ANALOGICTECH AAT1154

AAT1154
1MHz 3A Buck DC/DC Converter
General Description
Features
The AAT1154 SwitchReg™ is a member of
AnalogicTech™'s Total Power Management™ IC
product family. The Step-down switching converter
is ideal for applications where high efficiency, small
size, and low ripple are critical. Able to deliver 3A
with an internal power MOSFET, the current-mode
controlled IC provides high efficiency. Fully internally compensated, the AAT1154 simplifies system
design and lowers external part count.
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VIN Range: 2.7-5.5Volts
Fixed or adjustable VOUT: 1.0V - 4.2V
3A output current
Up to 95% efficiency
Integrated low on resistance power switch
Internally compensated current mode control
1MHz switching frequency
Constant PWM mode
Low output ripple with light load
Internal softstart
Current limit protection
Over-Temperature protection
SOP-8 package
-40 to 85°C Temperature Range
Preliminary Information
The AAT1154 is available in an SOP-8 package,
rated over -40 to 85°C.
SwitchReg™
Applications
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Computer Peripherals
Set Top Boxes
Network Cards
Cable/DSL Modems
High efficiency conversion from 5V or 3.3V
supply
Typical Application
INPUT
VP
10µF
100Ω
FB
AAT1154
VCC
1.5µH
LX
ENABLE
0.1µF
OUTPUT
GND
1154.2003.08.0.91
120µF
1
AAT1154
1MHz 3A Buck DC/DC Converter
Pin Descriptions
Pin #
Symbol
Function
1
FB
2
GND
3
EN
4
VCC
5, 8
VP
Input Supply Voltage for converter power stage.
6, 7
LX
Inductor connection pins. These pins should be connected to the
output inductor. Internally, pins 6 & 7 are connected to the drain of
the P-channel switch.
Feedback input pin. This pin must be connected to the converter’s
output. It is used to set the output of the converter to regulate to the
desired value.
Ground connection.
Enable input pin. When connected high, AAT1154 is in normal
operation. When connected low, it is powered down. This pin
should not be left floating.
Power supply. It supplies power for the internal circuitry.
Pin Configuration
SO-8
2
8
7
2
2
1
1
FB
GND
EN
VCC
3
6
4
5
VP
LX
LX
VP
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Absolute Maximum Ratings
Symbol
VCC, VP
VLX
VFB
VEN
TJ
VESD
(TA=25°C unless otherwise noted)
Description
VCC, VP to GND
LX to GND
FB to GND
EN to GND
Operating Junction Temperature Range
ESD Rating 1 - HBM
Value
Units
6
-0.3 to VP+0.3
-0.3 to VCC+0.3
-0.3 to VCC+0.3
-40 to 150
3000
V
V
V
V
°C
V
Note: 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.
Note 1: Human body model is a 100pF capacitor discharged through a 1.5K resistor into each pin.
Thermal Characteristics
Symbol
ΘJA
PD
Description
Thermal Resistance 2
Maximum Power Dissipation (TA = 25°C)
2, 3
Value
Units
110
909
°C/W
mW
Rating
Units
-40 to +85
°C
Note 2: Mounted on a demo board (FR4, in still air).
Note 3: Derate 9.1mW/°C above 25°C.
Recommended Operating Conditions
Symbol
T
1154.2003.08.0.91
Description
Ambient Temperature Range
3
AAT1154
1MHz 3A Buck DC/DC Converter
Electrical Characteristics
(VIN = VCC = VP = 5V, TA= -40 to 85°C unless otherwise noted. Typical
values are at TA = 25°C)
Symbol
VIN
VOUT
Input Voltage Range
Output Voltage Tolerance
VUVLO
Under Voltage Lockout
VUVLO(HYS)
IQ
ISHDN
ILIM
RDS(ON)L
η
∆VOUT (VOUT*∆VIN)
∆VOUT/VOUT
FOSC
VEN(L)
VEN(H)
TSD
THYS
4
Description
Under Voltage Lockout Hysteresis
Quiescent Supply Current
Shutdown Current
Current Limit
High Side Switch On Resistance
Efficiency
Load Regulation
Line Regulation
Oscillator Frequency
Enable Threshold Low
Enable Threshold High
Over Temp Shutdown Threshold
Over Temp Shutdown Hysteresis
Conditions
VIN = VOUT + 0.2 to 5.5V,
IOUT = 0 to 3A
VIN Rising
VIN Falling
No Load, VFB= 0 V
VEN = 0 V, VIN= 5.5V
TA = 25°C
TA = 25°C
IOUT = 1.0 A
ILOAD = 0 - 3A
VIN= 2.7 to 5.5V
TA = 25°C
Min Typ Max Units
2.7
-5.0
5.5
5.0
V
%
2.5
V
V
mV
µA
µA
A
mΩ
1.2
250
630
1000
1.0
4.4
60
92
±2.6
0.75
1
0.6
1.4
140
15
%
%/V
MHz
V
V
°C
°C
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Typical Characteristics
Oscillator Frequency Variation vs.
