AAT2113AIXS-1.2-T1 - AnalogicTech

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 1

www.analogictech.com

General Description

The AAT2113A SwitchReg™ is a 1.5A step-down con-

verter 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 foot-

print and high efficiency make the AAT2113A an ideal

choice for portable applications.

The AAT2113A delivers 1.5A maximum output current

while consuming only 55A 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 dur-

ing 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.

Features

• 5mm x 5mm Total Solution Size

• 1.5A Maximum Output Current

• Tiny 0.47H 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

• 55A No Load Quiescent Current

• 100% Duty Cycle Low-Dropout Operation

• Internal Soft Start

• Over-Temperature and Current Limit Protection

• <1A Shutdown Current

• -40°C to 85°C Temperature Range

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

= 5V; V

OUT

= 1.2V; I

OUT

= 10% to 100%;

OUT

= 10µF, 6.3V, 0603)

Time (20µs/div)

150mA

1.1V

1.15V

1.2V

1.25V

1.3V

1.5A

100mV

1.2V/1.5A

0.47µH

2.7V to 5.5V

4.7µF

6.3V

0603

1.0µF

6.3V

0402

10µF

6.3V

0603

VIN VOUT

PGND

VCC

VP LX

AGND

FTDFN 22-8

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2 2113A.2009.06.1.1

www.analogictech.com

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2 2113A.2009.06.1.1

www.analogictech.com

Pin Descriptions

Pin # Symbol Function

1 PGND Main power ground return pin. Connect to the output and input capacitor return.

2 VP Input power supply tied to the source of the high side P-channel MOSFET.

3 VCC Power supply; supplies power for the internal circuitry.

4FB

Feedback input pin. This pin is connected directly to the converter output for the 1.2V ﬁ xed output version,

or connected to an external resistor divider for the adjustable output version.

5 AGND Analog Ground. This pin is internally connected to the analog ground of the control circuitry.

6EN

Enable pin. A logic low disables the converter and it consumes less than 1A of current. When connected

high, it resumes normal operation.

7, 8 LX 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)

VCC

PGND

AGND

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 3

www.analogictech.com

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 3

www.analogictech.com

Absolute Maximum Ratings1

TA = 25°C unless otherwise noted.

Symbol Description Value Units

VCC, VP VP, VCC to GND 6.0 V

VLX LX to GND -0.3 to VP + 0.3 V

VFB FB to GND -0.3 to VP + 0.3 V

EN EN to GND -0.3 to VCC + 0.3 V

TJOperating Junction Temperature Range -40 to 150 °C

TLEAD Maximum Soldering Temperature (at leads, 10 sec.) 300 °C

Thermal Characteristics

Symbol Description Value Units

JA Maximum Thermal Resistance 70 °C/W

PDMaximum Power Dissipation2, 3 1.4 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 25°C.

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

4 2113A.2009.06.1.1

www.analogictech.com

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

4 2113A.2009.06.1.1

www.analogictech.com

Electrical Characteristics1

VIN = 3.3V, TA = -40°C to 85°C unless otherwise noted. Typical values are at TA = 25°C.

Symbol Description Conditions Min Typ Max Units

VIN Input Voltage 2.7 3.3 5.5 V

VOUT Output Voltage Range 1 1.2 1.8 V

VUVLO UVLO Threshold

VIN rising 2.4 V

Hysteresis 180 mV

VIN falling 1.6 V

VOUT Output Voltage Tolerance IOUT = 0A to 1.5A, VIN = 3.3V, VOUT = 1.2V

ﬁ xed -3.0 +3.0 %

IQQuiescent Current No Load 55 90 A

ISHDN Shutdown Current EN = GND 1.0 A

ILIM Current Limit 23 A

RDS(ON)H High Side Switch On-Resistance 140 m

RDS(ON)L Low Side Switch On-Resistance 100 m

ΔVLOADREG Load Regulation ILOAD = 0A to 1.5A 0.5 %

ΔVLINEREG/

ΔVIN

Line Regulation VIN = 3.3V to 4.0V 0.3 %/V

VFB

Feedback Threshold Voltage Accuracy

(Adjustable Version) No load, TA = 25°C 0.0591 0.60 0.609 V

ILXLEAK,R LX Reverse Leakage Current VIN unconnected, VLX = 5.5V, EN = GND 1.0 A

IFBLEAK FB Leakage Current VOUT = 1.2V 0.2 A

FOSC Internal Oscillator Frequency 2.6 3 3.4 MHz

TSStart-up Time Enable to Output Regulation 60 s

TSD Over-Temperature Shutdown Threshold 140 °C

THYS Over-Temperature Shutdown Hysteresis 25 °C

EN Logic

VIL EN Threshold Low 0.4 V

VIH EN Threshold High 1.4 V

ILEAK EN Leakage Current VEN = 5.5V -1.0 1.0 A

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 cor-

relation with statistical process controls.

