Analogic AAT2113A 3mhz, fast transient 1.5a step-down converter in 2mm x 2mm package Datasheet

PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
General Description
Features
The AAT2113A SwitchReg™ is a 1.5A step-down converter with a typical input voltage of 3.3V and a fixed
output voltage of 1.2V or an adjustable output. The
3MHz switching frequency enables the use of small
external components. The ultra-small 2mm x 2mm footprint and high efficiency make the AAT2113A an ideal
choice for portable applications.
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The AAT2113A delivers 1.5A maximum output current
while consuming only 55μA no-load quiescent current.
Low RDS(ON) integrated MOSFETs and 100% duty cycle
operation make the AAT2113A the ideal choice for high
output voltage, high current applications which require a
low dropout threshold.
The AAT2113A provides excellent transient response and
output accuracy across the operating range. No external
compensation is required.
The AAT2113A maintains high efficiency throughout the
load range. The unique low-noise architecture reduces
ripple and spectral noise. The AAT2113A automatically
optimizes efficiency during Light Load mode (LL) and
maintains constant frequency and low output ripple during PWM mode.
Over-temperature and short circuit protection safeguard
the AAT2113A and system components from damage.
The AAT2113A is available in a Pb-free, ultra-small, low
profile, 8-pin 2mm x 2mm FTDFN package. The product
is rated over a temperature range of -40°C to 85°C.
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•
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•
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5mm x 5mm Total Solution Size
1.5A Maximum Output Current
Tiny 0.47μH Chip Inductor
Excellent Transient Response
Input Voltage: 2.7V to 5.5V
Ultra-small, Low Profile 8-pin 2mm x 2mm FTDFN
Package
Fixed or Adjustable Output Voltage Options:
▪ Fixed Output Voltage: 1.2V
▪ Adjustable Output Voltage: 1.0V to 1.8V
High Efficiency, Low Noise Architecture
3MHz Switching Frequency
No External Compensation Required
55μA No Load Quiescent Current
100% Duty Cycle Low-Dropout Operation
Internal Soft Start
Over-Temperature and Current Limit Protection
<1μA Shutdown Current
-40°C to 85°C Temperature Range
Applications
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Cellular Phones
Digital Cameras
Hard Disk Drives
MP3 Players
PDAs and Handheld Computers
Portable Media Players
USB Devices
Wireless Network Cards
Typical Application
Load Transient Response
VIN
2.7V to 5.5V
(VIN = 5V; VOUT = 1.2V; IOUT = 10% to 100%;
COUT = 10µF, 6.3V, 0603)
U1
1.3V
1.25V
1.2V
100mV
1.15V
1.1V
1.5A
C1
4.7µF
6.3V
0603
C3
1.0µF
6.3V
0402
L1
VP
LX
EN
LX
AAT2113A
VCC
AGND
FB
VOUT
1.2V/1.5A
0.47µH
C3
10µF
6.3V
0603
PGND
FTDFN 22-8
150mA
Time (20µs/div)
2113A.2009.06.1.1
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1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Pin Descriptions
Pin #
Symbol
1
2
3
PGND
VP
VCC
4
FB
5
AGND
6
EN
7, 8
LX
Function
Main power ground return pin. Connect to the output and input capacitor return.
Input power supply tied to the source of the high side P-channel MOSFET.
Power supply; supplies power for the internal circuitry.
Feedback input pin. This pin is connected directly to the converter output for the 1.2V fixed output version,
or connected to an external resistor divider for the adjustable output version.
Analog Ground. This pin is internally connected to the analog ground of the control circuitry.
Enable pin. A logic low disables the converter and it consumes less than 1μA of current. When connected
high, it resumes normal operation.
Switching node. Connect the inductor to this pin. It is internally connected to the drain of both high and
low side MOSFETs.
Pin Configuration
FTDFN22-8
(Top View)
PGND
VP
VCC
FB
2
1
8
2
7
3
6
4
5
LX
LX
EN
AGND
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2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Absolute Maximum Ratings1
TA = 25°C unless otherwise noted.
Symbol
VCC, VP
VLX
VFB
EN
TJ
TLEAD
Description
VP, VCC to GND
LX to GND
FB to GND
EN to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec.)
