View AAT1154_973621.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

1MHz 3A Buck DC/DC Converter General Description
The AAT1154 SwitchRegTM is a member of AnalogicTechTM's Total Power ManagementTM 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. The AAT1154 is available in an SOP-8 package, rated over -40 to 85C.
AAT1154
Features
* * * * * * * * * * * * * * *
SwitchRegTM
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 Fixed or adjustable VOUT: 1.0 to 4.2V Constant PWM mode Low output ripple with light load Internal softstart Current limit protection Over-Temperature protection SOP-8 package -40 to 85C Temperature Range
Applications
* * * * * Computer Peripherals Set Top Boxes Network Cards Cable/DSL Modems High efficiency conversion from 5V or 3.3V supply
Typical Application
INPUT VP FB
10F 100
AAT1154
VCC LX
1.5H
ENABLE 0.1F GND 120F OUTPUT
1154.2004.08.1.2
1
1MHz 3A Buck DC/DC Converter Pin Descriptions
Pin #
1
AAT1154
Symbol
FB
Function
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. Input Supply Voltage for converter power stage. 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.
2 3
GND EN
4 5, 8 6, 7
VCC VP LX
Pin Configuration
SO-8
FB GND EN VCC
1
8
VP LX LX VP
1
2 2
7
3
6
4
5
2
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter Absolute Maximum Ratings
Symbol
VCC, VP VLX VFB VEN TJ VESD
AAT1154
(TA=25C unless otherwise noted) Value
6 -0.3 to VP+0.3 -0.3 to VCC+0.3 -0.3 to VCC+0.3 -40 to 150 3000
Description
VCC, VP to GND LX to GND FB to GND EN to GND Operating Junction Temperature Range ESD Rating 1 - HBM
Units
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
JA PD
Description
Thermal Resistance 2 Maximum Power Dissipation (TA = 25C)
2, 3
Value
110 909
Units
C/W mW
Note 2: Mounted on a demo board (FR4, in still air). Note 3: Derate 9.1mW/C above 25C.
Recommended Operating Conditions
Symbol
T
Description
Ambient Temperature Range
Rating
-40 to +85
Units
C
1154.2004.08.1.2
3
1MHz 3A Buck DC/DC Converter Electrical Characteristics
values are at TA = 25C) Symbol
VIN VOUT VUVLO VUVLO(HYS) IQ ISHDN ILIM RDS(ON)L VOUT (VOUT*VIN) VOUT/VOUT FOSC VEN(L) VEN(H) TSD THYS
AAT1154
(VIN = VCC = VP = 5V, TA= -40 to 85C unless otherwise noted. Typical
Description
Input Voltage Range Output Voltage Tolerance Under Voltage Lockout 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 = 25C TA = 25C IOUT = 1.0 A ILOAD = 0 - 3A VIN= 2.7 to 5.5V TA = 25C
Min Typ Max Units
2.7 -5.0 5.5 5.0 2.5 1.2 250 630 4.4 60 92 2.6 0.75 1 0.6 1.4 140 15 1000 1.0 V % V V mV A A A m % %/V MHz V V C C
4
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter Typical Characteristics
RDS(ON) vs. Temperature
90
0.5
AAT1154
Oscillator Frequency Variation vs. Supply Voltage
VIN = 2.7V
80
VIN = 4.2V Variation (%)
120
0.25
RDS(ON) (m)
VIN = 3.6V
70 60
0
VIN = 5.5V
50 40 -20 0 20 40 60 80 100
VIN = 5V
-0.25
-0.5 3.5 4 4.5 5 5.5
Temperature (C)
Input Voltage (V)
RDS(ON) vs. VIN, IDS = 1A
70 65
Oscillator Frequency Variation vs. Temperature VIN = 5V
1 0
RDS(ON) (m)
Variation (%)
2.5 3 3.5 4 4.5 5 5.5
60 55 50 45 40
-1 -2 -3 -4 -20 0 20 40 60 80 100
Input Voltage (V)
Temperature (C)
Enable Threshold vs. Input Voltage
1.2 0.4 0.2
Output Voltage vs. Temperature IOUT=2A
Enable Threshold (V)
1.1 1 0.9 0.8 0.7 0.6 2.5 3 3.5 4 4.5 5 5.5
Variation (%)
EN(H)
0 -0.2 -0.4 -0.6 -0.8
-20 0 20 40 60 80 100
EN(L)
Input Voltage (V)
Temperature (C)
1154.2004.08.1.2
5
1MHz 3A Buck DC/DC Converter Typical Characteristics
Line Regulation VOUT=3.3V
1
AAT1154
