ADP1828 Low Voltage DC-DC Switching Power

Low Voltage DC-DC Switching Power
Reference Design
Preliminary Technical Data
FCDC 00105b
FEATURES
A high density and cost-effective solution for low voltage DC-DC power conversion
Input Voltage Range: 10.8 V – 13.2 V
Output Voltage: 2.5 V
Output Current: 4 A
Single sided 1” x1” PCB
Convenient access to many of the features of the ADP1828
LOW VOLTAGE DC-DC SWITCHING POWER REFERENCE DESIGN DESCRIPTION
The ADP1828 Demo Board uses the single channel voltage mode ADP1828 switching controller IC to offer a high density and
cost effective solution for converting a 10.8 V to 13.2 V input voltage to 2.5 V capable of supplying 4 A of load current. The demo
board is a single sided PCB that is 1” x 1”. The converter switches at 600kHz nominally, which allows the design to use a small
output inductor and small MLCC output capacitors and still perform well during a high slew rate load transient event (see
Performance section).
The ADP1828 Demo Board has multiple pins easily accessible on the board.
•
EN (input): Logic High enables the converter. Logic Low disables the converter. See ADP1828 datasheet for threshold and
tolerances. Shipped configuration connects EN to Vin via a 0-ohm jumper. Remove Ren1 to use this feature.
•
TRK (input): Drive this pin from a voltage divider from the master voltage. Shipped configuration bypasses this feature by
connecting the TRK to the VREG node. Remove 0-ohm jumper (Rt3) to use this feature.
•
PwrGd (output): Indicates when the output voltage is within regulation. See ADP1828 datasheet for tolerances.
•
Sync (input): An external signal applied to this pin will cause the IC to switch at the corresponding frequency. Shipped
configuration bypasses this feature by pulling the Sync pin low. Remove this 0-ohm jumper (Rsync) to use this feature.
•
CKout (output): To synchronize another switching controller (ADP1829 or another ADP1828) to the internal clock
frequency of the ADP1828 connect the Sync pin of the other IC to this pin on the demo board.
Figure 1.
ADP1828 Demo Board
Rev. A
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©2007 Analog Devices, Inc. All rights reserved.
Preliminary Technical Data
FCDC 00105b
TABLE OF COTENTS
Features....................................................................................................................................................................................................... 1
Low Voltage DC-DC Switching Power Reference Design Description............................................................................................. 1
Revision History........................................................................................................................................................................................ 3
ADP1828 General Description ............................................................................................................................................................... 4
Powering the ADP1828 Demo Board .................................................................................................................................................... 4
Input Power Source .............................................................................................................................................................................. 4
Output Load .......................................................................................................................................................................................... 4
Input and Output Voltmeters.............................................................................................................................................................. 4
Turning On the Evaluation Board...................................................................................................................................................... 5
Schematic ................................................................................................................................................................................................... 5
Bill of Materials ......................................................................................................................................................................................... 6
Performance............................................................................................................................................................................................... 7
PCB Layout Files ..................................................................................................................................................................................... 15
Notes: ........................................................................................................................................................................................................ 21
TABLE OF FIGURES
Figure 1.
ADP1828 Demo Board ...................................................................................................................................................... 1
Figure 2.
Schematic ............................................................................................................................................................................. 5
Figure 3.
Efficiency.............................................................................................................................................................................. 7
Figure 4.
Load Regulation .................................................................................................................................................................. 7
Figure 5.
Switching regulator turn on at no load: Ch1 = 2.5 V, Ch2 = Vin ................................................................................. 8
Figure 6.
Switching regulator turn on at full load: Ch1 = 2.5 V, Ch2 = Vin............................................................................... 8
Figure 7.
Switching regulator turn off at no load: Ch1 = 3.5 V, Ch2 = Vin................................................................................ 9
Figure 8.
Switching regulator turn off at full load: Ch1 = 2.5 V, Ch2 = Vin............................................................................... 9
Figure 9.
Vin and Vout Ripple. Load current = 0A. Vin = 13.2V ............................................................................................. 10
Figure 10.
