MAXIM公司的MAX15015是一款降压DC-DC变换器和一个50mA、低静态电流低压差(LDO)稳压器。LDO稳压器非常适合为汽车应用中的不关断电路供电。MAX15015的DC-DC变换器输入电压范围为4.5V至40V。DC-DC变换器的输出电压可调范围为1.26V至32V，可提供最大1A负载电流。这些器件采用前馈电压模式控制方案，在高压开关环境中可以提供良好的抗噪声性能，还提供外部补偿允许在较宽的范围内灵活选择电感值和电容类型。按照选用的器件型号，开关频率在内部固定为135kHz和500kHz。此外，通过SYNC输入，开关频率还可与外部时钟信号同步。通过自动切换到脉冲模式，可以提高轻载效率。软启动时间可由外部电容调整。DC-DC转换器可独立于LDO被禁止，从而把静态电流降低到47µA (典型值)。此外，输出电压还可通过外部电阻分压器从1.5V至11V进行调整。LDO部分还具有可调整延时周期的/RESET输出。保护功能包括逐周期限流、打嗝式短路保护和过热关断。本文首先介绍芯片的简介、特性、内部框图及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。

The MAX15014–MAX15017 combine a step-down DCDC converter and a 50mA, low-quiescent-current low-dropout (LDO) regulator. The LDO regulator is ideal for powering always-on circuitry in automotive applications. The DC-DC converter input voltage range is 4.5V to 40V for the MAX15015/MAX15016, and 7.5V to 40V for the MAX15014/MAX15017.

The DC-DC converter output is adjustable from 1.26V to 32V and can deliver up to 1A of load current. These devices utilize a feed-forward voltage-mode control scheme for good noise immunity in the high-voltage switching environment and offer external compensation allowing for maximum flexibility with a wide selection of inductor values and capacitor types. The switching frequency is internally fixed at 135kHz and 500kHz, depending on the version chosen. Moreover, the switching frequency can be synchronized to an external clock signal through the SYNC input. Light load efficiency is improved by automatically switching to a pulse-skip mode. The soft-start time is adjustable with an external capacitor. The DC-DC converter can be disabled independent of the LDO, thus reducing the quiescent current to 47µA (typ).

The LDO linear regulators operate from 5V to 40V and deliver a guaranteed 50mA load current. The devices feature a preset output voltage of 5V (MAX1501_A) or 3.3V (MAX1501_B). Alternatively, the output voltage can be adjusted from 1.5V to 11V by using an external resistive divider. The LDO section also features an active-low RESET output with adjustable timeout period. Protection features include cycle-by-cycle current limit, hiccup-mode output short-circuit protection, and thermal shutdown. All devices are available in a space-saving, high-power (2.86W), 36-pin TQFN package and are rated for operation over the -40°C to +125°C automotive temperature range.

MAX15015主要特性：

Combined DC-DC Converters and Low-Quiescent-Current LDO Regulators
1A DC-DC Converters Operate from 4.5V to 40V (MAX15015/MAX15016) or 7.5V to 40V (MAX15014/MAX15017)
Switching Frequency of 135kHz (MAX15014/MAX15016) or 500kHz (MAX15015/MAX15017)
50mA LDO Regulator Operates from 5V to 40V Independent of the DC-DC Converter
47µA Quiescent Current with DC-DC Converter Off and LDO On
6µA System Shutdown Current
Frequency Synchronization Input
Shutdown/Enable Inputs
Adjustable Soft-Start Time
Open-Drain Active-Low RESET Output with Programmable Timeout Delay
Thermal Shutdown and Output Short-Circuit Protection
Space-Saving (6mm x 6mm) Thermally Enhanced 36-Pin TQFN Package

MAX15015应用：

Automotive Body Control Modules
Automotive Instrument Cluster
Car Radios
Navigation Systems

 

图1. MAX15015内部方框图

MAX15015方案介绍：

The MAX15015A evaluation kit (EV kit) is a fully assembled and tested PCB that evaluates the MAX15015A PWM/PFM step-down converter, which integrates a high-side switch and an LDO regulator. The MAX15015A EV kit operates over a wide input-voltage range of 4.5V to 40V and provides up to 1A at the 3.3V output. The LDO regulator provides up to 50mA at the preset 5V output. The MAX15015A features undervoltage lockout, overcurrent, and thermal-shutdown protection.

The MAX15015A normally operates as a PWM converter and automatically switches to PFM mode at light loads to improve efficiency. The MAX15015A switching frequency is preset to 500kHz and features a SYNC input to provide external frequency synchronization for sensitive applications. The EV kit provides PCB pads to evaluate the SYNC and ENABLE features of the MAX15015A. The EV kit board can also be used to evaluate the MAX15015B. The MAX15015A can operate over the automotive temperature range of -40°C to +125°C.

Key Features

3.3V, 1A, 500kHz Step-Down Converter
5V, 50mA LDO Regulator
LDO Voltage Adjustable Up to 11V
Independent Turn On/Off Control for Step-Down Converter (EN_SW)
Regulator Power-On Reset with Adjustable Timeout Period
84% High Efficiency at V_IN = 12V and I_OUT = 1A
Automatic PWM/PFM Mode
Overcurrent and Thermal-Shutdown Protection
Fully Assembled and Tested

MAX15015方案原理图：

  

图2. MAX15015方案原理图

MAX15015方案材料清单：





PCB元件布局图：