Over Temp Current vs. Input Voltage VOUT = 3.3V
3.6
Output Current (A)
Output Voltge Error (%)
0 -1 -2 -3 -4 -5 3
IO = 0.3A
3.4 3.2 3 2.8 2.6 2.4 2.2
70C
85C 100C
3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5
IO = 3.0A
2
3.5 4 4.5 5 5.5 6
Input Voltage (V)
Input Voltage (V)
Load Regulation VIN = 5.0V, VIN = 3.3V
0.0 -1.0
Non-Switching Operating Current vs. Temperature FB = 0V
0.8
Operating Current (mA)
VIN = 5.5V
0.7
VIN = 5.0V
Output Error (%)
-2.0 -3.0 -4.0 -5.0 -6.0 -7.0 -8.0 -9.0 -10.0 0.01 0.1 1 10
0.6
VIN = 4.2V
0.5
VIN = 3.6V VIN = 2.7V
0.4 -20 0 20 40 60 80 100 120
Load Current (A)
Temperature (C)
Over Temp Shutdown Current vs. Temperature VOUT = 3.3V, VIN = 5.0V, L = 1.5H
6 5.5
Inrush and Output Overshoot Characteristic 3A Load
14 12
Inductor Current
6 4 2 0 -2
Output Current (A)
Voltage (V) (bottom traces)
5 4.5 4 3.5 3 2.5 2 10 20 30 40 50 60 70 80 90 100
10 8 6 4 2 0 -2 0 0.4 0.8 1.2 1.6 2
Current (A) (top trace)
Input Output
-4 -6 -8 -10
Temperature (C)
Time (millisec)
6
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter Typical Characteristics
Inrush and Output Overshoot Characteristic No Load
14 12 6
4 2
AAT1154
Output Ripple IOUT = 3.0A, VOUT = 3.3V, VIN = 5.0V
7 6
Inductor Current
4
AC Output Ripple top (mV)
Voltage (V) (bottom traces)
Inductor Current bottom (A)
10 8 6 4 2 0 -2 0 0.4 0.8 1.2 1.6 2
2 0 -2
0 -2 -4 -6 -8 -10 -12 0 1 2 3 4 5
5 4 3 2
Current (A) (top trace)
Input Output
-4 -6 -8 -10
300 F 6.3VCeramic TDK P/N C3325X5R0J107M
1 0 -1
Time (millisec)
Time (sec)
Output Ripple IOUT = 3.0A, VOUT = 3.3V, VIN = 5.0V
AC Output Ripple (top) (mV)
4 2 7 6
Tantalum Output Ripple IOUT = 3.0A, VOUT = 3.3V, VIN = 5.0V
40 20 0 -20 -40 -60 -80 -100 -120 0 1 2 3 4 5 7 6
Inductor Current (bottom) (A)
AC Output Ripple (top) (mV)
Inductor Current (bottom) (A)
0 -2 -4 -6 -8 -10 -12 0 1 2 3 4 5
5 4 3 2
5 4 3 2
200 uF 6.3V Ceramic TDK P/N C3325X5R0J107M
1 0 -1
120 F 6.3V Tantalum Vishay P/N 594D127X96R3C2T
1 0 -1
Time (sec)
Time (sec)
Loop Crossover Gain and Phase
16 12 8 180 135 16 12
Loop Crossover Gain and Phase
120 F 6.3V Tantalum Vishay P/N 594D127X96R3C2T Phase
180 135
Phase (Degrees)
Phase (Degrees)
Phase
90 45
8
90 45 0
Gain (dB)
4 0 -4 -8 -12
Gain (dB)
4 0 -4 -8 -12 -16 10000
3x 100F 2x 100F 100F 6.3V Ceramic TDK P/N C3225X5R0J107M
0 -45 -90 -135 -180 100000
Gain
-45 -90 -135 -180 100000
-16 10000
Frequency (Hz)
Frequency (Hz)
1154.2004.08.1.2
7
1MHz 3A Buck DC/DC Converter Typical Characteristics
Transient Response IOUT = 0 to 3.0A, VOUT = 3.3V, VIN = 5.0V
100 0 3x 100F 6.3V Ceramic TDK P/N C3325X5R0J107M 7 6
AAT1154
Transient Response IOUT = 0 to 3.0A, VOUT = 3.3V, VIN = 5.0V
100 0 2x 100 uF 6.3V Ceramic TDK P/N C3325X5R0J107M 7 6
Inductor Current (bottom) (A)
Inductor Current (bottom) (A)
Output Voltage (top) (mV)
-200 -300 -400 -500 -600 -700 0 100 200 300 400
4 3 2 1 0 -1 500
Output Voltage (top) (mV)
-100
5
-100 -200 -300 -400 -500 -600 -700 0 100 200 300 400
5 4 3 2 1 0 -1 500
Time (s)
Time (s)
Tantalum Transient Response IOUT = 0 to 3.0A, VOUT = 3.3V, VIN = 5.0V
100 0 7 6
Inductor Current (bottom) (A)
Output Voltage (top) (mV)
-100 -200 -300 -400 -500 -600 -700 0 120F 6.3V Tantalum Vishay P/N 594D127X96R3C2T 100 200 300 400 500
5 4 3 2 1 0 -1
Time (s)
8
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter Functional Block Diagram
VCC VP= 2.7V- 5.5V
AAT1154
REF
FB
OP. AMP
CMP
DH
LOGIC
LX
OSC
Temp. Sensing
GND
EN
Applications Information
Main Control Loop
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.
