Maxim MAX6948高效PWM LED驱动方案

Maxim 公司的MAX6948是高效GPIO外设PWM LED驱动器,包含有5个通用输入/输出端口(GPIO),用来驱动多达6串白光LED(WLED). MAX6948集成了2MHz的升压转换器,内置10位PWM控制以提高效率,工作电压2.7V到5V.本文介绍了MAX6948主要特性,功能框图, 简化I/O端口电路图和典型应用电路.

The MAX6948B general-purpose input/output (GPIO) peripheral drives a series string of white LEDs (WLEDs), and contains up to five general-purpose input/output (GPIO) ports to drive additional LEDs.

The integrated 2MHz boost converter minimizes the size and cost of external components and supplies 30mA of load current at up to 28V. The converter is stable under all load conditions from 5V up to 28V and includes open-circuit detection to prevent damage to the IC. An I²C-programmable 10-bit pulse-width modulation (PWM) signal enables 1024 levels of WLED intensity.

The five GPIO ports function as logic inputs, open-drain logic outputs, or constant-current sinks in any combination. Ports withstand 5.5V independent of the MAX6948Bs supply voltage. Two of the ports drive additional LEDs up to 30mA/port, while the other three ports drive LEDs at up to 10mA/port. The MAX6948B features shutdown and standby modes for low-power dissipation. The constant-current drivers contain programmable PWM outputs and allow staggering to reduce the input peak-current requirements. The I/O ports also feature ramp-up and ramp-down controls.

The MAX6948B features a single input to select from four I²C slave addresses. Programming and functionality for the five GPIO ports is identical to the MAX6946/MAX6947 I/O expanders.

The MAX6948B is available in a 25-bump (2.31mm x 2.31mm) WLP package for cell phones, PDAs, and other portable consumer electronic applications. The MAX6948B operates over the -40°C to +105°C temperature range.

MAX6948主要特性:

28V Step-Up DC-DC Converter with Integrated nMOS Power Switch

Built-In 10-Bit PWM Control for Improved Efficiency

No Discharge Path During PWM Off Period for Increased Battery Life

Fixed 2MHz Switching for Smaller Components

Drives up to 6 Series WLEDs

±8kV Human Body Model (HBM) ESD Protection for GPIOs and Boost-Converter Output

Five Open-Drain GPIOs Capable of Constant-Current LED Drive with Individual 8-Bit PWM Intensity Control
2.7V to 5V Power-Supply Operation

Register Compatible with MAX6946/MAX6947 GPIO Port Expanders

400kbps, 5.5V Tolerant I²C Interface

Four I²C Slave Address Choices

Active-Low RST Input Clears Serial Interface and Exits Shutdown (Reset-Run Option)

Small (2.31mm x 2.31mm) WLP Package

MAX6948应用:

Cell Phones

Handheld Games

LED Backlighting for LCDs

PDAs

Portable Consumer Electronics

图1.MAX6948功能方框图

图2.MAX6948简化I/O端口电路图

图3.MAX6948典型应用电路