Vin and Vout Ripple. Load Current = 4A. Vin =13.2V......................................................................................... 10
Figure 11.
Vin and Vout Ripple. Load Current=0A Vin=10.8V............................................................................................. 11
Figure 12.
Vin and Vout Ripple. Load Current = 4A. Vin = 10.8V........................................................................................ 11
Figure 13.
Transient. 2A Load Step (2A -> 4A). 2A Load Release (4A ->2A). Vin=10.8) (infinite persistence)............ 12
Figure 14.
2A Load Step (2A->4A). Vin=13.2V (infinite persistence) .................................................................................. 12
Figure 15.
2A Load Release (4A-> 2A). Vin = 13.2V (infinite persistence).......................................................................... 13
Figure 16.
Load Transient. 2A Load Step (2A -> 4A). 2A Load Release (4A ->2A). Vin=10.8V ..................................... 13
Figure 17.
(infinite persistence) .................................................................................................................................................... 13
Figure 18.
2A Load Step (2A ->4A). Vin=10.8V (infinite persistence) ................................................................................. 14
Figure 19.
2A Load Release (4A -> 2A). Vin=10.8V (infinite persistence)........................................................................... 14
Figure 20.
Top PCB Layer .............................................................................................................................................................. 15
Figure 21.
Second PCB Layer ........................................................................................................................................................ 16
Figure 22.
Third PCB Layer........................................................................................................................................................... 17
Rev. A | Page 2 of 21
Preliminary Technical Data
FCDC 00105b
Figure 23.
Fourth PCB Layer......................................................................................................................................................... 18
Figure 24.
Fifth PCB Layer............................................................................................................................................................. 19
Figure 25.
Sixth and Bottom PCB Layer ...................................................................................................................................... 20
REVISION HISTORY
2/28/2008—Revision 0: Initial Version
Rev. A | Page 3 of 21
Preliminary Technical Data
FCDC 00105b
ADP1828 GENERAL DESCRIPTION
The ADP1828 is a versatile and synchronous PWM voltage mode buck controller. It drives an all N-channel power stage to
regulate an output voltage as low as 0.6 V to 85% of the input voltage and is sized to handle large MOSFETs for point-of-load
regulators. The ADP1828 is ideal for a wide range of high power applications, such as DSP and processor core I/O power, and
general-purpose power in telecommunications, medical imaging, PC, gaming, and industrial applications. It operates from input
bias voltages of 3 V to 18 V with an internal LDO that generates a 5 V output for input bias voltages greater than 5.5 V. The
ADP1828 operates at a pin-selectable, fixed switching frequency of either 300 kHz or 600 kHz, or at any frequency between 300
kHz and 600 kHz with a resistor. The switching frequency can also be synchronized to an external clock up to 2× the part’s
nominal oscillator frequency. The clock output can be used for synchronizing additional ADP1828s (or the ADP1829 controllers),
thus eliminating the need for an external clock source. The ADP1828 includes soft start protection to limit any inrush current
from the input supply during startup, reverse current protection during soft start for a precharged output, as well as a unique
adjustable lossless current-limit scheme utilizing external MOSFET RDSON sensing. For applications requiring power-supply
sequencing, the ADP1828 provides a tracking input that allows the output voltage to track during startup, shutdown, and faults.
The additional supervisory and control features include thermal overload, undervoltage lockout, and power good. The ADP1828
operates over the −40°C to +125°C junction temperature range and is available in a 20-lead QSOP.
POWERING THE ADP1828 DEMO BOARD
INPUT POWER SOURCE
1.
Before connecting the power source to the ADP1828 Demo Board, make sure that it is turned off. If the input power source
includes a current meter, use that meter to monitor the input current.
2.
Connect the positive terminal of the power source to the VIN terminal on the evaluation board, and the negative terminal of
the power source to the GND terminal
3.
If the power source does not include a current meter, connect a current meter in series with the input source voltage.
4.
Connect the positive lead (+) of the power source to the ammeter positive (+) connection, the negative lead (−) of the power
source to the GND terminal, and the negative lead (−) of the ammeter to the VIN terminal on the board.