The crossover frequency and phase margin are set by the output capacitor value. 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.
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 1A.
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
1154.2004.08.1.2
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 140C nominal and has 15C of hysteresis. Typical graphs of the over temp load current vs. input voltage and ambient temperature are shown in the Typical Characteristics section.
AAT1154
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
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 = VOUT VOUT * k * FSW * 1 - VIN(MAX)
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 1.5H inductor selected from the Sumida CDRH6D38 series has a 11m 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 125C maximum junction temperature and a 120C/W thermal resistance the maximum average current is
IAVG = T J(MAX)- T AMB = 125C - 70C = 1.14A 120 C/ W * 0.4V
J-A * VFWD
OUT
3.3V * 1 - 3.3V 3.0A * 0.3 * 1MHz 5.25V
= 1.36H
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.
10
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter
Diodes Inc. ROHM Micro Semi B340LA RB050L-40 5820SM 0.45V@3A 0.45@3A 0.46V@3A
AAT1154
IRMS =
1 2* 3
*
( VOUT+ VFWD) * (VIN - VOUT) L * F * VIN
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 1F to 10 F. 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.
VO V * 1- O VIN 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.
IRMS = IO *
A high ESR tantalum with a value about 10 times the input ceramic capacitor may also be required when using a 10F 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 200F 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
1154.2004.08.1.2
11
1MHz 3A Buck DC/DC Converter
AAT1154
Figure 1. AAT1154 Fixed Output Top Side Layout
Figure 2. AAT1154 Fixed Output Bottom 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.
P = I RMS2 * RDS(ON) ON
Once the total losses have been determined the junction temperature can be derived. The thermal resistance (JA) for the SO-8 package mounted on an FR4 printed circuit board in still air is 110C/W. TJ = P * JA + TAMB TAMB is the maximum ambient temperature and TJ is the resultant maximum junction temperature.
Design Example
IOUT 3A IRIPPLE 30% of full load at max Vin VOUT 3.3V VIN 5V 5% FS 1MHz TMAX = 70C Inductor Selection
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=
VO + VF VIN + VF
L= =
VOUT VOUT * 1IO * k * F VIN
IQ is the peak to peak inductor ripple current. A simplified form of calculating the RDS(ON) and switching losses is given by
3.3V 3.3 V * 1= 1.25H 3A * 0.3 *1MHz 5V
Use standard value of 1.5 H
P=
I O 2 * R DS(ON) Vo + tSW *F * I O + I Q * VIN VIN
where IQ is the AAT1154 quiescent current. 12
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter
Sumida inductor Series CDRH6D38.
AAT1154
I =
VO V 1- O = L * F VIN
Given a case to ambient thermal resistance of 120C/W from the manufacturer's data sheet, TJ(MAX) of the diode is
3.3V 3.3V 1= 0.82A 1.5H * 1MHz 5.25V
I PK = IOUT + I = 2
T J(MAX) = T AMB + JA * P = 70C + 120C / W * 0.354W = 112C
3A + 0.41A = 3.41A
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 200F 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 120F Vishay 594D tantalum capacitor has an ESR of 85 m 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
AAT1154 Junction Temperature
IO2 * RDS(ON) * VO tSW * F * IO + IQ * VIN = + VIN 2
P= ON
32 * 65m * 3.3V 20ns * 1MHz * 3A + + 750A * 5V = 5V 2 0.539 Watts
TJ(MAX)= TAMB + JA * P = 70C + 110C / W * 0.54W = 129C
Diode
V IDIODE= IO * 1 - O = VIN 3.3V = 1.02A 3A * 1 5V
VFW = 0.35V
P DIODE = VFW * IDIODE =
0.35V * 1.01A = .354W
ESR
VRIPPLE 100 mV = = 121 m I 0.82A
1 *
IRMS =
(VOUT+ VFWD) * (VIN - VOUT)
L * F * VIN
2* 3
=
1 3.65V *1.7 V * = 240mArms 2 * 3 1.5H * 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.
