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PRODUCT DATASHEET
AAT2113A
SwitchRegTM 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Features
* * * * * * * 5mm x 5mm Total Solution Size 1.5A Maximum Output Current Tiny 0.47H 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 55A No Load Quiescent Current 100% Duty Cycle Low-Dropout Operation Internal Soft Start Over-Temperature and Current Limit Protection <1A Shutdown Current -40C to 85C Temperature Range
General Description
The AAT2113A SwitchRegTM 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. The AAT2113A delivers 1.5A maximum output current while consuming only 55A 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 -40C to 85C.
* * * * * * * * *
Applications
* * * * * * * * 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 = 5V; VOUT = 1.2V; IOUT = 10% to 100%; COUT = 10F, 6.3V, 0603)
1.3V 1.25V 1.2V 1.15V 1.1V 1.5A 100mV
VIN 2.7V to 5.5V
U1 VP EN LX LX FB
L1 0.47H
VOUT 1.2V/1.5A
C1 4.7F 6.3V 0603
C3 1.0F 6.3V 0402
VCC
AAT2113A
C3 10F 6.3V 0603
AGND
PGND
150mA
FTDFN 22-8
Time (20s/div)
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Pin Descriptions
Pin #
1 2 3 4 5 6 7, 8
Symbol
PGND VP VCC FB AGND EN 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 1A 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
1 2 3 4
8 7 6 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 = 25C 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
6.0 -0.3 to VP + 0.3 -0.3 to VP + 0.3 -0.3 to VCC + 0.3 -40 to 150 300
Units
V V V V C C
Thermal Characteristics
Symbol
JA PD
Description
Maximum Thermal Resistance Maximum Power Dissipation2, 3
Value
70 1.4
Units
C/W W
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 25C.
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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 = -40C to 85C unless otherwise noted. Typical values are at TA = 25C. Symbol
VIN VOUT VUVLO VOUT IQ ISHDN ILIM RDS(ON)H RDS(ON)L VLOADREG VLINEREG/ VIN VFB ILXLEAK,R IFBLEAK FOSC TS TSD THYS EN Logic VIL VIH ILEAK
Description
Input Voltage Output Voltage Range UVLO Threshold Output Voltage Tolerance Quiescent Current Shutdown Current Current Limit High Side Switch On-Resistance Low Side Switch On-Resistance Load Regulation 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
Conditions
Min
2.7 1
Typ
3.3 1.2 180
Max
5.5 1.8 2.4
Units
V V V mV V % A A A m m % %/V
VIN rising Hysteresis VIN falling IOUT = 0A to 1.5A, VIN = 3.3V, VOUT = 1.2V fixed No Load EN = GND
1.6 -3.0 55 2 3 140 100 0.5 0.3 0.0591 0.60 0.609 1.0 0.2 3.4 +3.0 90 1.0
ILOAD = 0A to 1.5A VIN = 3.3V to 4.0V No load, TA = 25C VIN unconnected, VLX = 5.5V, EN = GND VOUT = 1.2V 2.6 Enable to Output Regulation
V A A MHz s C C V V A
3 60 140 25
0.4 VEN = 5.5V 1.4 -1.0 1.0
1. The AAT2113A is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
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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
Efficiency vs. Output Current
(VOUT = 1.2V; L = 0.47H)
100 90 80 100 90 80
Efficiency vs. Output Current
(VOUT = 1.8V; L = 0.47H)
Efficiency (%)
70 60 50 40 30 20 10 0 0.1 1 10 100
Efficiency (%)
70 60 50 40 30 20 10 0 0.1 1 10 100
VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V
1000 10000
VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V
1000 10000
Output Current (mA)
Output Current (mA)
Load Regulation
(VOUT = 1.2V; L = 0.47H)
1.0 0.8
VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V
Load Regulation
(VOUT = 1.8V; L = 0.47H)
1.0 0.8
VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V
Load Regulation (%)
Load Regulation (%)
0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0.1 1 10 100 1000
0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0.1 1 10 100 1000
10000
10000
Output Current (mA)
Output Current (mA)
Line Regulation
(VOUT = 1.2V; L = 0.47F)
1.0 0.8 1.0
Line Regulation
(VOUT = 1.8V; L = 0.47F)
IOUT = 1500mA IOUT = 1000mA IOUT = 500mA IOUT = 1mA
0.8
Line Regulation (%)
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