Value
Units
6.0
-0.3 to VP + 0.3
-0.3 to VP + 0.3
-0.3 to VCC + 0.3
-40 to 150
300
V
V
V
V
°C
°C
Value
Units
70
1.4
°C/W
W
Thermal Characteristics
Symbol
ΘJA
PD
Description
Maximum Thermal Resistance
Maximum Power Dissipation2, 3
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. Mounted on an FR4 board.
3. Derate 14mW/°C above 25°C.
2113A.2009.06.1.1
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Electrical Characteristics1
VIN = 3.3V, TA = -40°C to 85°C unless otherwise noted. Typical values are at TA = 25°C.
Symbol
Description
VIN
VOUT
Input Voltage
Output Voltage Range
VUVLO
UVLO Threshold
VOUT
IQ
ISHDN
ILIM
RDS(ON)H
RDS(ON)L
ΔVLOADREG
ΔVLINEREG/
ΔVIN
VFB
ILXLEAK,R
IFBLEAK
FOSC
TS
TSD
THYS
EN Logic
VIL
VIH
ILEAK
Conditions
Typ
Max
Units
2.7
1
3.3
1.2
5.5
1.8
2.4
V
V
V
mV
V
+3.0
%
90
1.0
ILOAD = 0A to 1.5A
3
140
100
0.5
μA
μA
A
mΩ
mΩ
%
VIN = 3.3V to 4.0V
0.3
%/V
VIN rising
Hysteresis
VIN falling
IOUT = 0A to 1.5A, VIN = 3.3V, VOUT = 1.2V
fixed
No Load
EN = GND
Output Voltage Tolerance
Quiescent Current
Shutdown Current
Current Limit
High Side Switch On-Resistance
Low Side Switch On-Resistance
Load Regulation
180
1.6
-3.0
55
2
Line Regulation
Feedback Threshold Voltage Accuracy
(Adjustable Version)
LX Reverse Leakage Current
FB Leakage Current
Internal Oscillator Frequency
Start-up Time
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
EN Threshold Low
EN Threshold High
EN Leakage Current
Min
No load, TA = 25°C
0.0591
0.60
VIN unconnected, VLX = 5.5V, EN = GND
VOUT = 1.2V
2.6
Enable to Output Regulation
VEN = 5.5V
1.4
-1.0
3
60
140
25
0.609
V
1.0
0.2
3.4
μA
μA
MHz
μs
°C
°C
0.4
V
V
μA
1.0
1. The AAT2113A 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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2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Efficiency vs. Output Current
Efficiency vs. Output Current
(VOUT = 1.2V; L = 0.47µH)
(VOUT = 1.8V; L = 0.47µH)
100
100
90
90
80
80
Efficiency (%)
Efficiency (%)
Typical Characteristics
70
60
50
VIN = 5.5V
VIN = 5.0V
VIN = 4.2V
VIN = 3.6V
VIN = 3.0V
VIN = 2.7V
40
30
20
10
0
0.1
1
10
100
1000
70
60
50
VIN = 5.5V
VIN = 5.0V
VIN = 4.2V
VIN = 3.6V
VIN = 3.0V
VIN = 2.7V
40
30
20
10
0
0.1
10000
1
10
Load Regulation
Load Regulation
(VOUT = 1.2V; L = 0.47µH)
(VOUT = 1.8V; L = 0.47µH)
1.0
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
10
100
1000
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0.1
10000
1
10
Line Regulation
Line Regulation
(VOUT = 1.2V; L = 0.47µF)
(VOUT = 1.8V; L = 0.47µF)
1000
1.0
1.0
IOUT = 1500mA
IOUT = 1000mA
IOUT = 500mA
IOUT = 1mA
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
2.7
Input Voltage (V)
2113A.2009.06.1.1
10000
IOUT = 1500mA
IOUT = 1000mA
IOUT = 500mA
IOUT = 1mA
0.8
Line Regulation (%)
Line Regulation (%)
100
Output Current (mA)
Output Current (mA)
0.8
10000
VIN = 5.5V
VIN = 5.0V
VIN = 4.2V
VIN = 3.6V
VIN = 3.0V
VIN = 2.7V
0.8
Load Regulation (%)
Load Regulation (%)
0.6
1
1000
1.0
VIN = 5.5V
VIN = 5.0V
VIN = 4.2V
VIN = 3.6V
VIN = 3.0V
VIN = 2.7V
0.8
-1.0
0.1
100
Output Current (mA)
Output Current (mA)
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Typical Characteristics
Output Voltage vs. Input Voltage
Output Voltage vs. Input Voltage
(VOUT = 1.8V; IOUT = 1A)
1.25
1.85
1.24
1.84
1.23
1.83
Output Voltage (V)
Output Voltage (V)
(VOUT = 1.2V; IOUT = 1A)
1.22
1.21
1.20
1.19
1.18
T = 85°C
T = 25°C
T = -40°C
1.17
1.16
1.15
2.7
3.1
3.5
3.9
4.3
4.7
5.1
1.82
1.81
1.80
1.79
1.78
1.77
1.76
1.75