1154.2004.08.1.2
13
1MHz 3A Buck DC/DC Converter
Input Capacitor
The input capacitor ripple is:
AAT1154
IRMS = I O *
V V O * 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 Vout 3. V @ 3A 3
Efficiency vs. Load Current VIN = 5.0V, VOUT = 3.3V
100 95
R1 100 C4 100F
R2 100k
U1 AAT1154-3. 3 FB VP
EN C1 10F C3 0.1F
LX D1 B340LA C2 120F
+ -
Efficiency (%)
GND LX
L1 1.5H
90 85 80 75 70 65 60 0.01 0.1 1 10
VCC VP
rtn
C1 Murata 10F 6.3V X5R GRM42-6X5R106K6.3 C2 Vishay120F 6.3V 594D127X96R6R3C2T C3 0. F 0603ZD104M AVX 1 C4 Vishay Sprague 100F 16V 595D107X0016C 100F 16V D1 B340LA Diodes Inc. L1 CDRH6D28-1.5H Sumida Options C2 MuRata 100F 6.3V GRM43-2 X5R 107M 100F 6.3V (two or three in parallel C2 TDK 100F 6.3V C3325X5R0J107M 100F 6.3V (two or three in parallel)
Output Current (A)
Figure 3. 3.3 Volt 3 Amp Output
Figure 4. 5 Volt Input 3.3 Volt Output accurate results (less than 1% error for all outputs) select R4 to be 10k. Once R4 has been selected R3 can be calculated. For a 1.25 Volt output with R4 set to 10k R3 is 2.5k. R3 = (VO - 1) * R4 = 0.25 * 10k = 2.5k
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
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter
Vin 2.7V-5.5V VOUT 1.25V @ 3A R3 2.55k
AAT1154
R1 100 C4 100F
R2 100k
U1 AAT1154-1. 0 FB VP L1 1.5H
GND LX EN C1 10F C3 0.1F R4 10.0k LX
VCC VP
D1 B340LA
C2 120F
rtn
C1 Murata 10F 6.3V X5R GRM42-6X5R106K6.3 C2 Vishay 120F 6.3V 594D127X96R6R3C2T C3 0. F 0603ZD104M AVX 1 C4 Vishay Sprague 100F 16V 595D107X0016C 100F 16V D1 B340LA Diodes Inc. L1 CDRH6D28-1.5H Sumida Options C2 MuRata 100uF 6.3V GRM43-2 X5R 107M 100F 6.3V (two or three in parallel) C2 TDK 100F 6.3V C3325X5R0J107M 100F 6.3V (two or three in parallel)
Figure 5. AAT1154 Evaluation Board with adjustable output
Figure 6. Evaluation Board Top Side
Figure 7. Evaluation Board Bottom Side
1154.2004.08.1.2
15
1MHz 3A Buck DC/DC Converter
Capacitors Part Number
C4532X5ROJ107M GRM43-2 X5R 107M 6.3 GRM43-2 X5R 476K 6.3 GRM42-6 X5R 106K 6.3 594D127X_6R3C2T 595D107X0016C
AAT1154
Manufacturer
TDK MuRata MuRata MuRata Vishay Vishay
Capacitance (F)
100 100 47 10 120 100
Voltage (V)
6.3 6.3 6.3 6.3 6.3 16
Temp Co.
X5R X5R X5R X5R
Case
1812 1812 1812 1206 C case C case
Inductors Part Number
CDRH6D38-4763-T055 N05D B1R5M NP06DB B1R5M LQH55DN1R5M03 LQH66SN1R5M03
Manufacturer
Sumida Taiyo Yuden Taiyo Yuden MuRata MuRata
Inductance (H)
1.5 1.5 1.5 1.5 1.5
I (Amps)
4.0 3.2 3.0 3.7 3.8
DCR ()
.014 .025 .022 .022 .016
Height (mm)
4.0 2.8 3.2 4.7 4.7 shielded Non shielded shielded Non shielded shielded
Diodes Manufacturer
Diodes Inc. ROHM Micro Semi
Part Number
B340LA RB050L-40 5820SM
Vfwd
0.45V @ 3A 0.45 @ 3A 0.46V @ 3A
16
1154.2004.08.1.2
1MHz 3A Buck DC/DC Converter Ordering Information
Output Voltage 1.0V (Adj. VOUT 1.0V) 1.8V 2.5V 3.3V Package SO-8 SO-8 SO-8 SO-8 Marking Part Number (Tape and Reel) AAT1154IAS-1.0-T1 AAT1154IAS-1.8-T1 AAT1154IAS-2.5-T1 AAT1154IAS-3.3-T1
AAT1154
Package Information
SO-8
3.90 0.10 4.90 0.10
6.00 0.20
0.375 0.125
45
1.55 0.20
0.175 0.075
4 4
0.235 0.045 0.825 0.445
0.42 0.09 x 8
1.27 BSC
All dimensions in millimeters.
1154.2004.08.1.2
17
1MHz 3A Buck DC/DC Converter
AAT1154
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 version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 18
1154.2004.08.1.2

▲Up To Search▲

Price & Availability of AAT1154

	To Download AAT1154 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .