Datasheet

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General Description

The MAX15020 high-voltage step-down DC-DC converter

operates over an input voltage range of 7.5V to 40V. The

device integrates a 0.2Ω high-side switch and is capable

of delivering 2A load current with excellent load and line

regulation. The output is dynamically adjustable from

0.5V to 36V through the use of an external reference

input (REFIN). The MAX15020 consumes only 6μA in

shutdown mode.

The device utilizes feed-forward voltage-mode architecture

for good noise immunity in the high-voltage switching envi-

ronment and offers external compensation for maximum

flexibility. The switching frequency is selectable to 300kHz

or 500kHz and can be synchronized to an external clock

signal of 100kHz to 500kHz by using the SYNC input. The

IC features a maximum duty cycle of 95% (typ) at 300kHz.

The device includes configurable undervoltage lockout

(UVLO) and soft-start. Protection features include cycle-

by-cycle current limit, hiccup-mode for output short-circuit

protection, and thermal shutdown. The MAX15020 is avail-

able in a 20-pin TQFN 5mm x 5mm package and is rated

for operation over the -40°C to +125°C temperature range.

Applications

● Printer Head Driver Power Supply

● Industrial Power Supply

● Step-Down Power Supply

Features

● Wide 7.5V to 40V Input Voltage Range

● 2A Output Current, Up to 96% Efficiency

● Dynamic Programmable Output Voltage (0.5V to 36V)

● Maximum Duty Cycle of 95% (typ) at 300kHz

● 100kHz to 500kHz Synchronizable SYNC Frequency

Range

● Configurable UVLO and Soft-Start

● Low-Noise, Voltage-Mode Step-Down Converter

● Programmable Output-Voltage Slew Rate

● Lossless Constant Current Limit with Fixed

● Timeout to Hiccup Mode

● Extremely Low-Power Consumption (< 6μA typ) in

Shutdown Mode

● 20-Pin (5mm x 5mm) Thin QFN Package

Pin Configuration appears at end of data sheet.

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

MAX15020ATP+ -40°C to +125°C 20 TQFN-EP*

MAX15020

ON/OFF

DVREG

OUT

(0.5V TO 36V)

REFOUT

REFIN

PWM

INPUT

(7.5V TO 40V)