2.7
5.5
T = 85°C
T = 25°C
T = -40°C
3.1
3.5
Input Voltage (V)
Output Voltage Error vs. Temperature
5.1
5.5
1.5
Output Voltage Error (%)
Output Voltage Error (%)
4.7
(VOUT = 1.8V; VIN = 3.3V; IOUT = 1A)
1.0
0.5
0.0
-0.5
-1.0
-1.5
-40 -30 -20 -10
0
10
20
30
40
50
60
70
80
1.0
0.5
0.0
-0.5
-1.0
-1.5
-40 -30 -20 -10
90
10
20
30
40
50
60
70
80
90
Quiescent Current vs. Input Voltage
Switching Frequency vs. Temperature
(No Load)
(VOUT = 1.2V; IOUT = 1A)
3.04
80
Supply Current (µA)
3.02
3.00
2.98
2.96
2.94
2.92
2.90
2.88
2.86
2.84
-40 -30 -20 -10
0
Temperature (°C)
Temperature (°C)
Switching Frequency (MHz)
4.3
Output Voltage Error vs. Temperature
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1A)
70
60
50
40
30
20
T = 85°C
T = 25°C
T = -40°C
10
0
0
10
20
30
40
50
60
70
80
90
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Temperature (°C)
6
3.9
Input Voltage (V)
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2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Typical Characteristics
Load Transient
(VOUT = 1.8V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10µF)
1.90
1.25
1.85
1.10
1.5
1.0
0.5
0.0
1.80
Output Voltage
(top) (50mV/div)
1.20
1.15
1.75
1.70
1.5
1.0
0.5
0.0
Output Current
(bottom) (500mA/div)
1.30
Output Current
(bottom) (500mA/div)
Output Voltage
(top) (50mV/div)
Load Transient
(VOUT = 1.2V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10µF)
-0.5
Time (20µs/div)
Time (20µs/div)
Load Transient
(VOUT = 1.8V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10µF)
1.85
1.20
1.15
1.5
1.10
1.0
0.5
0.0
Output Voltage
(top) (50mV/div)
1.90
1.25
1.80
1.75
1.5
1.70
1.0
0.5
0.0
Output Current
(bottom) (500mA/div)
1.30
Output Current
(bottom) (500mA/div)
Output Voltage
(top) (50mV/div)
Load Transient
(VOUT = 1.2V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10µF)
-0.5
Time (20µs/div)
Line Transient
Line Transient
(VOUT = 1.2V; VIN = 3.3V to 3.6V; IOUT = 1A)
(VOUT = 1.8V; VIN = 3.3V to 3.6V; IOUT = 1A)
4.0
3.5
3.5
1.210
1.205
1.200
1.195
1.190
Time (50µs/div)
2113A.2009.06.1.1
3.0
1.815
1.810
1.805
1.800
1.795
Output Voltage
(bottom) (5mV/div)
3.0
Input Voltage
(top) (500mV/div)
4.0
Output Voltage
(bottom) (5mV/div)
Input Voltage
(top) (500mV/div)
Time (20µs/div)
Time (20µs/div)
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Soft Start
(VOUT = 1.8V; VIN = 3.3V; IOUT = 1A)
4
3
1
0
2
1
0
-1
4
3
2
1
0
2
1
0
-1
Time (100µs/div)
Time (2ms/div)
Output Voltage Ripple
Output Voltage Ripple
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1mA)
(VOUT = 1.8V; VIN = 3.3V; IOUT = 1mA)
0.2
0.1
0
-0.1
Output Voltage
(top) (10mV/div)
Output Voltage
(top) (10mV/div)
0.3
1.81
1.80
0.3
1.79
0.2
0.1
0
-0.1
-0.2
-0.2
Time (10µs/div)
Time (10µs/div)
Output Voltage Ripple
Output Voltage Ripple
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1.5A)
(VOUT = 1.8V; VIN = 3.3V; IOUT = 1.5A)
2.0
1.5
1.0
0.5
Output Voltage
(top) (20mV/div)
Output Voltage
(top) (20mV/div)
1.18
1.82
Time (200ns/div)
1.80
1.78
2.0
1.5
1.0
Inductor Current
(bottom) (500mA/div)
1.20
Inductor Current
(bottom) (500mA/div)
1.22
8
Inductor Current
(bottom) (100mA/div)
1.20
Inductor Current
(bottom) (100mA/div)
1.21
1.19
Inductor Current
(bottom) (1A/div)
2
Enable Voltage (top) (1V/div)
Output Voltage (middle) (1V/div)
Soft Start
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1A)
Inductor Current
(bottom) (1A/div)
Enable Voltage (top) (1V/div)
Output Voltage (middle) (1V/div)
Typical Characteristics