Line Regulation (%)
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
IOUT = 1500mA IOUT = 1000mA IOUT = 500mA IOUT = 1mA
5.1
5.5
5.1
5.5
Input Voltage (V)
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
(VOUT = 1.2V; IOUT = 1A)
1.25 1.24 1.23 1.22 1.21 1.20 1.19 1.18 1.17 1.16 1.15 2.7 3.1 3.5 3.9 4.3 4.7 1.85 1.84 1.83 1.82 1.81 1.80 1.79 1.78 1.77 1.76 5.5 1.75 2.7
Output Voltage vs. Input Voltage
(VOUT = 1.8V; IOUT = 1A)
Output Voltage (V)
T = 85C T = 25C T = -40C
5.1
Output Voltage (V)
T = 85C T = 25C T = -40C
3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
Input Voltage (V)
Output Voltage Error vs. Temperature
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1A)
1.0
Output Voltage Error vs. Temperature
(VOUT = 1.8V; VIN = 3.3V; IOUT = 1A)
1.5
Output Voltage Error (%)
Output Voltage Error (%)
0 10 20 30 40 50 60 70 80 90
0.5 0.0 -0.5 -1.0 -1.5 -40 -30 -20 -10
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
90
Temperature (C)
Temperature (C)
Switching Frequency vs. Temperature
(VOUT = 1.2V; IOUT = 1A) Switching Frequency (MHz)
3.04 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 10 20 30 40 50 60 70 80 90 80 70 60 50 40 30 20 10 0
Quiescent Current vs. Input Voltage
(No Load)
Supply Current (A)
T = 85C T = 25C T = -40C
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Temperature (C)
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 = 1.2V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10F)
1.30 1.25 1.90 1.85
Load Transient
(VOUT = 1.8V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10F)
Output Current (bottom) (500mA/div)
Output Current (bottom) (500mA/div)
Output Voltage (top) (50mV/div)
1.15 1.10 1.5 1.0 0.5 0.0
Output Voltage (top) (50mV/div)
1.20
1.80 1.75 1.70 1.5 1.0 0.5 0.0 -0.5
Time (20s/div)
Time (20s/div)
Load Transient
(VOUT = 1.2V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10F)
1.30 1.25 1.90 1.85
Load Transient
(VOUT = 1.8V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10F)
Output Current (bottom) (500mA/div)
Output Current (bottom) (500mA/div)
Output Voltage (top) (50mV/div)
1.15 1.10 1.5 1.0 0.5 0.0 -0.5
Output Voltage (top) (50mV/div)
1.20
1.80 1.75 1.70 1.5 1.0 0.5 0.0
Time (20s/div)
Time (20s/div)
Line Transient
(VOUT = 1.2V; VIN = 3.3V to 3.6V; IOUT = 1A)
4.0 3.5 4.0 3.5
Line Transient
(VOUT = 1.8V; VIN = 3.3V to 3.6V; IOUT = 1A)
Output Voltage (bottom) (5mV/div)
Output Voltage (bottom) (5mV/div)
Input Voltage (top) (500mV/div)
3.0 1.210 1.205 1.200 1.195 1.190
Input Voltage (top) (500mV/div)
3.0 1.815 1.810 1.805 1.800 1.795
Time (50s/div)
Time (20s/div)
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Typical Characteristics
Soft Start
Enable Voltage (top) (1V/div) Output Voltage (middle) (1V/div)
4 3
Soft Start
Enable Voltage (top) (1V/div) Output Voltage (middle) (1V/div) (VOUT = 1.8V; VIN = 3.3V; IOUT = 1A)
4 3
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1A)
Inductor Current (bottom) (1A/div)
Inductor Current (bottom) (1A/div)
2 1 0 2 1 0 -1
2 1 0 2 1 0 -1
Time (100s/div)
Time (2ms/div)
Output Voltage Ripple
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1mA)
1.21 1.81
Output Voltage Ripple
(VOUT = 1.8V; VIN = 3.3V; IOUT = 1mA)
Inductor Current (bottom) (100mA/div)
Inductor Current (bottom) (100mA/div)
Output Voltage (top) (10mV/div)
Output Voltage (top) (10mV/div)
1.20 1.19 0.3 0.2 0.1 0 -0.1 -0.2
1.80 1.79 0.3 0.2 0.1 0 -0.1 -0.2
Time (10s/div)
Time (10s/div)
Output Voltage Ripple
(VOUT = 1.2V; VIN = 3.3V; IOUT = 1.5A)
1.22 1.82
Output Voltage Ripple
(VOUT = 1.8V; VIN = 3.3V; IOUT = 1.5A)
Inductor Current (bottom) (500mA/div)
Inductor Current (bottom) (500mA/div)
Output Voltage (top) (20mV/div)
1.18 2.0 1.5 1.0 0.5
Output Voltage (top) (20mV/div)
1.20
1.80 1.78 2.0 1.5 1.0
Time (200ns/div)
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 AAT2113A-1.2V Only VCC VP
Err Amp
DH
VREF = 0.6V
Comp
Logic
DL
LX
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 0.47H inductor and a 10F 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.