OUTPUT LOAD
1.
Although the ADP1828 Demo Board can sustain the sudden connection of the load, it is possible to damage the load if it is
not properly connected.
2.
Make sure that the board is turned off before connecting the load.
a)
If the load includes an ammeter, or if the current is not measured, connect the load directly to the evaluation board with
the positive (+) load connection to the VOUT terminal and negative (−) load connection to the GND terminal.
b)
If an ammeter is used, connect it in series with the load; connect the positive (+) ammeter terminal to the evaluation
board VOUT terminal, the negative (−) ammeter terminal to the positive (+) load terminal, and the negative (−) load
terminal to the evaluation board GND terminal
Once the load is connected, make sure that it is set to the proper current before powering the ADP1828 Demo Board.
INPUT AND OUTPUT VOLTMETERS
Measure the input and output voltages with voltmeters.
1.
Connect the voltmeter measuring the input voltage with the positive (+) lead connected to the VIN terminal on the test
board and the negative lead (−) connected to the GND terminal
2.
Connect the voltmeter measuring VOUT with the positive lead (+) connected to the VOUT terminal on the evaluation
board and the negative lead (−) connected to the GND terminal.
Rev. A | Page 4 of 21
Preliminary Technical Data
FCDC 00105b
3.
Make sure to connect the voltmeters to the appropriate evaluation board terminals and not to the load or power source
themselves.
4.
If the voltmeters are not connected directly to the evaluation board at these connection points, the measured voltages will be
incorrect due to the voltage drop across the leads connecting the evaluation board to both the source and load.
TURNING ON THE EVALUATION BOARD
Once the power source and loads are connected, the board can be powered for operation. Slowly increase the input power source
voltage until the input voltage exceeds the minimum input operating voltage of 3V. If the load is not already enabled, enable the
load and check that it is drawing the proper current and that the output voltage maintains voltage regulation.
SCHEMATIC
Figure 2.
Schematic
Rev. A | Page 5 of 21
Preliminary Technical Data
FCDC 00105b
BILL OF MATERIALS
Table 1. Bill of Materials
Designator
Part Number
Manufacturer
U1
ADP1828
Analog Devices
Value
Package
Comment
QH1, QL1
Si5404bdc
Vishay
L1
DR74-2R2-R
Coiltronics
2.2uH
Cin1
GRM32ER6K476K
Murata
47uF
1210
Input MLCC / X5R / 16V
Co1, Co2
grm32er60j107m
Murata
100uF
1210
Output MLCC / X5R / 6.3V
Cvin, Cv5, Cpv
C2012X7R1C105K
TDK
1uF
0603
MLCC / X7R / 16V
Rf1
Generic 1%
Vishay
6.34k
0402
Feedback Resistor
Rf2
Generic 1%
Vishay
20k
0402
Feedback Resistor
Rc3
Generic 10%
Vishay
76.8ohms
0402
Compensation Resistor
Cc3
Generic 10%
Vishay
860pF
0402
Compensation Capacitor
Rc1
Generic 10%
Vishay
12.1k
0402
Compensation Resistor
Cc1
Generic 10%
Vishay
1.2nF
0402
Compensation Capacitor
Cc0
Generic 10%
Vishay
47pF
0402
Compensation Capacitor
Css
Generic 10%
Vishay
10nF
0402
COG or X7R / Soft Start Capacitor
Rpg
Generic 10%
Vishay
100k
0402
POK1 Resistor
Rvcc, Rb0
Generic 10%
Vishay
10ohms
0402
Decoupling Resistor
Rcl1
Generic 10%
Vishay
5.49k
0402
Current Limit Resistor
Ccl1
Generic 10%
Vishay
33pF
0402
Current Limit Signal Filter Capacitor
Dbst
BAT54
Any
Cbst
Generic 10%
Vishay
QSOP-20L
1206-8
7.6mm x 7.6mm
SOD-323
100nF
Rt1, Rt2, Rpv, Rcl2,
Ren2, Rv5, Rflow,
Rcklow
NP
Rt3, Rbst, Ren1,
Rsync, Rfhigh, Rckhi
0ohms
Rev. A | Page 6 of 21
0402
0402
Voltage Mode Controller
N-Channel MOSFET
Power Inductor / DCR = 9.9mO / Ferrite
/ Shielded
Bootstrap Diode
COG or X7R / Boost Capacitor
Preliminary Technical Data
FCDC 00105b
PERFORMANCE
ADP1828 2.5V out @ 4A
0.9
0.88
0.86
Pout/Pin
0.84
13.2V Data
10.8V Data
0.82
0.8
0.78
0.76
0.74
0
1
2
3
4
5
6
Load Current (A)
Figure 3.