Supply Voltage
RDS(ON) vs. Temperature
90
0.5
VIN = 2.7V
VIN = 4.2V
VIN = 3.6V
Variation (%)
RDS(ON) (mΩ)
80
70
60
VIN = 5.5V
50
VIN = 5V
0.25
0
-0.25
40
-20
0
20
40
60
80
100
-0.5
120
3.5
4
4.5
Temperature (°C)
5
5.5
Input Voltage (V)
RDS(ON) vs. VIN, IDS = 1A
Oscillator Frequency Variation vs. Temperature
VIN = 5V
70
1
65
Variation (%)
RDS(ON) (mΩ
Ω)
0
60
55
50
45
-1
-2
-3
40
2.5
3
3.5
4
4.5
5
-4
5.5
-20
0
20
Input Voltage (V)
60
80
100
Temperature (°C)
Enable Threshold vs. Input Voltage
Output Voltage vs. Temperature
IOUT=2A
1.2
0.4
1.1
0.2
EN(H)
1
Variation (%)
Enable Threshold (V)
40
0.9
0.8
EN(L)
0.7
0
-0.2
-0.4
-0.6
0.6
-0.8
2.5
3
3.5
4
Input Voltage (V)
1154.2003.08.0.91
4.5
5
5.5
-20
0
20
40
60
80
100
Temperature (°°C)
5
AAT1154
1MHz 3A Buck DC/DC Converter
Typical Characteristics
Over Temp Current vs. Input Voltage
VOUT = 3.3V
Line Regulation
VOUT=3.3V
3.6
Output Current (A)
Output Voltge Error (%)
1
IO = 0.3A
0
-1
-2
IO = 3.0A
-3
3.4
70°C
3.2
3
2.8
85°C
2.6
2.4
-4
100°C
2.2
2
-5
3
3.5
4
4.5
5
5.5
3.5
6
3.75
4
4.25
Input Voltage (V)
Load Regulation
VIN = 5.0V, VIN = 3.3V
0.0
Operating Current (mA)
Output Error (%)
5
5.25
5.5
0.8
-2.0
-3.0
-4.0
-5.0
-6.0
-7.0
-8.0
-9.0
-10.0
0.01
0.1
1
10
VIN = 5.5V
0.6
VIN = 4.2V
VIN = 3.6V
0.5
VIN = 2.7V
0.4
-20
0
20
14
6
Voltage (V)
(bottom traces)
4.5
4
3.5
3
4
2
8
0
6
Temperature (°C)
80
90
100
-4
2
-2
70
-2
Input
4
2
60
120
6
Inductor Current
10
0
50
100
12
2.5
40
80
Current (A)
(top trace)
5
30
60
Inrush and Output Overshoot Characteristic
3A Load
5.5
20
40
Temperature (°C)
Over Temp Shutdown Current vs. Temperature
VOUT = 3.3V, VIN = 5.0V, L = 1.5µH
10
VIN = 5.0V
0.7
Load Current (A)
Output Current (A)
4.75
Non-Switching Operating Current vs. Temperature
FB = 0V
-1.0
6
4.5
Input Voltage (V)
-6
Output
-8
-10
0
0.4
0.8
1.2
1.6
2
Time (millisec)
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Typical Characteristics
Inrush and Output Overshoot Characteristic
No Load
Inductor Current
4
7
4
2
6
0
5
-2
4
-4
3
-6
2
10
2
8
0
6
-2
Input
4
-4
2
-6
Output
0
-8
-2
-10
0
0.4
0.8
1.2
1.6
-8
2
-1
0
1
2
5
-2
4
-4
3
-6
2
-8
1
200 uF 6.3V Ceramic
TDK P/N C3325X5R0J107M
0
-12
AC Output Ripple (top)
(mV)
AC Output Ripple
(top) (mV)
6
0
-1
3
4
40
7
20
6
0
5
-20
4
-40
3
-60
2
-80
5
16
135
12
100µF 6.3V Ceramic
TDK P/N C3225X5R0J107M
-16
10000
1154.2003.08.0.91
0
-45
-90
-135
-180
100000
Frequency (Hz)
4
5
120 µF 6.3V Tantalum
Vishay P/N 594D127X96R3C2T
8
Gain (dB)
Gain (dB)
-12
90
45
2x 100µF
3
135
90
Phase
4
0
-4
180
45
0
Gain
-45
-8
-90
-12
-135
-16
10000
Phase (Degrees)
Phase
Phase (Degrees)
-8
2
Loop Crossover Gain and Phase
180
3x 100µF
1
Time (µ
µsec)
12
0
-1
0
16
-4
0
-120
Loop Crossover Gain and Phase
4
1
120 µF 6.3V Tantalum Vishay
