliminates output voltage overshoot across
the full input voltage range for all load conditions.
Input Current Limit and
Over-Temperature Protection
The switching of the N-channel MOSFET terminates when
input current limit of 2.5A (typical) is exceeded. This
minimizes the power dissipation and component stresses
under overload and short-circuit conditions. Switching
resumes when the current decays below the limit.
Thermal protection disables the AAT1275A boost converter when the internal power dissipation becomes
excessive. The junction over-temperature threshold is
140°C with 15°C of temperature hysteresis. The output
voltage automatically recovers when the over-temperature or over-current fault condition is removed.
Shutdown and Output Disconnect
A typical synchronous step-up (boost) converter has a
conduction path from the input to the output via the
body diode of the P-channel MOSFET. The AAT1275A
design eliminates this conduction path. This enables the
AAT1275A to provide true load disconnect during shutdown and inrush current limit at turn-on.
Short-Circuit Protection
The P-channel synchronous output disconnect feature
also gives the AAT1275A the ability to provide output
short-circuit current limit protection.
Under-Voltage Lockout
Under-voltage lockout (UVLO) guarantees sufficient VIN
bias and proper operation of all internal circuitry prior to
soft start. Internal bias of all circuits is controlled via the
VCC input, which is connected to VIN.
Selecting the Boost Inductor
The AAT1275A boost controller utilizes hysteretic control
and the switching frequency varies with output load and
input voltage. The value of the inductor determines the
maximum switching frequency of the boost converter.
Increasing output inductance decreases the switching frequency, resulting in higher peak currents and increased
output voltage ripple. To maintain the 2MHz switching frequency and stable operation, an output inductor sized from
1.5μH to 2.7μH is recommended. Manufacturer’s specifications list both the inductor DC current rating, which is
a thermal limitation, and peak inductor current rating,
which is a function of the saturation characteristics.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
9
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Measure the inductor current at full load and high ambient temperature to ensure that the inductor does not
saturate or exhibit excessive temperature rise. Select
the output inductor (L) to avoid saturation at the minimum input voltage and maximum load. The RMS current
flowing through the boost inductor is equal to the DC
plus AC ripple components. The maximum inductor RMS
current occurs at the minimum input voltage and the
maximum load. Use the following equations to calculate
the maximum peak and RMS current:
DMAX =
IPP =
VO - VIN(MIN)
VO
VIN(MIN) · D
L · FS
IP =
IO
1-D
IPK = IP +
IPP
2
IV = IP - IPP
IRMS =
IPK2 + IPK · IV + IV2
3
PLOSS(INDUCTOR) = I2RMS · DCR
At light load and low output voltage, the controller
reduces the operating frequency to maintain maximum
efficiency. As a result, further reduction in output load
does not reduce the peak current. The minimum peak
current ranges from 0.5A to 0.75A.
Compare the RMS current values with the manufacturer’s temperature rise, or thermal derating guidelines. For
a given inductor type, smaller inductor size leads to an
increase in DCR winding resistance and, in most cases,
increased thermal impedance. Winding resistance
degrades boost converter efficiency and increases the
inductor’s operating temperature.
Shielded inductors provide decreased EMI and may be
required in noise sensitive applications. Unshielded chip
inductors provide significant space savings at a reduced
cost compared to shielded inductors. In general, chiptype inductors have increased winding resistance (DCR)
when compared to shielded, wound varieties.
10
Selecting the Step-Up
Converter Capacitors
The high output ripple inherent in the boost converter
necessitates low impedance output filtering. Multi-layer
ceramic (MLC) capacitors provide small size, adequate
capacitance, with low parasitic equivalent series resistance (ESR) and equivalent series inductance (ESL). This
makes them well suited for use with the AAT1275A. MLC
capacitors of type X7R or X5R ensure good capacitance
stability over the full operating range. MLC capacitors
exhibit significant capacitance reduction with an applied
DC voltage. Output ripple measurements can confirm
that the capacitance used meets the specific ripple
requirements. Voltage derating minimizes this factor, but
results may vary with package size and among specific
manufacturers.
Use a 4.7μF 10V ceramic output capacitor to minimize
output ripple for the 5V output. Small 0805 sized ceramic capacitors are available which meet these requirements.
Estimate the output capacitor required at the minimum
switching frequency (FS) of 800kHz (worst-case).
COUT =
IOUT · DMAX
FS · ΔVOUT
The boost converter input current flows during both ON
and OFF switching intervals. The input ripple current is
less than the output ripple and, as a result, less input
capacitance is required. A ceramic output capacitor from
1μF to 4.7μF is recommended. Minimum 6.3V rated
capacitors are required at the input. Ceramic capacitors
sized as small as 0603 are available which meet these
requirements.
Setting the Output Voltage
Program the output voltage through a resistive divider
located from the output to the FB pin to ground. The
internal error amplifier reference voltage is 0.6V. A
59.0k programming resistor value from VFB to GND
with a 432k resistor from FB to the output will set the
output voltage to 5V.