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 5

www.analogictech.com

Typical Characteristics

Efficiency vs. Output Current

OUT

= 1.2V; L = 0.47µH)

Output Current (mA)

Efficiency (%)

0.1 1 10 100 1000 10000

100

VIN = 5.5V

VIN = 5.0V

VIN = 4.2V

VIN = 3.6V

VIN = 3.0V

VIN = 2.7V

Efficiency vs. Output Current

OUT

= 1.8V; L = 0.47µH)

Output Current (mA)

Efficiency (%)

0.1 1 10 100 1000 10000

100

VIN = 5.5V

VIN = 5.0V

VIN = 4.2V

VIN = 3.6V

VIN = 3.0V

VIN = 2.7V

Load Regulation

OUT

= 1.2V; L = 0.47µH)

Output Current (mA)

Load Regulation (%)

0.1 1 10 100 1000 10000

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

VIN = 5.5V

VIN = 5.0V

VIN = 4.2V

VIN = 3.6V

VIN = 3.0V

VIN = 2.7V

Load Regulation

OUT

= 1.8V; L = 0.47µH)

Output Current (mA)

Load Regulation (%)

0.1 1 10 100 1000 10000

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

VIN = 5.5V

VIN = 5.0V

VIN = 4.2V

VIN = 3.6V

VIN = 3.0V

VIN = 2.7V

Line Regulation

OUT

= 1.2V; L = 0.47µF)

Input Voltage (V)

Line Regulation (%)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

IOUT = 1500mA

IOUT = 1000mA

IOUT = 500mA

IOUT = 1mA

Line Regulation

OUT

= 1.8V; L = 0.47µF)

Input Voltage (V)

Line Regulation (%)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

IOUT = 1500mA

IOUT = 1000mA

IOUT = 500mA

IOUT = 1mA

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

6 2113A.2009.06.1.1

www.analogictech.com

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

6 2113A.2009.06.1.1

www.analogictech.com

Typical Characteristics

Output Voltage vs. Input Voltage

OUT

= 1.2V; I

OUT

= 1A)

Input Voltage (V)

Output Voltage (V)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

1.15

1.16

1.17

1.18

1.19

1.20

1.21

1.22

1.23

1.24

1.25

T = 85°C

T = 25°C

T = -40°C

Output Voltage vs. Input Voltage

OUT

= 1.8V; I

OUT

= 1A)

Input Voltage (V)

Output Voltage (V)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

1.75

1.76

1.77

1.78

1.79

1.80

1.81

1.82

1.83

1.84

1.85

T = 85°C

T = 25°C

T = -40°C

Output Voltage Error vs. Temperature

OUT

= 1.2V; V

= 3.3V; I

OUT

= 1A)

Temperature (°C)

Output Voltage Error (%)

-40 -20 0 20 40 60 80-30 -10 10 30 50 70 90

-1.5

-1.0

-0.5

0.0

0.5

1.0

Output Voltage Error vs. Temperature

OUT

= 1.8V; V

= 3.3V; I

OUT

= 1A)

Temperature (°C)

Output Voltage Error (%)

-40 -20 0 20 40 60 80-30 -10 10 30 50 70 90

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Switching Frequency vs. Temperature

OUT

= 1.2V; I

OUT

= 1A)

Temperature (°C)

Switching Frequency (MHz)

-40 -20 0 20 40 60 80-30 -10 10 30 50 70 90

2.84

2.86

2.88

2.90

2.92

2.94

2.96

2.98

3.00

3.02

3.04

Quiescent Current vs. Input Voltage

(No Load)

Input Voltage (V)

Supply Current (µA)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

T = 85°C

T = 25°C

T = -40°C

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 7

www.analogictech.com

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 7

www.analogictech.com

Typical Characteristics

Load Transient

(VOUT = 1.2V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10µF)

Time (20µs/div)

Output Voltage

(top) (50mV/div)

Output Current

(bottom) (500mA/div)

1.10

1.15

1.20

1.25

1.30

0.0

0.5

1.0

1.5

Load Transient

(VOUT = 1.8V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10µF)

Time (20µs/div)

Output Voltage

(top) (50mV/div)

Output Current

(bottom) (500mA/div)