P/N 594D127X96R3C2T
-100
Time (µ
µsec)
8
5
Inductor Current
(bottom) (A)
2
Inductor Current
(bottom) (A)
7
2
4
Tantalum Output Ripple
IOUT = 3.0A, VOUT = 3.3V, VIN = 5.0V
4
1
3
Time (µ
µsec)
Output Ripple
IOUT = 3.0A, VOUT = 3.3V, VIN = 5.0V
0
0
-12
Time (millisec)
-10
1
300 µF 6.3VCeramic
TDK P/N C3325X5R0J107M
-10
Inductor Current
bottom (A)
6
Current (A)
(top trace)
Voltage (V)
(bottom traces)
12
AC Output Ripple
top (mV)
14
Output Ripple
IOUT = 3.0A, VOUT = 3.3V, VIN = 5.0V
-180
100000
Frequency (Hz)
7
AAT1154
1MHz 3A Buck DC/DC Converter
Typical Characteristics
Transient Response
IOUT = 0 to 3.0A, VOUT = 3.3V, VIN = 5.0V
100
3x 100µF 6.3V Ceramic
TDK P/N C3325X5R0J107M
7
100
6
0
5
-200
4
-300
3
-400
2
-500
1
-600
0
-700
-1
-700
0
100
200
300
400
500
Output Voltage
(top) (mV)
-100
6
-100
5
-200
4
-300
3
-400
2
-500
1
-600
0
-1
0
Time (µ
µs)
7
2x 100 uF 6.3V Ceramic
TDK P/N C3325X5R0J107M
Inductor Current
(bottom) (A)
Inductor Current
(bottom) (A)
Output Voltage
(top) (mV)
0
Transient Response
IOUT = 0 to 3.0A, VOUT = 3.3V, VIN = 5.0V
100
200
300
400
500
Time (µ
µs)
100
7
0
6
-100
5
-200
4
-300
3
-400
2
-500
1
-600
0
120µF 6.3V Tantalum
Vishay P/N 594D127X96R3C2T
-700
0
100
200
300
Inductor Current
(bottom) (A)
Output Voltage
(top) (mV)
Tantalum Transient Response
IOUT = 0 to 3.0A, VOUT = 3.3V, VIN = 5.0V
-1
400
500
Time (µ
µs)
8
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Functional Block Diagram
VCC
VP= 2.7V- 5.5V
REF
FB
OP. AMP
CMP
DH
LOGIC
OSC
LX
Temp.
Sensing
GND
EN
Applications Information
The crossover frequency and phase margin are set
by the output capacitor value.
Main Control Loop
Duty cycle extends to 100% as the input voltage
approaches the output voltage. Thermal shutdown
protection disables the device in the event of a
short circuit or overload condition.
The AAT1154 is a peak current mode buck converter. The inner wide bandwidth loop controls the
inductor peak current. The inductor current is
sensed as it flows through the internal P-Channel
MOSFET. A fixed slope compensation signal is
then added to the sensed current to maintain stability for duty cycles greater than 50%. The inner
loop appears as a voltage programmed current
source in parallel with the output capacitor.
The voltage error amplifier output programs the current loop for the necessary inductor current to force
a constant output voltage for all load and line conditions. The feedback resistive divider is internal,
dividing the output voltage to the error amplifier reference voltage of 1.0V. The error amplifier has a
limited DC gain. This eliminates the need for external compensation components while still providing
sufficient DC loop gain for good load regulation.
