202048A.pdf

DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
General Description
Features
The AAT3183 is a high efficiency step-down charge pump
converter providing up to 300mA of output current. The
1/2x (gain) charge pump converter topology provides
enhanced efficiency over conventional LDO regulators
and requires only three low cost ceramic capacitors. No
inductor is required, saving space and cost when compared to inductive switching regulators.
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The AAT3183 typically consumes 35μA of no load (zero
output current) quiescent current, making it ideal for
portable battery powered systems. Shutdown current is
less than 1μA.
The AAT3183 soft-start prevents excessive inrush current while providing monotonic turn-on characteristics.
The device includes integrated short-circuit and overtemperature (thermal) protection to safeguard system
components.
VIN Range: 2.7V to 5.5V
VOUT: 1.5V
300mA Maximum Output Current
Ultra-Small Solution for Portable Applications
▪ Small Footprint
▪ Only Three External Ceramic Capacitors Required
▪ No Inductor
High Efficiency over the Output Current Range
Excellent Transient Performance
35μA Typical Quiescent Current
<1.0μA Shutdown Current
Up to 2MHz Switching Frequency
Integrated Soft-Start
Short-Circuit and Thermal Protection
2.0x2.1mm SC70JW-8 Package
-40°C to 85°C Temperature Range
Applications
The AAT3183 is available in a Pb-free 2.0x2.1mm
SC70JW-8 package. Operating temperature range is
-40°C to +85°C.
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Camcorders
Digital Still Cameras
DSP Core Supplies
PDAs, Handheld Devices, Notebook PCs
Smart Phones
Typical Application
CFLY
1μF
C1VIN
IN
C1+
VOUT
OUT
CIN
1μF
AAT3183
VENABLE
EN
COUT
4.7μF
GND
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Pin Descriptions
Pin #
Symbol
1
2
3
4
5
6, 7, 8
OUT
C1+
C1IN
EN
GND
Function
Charge pump converter output. Requires a ceramic capacitor to ground.
Flying capacitor positive terminal. Connect flying capacitor between C1+ and C1-.
Flying capacitor negative terminal. Connect flying capacitor between C1+ and C1-.
Charge pump converter input. Requires a ceramic capacitor to ground.
Enable pin. Active high.
Ground.
Pin Configuration
SC70JW-8
(Top View)
2
OUT
1
8
GND
C1+
2
7
GND
C1-
3
6
GND
IN
4
5
EN
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Absolute Maximum Ratings1
Symbol
VIN
VEN
TJ
TS
TLEAD
Description
Input Voltage to Ground
Enable Voltage to Ground
Operating Junction Temperature Range2
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec.)
Value
Units
-0.3 to 6.0
-0.3 to 6.0
-40 to 150
-65 to 150
300
V
V
°C
°C
°C
Value
Units
160
625
°C/W
mW
Thermal Information
Symbol
JA
PD
Description
Thermal Resistance3
Maximum Power Dissipation at TA = 25°C
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + PD · JA.
3. Mounted on an FR4 board.
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Electrical Characteristics1
VIN = 3.6V, CIN = CFLY = 1.0μF, COUT = 4.7μF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA =
25°C.