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 55A. Thermal protection completely disables switching when the maximum junction temperature is detected. The junction over-temperature threshold is 140C with 15C 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
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.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
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 40m 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.
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 1A.
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 140C with 15C of hys-
Manufacturer Murata Coilcraft
Part Number LQM2HPNR47MG0 EPL2010-421ML EPL2010-681ML
Value (H) 0.47 20% 0.42 20% 0.68 20%
DC Resistance () 0.04 25% 0.04 25% 0.058 25%
Size (mm) 2.5x2.0x1.0 2.0x2.0x1.0 2.0x2.0x1.0
Table 1: AAT2113A List of Inductors.
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2113A.2009.06.1.1
PRODUCT DATASHEET
AAT2113A
SwitchRegTM
Input Capacitor
Select a 4.7F to 10F 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.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
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.
VO V * 1- O VIN VIN
for VIN = 2 * VO
=
D * (1 - D) =
0.52 =
1 2
CIN =
V VO * 1- O VIN VIN
VPP - ESR * FS IO
IRMS(MAX) =
IO 2
VO V 1 * 1 - O = for VIN = 2 * VO VIN VIN 4 CIN(MIN) = 1
VPP - ESR * 4 * FS IO
Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value. For example, the capacitance of a 10F, 6.3V, X5R ceramic capacitor with 3.5V DC applied is actually about 5F. Some examples of DC bias voltage versus capacitance for different package sizes are shown in Figure 1.
12 10 8 6 4 2 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Capacitance (F)
0603 Package 0805 Package
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).
VO
V * 1- O
DC Bias Voltage (V)
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.
Figure 1: 10F Capacitor Value vs. DC Bias Voltage for Different Package Sizes. The maximum input capacitor RMS current is:
IRMS = IO *
VO V * 1- O VIN VIN
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
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. R2 = 59k R1 (k)
39.2 49.9 59 68.1 78.7 88.7 97.6 107 118
Output Capacitor
The output capacitor limits the output ripple and prevents the output voltage droop during large load transitions. A 10F to 22F 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:
VOUT (V)
1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8
R2 = 200k R1 (k)
133 165 200 232 267 301 332 365 400
Table 2: Feedback Resistor Selection for Adjustable Output Voltage Version.
COUT =
3 * ILOAD VDROOP * FS
Thermal Calculations
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:
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 10F. 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
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 200k. Table 1 summarizes the resistor values for various output voltages with R2 set to either 59k or 200k. Alternately, the feedback resistor may be calculated using the following equation:
PTOTAL =
IO2 * (RDS(ON)H * VO + RDS(ON)L * [VIN - VO]) 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 * 200k = 400k REF
PTOTAL= IO2 * RDS(ON)H + IQ * VIN
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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
3. 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. 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. Given the total losses, the maximum junction temperature can be derived from the JA for the FTDFN22-8 package, which is 70C/W.
TJ(MAX) = PTOTAL * JA + 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.
4.
5.
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
U1 2 VP LX 8 VOUT 1.2V/1.5A VIN 2.7V to 5.5V L1 0.47H EN C1 4.7F C3 1F 6 EN LX 7 C2 10F
AAT2113A
3 VCC FB 4
5
AGND
PGND
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, 4.7F/6.3V, 0603 (HMAX = 0.9mm) LQM2HPNR47MGO, Murata, 0.47H, ISAT = 1800mA, DCR = 40m, 2.5 x 2 x 0.9 mm, shielded chip inductor GRM188R60J106ME47D, Murata, Cap, MLC, 10F/6.3V, 0603 (HMAX = 0.9mm) GRM155R60J105KE19D, Murata, Cap, MLC, 1F/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.