1154.2003.08.0.91
Soft Start/Enable
Soft-start controls the current limit when the input
voltage or enable is applied. It limits the current
surge seen at the input and eliminates output voltage overshoot.
The enable input, when pulled low, forces the
device into a low power non-switching state. The
total input current during shutdown is less than 1µA.
Power and Signal Source
Separate small signal ground and power supply
pins isolate the internal control circuitry from
switching noise. In addition, the low pass filter R1
and C3 in figure 3 filters noise associated with the
power switching.
9
AAT1154
1MHz 3A Buck DC/DC Converter
Current Limit and Over Temp
Protection
The AAT1154 over temp and current limit circuitry
protects the AAT1154 as well as the external
Schottky diode during overload, short circuit and
excessive ambient temperature conditions. The
junction over temp threshold is 140°C nominal and
has 15°C of hysteresis. Typical graphs of the over
temp load current vs. input voltage and ambient temperature are shown in the Typical Characteristics
section.
Inductor
The output inductor is selected to limit the ripple
current to 20-40% of the full load current at the
maximum input voltage. 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 inductor saturation
characteristics. The inductor should not show any
appreciable saturation under all normal load conditions. During overload and short circuit conditions
the inductor can exceed its peak current rating
without affecting the converter performance. Some
inductors may have sufficient peak and average
current ratings yet result in excessive losses due to
a high DC resistance (DCR). The losses associated with the DCR and its affect on the total converter efficiency must be considered.
For a 3 Amp load and the ripple current set to 30%
at the maximum input voltage, the maximum peak
to peak ripple current is 0.9Amp. Assuming a 5V ±
5% input voltage and 30% ripple the output inductance required is
L =I
OUT
=
VOUT
VOUT 

· k · FSW · 1 - VIN(MAX)
3.3V




· 1 - 3.3V
 3.0A · 0.3 · 1MHz 
 5.25V
= 1.36µH
10
The factor "k" is the fraction of the full load (30%)
selected for the ripple current at the maximum input
voltage.
The corresponding inductor RMS current is:
IRMS =
 2 ∆I 2 
I +
≈ I O = 3A
 O
12 
∆I is the peak to peak ripple current which is fixed by
the inductor selection above. For a peak to peak current of 30% of the full load current the peak current
at full load will be 115% of the full load. The 1.5µH
inductor selected from the Sumida CDRH6D38
series has a 11mΩ DCR and a 4.0 Amp DC current
rating with a height of 4 mm. At full load the inductor
DC loss is 99 mW for a 1 % loss in efficiency.
Schottky Freewheeling Diode
The Schottky average current is the load current
times one minus the duty cycle. For VIN at 5 Volts
and Vout at 3.3 Volts the average diode current is
V
3.3V 
= 1A
I AVG = IO · 1 - O  = 3A · 1  VIN 
 5.0V 
With a 125°C maximum junction temperature and a
120°C/W thermal resistance the maximum average
current is
IAVG =
TJ(MAX)- TAMB
θJ-A · VFWD
=
125°C - 70°C
= 1.14A
120 °C/ W · 0.4V
For overload, short circuit, and excessive ambient
conditions the AAT1154 enters the over-temperature shutdown mode protecting the AAT1154 as well
as the output Schottky. In this mode the output current is limited internally until the junction temperature reaches the temperature limit (see over temp
characteristics graphs). The diode reverse voltage
must be rated to withstand the input voltage.
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Diodes Inc.
ROHM
Micro Semi
B340LA
RB050L-40
5820SM
[email protected]
[email protected]
[email protected]
3 Amp Surface Mount Schottky Diodes
Input Capacitor Selection
The primary function of the input capacitor is to provide a low impedance loop for the edges of pulsed
current drawn by the AAT1154. A low ESR/ESL
ceramic capacitor is ideal for this function. To minimize the stray inductance the capacitor should be
placed as close as possible to the IC. This also
keeps the high frequency content of the input current localized, minimizing the radiated and conducted EMI while facilitating optimum performance
of the AAT1154. The proper placement of the input
capacitor C1 is shown in the layout in figure 1.
