Datasheet ADP1851 (Analog Devices)

Wide Range Input, Synchronous, Step-Down DC-to-DC Controller Data Sheet ADP1851 FEATURES TYPICAL OPERATION CIRCUIT Input voltage range: 2.75 V to 20 V VIN RRAMP Output voltage range: 0.6 V to 90% VIN Maximum output current of more than 25 A RAMP VIN M1 L DH Current mode architecture EN V BST OUT Configurable to voltage mode SW VCCO ILIM ±1% output voltage accuracy over temperature FB Voltage tracking ADP1851 M2 DL Programmable frequency: 200 kHz to 1.5 MHz SYNC R HIGH CSG Synchronization input PGND LOW FREQ Power saving mode at light load SS/TRK COMP Precision enable input PGOOD Power good with internal pull-up resistor AGND (EP)
001 95-
Adjustable soft start
105
Programmable current sense gain
Figure 1.
Integrated bootstrap diode Starts into a precharged load Externally adjustable slope compensation Suitable for any output capacitor Overvoltage and overcurrent-limit protection
The ADP1851 provides a high speed, high peak current gate
Thermal overload protection
driving capability to enable energy efficient power conversion.
Input undervoltage lockout (UVLO)
The device can be configured to operate in power saving mode
Available in 16-lead, 4 mm × 4 mm LFCSP
by skipping pulses, reducing switching losses, and improving
Supported by ADIsimPower design tool
efficiency at light load and standby conditions.
APPLICATIONS
The accurate current limit allows design within a narrower
Intermediate bus and POL systems requiring sequencing and
range of tolerances and can reduce overall converter size and
tracking, including
cost. The ADP1851 can regulate down to 0.6 V output using a
Telecom base station and networking
high accuracy reference with ±1% tolerance over the
Industrial and instrumentation
temperature range of −40°C to +125°C.
Medical and healthcare
With its wide range input voltage, the ADP1851 provides the designer with maximum flexibility for use in a variety of system
GENERAL DESCRIPTION
configurations; loop compensation, soft start, frequency setting, The ADP1851 is a wide range input, dc-to-dc, synchronous power saving mode, current limit, and current sense gain can buck controller capable of running from commonly used 3.3 V all be programmed using external components. In addition, the to 12 V (up to 20 V) voltage inputs. The device nominally external RAMP resistor allows the selection of optimal slope operates in current mode with valley current sensing providing and VIN feedforward in both current and voltage modes for the fastest step response for digital loads. It can also be config- excellent line rejection. The linear regulator and the bootstrap ured as a voltage mode controller with low noise and crosstalk diode for the high-side driver are internal. for sensitive loads. Protection features include undervoltage lockout, overvoltage, The ADP1851 is ideal in system applications requiring multiple overcurrent/short circuit, and overtemperature. output voltages. The ADP1851 includes a synchronization feature to eliminate beat frequencies between switching devices. It also provides accurate tracking capability between supplies and includes precision enable and power-good functions for simple, robust sequencing.
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Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION TYPICAL OPERATION CIRCUIT REVISION HISTORY SIMPLIFIED BLOCK DIAGRAM SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION CONTROL ARCHITECTURE OSCILLATOR FREQUENCY SYNCHRONIZATION PWM AND PULSE SKIP MODES OF OPERATION SYNCHRONOUS RECTIFIER AND DEAD TIME INPUT UNDERVOLTAGE LOCKOUT INTERNAL LINEAR REGULATOR OVERVOLTAGE PROTECTION POWER GOOD SHORT-CIRCUIT AND CURRENT-LIMIT PROTECTION ENABLE/DISABLE CONTROL THERMAL OVERLOAD PROTECTION APPLICATIONS INFORMATION ADIsimPower DESIGN TOOL SETTING THE OUTPUT VOLTAGE SOFT START SETTING THE CURRENT LIMIT ACCURATE CURRENT-LIMIT SENSING INPUT CAPACITOR SELECTION VIN PIN FILTER BOOST CAPACITOR SELECTION INDUCTOR SELECTION OUTPUT CAPACITOR SELECTION MOSFET SELECTION LOOP COMPENSATION—VOLTAGE MODE Type III Compensation LOOP COMPENSATION—CURRENT MODE Setting the Slope Compensation Setting the Current Sense Gain Type II Compensation SWITCHING NOISE AND OVERSHOOT REDUCTION VOLTAGE TRACKING Coincident Tracking Ratiometric Tracking PCB LAYOUT GUIDELINES TYPICAL OPERATING CIRCUITS OUTLINE DIMENSIONS ORDERING GUIDE