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Analog Devices Semiconductor Electronic Components Datasheet

ADP1874 Datasheet

(ADP1874 / ADP1875) Synchronous Buck Controller

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Synchronous Buck Controller with Constant
On-Time and Valley Current Mode
ADP1874/ADP1875
FEATURES
Power input voltage range: 2.95 V to 20 V
On-board bias regulator
Minimum output voltage: 0.6 V
0.6 V reference voltage with ±1.0% accuracy
Supports all N-channel MOSFET power stages
Available in 300 kHz, 600 kHz, and 1.0 MHz options
No current-sense resistor required
Power saving mode (PSM) for light loads (ADP1875 only)
Resistor programmable current limit
Power good with internal pull-up resistor
Externally programmable soft start
Thermal overload protection
Short-circuit protection
Standalone precision enable input
Integrated bootstrap diode for high-side drive
Starts into a precharged output
Available in a 16-lead QSOP package
APPLICATIONS
Telecom and networking systems
Mid- to high-end servers
Set-top boxes
DSP core power supplies
GENERAL DESCRIPTION
The ADP1874/ADP1875 are versatile current mode, synchronous
step-down controllers. They provide superior transient response,
optimal stability, and current-limit protection by using a constant
on-time, pseudo fixed frequency with a programmable current
limit, current control scheme. In addition, these devices offer
optimum performance at low duty cycles by using a valley, current
mode control architecture. This allows the ADP1874/ADP1875
to drive all N-channel power stages to regulate output voltages
to as low as 0.6 V.
The ADP1875 is the power saving mode (PSM) version of
the device and is capable of pulse skipping to maintain output
regulation while achieving improved system efficiency at light
loads (see the ADP1875 Power Saving Mode (PSM) section for
more information).
Available in three frequency options (300 kHz, 600 kHz, and
1.0 MHz, plus the PSM option), the ADP1874/ADP1875 are well
suited for a wide range of applications that require a single-input
power supply range from 2.95 V to 20 V. Low voltage biasing is
supplied via a 5 V internal low dropout regulator (LDO).
TYPICAL APPLICATIONS CIRCUIT
VIN = 2.95V TO 20V
CC
RC CC2
VREG
VOUT
10k
RTOP
RBOT
CVREG2
CVREG
RRES
VIN
ADP1874/
ADP1875
COMP BST
EN DRVH
FB SW
GND
DRVL
VREG PGOOD
VREG_IN SS
RES
TRACK
PGND
CIN
CBST
Q1 L
COUT
Q2
VOUT
LOAD
RPGD
VEXT
CSS
RTRK2
RTRK1
VMASTER
Figure 1. Typical Applications Circuit
100
95 VIN = 5V (PSM)
90
85
80
75
70 VIN = 16.5V
65
60 VIN = 13V
55 VIN = 13V (PSM)
50
45
40 VIN = 16.5V (PSM)
35
30
25
10
100
TA = 25°C
fVSOWUT=
= 1.8V
300kHz
WÜRTH INDUCTOR:
744325120, L = 1.2µH, DCR = 1.8m
INFINEON FETs:
BSC042N03MS G (UPPER/LOWER)
1k 10k 100k
LOAD CURRENT (mA)
Figure 2. ADP1874/ADP1875 Efficiency vs. Load Current (VOUT = 1.8 V, 300 kHz)
In addition, soft start programmability is included to limit input in-
rush current from the input supply during startup and to
provide reverse current protection during precharged output
conditions. The low-side current sense, current gain scheme, and
integration of a boost diode, along with the PSM/forced pulse-
width modulation (PWM) option, reduce the external part count
and improve efficiency.
The ADP1874/ADP1875 operate over the −40°C to +125°C
junction temperature range and are available in a 16-lead QSOP
package.
Rev. 0
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
©2011 Analog Devices, Inc. All rights reserved.


Analog Devices Semiconductor Electronic Components Datasheet

ADP1874 Datasheet

(ADP1874 / ADP1875) Synchronous Buck Controller

No Preview Available !

ADP1874 pdf
ADP1874/ADP1875
TABLE OF CONTENTS
Features .............................................................................................. 1 
Applications....................................................................................... 1 
General Description ......................................................................... 1 
Typical Applications Circuit............................................................ 1 
Revision History ............................................................................... 2 
Specifications..................................................................................... 3 
Absolute Maximum Ratings............................................................ 6 
Thermal Resistance ...................................................................... 6 
Boundary Condition.................................................................... 6 
ESD Caution.................................................................................. 6 
Pin Configuration and Function Descriptions............................. 7 
Typical Performance Characteristics ............................................. 8 
ADP1874/ADP1875 Block Digram.............................................. 18 
Theory of Operation ...................................................................... 19 
Startup.......................................................................................... 19 
Soft Start ...................................................................................... 19 
Precision Enable Circuitry ........................................................ 19 
Undervoltage Lockout ............................................................... 19 
On-Board Low Dropout Regulator.......................................... 20 
Thermal Shutdown..................................................................... 20 
Programming Resistor (RES) Detect Circuit.......................... 20 
Valley Current-Limit Setting .................................................... 20 
Hiccup Mode During Short Circuit......................................... 22 
Synchronous Rectifier................................................................ 22 
ADP1875 Power Saving Mode (PSM) ..................................... 22 
REVISION HISTORY
2/11—Revision 0: Initial Version
Timer Operation ........................................................................ 23 
Pseudo-Fixed Frequency ........................................................... 24 
Power Good Monitoring ........................................................... 24 
Voltage Tracking......................................................................... 25 
Applications Information .............................................................. 27 
Feedback Resistor Divider ........................................................ 27 
Inductor Selection ...................................................................... 27 
Output Ripple Voltage (ΔVRR) .................................................. 27 
Output Capacitor Selection....................................................... 27 
Compensation Network ............................................................ 28 
Efficiency Consideration........................................................... 29 
Input Capacitor Selection.......................................................... 30 
Thermal Considerations............................................................ 31 
Design Example.......................................................................... 32 
External Component Recommendations.................................... 34 
Layout Considerations................................................................... 36 
IC Section (Left Side of Evaluation Board)............................. 38 
Power Section ............................................................................. 38 
Differential Sensing.................................................................... 39 
Typical Application Circuits ......................................................... 40 
12 A, 300 kHz High Current Application Circuit.................. 40 
5.5 V Input, 600 kHz Application Circuit ............................... 40 
300 kHz High Current Application Circuit ............................ 41 
Outline Dimensions ....................................................................... 42 
Ordering Guide .......................................................................... 42 
Rev. 0 | Page 2 of 44


Part Number ADP1874
Description (ADP1874 / ADP1875) Synchronous Buck Controller
Maker Analog Devices
Total Page 30 Pages
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