BST

COMP

SYNC GND FSEL

PGND

REG

MAX15020 2A, 40V Step-Down DC-DC Converter with

Dynamic Output-Voltage Programming

19-0811; Rev 2; 4/14

Typical Operating Circuit

Ordering Information

EVALUATION KIT AVAILABLE

Summary of content (18 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming General Description The MAX15020 high-voltage step-down DC-DC converter operates over an input voltage range of 7.5V to 40V. The device integrates a 0.2Ω high-side switch and is capable of delivering 2A load current with excellent load and line regulation. The output is dynamically adjustable from 0.5V to 36V through the use of an external reference input (REFIN).
PAGE 2
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Absolute Maximum Ratings IN, ON/OFF to GND........…. ...................................-0.3V to +45V LX to GND................................................-0.715V to (VIN + 0.3V) BST to GND .................................................-0.3V to (VIN + 12V) BST to LX................................................................-0.3V to +12V PGND, EP to GND.................................................-0.3V to +0.
PAGE 3
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Electrical Characteristics (continued) (VIN = 36V, VREG = VDVREG, VPGND = VGND = VEP = 0V, VSYNC = 0V, CREFOUT = 0.1μF, TA = TJ = -40°C to +125°C, FSEL = REG, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SOFT-START/REFIN/REFOUT/FB Soft-Start Current ISS REFOUT Output Voltage REFIN Input Range 8 15 26 µA 0.97 0.98 1.01 V 3.6 V 0.98 1.
PAGE 4
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Typical Operating Characteristics 0.7 0.6 0.5 0.4 0.3 0.2 0.1 10 35 60 85 110 0.10 0.05 5 4 3 2 1 0 -40 -15 10 35 60 85 110 135 10 0 20 30 TEMPERATURE (C) TEMPERATURE (C) INPUT VOLTAGE (V) NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE OPERATING FREQUENCY vs. TEMPERATURE MAXIMUM DUTY CYCLE vs.
PAGE 5
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Typical Operating Characteristics (continued) (VIN = 36V, Circuit of Figure 2, TA = +25°C, unless otherwise noted.) MAX15020 toc10 5V/div 5V/div VON/OFF 0V 1.05 VOUT 1V/div 0V VOUT 1V/div 0V 0V VIN = 12V, RLOAD = 27Ω VIN = 40V, RLOAD = 27Ω 10ms/div 1.03 REFOUT VOLTAGE (V) VON/OFF REFOUT VOLTAGE vs. TEMPERATURE TURN-ON/TURN-OFF WAVEFORM MAX15020 toc09 1.01 0.99 0.97 0.
PAGE 6
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Typical Operating Characteristics (continued) (VIN = 36V, Circuit of Figure 2, TA = +25°C, unless otherwise noted.) LOAD TRANSIENT LOAD TRANSIENT MAX15020 toc16 50mV/div AC-COUPLED VOUT MAX15020 toc17 50mV/div AC-COUPLED VOUT 2A 1.1A 1A IOUT IOUT 0.
PAGE 7
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Typical Operating Characteristics (continued) (VIN = 36V, Circuit of Figure 2, TA = +25°C, unless otherwise noted.) MAX15020 toc23 MAX15020 toc22 10 CSS = 0.1F VSS dv/dt (V/ms) VSS AND VOUT RESPONSE TO REFIN PWM SOFT-START VOLTAGE RISE vs. REFIN VOLTAGE RISE 20V/div VOUT 0V 1 1V VSS 0.5V 1V/div VREFIN 0.1 10kΩ and 0.1µF RC ON REFIN CSS = 0.01F 0.01 VPWM 0.01 0.
PAGE 8
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Pin Description PIN NAME 1 COMP 2 FB FUNCTION Voltage-Error-Amplifier Output. Connect COMP to the necessary compensation feedback network. Feedback Regulation Point. Connect to the center tap of an external resistor-divider connected between the output and GND to set the output voltage. The FB voltage regulates to the voltage applied to REFIN. 3 ON/OFF ON/OFF Control.
PAGE 9
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming ON/OFF IN LDO REF REG REF EN MAX15020 REF REFOUT OK THERMAL VPOK SHDN REF ENABLE SWITCHING REGOK ICSS IN OVERLOAD MANAGEMENT SSA REFIN CLK ILIM HIGH-SIDE CURRENT SENSE REF_ILIM SS BST E/A FB LOGIC COMP LX IN SYNC EN OSC DVREG CPWM RAMP PGND FSEL CLK GND Figure 1. Functional Diagram www.maximintegrated.
PAGE 10
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming VIN 7.5V TO 40V C3 0.1µF C1 560µF D2 R1 97.5kΩ ON/OFF IN DVREG R2 4.02kΩ D1 MAX15020 REG C2 1µF R3 10kW PWM INPUT LX R5 10Ω C10 1µF C4 1µF BST R6 10kΩ C11 0.027µF FB REFIN C13 330pF SS C8 0.22µF VOUT R7 10kΩ C7 0.1µF R8 340Ω COMP C9 0.1µF 0Ω L1 22µH C6 560µF REFOUT SYNC GND FSEL PGND EP C5 0.1µF C12 0.1µF R9 15.8kΩ Figure 2.
PAGE 11
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Soft-Start (SS) At startup, after VIN is applied and the UVLO threshold is reached, a 15μA (typ) current is sourced into the capacitor (CSS) connected from SS to GND forcing the VSS voltage to ramp up slowly. If VREFIN is set to a DC voltage or has risen faster than the CSS charge rate, then VSS will stop rising once it reaches VREFIN. If VREFIN rises at a slower rate, VSS will follow the VREFIN voltage rise rate.
PAGE 12
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Applications Information Setting the ON/OFF Threshold When the voltage at ON/OFF rises above 1.225V, the MAX15020 turns on. Connect a resistive divider from IN to ON/OFF to GND to set the turn-on voltage (see Figure 2).
PAGE 13
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Input Capacitor Selection The discontinuous input current of the buck converter causes large input ripple currents and therefore the input capacitor must be carefully chosen to keep the input-voltage ripple within design requirements. The input-voltage ripple is comprised of ΔVQ (caused by the capacitor discharge) and ΔVESR (caused by the ESR (equivalent series resistance) of the input capacitor).
PAGE 14
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Compensation Design The MAX15020 uses a voltage-mode control scheme that regulates the output voltage by comparing the erroramplifier output (COMP) with an internal ramp to produce the required duty cycle. The output lowpass LC filter creates a double pole at the resonant frequency, which has a gain drop of -40dB/decade.
PAGE 15
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming C13 C11 VOUT C13 R9 R6 C11 C12 R7 VOUT FB R8 ERROR AMPLIFIER R9 R6 C12 R7 FB COMP R8 SS CLOSED-LOOP GAIN ERRORAMPLIFIER GAIN GAIN (dB) fZ2 fC fP2 fP3 FREQUENCY (Hz) Figure 3.
PAGE 16
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Power Dissipation The MAX15020 is available in a thermally enhanced package and can dissipate up to 2.7W at TA = +70°C. When the die temperature reaches +160°C, the part shuts down and is allowed to cool. After the parts cool by 20°C, the device restarts with a soft-start.
PAGE 17
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Pin Configuration Chip Information PROCESS: BiCMOS LX LX LX BST N.C. TOP VIEW 15 14 13 12 11 IN 16 10 PGND IN 17 9 DVREG 8 SYNC 7 FSEL 6 REFIN IN 18 MAX15020 REG 19 1 2 3 4 5 FB ON/OFF REFOUT SS + COMP GND 20 Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages.
PAGE 18
MAX15020 2A, 40V Step-Down DC-DC Converter with Dynamic Output-Voltage Programming Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 4/07 Initial release — 1 5/11 Corrected the feedback resistor reference from R6 to R9 in the Compensation When fC < fESR section 14 2 4/14 No /V OPNs; removed Automotive reference from Applications section 1 DESCRIPTION For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s webs