1.70

1.75

1.80

1.85

1.90

-0.5

0.0

0.5

1.0

1.5

Load Transient

(VOUT = 1.2V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10µF)

Time (20µs/div)

Output Voltage

(top) (50mV/div)

Output Current

(bottom) (500mA/div)

1.10

1.15

1.20

1.25

1.30

-0.5

0.0

0.5

1.0

1.5

Load Transient

(VOUT = 1.8V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10µF)

Time (20µs/div)

Output Voltage

(top) (50mV/div)

Output Current

(bottom) (500mA/div)

1.70

1.75

1.80

1.85

1.90

0.0

0.5

1.0

1.5

Line Transient

(VOUT = 1.2V; VIN = 3.3V to 3.6V; IOUT = 1A)

Time (50µs/div)

Input Voltage

(top) (500mV/div)

Output Voltage

(bottom) (5mV/div)

3.0

3.5

4.0

1.190

1.195

1.200

1.205

1.210

Line Transient

(VOUT = 1.8V; VIN = 3.3V to 3.6V; IOUT = 1A)

Time (20µs/div)

Input Voltage

(top) (500mV/div)

Output Voltage

(bottom) (5mV/div)

3.0

3.5

4.0

1.795

1.800

1.805

1.810

1.815

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

8 2113A.2009.06.1.1

www.analogictech.com

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

8 2113A.2009.06.1.1

www.analogictech.com

Typical Characteristics

Soft Start

(VOUT = 1.2V; VIN = 3.3V; IOUT = 1A)

Time (100µs/div)

Enable Voltage (top) (1V/div)

Output Voltage (middle) (1V/div)

Inductor Current

(bottom) (1A/div)

-1

Soft Start

(VOUT = 1.8V; VIN = 3.3V; IOUT = 1A)

Time (2ms/div)

Enable Voltage (top) (1V/div)

Output Voltage (middle) (1V/div)

Inductor Current

(bottom) (1A/div)

-1

Output Voltage Ripple

(VOUT = 1.2V; VIN = 3.3V; IOUT = 1mA)

Time (10µs/div)

Output Voltage

(top) (10mV/div)

Inductor Current

(bottom) (100mA/div)

1.19

1.20

1.21

-0.2

-0.1

0.1

0.2

0.3

Output Voltage Ripple

(VOUT = 1.8V; VIN = 3.3V; IOUT = 1mA)

Time (10µs/div)

Output Voltage

(top) (10mV/div)

Inductor Current

(bottom) (100mA/div)

1.79

1.80

1.81

-0.2

-0.1

0.1

0.2

0.3

Output Voltage Ripple

(VOUT = 1.2V; VIN = 3.3V; IOUT = 1.5A)

Time (200ns/div)

Output Voltage

(top) (20mV/div)

Inductor Current

(bottom) (500mA/div)

1.18

1.20

1.22

0.5

1.0

1.5

2.0

Output Voltage Ripple

(VOUT = 1.8V; VIN = 3.3V; IOUT = 1.5A)

Time (200ns/div)

Output Voltage

(top) (20mV/div)

Inductor Current

(bottom) (500mA/div)

1.78

1.80

1.82

1.0

1.5

2.0

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 9

www.analogictech.com

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 0.47H inductor and a 10F ceramic capaci-

tor 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 inte-

grates 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 55A.

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 automati-

cally recovers.

Peak current mode control and optimized internal com-

pensation 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.

Functional Block Diagram

Err

Amp

Logic

PGND

AGND

VREF =

0.6V

Input

Comp

VCC

AAT2113A-1.2V Only

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

10 2113A.2009.06.1.1

www.analogictech.com

Control Loop

The AAT2113A is a peak current mode step-down con-

verter. The current through the P-channel MOSFET (high

side) is sensed for current loop control, as well as short-

circuit and overload protection. A fixed slope compensa-

tion signal is added to the sensed current to maintain

stability for duty cycles greater than 50%. The peak cur-

rent mode loop appears as a voltage-programmed cur-

rent 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 con-

verter 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 shut-

down is less than 1A.

Current Limit and

Over-Temperature Protection

For overload conditions, the peak input current is limit-

ed. 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 suffi-

cient VIN bias and proper operation of all internal cir-

cuitry prior to activation.

Component Selection

Inductor Selection

The step-down converter uses peak current mode con-

trol 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 satura-

tion 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 rat-

ing, 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 0.47 ± 20% 0.04 ± 25% 2.5x2.0x1.0

Coilcraft EPL2010-421ML 0.42 ± 20% 0.04 ± 25% 2.0x2.0x1.0

EPL2010-681ML 0.68 ± 20% 0.058 ± 25% 2.0x2.0x1.0

Table 1: AAT2113A List of Inductors.

