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ADP1823 Controller Datasheet |
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| Part Number | ADP1823 |
| Description | Step-Down DC-to-DC Controller |
| Manufacture | Analog Devices |
| Total Page | 30 Pages |
| Datasheet |
www.DataSheet4U.com
Dual, Interleaved, Step-Down
DC-to-DC Controller with Tracking
ADP1823
FEATURES
Fixed-frequency operation: 300 kHz, 600 kHz, or
synchronized operation up to 1 MHz
Supply input range: 2.9 V to 20 V
Interleaved operation results in smaller, low cost input
capacitor
All-N-channel MOSFET design for low cost
±0.85% accuracy at 0°C to 70°C
Soft start, thermal overload, current-limit protection
10 μA shutdown supply current
Internal linear regulator
Lossless RDSON current-limit sensing
Reverse current protection during soft start for handling
precharged outputs
Independent Power OK outputs
Voltage tracking for sequencing or DDR termination
Available in 5 mm × 5 mm, 32-lead LFCSP
APPLICATIONS
Telecommunications and networking systems
Medical imaging systems
Base station power
Set-top boxes
Printers
DDR termination
GENERAL DESCRIPTION
The ADP1823 is a versatile, dual, interleaved, synchronous
PWM buck controller that generates two independent output
rails from an input of 2.9 V to 20 V. Each controller can be con-
figured to provide output voltages from 0.6 V to 85% of the
input voltage and is sized to handle large MOSFETs for point-
of-load regulators. The two channels operate 180° out of phase,
reducing stress on the input capacitor and allowing smaller, low
cost components. The ADP1823 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.
The ADP1823 operates at a pin-selectable, fixed switching
frequency of either 300 kHz or 600 kHz, minimizing external
component size and cost. For noise-sensitive applications, it can
also be synchronized to an external clock to achieve switching
TYPICAL APPLICATION CIRCUIT
IN = 12V
180µF
1µF
PV IN
TRK1
TRK2
VREG
EN1
EN2
180µF
IRLR7807Z
0.47µF
1.2V,
6A
560µF
2.2µH
2kΩ
2kΩ
IRFR3709Z
BST1 BST2
0.47µF
DH1 DH2
ADP1823
SW1
SW2
CSL1
DL1
CSL2
DL2
PGND2
2kΩ
IRFR3709Z
IRLR7807Z
2.2µH
2kΩ
1.8V,
8A
560µF
390pF
2kΩ
4.53kΩ 3900pF
PGND1 FB2
FB1 COMP2
COMP1
FREQ
LDOSD
GND SYNC
390pF
1kΩ
3900pF 4.53kΩ
Figure 1. Typical Application Circuit
frequencies between 300 kHz and 1 MHz. The ADP1823
includes soft start protection to prevent inrush current from the
input supply during startup, reverse current protection during
soft start for precharged outputs, as well as a unique adjustable
lossless current-limit scheme utilizing external MOSFET
sensing.
For applications requiring power supply sequencing, the
ADP1823 also provides tracking inputs that allow the output
voltages to track during startup, shutdown, and faults. This
feature can also be used to implement DDR memory bus
termination.
The ADP1823 is specified over the −40°C to +85°C ambient
temperature range, and is available in a 32-lead LFCSP package.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.
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ADP1823
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
Typical Application Circuit ............................................................. 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Functional Block Diagram .............................................................. 6
Pin Configuration and Function Descriptions............................. 7
Typical Performance Characteristics ............................................. 9
Theory of Operation ...................................................................... 13
Input Power ................................................................................. 13
Start-Up Logic............................................................................. 13
Internal Linear Regulator .......................................................... 13
Oscillator and Synchronization ................................................ 13
Error Amplifier ........................................................................... 14
Soft Start ...................................................................................... 14
Power OK Indicator ................................................................... 14
REVISION HISTORY
11/06—Rev. 0 to Rev. A
Changes to Features and Applications Sections ........................... 1
Changes to Specifications Section.................................................. 3
Changes to Absolute Maximum Ratings Section......................... 5
Replaced Theory of Operation Section ....................................... 13
Added Feedback Voltage Divider Section ................................... 18
Changes to Ratiometric Tracking Section................................... 23
Replaced PCB Layout Guidelines Section................................... 25
Added Application Circuits Section............................................. 29
Changes to Ordering Guide .......................................................... 31
4/06—Revision 0: Initial Version
Tracking ....................................................................................... 14
MOSFET Drivers........................................................................ 15
Current Limit.............................................................................. 15
Applications Information .............................................................. 16
Selecting the Input Capacitor ................................................... 16
Selecting the MOSFETS ............................................................ 17
Setting the Current Limit .......................................................... 18
Feedback Voltage Divider ......................................................... 18
Compensating the Voltage Mode Buck Regulator................. 18
Soft Start ...................................................................................... 22
Voltage Tracking......................................................................... 22
Coincident Tracking .................................................................. 22
Ratiometric Tracking ................................................................. 23
Thermal Considerations............................................................ 24
PCB Layout Guidelines.................................................................. 25
LFCSP Package Considerations................................................ 26
Application Circuits ....................................................................... 29
Outline Dimensions ....................................................................... 31
Ordering Guide .......................................................................... 31
Rev. A | Page 2 of 32
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| Features | www.DataSheet4U.com Dual, Interleaved, Step-Down DC-to-DC Controller with Trac king ADP1823 FEATURES Fixed-frequency o peration: 300 kHz, 600 kHz, or synchron ized operation up to 1 MHz Supply input range: 2.9 V to 20 V Interleaved opera tion results in smaller, low cost input capacitor All-N-channel MOSFET design for low cost ±0.85% accuracy at 0°C t o 70°C Soft start, thermal overload, c urrent-limit protection 10 μA shutdown supply current Internal linear regulat or Lossless RDSON current-limit sensing Reverse current protection during soft start for handling precharged outputs Independent Power OK outputs Voltage tr acking for sequencing or DDR terminatio n Available in 5 mm × 5 mm, 32-lead LF CSP 180µF 1µF PV IN TRK1 TRK2 VREG BS T1 DH1 EN1 EN2 TYPICAL APPLICATION CIR CUIT IN = 12V 180µF BST2 DH2 0.47µF IRLR7807Z 1.2V, 6A 0.47µF IRLR7807Z 1.8V, 8A ADP1823 2.2µH SW1 2kΩ SW2 CSL2 DL2 PGND2 PGND1 FB1 390pF 2kΩ CO MP1 FREQ 4.53kΩ 3900pF GND LDOSD SYNC 3900pF 4.53kΩ FB2 390pF 1kΩ IRFR3709Z 2k. |
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