Ceramic X5R or X7R capacitors are ideal. The
size required will vary depending on the load, output voltage, and input voltage source impedance
characteristics. Typical values range from 1µF to
10 µF. The input capacitor RMS current varies with
the input voltage and the output voltage. It is highest when the input voltage is double the output voltage where it is one half of the load current.
IRMS = IO ·
VO 
V
· 1- O 
VIN  VIN 
A high ESR tantalum with a value about 10 times
the input ceramic capacitor may also be required
when using a 10µF or smaller ceramic input bypass
capacitor. This dampens out any input oscillations
that may occur due to the source inductance resonating with the converter input impedance
Output Capacitor
With no external compensation components, the
output capacitor has a strong effect on the loop stability. Larger output capacitance will reduce the
crossover frequency with greater phase margin. A
200µF ceramic capacitor provides sufficient bulk
capacitance to stabilize the output during large load
transitions and has ESR and ESL characteristics
necessary for very low output ripple. The RMS ripple current is given by
1154.2003.08.0.91
IRMS =
1
2· 3
·
( VOUT+ VFWD) · (VIN - VOUT)
L · F · VIN
For a ceramic output capacitor the dissipation due
to the RMS current and output ripple associated
with are negligible.
Tantalum capacitors, with sufficiently low ESR to
meet output ripple requirements, generally have an
RMS current rating much greater than that actually
seen in this application. The maximum tantalum
output capacitor ESR is
ESR ≤
VRIPPLE
∆I
Where ∆I is the peak to peak inductor ripple current.
Due to the ESR zero associated with the tantalum
capacitor, smaller values than those required with
ceramic capacitors provide more phase margin a
with greater loop crossover frequency.
Layout
Figures 1 and 2 display the suggested PCB layout
for the AAT1154. The following guidelines should
be used to help insure a proper layout.
1. The connection from the input capacitor to the
Schottky anode should be as short as possible.
2. The input capacitor should connect as closely as
possible to VPOWER (pins 5 and 8) and GND (pin 2).
3. C1, L1, and CR1 should be connected as
closely as possible. The connection from the cathode of the Schottky to the LX node should be as
short as possible.
4. The feedback trace (pin 1) should be separate
from any power trace and connect as closely as
possible to the load point. Sensing along a high
current load trace can degrade DC load regulation.
5. The resistance of the trace from the load
return to the gnd (pin 2) 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 reference ground and the load rtn.
6. R1 and C3 are required in order to provide
a cleaner power source for the AAT1154 control
circuitry.
11
AAT1154
1MHz 3A Buck DC/DC Converter
Figure 1. AAT1154 Fixed Output Top Side
Layout
Thermal
The losses associated with the AAT1154 output
switching MOSFET are due to switching losses
and conduction losses. The conduction losses are
associated with the RDS(ON) characteristics of the
output switching device. At the full load condition,
assuming continuous conduction mode (CCM), an
accurate calculation of the RDS(ON) losses can be
derived from the following equations.
PON = I RMS2 · RDS(ON)
Figure 2. AAT1154 Fixed Output Bottom
Side Layout
Once the total losses have been determined the
junction temperature can be derived. The thermal
resistance (ΘJA) for the SO-8 package mounted on
an FR4 printed circuit board in still air is 110°C/W.
TJ = P · ΘJA + TAMB
TAMB is the maximum ambient temperature and TJ
is the resultant maximum junction temperature.
Design Example
IOUT 3A
RDS(ON) losses
∆I 2 

·D
IRMS = I O2 +

12 
Internal switch RMS current
D is the duty cycle and VF is the forward drop of the
Schottky diode.
D=
IRIPPLE 30% of full load at max Vin
VOUT 3.3V
VIN 5V ± 5%
FS 1MHz
TMAX = 70°C
Inductor Selection
VO + VF
VIN + VF
IQ is the peak to peak inductor ripple current.
A simplified form of calculating the RDS(ON) and
switching losses is given by
P=
L=
=
VOUT  VOUT
· 1IO · k · F 
VIN 
3.3V
 3.3 V 
· 1= 1.25µH
3A · 0.3 ·1MHz 
5V 
Use standard value of 1.5 µH
I O 2 · R DS(ON) Vo
+ tSW ·F · I O + I Q · VIN
VIN
where IQ is the AAT1154 quiescent current.
12
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Sumida inductor Series CDRH6D38.