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

2113A.2009.06.1.1 11

www.analogictech.com

Input Capacitor

Select a 4.7F to 10F 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 volt-

age and is a maximum when VIN is double the output

voltage.

⎛⎞

· 1 -

⎝⎠

VIN

CIN =

VIN

⎛⎞

- ESR · FS

⎝⎠

VPP

⎛⎞

· 1 - = for VIN = 2 · VO

⎝⎠

VIN

CIN(MIN) = 1

⎛⎞

- ESR · 4 · FS

⎝⎠

VPP

Always examine the ceramic capacitor DC voltage coef-

ficient characteristics when selecting the proper value.

For example, the capacitance of a 10F, 6.3V, X5R

ceramic capacitor with 3.5V DC applied is actually about

5F. Some examples of DC bias voltage versus capaci-

tance for different package sizes are shown in Figure 1.

DC Bias Voltage (V)

Capacitance (µF)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

0603 Package

0805 Package

Figure 1: 10μF Capacitor Value vs. DC Bias

Voltage for Different Package Sizes.

The maximum input capacitor RMS current is:

IRMS = IO · · 1 -

VIN

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.

· 1 - = D · (1 - D) = 0.52 =

VIN

for VIN = 2 · VO

RMS(MAX)

The term

⎛⎞

· 1 -

⎝⎠

VIN

VIN appears in both the input voltage

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 eval-

uation 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 dur-

ing 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 induc-

tance cannot be reduced to a level that does not affect

the converter performance, a high ESR tantalum or alu-

minum electrolytic should be placed in parallel with the

low ESR/ESL bypass ceramic capacitor. This dampens

the high Q network and stabilizes the system.

AAT2113A

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Output Capacitor

The output capacitor limits the output ripple and pre-

vents the output voltage droop during large load transi-

tions. A 10F to 22F 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 out-

put 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

Once the average inductor current increases to the DC

load level, the output voltage recovers. The above equa-

tion 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 10F. This is due to

its effect on the loop crossover frequency (bandwidth),

phase margin, and gain margin. Increased output capac-

itance 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 vari-

ous output voltages with R2 set to either 59k or 200k.

Alternately, the feedback resistor may be calculated

using the following equation:

R1 = -1 · R2 = - 1 · 200kΩ = 400kΩ

VOUT

VREF

1.8V

0.6V

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 39.2 133

1.1 49.9 165

1.2 59 200

1.3 68.1 232

1.4 78.7 267

1.5 88.7 301

1.6 97.6 332

1.7 107 365

1.8 118 400

Table 2: Feedback Resistor Selection for

Adjustable Output Voltage Version.

Thermal Calculations

There are three types of losses associated with the

AAT2113A step-down converter: switching losses, con-

duction 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 con-

duction mode (CCM), a simplified form of the losses is

given by:

PTOTAL

2 · (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 con-

verter switching losses. For the condition where the

step-down converter is in dropout at 100% duty cycle,

the total device dissipation reduces to:

PTOTAL= IO

2 · RDS(ON)H + IQ · VIN

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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Since RDS(ON), quiescent current, and switching losses all

vary with input voltage, the total losses should be inves-

tigated over the complete input voltage range.

Given the total losses, the maximum junction tempera-

ture can be derived from the JA 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 (adjust-

able version). The following guidelines should be used to

help ensure a proper layout:

1. The input capacitor (C1) should be connected as

close as possible to VP and PGND.

2. 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.

3. For the fixed version, the feedback trace or FB pin

should be separated from any power trace and con-

nected 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.

4. 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 differ-

ences in the potential of the internal signal ground

and the power ground.

5. Connect unused signal pins to ground to avoid

unwanted noise coupling.

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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1.2V/1.5A

U1 AAT2113AIXS-1.2V-T1 AnalogicTech, 3MHz Fast Transient, 1.5A Step-Down Converter , FTDFN22-8, 2x2mm

C1 GRM188R60J475KE19D, Murata, Cap, MLC, 4.7µF/6.3V, 0603 (HMAX = 0.9mm)

L1 LQM2HPNR47MGO, Murata, 0.47µH, ISAT = 1800mA, DCR = 40mΩ, 2.5 x 2 x 0.9 mm, shielded chip inductor

C2 GRM188R60J106ME47D, Murata, Cap, MLC, 10µF/6.3V, 0603 (HMAX = 0.9mm)

C3 GRM155R60J105KE19D, Murata, Cap, MLC, 1µF/6.3V, 0402

0.47µH

2.7V to 5.5V

4.7µF

1µF

10µF

VIN VOUT

LX 7

PGND 1

VCC

LX 8

AGND

FTDFN22-8

AAT2113A

Figure 2: AAT2113A Evaluation Board Schematic For 1.2V Fixed Output Voltage Version.