Time (200ns/div)
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2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Functional Block Diagram
FB
VCC
VP
AAT2113A-1.2V Only
Err
Amp
VREF =
0.6V
DH
Comp
LX
Logic
DL
EN
Input
PGND
AGND
Functional Description
The AAT2113A SwitchReg is a 1.5A step-down converter
with a typical input voltage of 3.3V and a fixed output
voltage of 1.2V. The 3MHz switching frequency enables
the use of small external components. The ultra-small,
2mm x 2mm footprint and high efficiency make the
AAT2113A an ideal choice for portable applications.
Typically, a 0.47μH inductor and a 10μF ceramic capacitor are recommended for a 1.2V output (see Figure 2 for
recommended values).
At dropout, the converter duty cycle increases to 100%
and the output voltage tracks the input voltage minus
the RDS(ON) drop of the P-channel high-side MOSFET (plus
the DC drop of the external inductor). The device integrates extremely low RDS(ON) MOSFETs to achieve low
dropout voltage during 100% duty cycle operation.
The integrated low-loss MOSFET switches can provide
excellent efficiency at heavy loads. Light load operation
maintains high efficiency, low ripple and low spectral
noise even at lower currents (typically <150mA). PWM
mode operation maintains constant frequency and low
output ripple at output loads greater than 200mA.
2113A.2009.06.1.1
In battery-powered applications, as VIN decreases, the
converter dynamically adjusts the operating frequency
prior to dropout to maintain the required duty cycle and
provide accurate output regulation. Output regulation is
maintained until the dropout voltage, or minimum input
voltage, is reached. At 1.5A output load, dropout voltage
headroom is approximately 200mV.
The AAT2113A typically achieves better than ±0.5%
output regulation across the input voltage and output
load range. A current limit of 3.0A (typical) protects the
IC and system components from short-circuit damage.
Typical no load quiescent current is 55μA.
Thermal protection completely disables switching when
the maximum junction temperature is detected. The
junction over-temperature threshold is 140°C with 15°C
of hysteresis. Once an over-temperature or over-current
fault condition is removed, the output voltage automatically recovers.
Peak current mode control and optimized internal compensation provide high loop bandwidth and excellent
response to input voltage and fast load transient events.
Soft start eliminates output voltage overshoot when the
enable or the input voltage is applied. Under-voltage
lockout prevents spurious start-up events.
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Control Loop
The AAT2113A is a peak current mode step-down converter. The current through the P-channel MOSFET (high
side) is sensed for current loop control, as well as shortcircuit and overload protection. A fixed slope compensation signal is added to the sensed current to maintain
stability for duty cycles greater than 50%. The peak current mode loop appears as a voltage-programmed current source in parallel with the output capacitor.
The output of the voltage error amplifier programs the
current mode loop for the necessary peak switch current
to force a constant output voltage for all load and line
conditions. Internal loop compensation terminates the
transconductance voltage error amplifier output. The
reference voltage is internally set to program the converter output voltage greater than or equal to 0.6V.