Symbol
Description
VIN
Input Voltage
VOUT
Output Voltage Accuracy
VUVLO
Under-Voltage Lockout (UVLO)
IOUT
IQ
VPP
ΔVOUT/ΔVIN
ΔVOUT/ΔIOUT
TSS
FCLK
VEN(L)
VEN(H)
IEN
ROUT
TSD
THYS
Output Current
Quiescent Current
Shutdown Current
Output Voltage Ripple
Line Regulation
Load Regulation
Soft-Start Time
Clock Frequency
Enable Threshold Low
Enable Threshold High
EN Input Leakage
Output Impedance
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
Conditions
No Load, TA = 25°C
No Load
VIN Rising
Hysteresis
VIN Falling
Min
Typ
2.7
-1
-2
1.5
0.15
Max
Units
5.5
+1
+2
2
V
%
V
1.3
VEN = VIN, No Load
VEN = GND
IOUT = 300mA
IOUT = 150mA
IOUT = 100mA
IOUT = 10mA
3.2V ≤ VIN ≤ 5.5V, IOUT = 50mA
0mA ≤ IOUT ≤ 150mA
35
300
60
1
12
16
17
17
2.9
0.053
100
2
IOUT = 300mA
mA
μA
mV
0.4
1.4
1
1
150
15
mV/V
mV/mA
μs
MHz
V
V
μA

°C
°C
1. The AAT3183 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
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Typical Characteristics
Output Voltage Error vs. Output Current
(VOUT = 1.5V)
(VOUT = 1.5V)
90
VIN = 3.6V
80
Efficiency (%)
Output Voltage Error (mV)
Efficiency vs. Output Current
VIN = 4.2V
70
60
50
40
VIN = 5.5V
30
VIN = 5.0V
20
10
0
0.1
1
10
100
1000
20
VIN = 5.5V
10
VIN = 4.2V
0
VIN = 3.6V
-10
-20
-30
-40
-50
0.1
1
Output Current (mA)
0
Output Voltage Error vs. Temperature
(VIN = 3.6V; VOUT = 1.5V; IOUT = 150mA)
50mA
-4
150mA
-6
-8
3.1
3.5
3.9
4.3
4.7
5.1
8.0
6.0
4.0
2.0
0.0
-2.0
-4.0
-6.0
-8.0
5.5
-40
-25
-10
Input Voltage (V)
35
50
65
80
95
Temperature (°C)
No Load Quiescent Current vs. Input Voltage
(VOUT = 1.5V)
100
Supply Current (µA)
50mA
80
Efficiency (%)
20
(VOUT = 1.5V)
90
300mA
50
40
30
20
10
90
80
70
25°C
60
3.1
3.5
3.9
4.3
Input Voltage (V)
4.7
5.1
5.5
85°C
50
40
30
20
10
-40°C
0
0
2.7
5
Efficiency vs. Input Voltage
100
60
1000
(VOUT = 1.5V)
-2
70
100
Output Error vs. Input Voltage
.001mA 10mA
-10
2.7
10
Output Current (mA)
Output Voltage Error (mV)
Output Error (%)
2
VIN = 5.0V
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Typical Characteristics
Output Voltage Ripple vs. Input Voltage
Output Impedance vs. Input Voltage
100
1.8
90
80
Output Impedance (Ω
Ω)
Output Voltage Ripple (mVpp)
(CIN/CFLY = 1µF; COUT = 4.7µF; IOUT = 300mA)
No Post Filter
70
60
50
40
30
100pF Post Filter
20
10
0
3
3.6
4.2
4.8
5.4
25°C
1.2
0.9
0.6
2.7
6
3.1
3.3
3.5
Line Transient
(VIN = 3.6V to 4.2V)
1.52
0.6
1.5
0.5
1.48
0.4
1.46
0.3
1.44
0.2
1.42
0.1
0
1.4
1.38
3.7
3.9
-0.1
1.51
6.9
1.505
6.4
1.5
5.9
1.495
5.4
1.49
4.9
1.485
4.4
1.48
3.9
1.475
3.4
1.47
2.9
Time (50µs/div)
Time (500µs/div)
Output Ripple
Output Ripple
(VIN = 3.6V; VOUT = 1.5V; IOUT = 300mA)
(VIN = 3.6V; VOUT = 1.5V; IOUT = 150mA)
1.54
1.53
1.53
Output Ripple (V)
1.54
1.52
1.51
1.5
1.49
1.48
1.52
1.51
1.5
1.49
1.48
1.47
1.47
1.46
1.46
Time (500ns/div)
4.1
Time (500ns/div)
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Input Voltage (bottom) (V)
0.7
Output Voltage (top) (V)
Load Transient Response
Output Current (bottom) (A)
Output Voltage (top) (V)
2.9
(VIN = 3.6V; VOUT = 1.5V; IOUT = 5mA to 150mA)
1.54
Output Ripple (V)
-40°C
Input Voltage (V)
Input Voltage (V)
6
85°C
1.5
DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Typical Characteristics
Short Circuit
(VIN = 3.6V; VOUT = 1.5V)
Enable Voltage (top) (V)
1
2.5
0.5
2
0
1.5
-0.5
1
0.5
-1
-1.5
0
-2
-0.5
Time (50µs/div)
2.00
3.50
1.50
3.00
1.00
2.50
0.50
2.00
0.00
1.50
-0.50
1.00
-1.00
0.50
-1.50
0.00
-2.00
-0.50
Load Current (bottom) (A)
3
Output Voltage (bottom) (V)
3.5
2
1.5
Output Voltage (top) (V)
Soft Start
(VIN = 3.6V; IOUT = 150mA)
Time (100µs/div)
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Functional Block Diagram
IN
Thermal
Protection,
Current Limit
C1+
EN
Oscillator,
Soft Start
Charge
Transfer
C1-
OUT
VREF
GND
Functional Description
The AAT3183 is a 1/2x (gain) charge pump converter
providing an output voltage which is less than the input
voltage. The step-down (buck) charge pump converter
provides a regulated output voltage for input voltages
greater than 2x the output voltage plus the required
input voltage headroom (see the Applications Information
section for more details). The output current range is
0mA (no load) to 300mA.
