Datasheet ADP1872, ADP1873 (Analog Devices)

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Synchronous Current-Mode with Constant On-Time, PWM Buck Controller Data Sheet ADP1872/ ADP1873 FEATURES TYPICAL APPLICATIONS CIRCUIT Power input voltage as low as 2.75 V to 20 V VIN = 2.75V TO 20V Bias supply voltage range: 2.75 V to 5.5 V Minimum output voltage: 0.6 V VIN CC ADP1872/ 0.6 V reference voltage with ±1.0% accuracy C C C2 IN RC ADP1873 Supports all N-channel MOSFET power stages COMP/EN BST R CBST Q1 Available in 300 kHz, 600 KHz, and 1.0 MHz options TOP V L OUT FB DRVH VOUT No current-sense resistor required RBOT + GND SW COUT Power saving mode (PSM) for light loads (ADP1873 only) C Q2 VDD2 VDD DRVL Resistor-programmable current-sense gain VDD = 2.75V PGND TO 5.5V RRES LOAD Thermal overload protection 5A
001
CVDD Short-circuit protection
08297-
Precision enable input
Figure 1.
Integrated bootstrap diode for high-side drive 100 140 µA shutdown supply current VDD = 5.5V, VIN = 5.5V (PSM) VDD = 5.5V, VIN = 5.5V 95 Starts into a precharged load 90 Small, 10-lead MSOP package 85 APPLICATIONS 80 %) VDD = 5.5V, VIN = 13.0V (PSM) ( Telecom and networking systems 75 NCY E VDD = 5.5V, VIN = 16.5V (PSM) Mid to high end servers 70 ICI F Set-top boxes F 65 E TA = 25°C DSP core power supplies 60 VOUT = 1.8V fSW = 300kHz 55 WURTH INDUCTOR: 744325120, L = 1.2µH, DCR = 1.8mΩ 50 INFINEON FETs: BSC042N03MS G (UPPER/LOWER) 45 100 1k 10k 100k
002
LOAD CURRENT (mA)
08297- Figure 2. ADP1872 Efficiency vs. Load Current (VOUT = 1.8 V, 300 kHz)
GENERAL DESCRIPTION
The ADP1872/ADP1873 are versatile current-mode, synchronous Available in three frequency options (300 kHz, 600 kHz, and step-down control ers that provide superior transient response, 1.0 MHz, plus the PSM option), the ADP1872/ADP1873 are optimal stability, and current limit protection by using a constant well suited for a wide range of applications. These ICs not only on-time, pseudo-fixed frequency with a programmable current- operate from a 2.75 V to 5.5 V bias supply, but can also accept a sense gain, current-control scheme. In addition, these devices offer power input as high as 20 V. optimum performance at low duty cycles by using valley current- In addition, an internal y fixed, soft start period is included to limit mode control architecture. This al ows the ADP1872/ADP1873 input in-rush current from the input supply during startup and to drive al N-channel power stages to regulate output voltages to provide reverse current protection during soft start for a pre- as low as 0.6 V. charged output. The low-side current-sense, current-gain scheme The ADP1873 is the power saving mode (PSM) version of the and integration of a boost diode, along with the PSM/forced pulse- device and is capable of pulse skipping to maintain output width modulation (PWM) option, reduce the external part count regulation while achieving improved system efficiency at light and improve efficiency. loads (see the Power Saving Mode (PSM) Version (ADP1873) The ADP1872/ADP1873 operate over the −40°C to +125°C section for more information). junction temperature range and are available in a 10-lead MSOP.
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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 ADP1872/ADP1873 Block Digram Theory of Operation Startup Soft Start Precision Enable Circuitry Undervoltage Lockout Thermal Shutdown Programming Resistor (RES) Detect Circuit Valley Current-Limit Setting Hiccup Mode During Short Circuit Synchronous Rectifier Power Saving Mode (PSM) Version (ADP1873) Timer Operation Pseudo-Fixed Frequency 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 Dual-Input, 300 kHz High Current Application Circuit Single-Input, 600 kHz Application Circuit Dual-Input, 300 kHz High Current Application Circuit Outline Dimensions Ordering Guide