Soft Start/Enable
Soft start limits the current surge seen at the input and
eliminates output voltage overshoot. The enable input,
when pulled low, forces the AAT2113A into a low-power,
non-switching state. The total input current during shutdown is less than 1μA.
Current Limit and
Over-Temperature Protection
For overload conditions, the peak input current is limited. To minimize power dissipation and stresses under
current limit and short-circuit conditions, switching is
terminated after entering current limit for a series of
pulses. Switching is terminated for seven consecutive
clock cycles after a current limit has been sensed for a
series of four consecutive clock cycles.
Thermal protection completely disables switching when
internal dissipation becomes excessive. The junction
over-temperature threshold is 140°C with 15°C of hys-
teresis. Once an over-temperature or over-current fault
condition is removed, the output voltage automatically
recovers.
Under-Voltage Lockout
Internal bias of all circuits is controlled via the VCC
input. Under-voltage lockout (UVLO) guarantees sufficient VIN bias and proper operation of all internal circuitry prior to activation.
Component Selection
Inductor Selection
The step-down converter uses peak current mode control with slope compensation to maintain stability for
duty cycles greater than 50%. The output inductor value
must be selected so the inductor current down slope
meets the internal slope compensation requirements.
For applications where the duty cycle is less than 50%,
the inductor values can be chosen freely.
Manufacturer’s specifications list both the inductor DC
current rating, which is a thermal limitation, and the
peak current rating, which is determined by the saturation characteristics. The inductor should not show any
appreciable saturation under normal load conditions.
Some inductors may meet the peak and average current
ratings yet result in excessive losses due to a high DCR.
Always consider the losses associated with the DCR and
its effect on the total converter efficiency when selecting
an inductor.
For low cost application and a sufficiently small footprint
in a 5x5mm area, the LQM2HPNR47MG0 shielded chip
inductor, which has 40mΩ DCR and 1.8A DC current rating, is selected for 1.2V output.
The inductors listed in Table 1 have been used with the
AAT2113A.
Manufacturer
Part Number
Value (μH)
DC Resistance (Ω)
Size (mm)
Murata
LQM2HPNR47MG0
EPL2010-421ML
EPL2010-681ML
0.47 ± 20%
0.42 ± 20%
0.68 ± 20%
0.04 ± 25%
0.04 ± 25%
0.058 ± 25%
2.5x2.0x1.0
2.0x2.0x1.0
2.0x2.0x1.0
Coilcraft
Table 1: AAT2113A List of Inductors.
10
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2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Input Capacitor
Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for
the input. To estimate the required input capacitor size,
determine the acceptable input ripple level (VPP) and
solve for C. The calculated value varies with input voltage and is a maximum when VIN is double the output
voltage.
CIN =
⎛ VPP
⎞
- ESR · FS
⎝ IO
⎠
VO
1
⎛ VPP
⎞
- ESR · 4 · FS
⎝ IO
⎠
Capacitance (µF)
12
0603 Package
0805 Package
10
8
6
4
2
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
DC Bias Voltage (V)
Figure 1: 10μF Capacitor Value vs. DC Bias
Voltage for Different Package Sizes.
The maximum input capacitor RMS current is:
IRMS = IO ·
2113A.2009.06.1.1
VO
V
· 1- O
VIN
VIN
=
D · (1 - D) =
IRMS(MAX) =
Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value.
For example, the capacitance of a 10μF, 6.3V, X5R
ceramic capacitor with 3.5V DC applied is actually about
5μF. Some examples of DC bias voltage versus capacitance for different package sizes are shown in Figure 1.
0
VO
V
· 1- O
VIN
VIN
for VIN = 2 · VO
V ⎞
VO ⎛
· 1- O
VIN ⎝
VIN ⎠
VO ⎛
V ⎞
1
· 1 - O = for VIN = 2 · VO
VIN ⎝
VIN ⎠
4
CIN(MIN) =
The input capacitor RMS ripple current varies with the
input and output voltage and will always be less than or
equal to half of the total DC load current.