The AAT3183 provides an ultra-small DC-DC solution
achieving improved efficiency over LDO step-down regulators. The high switching frequency allows the use of
small external capacitors. Only three ceramic capacitors
are required to achieve a complete step-down converter
solution.
8
Output regulation is maintained with a pulse frequency
modulation (PFM) control scheme. PFM compensates for
input voltage and output current variations by modulating the frequency of charge pump switching intervals.
Switching frequency increases with high output currents
(heavy loads) and decreases with low output currents
(light loads); with a maximum switching frequency of
2MHz. PFM control provides decreased switching losses
and increased efficiency with light loads. This extends
battery life under lightly loaded operating conditions.
The AAT3183 responds quickly to changes in line voltage
and/or output current, providing stable operation with
excellent line and load transient behavior.
No load (zero output current) quiescent current is 35μA
(typical). When disabled, the device consumes less than
1μA of current (shutdown).
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Integrated soft-start limits inrush current, maintains
monotonic turn-on characteristics and eliminates output
voltage overshoot. The device includes short-circuit protection and a self-recovering over-temperature (thermal)
protection.
Charge Pump Operation
The AAT3183 step-down charge pump is implemented
using a fixed 1/2x (gain) converter topology. This configuration allows efficient energy transfer with a single
ceramic flying capacitor. The arrangement of the internal
switches requires that the voltage on the flying capacitor
is greater than the output voltage plus the input voltage
headroom to account for a parasitic voltage drop.
Energy is transferred to the flying capacitor and output
during alternate ‘charge’ and ‘discharge’ intervals. The
amount of energy transferred from the input voltage
source to flying capacitor is proportional to the differential
voltage across the flying capacitor (VDIFF = VIN - VOUT)
which occurs during the ‘charge’ interval multiplied by the
switching frequency. The step-down charge pump transfers energy to the output during both the ‘charge’ and
‘discharge’ intervals. Figure 1 illustrates the energy transfer mechanism during ‘charge’ and ‘discharge’ intervals.
the voltage at the input to the error amplifier decreases.
The error signal increases the effective switching frequency; providing increased current to the output current
thus maintaining the desired output voltage. At light
loads, the effective switching frequency is greatly reduced
which maintains output regulation while minimizing
switching losses.
Operating efficiency (η) is defined as the output power
divided by the input power.
POUT
η= P
IN
=
With a constant output current and 1/2x (gain) operation, the input current is constant regardless of input
voltage. The input current is equal to 50% [1/2x (gain)]
of the output current.
A conventional LDO regulator maintains input current
which is equal to the output current. Operation efficiency
(η) of an LDO regulator is as follows:
IIN = ½IOUT
PFM control compensates for changes in the input voltage
and output current by modulating the frequency of
switching intervals to maintain the desired output voltage. The output voltage is sensed through an internal
resistor divider and compared against a reference voltage
by an error amplifier. As the output voltage decreases,
ENERGY
TRANSFER
CFLY(CHARGE)
(VOUT · IOUT)
(VIN · IIN)
(VOUT · IOUT)
η = (V · ½I )
IN
OUT
=
2 · VOUT
VIN
ENERGY
TRANSFER
VOUT
VOUT
VDIFF
VIN
IOUT
COUT
RLOAD
CFLY(DISCHARGE)
VIN
RLOAD
GND
GND
Figure 1a: Step-Down Charge
Pump “CHARGE” Interval.
IOUT
COUT
Figure 1b: Step-Down Charge
Pump “DISCHARGE” Interval.
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Therefore, the AAT3183 provides a 100% efficiency
improvement over conventional LDO regulators, as illustrated in Figure 2.