∆I =
VO 
V 
1- O =
L · F  VIN 
3.3V
3.3V 

1= 0.82A
1.5µH · 1MHz  5.25V
I PK = IOUT +
AAT1154 Junction Temperature
IO2 · RDS(ON) · VO  tSW · F · IO
+ IQ · VIN =
+
VIN
2



32 · 65mΩ · 3.3V  20ns · 1MHz · 3A
+
+ 750µA · 5V =


5V
2
0.539 Watts
TJ(MAX)= TAMB + ΘJA · P =
70°C + 110°C / W · 0.54W = 129°C
Diode
 V 
IDIODE= IO · 1 - O =
 VIN 
 3.3V 
= 1.02A
3A · 1 
5V 
VFW = 0.35V
PDIODE =VFW · IDIODE =
0.35V · 1.01A = .354W
1154.2003.08.0.91
TJ(MAX) = TAMB + ΘJA · P =
70°C + 120°C / W · 0.354W =
112°C
∆I
=
2
3A + 0.41A = 3.41A
PON =
Given a case to ambient thermal resistance of
120°C/W from the manufacturer's data sheet,
TJ(MAX) of the diode is
Output Capacitor
The output capacitor value required for sufficient
loop phase margin depends on the type of capacitor selected. For a low ESR ceramic capacitor a
minimum value of 200µF is required. For a low
ESR tantalum capacitor lower values are acceptable. While the relatively higher ESR associated
with the tantalum capacitor will give more phase
margin and a more damped transient response, the
output voltage ripple will be higher.
The 120µF Vishay 594D tantalum capacitor has an
ESR of 85 mΩ and a ripple current rating of 1.48
Arms in a C case size. Although smaller case sizes
are sufficiently rated for this ripple current, their
ESR level would result in excessive output ripple.
The ESR requirement for a tantalum capacitor can
be estimated by
ESR ≤
IRMS =
VRIPPLE 100 mV
=
= 121 mΩ
∆I
0.82A
1
2· 3
·
(VOUT+ VFWD) · (VIN - VOUT)
L · F · VIN
=
1
3.65V ·1.7 V
·
= 240mArms
2 · 3 1.5µH · 1MHz · 5V
Two or three 1812 X5R 100uF 6.3V ceramic
capacitors in parallel also provide sufficient phase
margin. The low ESR and ESL associated with
ceramic capacitors also reduces output ripple significantly over that seen with tantalum capacitors.
Temperature rise due to ESR ripple current dissipation is also reduced.
13
AAT1154
1MHz 3A Buck DC/DC Converter
Input Capacitor
The input capacitor ripple is:
IRMS = I O ·
VO 
V 
· 1 - O = 1.42 Arms
VIN  VIN 
In the examples shown C1 is a ceramic capacitor
located as close to the IC as possible. C1 provides
the low impedance path for the sharp edges associated with the input current. C4 may or may not be
required depending upon the impedance characteristics looking back into the source. It serves to
dampen out any input oscillations that may arise
from a source that is highly inductive. For most
applications where the source has sufficient bulk
capacitance and is fed directly to the AA1154
through large PCB traces or planes it is not
required. When operating the AAT1154 evaluation
board on the bench C4 is required due to the
inductance of the wires running from the laboratory power supply to the evaluation board.
Vin 3.5V-5.5V
Efficiency vs. Load Current
VIN = 5.0V, VOUT = 3.3V
Vout 3.3V @ 3A
R2
100k
C4
100µF
U1
AAT1154-3. 3
FB
100
VP
95
L1
1.5µH
GND LX
EN
C1
10µF
C3
0.1µF
rtn
LX
VCC VP
D1
B340LA
C2
120µF
+
-
C1 Murata 10µF 6.3V X5R GRM42-6X5R106K6.3
C2 Vishay120µF 6.3V 594D127X96R6R3C2T
C3 0.1µF 0603ZD104M AVX
C4 Vishay Sprague 100µF 16V 595D107X0016C 100µF 16V
D1 B340LA Diodes Inc.