Figure 3: AAT2113A Evaluation Board Figure 4: AAT2113A Evaluation Board

Top Side Layout for 1.2V Fixed Bottom Side Layout for 1.2V Fixed

Output Voltage Version. Output Voltage Version.

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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1.2V/1.5A

U1 AAT2113AIXS-0.6-T1 AnalogicTech, 3MHz Fast Transient, 1.5A Step-Down Converter, FTDFN22-8, 2x2mm

C1 GRM188R60J475KE19D, Murata, Cap, MLC, 4.7µF/6.3V, 0603 (HMAX = 0.8mm)

C2 Optional, 22pF, 0201

L1 LQM2HPNR47MGO, Murata, 0.47μH, ISAT =1.8A, DCR = 0.04Ω, 2.5 x 2 x 1mm, shielded chip inductor

R1, R2 Carbon film resistor, 200kΩ, 1%, 0201

C3 GRM188R60J106ME47D, Murata, Cap, MLC, 10µF/6.3V, 0603 (HMAX = 0.8mm)

C4 GRM155R60J105KE19D, Murata, Cap, MLC, 1µF/6.3V, 0402

0.47µH

L12.7V–5.5V

4.7µF C4

1µF

10µF

22pF

200k

VIN VOUT

LX 7

AGND 1

VCC

LX 8

PGND

AAT2113A

Figure 5: AAT2113A Evaluation Board Schematic For Adjustable Output Voltage Version.

Figure 6: AAT2113A Evaluation Board Figure 7: AAT2113A Evaluation Board

Top Side Layout for Adjustable Bottom Side Layout for Adjustable

Output Voltage Version. Output Voltage Version.

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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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, 0.47H LQM2HPNNR47MG0 shielded chip inductor has a 40m DCR.

1.2

1.2V

ΔI =

· 1 - = · 1 - = 542m

L1 · F

0.47µH · 3MHz

3.3V

= I

OUT

+ ΔI = 1.5A + 0.271A = 1.8A

= I

OUT

· DCR = 1.5A

· 40mΩ = 90mW

Output Capacitor

For VDROOP = 0.12V (10% Output Voltage)

3 · ΔILOAD

VDROOP · FS

3 · 1.5A

0.12V · 3MHz

COUT = = = 12.5µF; use 10µF

For VDROOP = 0.06V (5% Output Voltage)

1 1.2V · (5V - 1.2V)

1.5µH · 3MHz · 5V

RMS(MAX)

IL · FS · VIN(MAX)

= ·

3 · ΔILOAD

VDROOP · FS

3 · 1.5A

0.06V · 3MHz

COUT = = = 25µF; use 22µF

· = 58.5mArms

VOUT · (VIN(MAX) - VOUT)=

PRMS = ESR · IRMS2 = 5mΩ · (58.5mA)2 = 17µW

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

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AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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Input Capacitor

For Input Ripple VPP = 30mV

CIN = = = 5.6µF; use 4.7µF

- ESR · 4 · FS

VPP

- 5mΩ · 4 · 3MHz

30mV

1.5A

IOUT1

RMS

P = ESR · (IRMS)2 = 5mΩ · (0.75A)2 = 2.8mW

== 0.75A

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 = IOUT

2 · RDS(ON)H + (tSW · FSW · IOUT + IQ) · VIN

= 416mW

= 1.5A2 · 152mΩ + (5ns · 3MHz · 1.5A + 50µA) · 3.3V

TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (70°C/W) · 416mW = 114°C

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

PRODUCT DATASHEET

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Ordering Information

Output Voltage Package Marking1Part Number (Tape and Reel)2

1.2V FTDFN22-8 8BXYY AAT2113AIXS-1.2-T1

Adjustable (0.6V) FTDFN22-8 8AXYY 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

2.000

0.050

Index Area

2.000

0.050

Top View

0.500

0.050

Detail "A"

0.400

0.050

Pin 1 Identification

0.000

0.100

- 0.000

Side View

0.230

0.050

0.750

0.050

Bottom View

0.450

0.0500.250

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.

AAT2113A

3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

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3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchRegTM

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Phone (408) 737-4600

Fax (408) 737-4611

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