R2⎞
⎛
VOUT = VREF · 1 + R3
⎝
⎠
432kΩ ⎞
⎛
= 0.6V · 1 + 59.0kΩ
⎝
⎠
= 5.0V
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
USB Load Switch
Application Information
Steady-State Maximum
Power Dissipation
Setting the Load Switch Current Limit
In most applications, the variation in ILIM must be taken
into account when determining RSET. The ILIM variation is
due to processing variations from part to part, as well as
variations in the voltages at OUT1 and OUT2, plus the
operating temperature. The typical RSET value for a
300mA load is in the range of 20 to 22k.
RSET (kΩ)
IOUT (mA)
11
12
14
16
18
20
30
40
740
690
590
550
450
420
160
100
The maximum power dissipation for the AAT1275A
occurs at the minimum input voltage, where it operates
in continuous conduction mode (CCM). The total power
dissipation at full load is dominated by the RDS(ON) losses
of the power MOSFET. The dissipation includes the losses
in the input and output switch, as well as both synchronous switches.
Due to the magnitude of the inductor ripple current, it
cannot be neglected when analyzing the RDS(ON) power
dissipation. Once the ripple current has been determined, the RMS current during the on and the off period
can be calculated.
DMAX =
IPP =
Table 1: Load Switch Current Limit vs. RSET.
A fault flag indicates when the OUT2 pin load current has
exceeded the current limit level set by RSET. The fault flag
is an active low, open-drain pin that requires 10k pullup to VIN. The fault signal has a 4ms blanking time to
prevent false over current indicator during the charging
of the USB bus capacitor.
VIN(MIN) · DMAX
L · FS
IP =
Operation in Current Limit
When a heavy load is applied to OUT2 of the AAT1275A,
the load current is limited to the value of ILIM (determined by RSET) causing a drop in the output voltage. This
increases the AAT1275A power dissipation and die temperature. When the die temperature exceeds the overtemperature limit, the AAT1275A shuts down until it has
cooled sufficiently, at which point it will start up again.
The AAT1275A will continue to cycle on and off until the
load is removed, power is removed, or until a logic low
level is applied to the EN pin.
VO - VIN(MIN)
VO
IO
1-D
IPK = IP +
IPP
2
IV = IP - IPP
IRMS(ON) =
IRMS(OFF) =
(IP2 + IPK · IV + IV2) · DMAX
3
(IP2 + IPK · IV + IV2) · (1 - DMAX)
3
PTOTAL = IRMS(ON)2 · (RDS(ON)IN + RDS(ON)N)
+ IRMS(OFF)2 · (RDS(ON)IN + RDS(ON)P + RDS(ON))
TJ(MAX) = PTOTAL · θJA + TAMB
RDS(ON)IN is the input disconnect switch, RDS(ON)N is the
high-side synchronous switch, RDS(ON)P is the low-side
synchronous switch, and RDS(ON) is the current limit load
switch.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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11
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
PCB Layout Guidelines
The step-up converter performance can be adversely
affected by poor layout. Possible impact includes high
input and output voltage ripple, poor EMI performance,
and reduced operating efficiency. Every attempt should
be made to optimize the layout in order to minimize
parasitic PCB effects (stray resistance, capacitance,
inductance) and EMI coupling from the high frequency
SW node.
A suggested PCB layout for the AAT1275A is shown in
Figures 1 and 2. The following PCB layout guidelines
should be considered:
Figure 1: AAT1275A TSOPJW-12 Package
Evaluation Board Top Side Layout.
12
1.
2.
3.
4.
Minimize the distance from capacitors C2 and C3 to
the IC. This is especially true for the output capacitor C2, which conducts high ripple current associated with the step-up converter output capacitor.
Place the feedback resistor close to the output terminals. Route the output pin directly to resistor R2 to
maintain good output regulation. R3 should be routed
close to the output GND pin and should not share a
significant return path with output capacitor C2.
Minimize the distance between L1 and the switching
pin SW; minimize the size of the PCB area connected
to the SW pin.
Maintain a ground plane and connect to the IC RTN
pin(s), as well as the GND terminals of C1 and C2.
Figure 2: AAT1275A TSOPJW-12 Package
Evaluation Board Bottom Side Layout.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
VIN
U1
AAT1275A
L1 2.2μH
GND
R4
4
SW
FLT
8
1
LIN
OUT2
6
7
16.9kΩ
C6
120μF
CCase
SET
OUT1
GND
EN
12
11
VCC
FB
9
PGND
3
VIN
FLT
VO2
VO1
5
10
2
VIN
R1
10K
J5
R2
432k
R3
59k
C3
4.7μF
10V
C2
4.7μF
10V
C1
4.7μF
GND
VIN
3
2
GND
1
Enable
Figure 3: AAT1275A TSOPJW-12 Package Evaluation Board Schematic.
Figure 4: AAT1275A TDFN34-16 Package
Evaluation Board Top Side Layout.