90
Efficiency (%)
80
AAT3183
70
60
50
40
LDO
30
20
10
0
50
100
150
200
250
300
Output Current (mA)
Figure 2: AAT3183 Efficiency Comparison vs. LDO.
Under-Voltage Lockout
Under-voltage lockout (UVLO) circuitry monitors the
input voltage (VIN) and ensures that the device will
remain in standby (VOUT = 0V) until a valid VIN is present.
When VIN is less than 1.5V (typical), the input current is
less than 1μA and the output voltage (VOUT) remains at
0V, regardless of the status of the enable pin (EN).
Typically, the UVLO turn-on threshold is 150mV greater
than the UVLO turn-off threshold. UVLO hysteresis minimizes spurious under-voltage detection and eliminates
output glitches.
Shutdown and Soft-Start
The AAT3183 offers an enable pin (EN). When VEN is
below 0.4V (maximum), the device is in standby (shutdown) mode and draws less than 1μA of input current.
The output will remain at 0V when EN voltage is low (VEN
10
≤ 0.4V). When EN is connected to a voltage greater than
1.4V (minimum), the AAT3183 will initiate soft-start and
resume normal operation.
The product features built-in soft-start circuitry to reduce
inrush current and eliminate output voltage overshoot.
The soft-start circuitry is enabled when input UVLO conditions are satisfied and the EN voltage is high (VEN ≥
1.4V). If EN is tied to IN, the soft start is initiated when
UVLO conditions are satisfied. The soft-start circuitry
ramps up the output voltage in a controlled manner and
minimizes output overshoot. Start-up time from EN
positive transitioning (VEN: ≤0.4V to ≥1.4V) to output
(VOUT) in regulation is 100μs (typical).
Thermal and Short-Circuit Protection
High device temperature may result at elevated ambient
temperatures or in cases where high output current
causes self heating of the device. The device will disable
all switching of the charge pump when the internal junction temperature exceeds 150°C (typical). The device
will restart and enable the soft-start sequence when the
temperature is reduced 15°C. This hysteresis ensures
that the absolute device temperature is maintained
below the over-temperature threshold and protects the
device from damage.
In the event of a short circuit, an internal current limit is
activated and limits the output current to 1A (typical).
This current is maintained until the output fault condition
is removed or device over-temperature is reached.
Under sustained short-circuit conditions, the device will
typically reach over-temperature and latch off. The
device will cool down after a short period and continue
to oscillate between active and over-temperature protection states until the fault is removed. Under these worst
case conditions, the device average junction temperature will be less than 150°C.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Applications Information
Input Voltage Headroom
The input voltage headroom is the required minimum
input voltage in excess of 2x the output voltage. The
following equation can be used to calculate the required
input voltage headroom:
VHR =
(IOUT · ROUT)
M
VHR: Input Voltage Headroom
IOUT: Output Current
ROUT: Output Impedance (see “Output Impedance vs.
Input Voltage” performance graph in the “Typical
Characteristics” section of this datasheet)
M: Charge Pump Gain [AAT3183: ½]
Design Example:
AAT3183 Application Conditions:
IOUT = 200mA (max)
VOUT = 1.5V
What is the required minimum input voltage?
Analysis:
Minimum Input Voltage: VIN(MIN) = VHR + 2 · VOUT
Input Voltage Headroom: VHR =
=
(IOUT · ROUT)
M
(0.2A · 1)
= 0.4V
½
Output Voltage: VOUT = 1.5V
Minimum Input Voltage: VIN(MIN) = 0.4V + 2 · 1.5V = 3.4V
Solution:
The required minimum input voltage is 3.4V.
Capacitor Selection
The AAT3183 requires three external capacitors; CIN, CFLY
and COUT. The capacitor size and type can have a significant impact on charge pump performance, including input
and output ripple, stability and operating efficiency.
Surface-mount X5R multi-layer ceramic (MLC) capacitors are a suitable choice due to their small size and
±15% capacitance tolerance over the -55°C to +85°C
operating temperature range. X7R MLC capacitors pro-
vide similar performance over the extended temperature
range of -55°C to +125°C. Initial tolerance of ±10% is
recommended. MLC capacitors offer superior size (high
energy density), low equivalent series resistance (ESR),
and low equivalent series inductance (ESL) when compared to tantalum and aluminum electrolytic capacitor
varieties. In addition, MLC capacitors are not polarized,
which simplifies placement on the printed circuit board.