L1 CDRH6D28-1.5µH Sumida
Efficiency (%)
R1
100
90
85
80
75
70
65
60
0.01
0.1
1
10
Output Current (A)
Options
C2 MuRata 100µF 6.3V GRM43-2 X5R 107M 100µF 6.3V (two or three in parallel
C2 TDK 100µF 6.3V C3325X5R0J107M 100µF 6.3V (two or three in parallel)
Figure 3. 3.3 Volt 3 Amp Output
Adjustable Output
For applications requiring an output other than the
fixed outputs available, the 1V version can be programmed externally. Resistors R3 and R4 of figure 5
force the output to regulate higher than 1 Volt. For
14
Figure 4. 5 Volt Input 3.3 Volt Output
accurate results (less than 1% error for all outputs)
select R4 to be 10kΩ. Once R4 has been selected
R3 can be calculated. For a 1.25 Volt output with R4
set to 10k R3 is 2.5kΩ.
R3 = (VO - 1) · R4 = 0.25 · 10kΩ = 2.5kΩ
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Vin 2.7V-5.5V
VOUT 1.25V @ 3A
R1
100
R2
100k
R3
2.55k
U1
AAT1154-1.0
FB
C4
100µF
VP
L1
1.5µH
GND LX
EN
C1
10µF
C3
0.1µF
rtn
LX
VCC VP
R4
10.0k
D1
B340LA
C2
120µF
C1 Murata 10µF 6.3V X5R GRM42-6X5R106K6.3
C2 Vishay 120µF 6.3V 594D127X96R6R3C2T
C3 0.1µF 0603ZD104M AVX
C4 Vishay Sprague 100µF 16V 595D107X0016C 100µF 16V
D1 B340LA Diodes Inc.
L1 CDRH6D28-1.5µH Sumida
Options
C2 MuRata 100uF 6.3V GRM43-2 X5R 107M 100µF 6.3V (two or three in parallel)
C2 TDK 100µF 6.3V C3325X5R0J107M 100µF 6.3V (two or three in parallel)
Figure 5. AAT1154 Evaluation Board with adjustable output
Figure 6. Evaluation Board Top Side
1154.2003.08.0.91
Figure 7. Evaluation Board Bottom Side
15
AAT1154
1MHz 3A Buck DC/DC Converter
Capacitors
Part Number
Manufacturer
C4532X5ROJ107M
GRM43-2 X5R 107M 6.3
GRM43-2 X5R 476K 6.3
GRM42-6 X5R 106K 6.3
594D127X_6R3C2T
595D107X0016C
TDK
MuRata
MuRata
MuRata
Vishay
Vishay
Capacitance
(µF)
Voltage
(V)
100
100
47
10
120
100
6.3
6.3
6.3
6.3
6.3
16
Temp Co.
Case
X5R
X5R
X5R
X5R
1812
1812
1812
1206
C case
C case
Inductors
Part Number
Manufacturer
CDRH6D38-4763-T055
N05D B1R5M
NP06DB B1R5M
LQH55DN1R5M03
LQH66SN1R5M03
Sumida
Taiyo Yuden
Taiyo Yuden
MuRata
MuRata
Inductance
(µH)
I
(Amps)
DCR
Ω)
(Ω
Height
(mm)
1.5
1.5
1.5
1.5
1.5
4.0
3.2
3.0
3.7
3.8
.014
.025
.022
.022
.016
4.0
2.8
3.2
4.7
4.7
shielded
Non shielded
shielded
Non shielded
shielded
Diodes
16
Manufacturer
Part Number
Vfwd
Diodes Inc.
ROHM
Micro Semi
B340LA
RB050L-40
5820SM
0.45V @ 3A
0.45 @ 3A
0.46V @ 3A
1154.2003.08.0.91
AAT1154
1MHz 3A Buck DC/DC Converter
Ordering Information
Output Voltage
Package
Marking
Part Number (Tape and Reel)
1.0V
SO-8
AAT1154IAS-1.0-T1
1.8V
SO-8
AAT1154IAS-1.8-T1
2.5V
SO-8
AAT1154IAS-2.5-T1
3.3V
SO-8
AAT1154IAS-3.3-T1
Package Information
6.00 ± 0.20
3.90 ± 0.10
SO-8
4.90 ± 0.10
0.42 ± 0.09 × 8
1.27 BSC
45°
4° ± 4°
0.175 ± 0.075
1.55 ± 0.20
0.375 ± 0.125
0.235 ± 0.045
0.825 ± 0.445
All dimensions in millimeters.
1154.2003.08.0.91
17
AAT1154
1MHz 3A Buck DC/DC Converter
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, and advise customers to obtain the latest
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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.
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830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
18
1154.2003.08.0.91