0.52 =
1
2
IO
2
⎛
V ⎞
· 1- O
VIN ⎠ appears in both the input voltage
The term VIN ⎝
ripple and input capacitor RMS current equations and is
a maximum when VO is twice VIN. This is why the input
voltage ripple and the input capacitor RMS current ripple
are a maximum at 50% duty cycle. The input capacitor
provides a low impedance loop for the edges of pulsed
current drawn by the AAT2113A. Low ESR/ESL X7R and
X5R ceramic capacitors are ideal for this function. To
minimize stray inductance, the capacitor should be
placed as closely as possible to the IC. This keeps the
high frequency content of the input current localized,
minimizing EMI and input voltage ripple. The proper
placement of the input capacitor (C1) can be seen in the
evaluation board layout in the Layout section of this
datasheet (see Figure 3).
A laboratory test set-up typically consists of two long
wires running from the bench power supply to the evaluation board input voltage pins. The inductance of these
wires, along with the low-ESR ceramic input capacitor,
can create a high Q network that may affect converter
performance. This problem often becomes apparent in
the form of excessive ringing in the output voltage during load transients. Errors in the loop phase and gain
measurements can also result.
Since the inductance of a short PCB trace feeding the
input voltage is significantly lower than the power leads
from the bench power supply, most applications do not
exhibit this problem.
In applications where the input power source lead inductance cannot be reduced to a level that does not affect
the converter performance, a high ESR tantalum or aluminum electrolytic should be placed in parallel with the
low ESR/ESL bypass ceramic capacitor. This dampens
the high Q network and stabilizes the system.
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11
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Output Capacitor
The output capacitor limits the output ripple and prevents the output voltage droop during large load transitions. A 10μF to 22μF X5R or X7R ceramic capacitor
typically provides sufficient bulk capacitance to stabilize
the output during large load transitions and has the ESR
and ESL characteristics necessary for low output ripple.
The output voltage droop due to a load transient is
dominated by the capacitance of the ceramic output
capacitor.
During a step increase in load current, the ceramic output capacitor alone supplies the load current until the
loop responds. Within two or three switching cycles, the
loop responds and the inductor current increases to
match the load current demand. The relationship of the
output voltage droop during the three switching cycles to
the output capacitance can be estimated by:
COUT =
3 · ΔILOAD
VDROOP · FS
The AAT2113A adjustable version, combined with an
external feed forward capacitor (C2 in Figure 5), delivers
enhanced transient response for extreme pulsed load
applications. The suggested value for C2 is in the range
of 22pF to 100pF.
VOUT (V)
R2 = 59kΩ
R1 (kΩ)
R2 = 200kΩ
R1 (kΩ)
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
39.2
49.9
59
68.1
78.7
88.7
97.6
107
118
133
165
200
232
267
301
332
365
400
Table 2: Feedback Resistor Selection for
Adjustable Output Voltage Version.
Thermal Calculations
Once the average inductor current increases to the DC
load level, the output voltage recovers. The above equation establishes a limit on the minimum value for the
output capacitor with respect to load transients.
The internal voltage loop compensation also limits the
minimum output capacitor value to 10μF. This is due to
its effect on the loop crossover frequency (bandwidth),
phase margin, and gain margin. Increased output capacitance will reduce the crossover frequency with greater
phase margin.
Feedback Resistor Selection
There are three types of losses associated with the
AAT2113A step-down converter: switching losses, conduction losses, and quiescent current losses. Conduction
losses are associated with the RDS(ON) characteristics of
the power output switching devices. Switching losses are
dominated by the gate charge of the power output
switching devices. At full load, assuming continuous conduction mode (CCM), a simplified form of the losses is
given by:
PTOTAL =
Resistors R1 and R2 of Figure 5 program the output to
regulate at a voltage higher than 0.6V for the AAT2113A
adjustable version. To limit the bias current required for
the external feedback resistor string while maintaining
good noise immunity, the suggested value for R2 is
200kΩ. Table 1 summarizes the resistor values for various output voltages with R2 set to either 59kΩ or 200kΩ.
Alternately, the feedback resistor may be calculated
using the following equation:
VIN
+ (tsw · FS · IO + IQ) · VIN
IQ is the step-down converter quiescent current. The
term tSW is used to estimate the full load step-down converter switching losses. For the condition where the
step-down converter is in dropout at 100% duty cycle,
the total device dissipation reduces to:
1.8V
VOUT
R1 = V
-1 · R2 = 0.6V - 1 · 200kΩ = 400kΩ
REF
12
IO2 · (RDS(ON)H · VO + RDS(ON)L · [VIN - VO])
www.analogictech.com
PTOTAL= IO2 · RDS(ON)H + IQ · VIN
2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Since RDS(ON), quiescent current, and switching losses all
vary with input voltage, the total losses should be investigated over the complete input voltage range.