Negligible circuit losses and fast charge/discharge rates
are possible with MLC capacitors due to their low ESR,
which is typically less than 10mΩ. Switching noise is
minimized due to their low ESL which produces voltage
spikes due to the fast switching current events in charge
pump converters. ESL is typically less than 1nH in MLC
capacitors.
MLC capacitance is reduced with an increasing DC bias
voltage. Capacitance derating varies with case size, voltage rating and vendor. It is recommended that circuit
performance, including output current capability and
input/output voltage ripple, be verified under worst-case
operating conditions.
The capacitor combinations listed in Table 1 are suitable
for output currents up to 220mA and 300mA. Smaller
capacitors may be considered for applications requiring
less than 300mA output current. Smaller solution size
can be achieved at the cost of increased input and output
voltage ripple and decreased output current capability.
CIN, CFLY and COUT should be located close to the AAT3183
device in order to minimize stray parasitics, specifically
ESR and ESL due to PCB layout traces. See the “PCB
Layout Guidelines” section of this datasheet for details.
An input capacitor (CIN) is required to maintain low input
voltage ripple as well as minimize noise coupling to
nearby circuitry. The size of the required input capacitor
can vary, and depends on the source impedance of the
input voltage source. A small 1μF to 2.2μF MLC input
capacitor is suitable in most applications. MLC capacitors
sized as small as 0402 are available which meet these
requirements.
The flying capacitor (CFLY) transfers energy to the output
during both ‘charge’ and ‘discharge’ intervals. CFLY is
sized to maintain the maximum output load and maintain acceptable output voltage ripple at the minimum
input voltage.
The ratio COUT to CFLY is determined by the input to output
voltage ratio and should be maintained near 5:1 for best
performance across the operating range.
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11
DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Input
Capacitor
Size
CIN
(μF/V)
Output
Capacitor
Size
COUT
(μF/V)
Input [1μF(min)]
and Flying
Capacitors Size
CFLY
(μF/V)
Maximum
Output Current
IOUT (mA)
0402
0603
2.2/6.3
4.7/6.3
0603
0603
2.2/6.3
4.7/6.3
0402
0402
0.47/10
1/10
220
300
Table 1: AAT3183 Capacitor Size Selection Chart
(see Table 2 for corresponding manufacturer part numbers).
Input and Output Capacitors
Input [1μF(min)] and Flying Capacitors
CIN/COUT
Value
Voltage
(size)
Mfg
Part Number
CFLY
Value
2.2μF
4.7μF
2.2μF
4.7μF
2.2μF
4.7μF
16V (0603)
10V (0603)
16V (0603)
6.3V (0603)
16V (0603)
10V (0603)
TDK
TDK
Murata
Murata
Taiyo-Yuden
Taiyo-Yuden
C1608X5R1C225K
C1608X5R1A475K
GRM188R61C225K
GRM188R60J475K
EMK107BJ225KA
LMK107BJ475KA
0.47μF
1μF
0.47μF
1μF
0.47μF
1μF
Voltage
(size)
10V
10V
10V
10V
10V
16V
(0402)
(0402)
(0402)
(0402)
(0402)
(0603)
Mfg
Part Number
TDK
TDK
Murata
Murata
Taiyo-Yuden
Taiyo-Yuden
C1005X5R1A474K
C1005X5R1A105K
GRM155R61A474K
GRM155R61A105K
LMK105BJ474KV
EMK107BJ105KA
Table 2: Ceramic Capacitors for the 300mA AAT3183 Step-Down Charge Pump Converter.
Input and Output Voltage Ripple:
Charge Pump Operation
The AAT3183 minimizes switching noise with PFM control. PFM switches only when required to maintain the
output load, reducing the total switching noise. PFM control generates a small amount of VIN and VOUT regulation
ripple (ΔVPFM) due to the charge and discharge of the
input and output capacitors. Additional voltage ripple is
due to the parasitic resistance and inductance distributed on circuit traces and within the input, fly, and output
capacitors themselves; see Figure 3 for the graphic illustration of the AC parasitic components of a AAT3183
typical application circuit.
During the charge pump switching events, an AC current
path (IAC) is established from the voltage source (VIN)
and input capacitor (CIN) through the flying capacitor
(CFLY) to the output capacitor (COUT) and returning
through the ground plane (GND).