Figure 5: AAT1275A TDFN34-16 Package
Evaluation Board Bottom Side Layout.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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13
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
L1
AAT1275A-TDFN34-16 2.2μH
U1
1
3
VIN
4
C6
120μF
R1
10K
15
3
2
1
LIN
LIN
VIN
SW
VCC
SW
VIN
OUT2
2
EN
OUT1
7
FLT
16
12
11
Feedback Option
1 2 3
9
VOUT2
10
Enable
R5 1k
1
FB
6
PGND SET
GND
PGND GND
8
R2
432k
FLT
13
C3
4.7μF
10V
14
C4
100pF
VOUT1
C2
4.7μF
10V
C1
4.7μF
10V
5
R4
16.9k
R3
59k
Figure 6: AAT1275A TDFN34-16 Package Evaluation Board Schematic.
Manufacturer
Part Number
Value
Voltage
Temp. Co.
Case
Murata
Murata
Murata
Murata
GRM21BR61A475KA73L
GRM18BR60J475KE19D
GRM21BR60J106KE19
GRM21BR60J226ME39
4.7μF
4.7μF
10μF
22μF
10V
6.3V
6.3V
6.3V
X5R
X5R
X5R
X5R
0805
0603
0805
0805
Table 2: Typical Surface Mount Capacitors.
Manufacturer
Part Number
Inductance (μH)
Max DC
Current (A)
DCR ()
Size (mm)
LxWxH
Type
Sumida
Sumida
Coiltronics
Coiltronics
CDRH2D14-2R2
CDRH4D11/HP-2R4
SD3112-2R2
SD3114-2R2
2.2
2.4
2.2
2.2
1.6
1.7
1.12
1.48
0.094
0.105
0.140
0.086
3.2x3.2x1.55
4.8x4.8x1.2
3.1x3.1x1.2
3.1x3.1x1.4
Shielded
Shielded
Shielded
Shielded
Table 3: Typical Surface Mount Inductors.
14
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Step-Up Converter Design Example
Specifications
VOUT = 5V
IOUT = 300mA
VIN = 2.7V to 4.2V (3.6V nominal)
TAMB = 50°C
Output Inductor
DMAX =
VOUT - VIN(MIN)
5V - 2.7V
=
= 0.46
VOUT
5V
From the characterization curves, the switching frequency at room temperature with a 300mA load and 2.2μH inductor
is about 800kHz.
IPP =
IP =
VIN(MIN) · DMAX
L · FS
IO
1-D
IPK = IP +
IPP
2
IV = IP - IPP
IV = IP - IPP = 0.9A - 0.7A = 0.20A
IRMS =
IPK2 + IPK · IV + IV2
=
3
0.9A2 + 0.9A · 0.2A + 0.2A2
= 0.59A
3
For the Sumida CDRH2D14-2R2 inductor, ISAT = 1.0A, IDC(MAX) = 1.6A and DCR = 94m.
PLOSS(INDUCTOR) = I2RMS · DCR = (590mA)2 · 94mΩ = 32mW
5V Output Capacitor
ΔVOUT = 0.05V
COUT(MIN) =
IOUT · DMAX
0.3A · 0.46
=
= 3.0µF; use 4.7µF 10V MLC
FS · ΔVOUT
800kHz · 0.05V
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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15
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
AAT1275A Losses
IRMS(ON) =
IRMS(OFF) =
(IPK2 + IPK · IV + IV2) · DMAX
=
3
(0.9A2 + 0.9A · 0.2A + 0.2A2) · 0.46
= 0.4A
3
(IPK2 + IPK · IV + IV2) · (1 - DMAX)
=
3
(0.9A2 + 0.9A · 0.2A + 0.2A2) · (1 - 0.46)
= 0.43A
3
PTOTAL = IRMS(ON)2 · (RDS(ON)IN + RDS(ON)N) + IRMS(OFF)2 · (RDS(ON)IN + RDS(ON)P + RDS(ON))
= 0.4A2 · (0.25Ω + 0.3Ω) + 0.422 · (0.25Ω + 0.3Ω + 0.2Ω) = 0.22W
TJ(MAX) = PTOTAL · θJA + TAMB = 0.22W ·
16
110°C
+ 85°C = 109°C
W
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TSOPJW-12
TDFN34-16
8EXYY
7YXYY
AAT1275AITP-0.6-T1
AAT1275AIRN-0.6-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information3
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.20 + 0.10
- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.04 REF
0.055 ± 0.045
0.15 ± 0.05
+ 0.10
1.00 - 0.065
0.9625 ± 0.0375
3.00 ± 0.10
4° ± 4°
0.45 ± 0.15
0.010
2.75 ± 0.25
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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17
DATA SHEET
AAT1275A
Boost Converter with USB Power Switch
TDFN34-16
3.000 ± 0.050
1.600 ± 0.050
Detail "A"
3.300 ± 0.050
4.000 ± 0.050
Index Area
0.350 ± 0.100
Top View
0.230 ± 0.050
Bottom View
C0.3
(4x)
0.050 ± 0.050
0.450 ± 0.050
0.850 MAX
Pin 1 Indicator
(optional)
0.229 ± 0.051
Side View
Detail "A"
All dimensions in millimeters.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a
service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes.
No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale.
THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR
PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES
NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM
THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper
use or sale.
Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product
design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters.
Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for
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18
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202060A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012