Datasheet ADP1874, ADP1875 (Analog Devices)

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Synchronous Buck Controller with Constant On-Time and Valley Current Mode Data Sheet ADP1874/ ADP1875 FEATURES TYPICAL APPLICATIONS CIRCUIT Power input voltage range: 2.95 V to 20 V VIN = 2.95V TO 20V On-board bias regulator Minimum output voltage: 0.6 V VIN CC ADP1874/ C 0.6 V reference voltage with ±1.0% accuracy CC2 IN RC ADP1875 Supports all N-channel MOSFET power stages COMP BST 10kΩ CBST Q1 Available in 300 kHz, 600 kHz, and 1.0 MHz options VREG EN L DRVH RTOP VOUT No current-sense resistor required VOUT FB SW COUT Power saving mode (PSM) for light loads (ADP1875 on ly) RBOT Q2 LOAD GND DRVL Resistor programmable current limit CVREG2 R VREG PGD Power good with internal pull-up resistor C PGOOD V VREG EXT VREG_IN SS Externally programmable soft start CSS RES R RTRK2 Thermal overload protection RES TRACK VMASTER Short-circuit protection PGND RTRK1
001
Standalone precision enable input
09347-
Integrated bootstrap diode for high-side drive
Figure 1. Typical Applications Circuit
Starts into a precharged output Available in a 16-lead QSOP package 100 95 VIN = 5V (PSM) APPLICATIONS 90 85 Telecom and networking systems 80 Mid- to high-end servers 75 %) Set-top boxes ( 70 VIN = 16.5V 65 DSP core power supplies NCY E 60 VIN = 13V ICI GENERAL DESCRIPTION F 55 V F IN = 13V (PSM) E 50 TA = 25°C V
The ADP1874/ADP1875 are versatile current mode, synchronous
45 OUT = 1.8V fSW = 300kHz V
step-down controllers. They provide superior transient response,
40 IN = 16.5V (PSM) WÜRTH INDUCTOR: 35 744325120, L = 1.2µH, DCR = 1.8mΩ
optimal stability, and current-limit protection by using a constant
30 INFINEON FETs:
on-time, pseudo fixed frequency with a programmable current
BSC042N03MS G (UPPER/LOWER) 25 10 100 1k 10k 100k
102 limit, current control scheme. In addition, these devices offer
LOAD CURRENT (mA)
09347- optimum performance at low duty cycles by using a valley, current Figure 2. ADP1874/ADP1875 Efficiency vs. Load Current (VOUT = 1.8 V, 300 kHz) mode control architecture. This allows the ADP1874/ADP1875 to drive al N-channel power stages to regulate output voltages In addition, soft start programmability is included to limit input to as low as 0.6 V. in-rush current from the input supply during startup and to provide reverse current protection during precharged output The ADP1875 is the power saving mode (PSM) version of conditions. The low-side current sense, current gain scheme, and the device and is capable of pulse skipping to maintain output integration of a boost diode, along with the PSM/forced pulse- regulation while achieving improved system efficiency at light width modulation (PWM) option, reduce the external part count loads (see the ADP1875 Power Saving Mode (PSM) section for and improve efficiency. more information). The ADP1874/ADP1875 operate over the −40°C to +125°C Available in three frequency options (300 kHz, 600 kHz, and junction temperature range and are available in a 16-lead QSOP 1.0 MHz, plus the PSM option), the ADP1874/ADP1875 are wel package. 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).
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Document Outline Features Applications General Description Typical Applications Circuit Table of Contents Revision History Specifications Absolute Maximum Ratings Thermal Resistance Boundary Condition ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics ADP1874/ADP1875 Block Digram Theory of Operation Startup Soft Start Precision Enable Circuitry Undervoltage Lockout On-Board Low Dropout Regulator Thermal Shutdown Programming Resistor (RES) Detect Circuit Valley Current-Limit Setting Hiccup Mode During Short Circuit Synchronous Rectifier ADP1875 Power Saving Mode (PSM) Timer Operation Pseudo-Fixed Frequency Power Good Monitoring Voltage Tracking 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 Switching Loss 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 Application Circuit 300 kHz High Current Application Circuit Outline Dimensions Ordering Guide