SiGe AATIAN31 1mhz 1.4a buck regulator Datasheet

EV-110
AAT1157 EVAL
1MHz 1.4A Buck Regulator
Introduction
The AAT1157 evaluation board demonstrates performance, along with the suggested size and placement of
external components, for the AAT1157 integrated buck regulator. The external components are selected for
minimum size and optimum operation up to 1.4A output current. Resistors R3 and R4 set the output voltage.
Please refer to the AAT1157 product datasheet for more details about this product.
Layout
As with all switching power supplies, board layout for the AAT1157 is critical (see Figure 1). Special care has
been taken with the placement of the external components. The input capacitor (C1) placement is critical. It
must be located immediately adjacent to the AAT1157. As shown in Figure 2, the LX node trace has been routed under C1 in order to facilitate a close placement of C1 next to the IC. The output voltage feedback trace
has been routed on the portion of the back side of the board which has a ground plane on the top side (see
Figure 3). The trace is also routed to avoid the LX node and associated noise.
Enable
12
C1
10µF
VP
FB
VP
LX
VP
LX
7
100kΩ
9
14
13
EN
LX
N/C
6
R6
100kΩ
L1
3.0µH
16
VCC
C2
0.1µF
R3
15
10
R2
VOUT+
4
11
R1
100Ω
LX
U1
AAT1157
VIN+
3
LL
PGND
N/C
PGND
8
2
5
C3-C7
2x 22µF
R4
59kΩ
1
SGND PGND
GND
LL
GND
Figure 1: AAT1157 Evaluation Board Schematic.
Specification
Input Voltage
Output Error Voltage
Output Current
Test Conditions
Min
Typ
Max
Units
2.7
3.6
±3
5.5
V
%
A
0
1.4
Table 1: AAT1157 Evaluation Board Specification.
EV-110.2005.04.1.1
1
EV-110
AAT1157 EVAL
1MHz 1.4A Buck Regulator
Figure 2: AAT1157 Evaluation
Board PCB Top Side.
Figure 3: AAT1157 Evaluation
Board PCB Bottom Side.
Test Equipment
1. 6.0V, 2.0A laboratory power supply: HP33401A or equivalent.
2. DC 0A to 1.4A capable of operation down to 0.6V: Keithley 2400 or equivalent. (When using the Keithley
2400, set the meter to operate in voltage source mode and set the load current by varying the current
compliance [maximum current] of the meter.)
3. DC voltmeter: HP34401A or equivalent.
4. Oscilloscope: Tektronix TDS744A or equivalent.
Setup and Test
A. Load and Line Regulation (see connection diagram in Figure 4)
1. Apply a DC power supply and DC voltmeter across input voltage terminals VIN+ (positive terminal) and
GND (negative terminal or return).
2. Apply a DC load and DC voltmeter to output terminals VO+ and GND.
3. Vary the load from 0A to 1.4 A and the input voltage from 2.7V to 5.5V while monitoring the output voltage.
4. The output voltage as measured at the output terminals of the evaluation boards should not vary by
more than ±3% of the nominal voltage.
B. Short-Circuit and Over-Temperature Protection
1. Raise the input voltage to 5.5V.
2. Apply a short from VO+ to GND at the evaluation board terminals.
3. Remove the short and verify that the output returns to its initial value.
C. Light Load Select
1. Remove the load from the output.
2. While monitoring the input current and the LX node with an oscilloscope, short the LL pin high to the
input voltage.
3. The input current should increase from approximately 270µA to 5.5mA and the LX node should increase
from single pulse light load (LL) mode to a 1.25MHz constant switching frequency.
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EV-110.2005.04.1.1
EV-110
AAT1157 EVAL
1MHz 1.4A Buck Regulator
D. Enable Input
1. Short the enable pin to GND. The output should decay to zero.
2. Remove the short applied to the enable pin. The output should recover to its initial value.
1.500V
Voltmeter
Load
0-1.4A
Power Supply
3.650V
0.147A
Oscilloscope
3.600V
Voltmeter
Figure 4: AAT1157 Connection Diagram.
Component
U1
C3-C7
C1
C2
R1
R2
R3
R4
L1
Part Number
Description
AAT1157IVN-0.6-T1
GRM21BR60J106KE19
GRM21BR60J226KE19
GRM319R60J106KE01
GRM155R61A104KA01
Chip Resistor
Chip Resistor
Chip Resistor
Chip Resistor
CDRH5D28-3R0
CDRH5D28-2R5
1MHz 1.4A Buck Converter
10µF, 6.3V, X5R, 10%, 0805 (see Table 3)
22µF, 6.3V, X5R, 10%, 0805 (see Table 3)
10µF, 6.3V, X5R, 10%, 1206
0.1µF, 25V,X5R, 10%, 0402
100kΩ, 5%, 1/16W, 0402
100kΩ, 5%, 1/16W, 0402
See Table 3, 1%, 1/16W, 0402
59K, 1%, 1/16W, 0402
3.0µH 24mΩ 2.4A Shielded (see Table 3)
2.5µH 18mΩ 2.6A Shielded (see Table 3)
Manufacturer
AnalogicTech
MuRata
MuRata
MuRata
Vishay
Vishay
Vishay
Vishay
Sumida
Table 2: AAT1157 EVAL Bill of Materials.
EV-110.2005.04.1.1
3
EV-110
AAT1157 EVAL
1MHz 1.4A Buck Regulator
Output Voltage
For an adjustable output, set R4 to 59kΩ and select R3 according to Table 3.
VO (V)
Ω)
R1 (kΩ
C3-C7 (µF)
L1 (µH)
0.8
1.0
1.25
1.3
1.4
1.5
1.6
1.7
1.8
1.85
1.9
2.0
2.1
2.2
2.3
2.4
2.5
3.3
19.6
39.2
63.4
68.1
78.7
88.7
97.6
110
118
121
127
137
147
158
169
178
187
267
3x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
2x 22
22
2.5
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
Ω).
Table 3: Component Selection for Adjustable Output Voltage (R4 = 59kΩ
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
4
EV-110.2005.04.1.1
Form#: FOR001 Rev. D
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