Figure 4: AAT2113A Evaluation Board Bottom Side Layout for 1.2V Fixed Output Voltage Version.
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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
U1
2
VIN 2.7V-5.5V
VP
LX
8
L1 0.47H
VOUT 1.2V/1.5A
EN C1 4.7F
6
EN
LX
7
AAT2113A
3
C2 22pF
R1 200k
C3 10F
VCC
FB
4
C4 1F
5
AGND
PGND
1
R2 200k
U1 C1 C2 L1 R1, R2 C3 C4
AAT2113AIXS-0.6-T1 AnalogicTech, 3MHz Fast Transient, 1.5A Step-Down Converter, FTDFN22-8, 2x2mm GRM188R60J475KE19D, Murata, Cap, MLC, 4.7F/6.3V, 0603 (HMAX = 0.8mm) Optional, 22pF, 0201 LQM2HPNR47MGO, Murata, 0.47H, ISAT =1.8A, DCR = 0.04, 2.5 x 2 x 1mm, shielded chip inductor Carbon film resistor, 200k, 1%, 0201 GRM188R60J106ME47D, Murata, Cap, MLC, 10F/6.3V, 0603 (HMAX = 0.8mm) GRM155R60J105KE19D, Murata, Cap, MLC, 1F/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.
Figure 7: AAT2113A Evaluation Board Bottom Side Layout for Adjustable Output Voltage Version.
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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 ILOAD = 1.5A VIN = 3.3V FS = 3MHz TAMB = 85C in 8-pin 2x2mm DFN low profile package
Output Inductor
For Murata, 0.47H LQM2HPNNR47MG0 shielded chip inductor has a 40m DCR.
I =
VO V 1.2V 1.2V * 1- O = * 1= 542mA L1 * FS VIN 0.47H * 3MHz 3.3V I = 1.5A + 0.271A = 1.8A 2
IPK = IOUT +
PL1 = IOUT2 * DCR = 1.5A2 * 40m = 90mW
Output Capacitor
For VDROOP = 0.12V (10% Output Voltage)
COUT =
3 * ILOAD 3 * 1.5A = = 12.5F; use 10F 0.12V * 3MHz VDROOP * FS
For VDROOP = 0.06V (5% Output Voltage)
COUT =
3 * ILOAD 3 * 1.5A = = 25F; use 22F VDROOP * FS 0.06V * 3MHz VOUT * (VIN(MAX) - VOUT) 1 1.2V * (5V - 1.2V) * = 58.5mArms = 1.5H * 3MHz * 5V L * FS * VIN(MAX) 2* 3 2* 3 1 *
IRMS(MAX) =
PRMS = ESR * IRMS2 = 5m * (58.5mA)2 = 17W
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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
For Input Ripple VPP = 30mV
CIN =
1 VPP - ESR * 4 * FS IO
IOUT1 = 0.75A 2
=
1 30mV - 5m * 4 * 3MHz 1.5A
= 5.6F; use 4.7F
IRMS =
P = ESR * (IRMS)2 = 5m * (0.75A)2 = 2.8mW
AAT2113A Losses
All values assume 85C ambient temperature and thermal resistance of 70C/W in the 8-pin 2x2mm DFN low profile package.
PTOTAL = IOUT2 * RDS(ON)H + (tSW * FSW * IOUT + IQ) * VIN
= 1.5A2 * 152m + (5ns * 3MHz * 1.5A + 50A) * 3.3V
= 416mW TJ(MAX) = TAMB + JA * PLOSS = 85C + (70C/W) * 416mW = 114C
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PRODUCT DATASHEET
AAT2113A
SwitchRegTM 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Ordering Information
Output Voltage
1.2V Adjustable (0.6V)
Package
FTDFN22-8 FTDFN22-8
Marking1
8BXYY 8AXYY
Part Number (Tape and Reel)2
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 Index Area Detail "A"
2.000 0.050
2.000 0.050
Bottom View
Top View
0.500 0.050
0.750 0.050
Side View
Pin 1 Identification
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.
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0.250 0.050
0.450 0.050
0.000
+ 0.100 - 0.000
0.230 0.050
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
(c) 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.
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