3.
Given the total losses, the maximum junction temperature can be derived from the θJA for the FTDFN22-8
package, which is 70°C/W.
TJ(MAX) = PTOTAL · ΘJA + TAMB
PCB Layout Considerations
The suggested PCB layout for the AAT2113A is shown in
Figures 3 and 4 (fixed version) or Figures 6 and 7 (adjustable version). The following guidelines should be used to
help ensure a proper layout:
1.
2.
The input capacitor (C1) should be connected as
close as possible to VP and PGND.
The output capacitor and L1 should be connected as
closely as possible. The connection of L1 to the LX
pin should be as short as possible.
2113A.2009.06.1.1
4.
5.
For the fixed version, the feedback trace or FB pin
should be separated from any power trace and connected as closely as possible to the load point.
Sensing along a high-current load trace will degrade
DC load regulation. For the adjustable version, the
trace connecting the FB pin to resistors R1 and R2
should be as short as possible by placing R1 and R2
immediately next to the AAT2113A. The sense trace
connection from R1 to the output voltage should be
separate from any power trace and connect as
closely as possible to the load point. The external
feed-forward capacitor C2 should be connected as
close as possible in parallel with R1 for enhanced
transient response.
The resistance of the trace from the load return to
PGND should be kept to a minimum. This will help to
minimize any error in DC regulation due to differences in the potential of the internal signal ground
and the power ground.
Connect unused signal pins to ground to avoid
unwanted noise coupling.
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13
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
VIN
2.7V to 5.5V
U1
2
VP
LX
8
L1
VOUT
1.2V/1.5A
0.47μH
6
EN
EN
LX
7
AAT2113A
C1
4.7μF
3
C3
1μF
5
VCC
AGND
FB
PGND
4
C2
10μF
1
FTDFN22-8
U1
C1
L1
C2
C3
AAT2113AIXS-1.2V-T1 AnalogicTech, 3MHz Fast Transient, 1.5A Step-Down Converter , FTDFN22-8, 2x2mm
GRM188R60J475KE19D, Murata, Cap, MLC, 4.7μF/6.3V, 0603 (HMAX = 0.9mm)
LQM2HPNR47MGO, Murata, 0.47μH, ISAT = 1800mA, DCR = 40mΩ, 2.5 x 2 x 0.9 mm, shielded chip inductor
GRM188R60J106ME47D, Murata, Cap, MLC, 10μF/6.3V, 0603 (HMAX = 0.9mm)
GRM155R60J105KE19D, Murata, Cap, MLC, 1μF/6.3V, 0402
Figure 2: AAT2113A Evaluation Board Schematic For 1.2V Fixed Output Voltage Version.
Figure 3: AAT2113A Evaluation Board
Top Side Layout for 1.2V Fixed
Output Voltage Version.
14
Figure 4: AAT2113A Evaluation Board
Bottom Side Layout for 1.2V Fixed
Output Voltage Version.
www.analogictech.com
2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
VIN
2.7V–5.5V
U1
2
6
EN
LX
EN
LX
L1
8
0.47μH
7
C2
22pF
AAT2113A
C1
4.7μF
U1
C1
C2
L1
R1, R2
C3
C4
VP
3
C4
1μF
5
VCC
AGND
FB
PGND
VOUT
1.2V/1.5A
R1
200k
C3
10μF
4
R2
200k
1
AAT2113AIXS-0.6-T1 AnalogicTech, 3MHz Fast Transient, 1.5A Step-Down Converter, FTDFN22-8, 2x2mm
GRM188R60J475KE19D, Murata, Cap, MLC, 4.7μF/6.3V, 0603 (HMAX = 0.8mm)
Optional, 22pF, 0201
LQM2HPNR47MGO, Murata, 0.47μH, ISAT =1.8A, DCR = 0.04Ω, 2.5 x 2 x 1mm, shielded chip inductor
Carbon film resistor, 200kΩ, 1%, 0201
GRM188R60J106ME47D, Murata, Cap, MLC, 10μF/6.3V, 0603 (HMAX = 0.8mm)
GRM155R60J105KE19D, Murata, Cap, MLC, 1μF/6.3V, 0402
Figure 5: AAT2113A Evaluation Board Schematic For Adjustable Output Voltage Version.