The AC voltage ripple signal is measured across CIN and
COUT and is highest at full load and high VIN. These AC
currents charge and discharge the flying capacitor and
flow through the ESR and ESL, which are parasitic elements within the capacitors. Circuit board traces can add
to ESR and ESL and will contribute to the AC voltage
12
ripple. Proper component selection and good layout
practice are critical in providing low ripple, low EMI performance. These parasitic elements should be minimized
to optimize loop transient response and achieve stable
operation.
The IAC current from the flying capacitor flows through
parasitic ESR and ESL. Voltage ripple across the input
and output capacitors due to ESR and ESL are approximated:
ΔVESR = ESRTOT · IAC
ΔVESL =
(ESLTOT · IAC)
ΔtRISE-FALL
The total AC voltage ripple (VRIPPLE) is the sum of the
individual AC voltage ripple signals.
VRIPPLE = ΔVESR + ΔVESL + ΔVPFM
Due to fast switching, a large amount of AC switching
noise due to the parasitic ESL within the CIN and COUT
ceramic capacitors is seen on the output ripple. This
noise may be attenuated with a small amount of input
and output filtering.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
CFLY
LTRACE
ESL
VIN
ESL
ESR
AAT3183
IAC
VOUT
ESL
COUT
CIN
ESR
LTRACE
RLOAD
ESR
GND
Figure 3: AC Parasitic Components of an AAT3183 Typical Application Circuit.
Thermal Performance
Power de-rating of the AAT3183 is not necessary in most
cases due to the low thermal resistance of the SC70JW-8
package, and the limited device losses. Under operating
conditions VOUT = 1.5V and IOUT = 300mA, the estimated
worst-case operating efficiency (η) is 68% (VIN = 4.2V).
160°C/W. The maximum junction temperature (TJ(MAX))
of the device at 85°C ambient is estimated: This is below
the maximum recommended device junction temperature of 125°C.
TJ(MAX) = TAMB(MAX) + (PD · RθJA)
= 85ºC + (211.8mW · 160°C/W)
P
η = OUT
PIN
= 119°C
(VOUT · IOUT)
= (V · I )
IN
IN
Device power dissipation (PD) can be estimated:
PD = PIN - POUT
=
POUT
- POUT
η
= VOUT · IOUT ·
PCB Layout Guidelines
Proper circuit board layout will maximize efficiency while
minimizing switching noise and EMI. The following guidelines should be observed when designing the printed circuit board layout for the AAT3183 step-down converter:
1.
(1 - η)
η
= 1.5V · 0.3A ·
(1 - 0.68)
0.68
= 211.8mW
The typical junction-to-ambient thermal resistance (RJA)
of a SC70JW-8 package mounted on an FR4 board is
2.
3.
Place the three external capacitors as close to the
AAT3183 device as possible. Maintain the circuit
board traces as short and wide as possible. This will
minimize noise resulting from parasitic ESR and ESL
in the AC current path.
Maintain short and wide traces from ground plane to
circuit nodes. This will minimize stray parasitics.
A good example of an optimal layout for the AAT3183
is the AAT3183 evaluation board shown in Figures 4
and 5. The evaluation board schematic is shown in
Figure 6.
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13
DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Figure 4: AAT3183 Evaluation Board
Top Layer.
Figure 5: AAT3183 Evaluation Board
Bottom Layer.
C2
[C FLY]
3
4
VIN
2
C1-
C1+
IN
OUT
1
VOUT
C1
AAT 3183
[C IN]
C3
[C OUT]
R1
5
EN
GND
6,7,8
JP1
Figure 6: AAT3183 Evaluation Board Schematic.
14
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202048A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 11, 2012
DATA SHEET
AAT3183
300mA Inductorless Step-Down Converter
Ordering Information
Output Voltage
Package
Marking1
Part Number (Tape and Reel)2
1.5V
SC70JW-8
UJXYY
AAT3183IJS-1.5-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.
Packaging Information
SC70JW-8
2.20 ± 0.20
1.75 ± 0.10
0.50 BSC 0.50 BSC 0.50 BSC
0.225 ± 0.075
2.00 ± 0.20
0.100
7° ± 3°
0.45 ± 0.10
4° ± 4°
0.05 ± 0.05
0.15 ± 0.05
1.10 MAX
0.85 ± 0.15
0.048REF
2.10 ± 0.30
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
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