Datasheet ADP1878, ADP1879 (Analog Devices)

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Synchronous Buck Controller with Constant On Time and Valley Current Mode Data Sheet ADP1878/ ADP1879 FEATURES TYPICAL APPLICATIONS CIRCUIT V Power input voltage range: 2.95 V to 20 V IN = 2.95V TO 20V On-board bias regulator Minimum output voltage: 0.6 V VIN CC 0.6 V reference voltage with ±1.0% accuracy ADP1878/ CC2 CIN R ADP1879 Supports all N-channel MOSFET power stages C COMP BST Available in 300 kHz, 600 kHz, and 1.0 MHz options 10kΩ CBST Q1 VREG EN DRVH L No current sense resistor required RTOP V V OUT OUT FB Power saving mode (PSM) for light loads (ADP1879 only) SW R COUT BOT LOAD GND Q2 Resistor programmable current limit DRVL CVREG2 Power good with internal pull-up resistor VREG CVREG RPGD Externally programmable soft start PGOOD VEXT RES Thermal overload protection SS RRES CSS PGND Short-circuit protection
01 0 1- 44
Standalone precision enable input
09
Integrated bootstrap diode for high-side drive
Figure 1.
Starts into a precharged output Available in a 14-lead LFCSP_WD package APPLICATIONS Telecommunications and networking systems Mid-to-high end servers Set-top boxes DSP core power supplies GENERAL DESCRIPTION
conditions. The low-side current sense, current gain scheme and The ADP1878/ADP1879 are versatile current-mode, synchronous integration of a boost diode, together with the PSM/forced step-down controllers. They provide superior transient response, pulse-width modulation (PWM) option, reduce the external optimal stability, and current-limit protection by using a constant device count and improve efficiency. on time, pseudo fixed frequency with a programmable current-limit, The ADP1878/ADP1879 operate over the −40°C to +125°C current control scheme. These devices offer optimum performance junction temperature range and are available in a 14-lead at low duty cycles by using a valley, current-mode control architec- LFCSP_WD package. ture allowing the ADP1878/ADP1879 to drive all N-channel power
100
stages to regulate output voltages to as low as 0.6 V.
95 VIN = 5V (PSM) 90
The ADP1879 is the power saving mode (PSM) version of the
85
device and is capable of pulse skipping to maintain output
80
regulation while achieving improved system efficiency at light
) 75 % ( 70 VIN = 16.5V
loads (see the ADP1879 Power Saving Mode (PSM) section for
Y C 65 N
more information).
IE 60 VIN = 13V 55 V
Available in three frequency options (300 kHz, 600 kHz, and
FFIC IN = 13V (PSM) E 50 TA = 25°C
1.0 MHz) plus the PSM option, the ADP1878/ADP1879 are well
V 45 OUT = 1.8V fSW = 300kHz
suited for a wide range of applications that require a single input
40 VIN = 16.5V (PSM) WÜRTH INDUCTOR:
power supply range from 2.95 V to 20 V. Low voltage biasing is
35 744325120, L = 1.2µH, DCR = 1.8mΩ 30 INFINEON FETs:
supplied via a 5 V internal low dropout regulator (LDO). In
BSC042N03MS G (UPPER/LOWER) 25
addition, soft start programmability is included to limit input
10 100 1k 10k 100k
-102 inrush current from the input supply during startup and to
LOAD CURRENT (mA)
09441 provide reverse current protection during precharged output Figure 2. ADP1878/ADP1879 Efficiency vs. Load Current (VOUT = 1.8 V, 300 kHz)
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Document Outline Features Applications Typical Applications Circuit General Description Revision History Specifications Absolute Maximum Ratings Thermal Resistance Boundary Condition ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Block Diagram Startup Soft Start Precision Enable Circuitry Undervoltage Lockout On-Board Low Dropout (LDO) Regulator Thermal Shutdown Programming Resistor (RES) Detect Circuit Valley Current-Limit Setting Hiccup Mode During Short Circuit Synchronous Rectifier ADP1879 Power Saving Mode (PSM) Timer Operation Pseudo Fixed Frequency Power-Good Monitoring Applications Information Feedback Resistor Divider Inductor Selection Output Ripple Voltage (ΔVRR) Output Capacitor Selection Compensation Network Output Filter Impedance (ZFILT) Error Amplifier Output Impedance (ZCOMP) Error Amplifier Gain (Gm) Current-Sense Loop Gain (GCS) Crossover Frequency Efficiency Consideration Channel Conduction Loss MOSFET Driver Loss MOSFET Switching Loss Body Diode Conduction Loss Inductor Loss Input Capacitor Selection Thermal Considerations Design Example Input Capacitor Inductor Current-Limit Programming Output Capacitor Feedback Resistor Network Setup Compensation Network Loss Calculations External Component Recommendations Layout Considerations IC Section (Left Side of Evaluation Board) Power Section Differential Sensing Typical Application Circuits 12 A, 300 kHz High Current Application Circuit 5.5 V Input, 600 kHz Current Application Circuit 300 kHz High Current Application Circuit Packaging and Ordering Information Outline Dimensions Ordering Guide