Figure 6: AAT2113A Evaluation Board
Top Side Layout for Adjustable
Output Voltage Version.
2113A.2009.06.1.1
Figure 7: AAT2113A Evaluation Board
Bottom Side Layout for Adjustable
Output Voltage Version.
www.analogictech.com
15
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
AAT2113A Design Example
Specifications
VOUT = 1.2V @ 1.5A, Pulsed Load ΔILOAD = 1.5A
VIN = 3.3V
FS = 3MHz
TAMB = 85°C in 8-pin 2x2mm DFN low profile package
Output Inductor
For Murata, 0.47μH LQM2HPNNR47MG0 shielded chip inductor has a 40mΩ DCR.
ΔI =
VO
V
1.2V
1.2V
· 1- O =
· 1= 542mA
L1 · FS
VIN
0.47μH · 3MHz
3.3V
IPK = IOUT +
ΔI
= 1.5A + 0.271A = 1.8A
2
PL1 = IOUT2 · DCR = 1.5A2 · 40mΩ = 90mW
Output Capacitor
For VDROOP = 0.12V (10% Output Voltage)
COUT =
3 · ΔILOAD
3 · 1.5A
=
= 12.5μF; use 10μF
0.12V · 3MHz
VDROOP · FS
For VDROOP = 0.06V (5% Output Voltage)
COUT =
3 · ΔILOAD
3 · 1.5A
=
= 25μF; use 22μF
VDROOP · FS 0.06V · 3MHz
IRMS(MAX) =
VOUT · (VIN(MAX) - VOUT)
1
1.2V · (5V - 1.2V)
·
= 58.5mArms
=
1.5μH
· 3MHz · 5V
·
V
L
·
F
2· 3
2· 3
S
IN(MAX)
1
·
PRMS = ESR · IRMS2 = 5mΩ · (58.5mA)2 = 17μW
16
www.analogictech.com
2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Input Capacitor
For Input Ripple VPP = 30mV
CIN =
IRMS =
1
VPP
- ESR · 4 · FS
IO
=
1
30mV
- 5mΩ · 4 · 3MHz
1.5A
= 5.6μF; use 4.7μF
IOUT1
= 0.75A
2
P = ESR · (IRMS)2 = 5mΩ · (0.75A)2 = 2.8mW
AAT2113A Losses
All values assume 85°C ambient temperature and thermal resistance of 70°C/W in the 8-pin 2x2mm DFN low profile
package.
PTOTAL = IOUT2 · RDS(ON)H + (tSW · FSW · IOUT + IQ) · VIN
= 1.5A2 · 152mΩ + (5ns · 3MHz · 1.5A + 50μA) · 3.3V
= 416mW
TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (70°C/W) · 416mW = 114°C
2113A.2009.06.1.1
www.analogictech.com
17
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Ordering Information
Output Voltage
Package
Marking1
Part Number (Tape and Reel)2
1.2V
Adjustable (0.6V)
FTDFN22-8
FTDFN22-8
8BXYY
8AXYY
AAT2113AIXS-1.2-T1
AAT2113AIXS-0.6-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means semiconductor
products that are in compliance with current RoHS standards, including the requirement that lead not exceed
0.1% by weight in homogeneous materials. For more information, please visit our website at
http://www.analogictech.com/about/quality.aspx.
Package Information
FTDFN22-83
0.400 ± 0.050
Detail "A"
2.000 ± 0.050
Index Area
Bottom View
2.000 ± 0.050
Top View
+ 0.100
- 0.000
Pin 1 Identification
0.250 ± 0.050
Side View
0.450 ± 0.050
0.000
0.230 ± 0.050
0.750 ± 0.050
0.500 ± 0.050
Detail "A"
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.
18
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2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Advanced Analogic Technologies, Inc.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737-4600
Fax (408) 737-4611
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual
property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and
conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate
design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to
support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other
brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
2113A.2009.06.1.1
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