Efficiency
Switching Regulator Load Regulation
2.4814
2.4812
2.481
Vout (V)
2.4808
2.4806
13.2V
10.8V
2.4804
2.4802
2.48
2.4798
2.4796
2.4794
0
1
2
3
4
Load Current (A)
Figure 4.
Load Regulation
Rev. A | Page 7 of 21
5
6
Preliminary Technical Data
FCDC 00105b
Figure 5.
Switching regulator turn on at no load: Ch1 = 2.5 V, Ch2 = Vin
Figure 6.
Switching regulator turn on at full load: Ch1 = 2.5 V, Ch2 = Vin
Rev. A | Page 8 of 21
Preliminary Technical Data
FCDC 00105b
Figure 7.
Switching regulator turn off at no load: Ch1 = 3.5 V, Ch2 = Vin
Figure 8.
Switching regulator turn off at full load: Ch1 = 2.5 V, Ch2 = Vin
Rev. A | Page 9 of 21
ADP1828 Demo Board Documentation
Figure 9.
Vin and Vout Ripple. Load current = 0A. Vin = 13.2V
Figure 10. Vin and Vout Ripple. Load Current = 4A. Vin =13.2V
Rev. A | Page 10 of 21
ADP1828 Demo Board Documentation
Figure 11. Vin and Vout Ripple. Load Current=0A Vin=10.8V
Figure 12. Vin and Vout Ripple. Load Current = 4A. Vin = 10.8V
Rev. A | Page 11 of 21
ADP1828 Demo Board Documentation
Figure 13. Transient. 2A Load Step (2A -> 4A). 2A Load Release (4A ->2A). Vin=10.8) (infinite persistence)
Figure 14. 2A Load Step (2A->4A). Vin=13.2V (infinite persistence)
Rev. A | Page 12 of 21
ADP1828 Demo Board Documentation
Figure 15. 2A Load Release (4A-> 2A). Vin = 13.2V (infinite persistence)
Figure 16. Load Transient. 2A Load Step (2A -> 4A). 2A Load Release (4A ->2A). Vin=10.8V
Figure 17. (infinite persistence)
Rev. A | Page 13 of 21
ADP1828 Demo Board Documentation
Figure 18. 2A Load Step (2A ->4A). Vin=10.8V (infinite persistence)
Figure 19. 2A Load Release (4A -> 2A). Vin=10.8V (infinite persistence)
Rev. A | Page 14 of 21
ADP1828 Demo Board Documentation
PCB LAYOUT FILES
Figure 20. Top PCB Layer
Rev. A | Page 15 of 21
ADP1828 Demo Board Documentation
Figure 21. Second PCB Layer
Rev. A | Page 16 of 21
ADP1828 Demo Board Documentation
Figure 22. Third PCB Layer
Rev. A | Page 17 of 21
ADP1828 Demo Board Documentation
Figure 23. Fourth PCB Layer
Rev. A | Page 18 of 21
ADP1828 Demo Board Documentation
Figure 24. Fifth PCB Layer
Rev. A | Page 19 of 21
ADP1828 Demo Board Documentation
Figure 25. Sixth and Bottom PCB Layer
Rev. A | Page 20 of 21
ADP1828 Demo Board Documentation
NOTES:
©2007 Analog Devices, Inc. All rights
reserved. Trademarks and registered
trademarks are the property of their
respective owners.
EB0561
Rev. A | Page 21 of 21
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