Atmel has released new AVR microcontrollers combining a USB controller and high performance analog features. The ATmega16U4 and ATmega32U4 are specifically targeted at reducing system cost in battery-powered devices.
Battery-powered devices can take advantage of being connected to a USB port to recharge. However, modern batteries require sophisticated algorithms to accelerate and optimise charging, while USB brings further constraints on the battery charging since it is limited both in the voltage and the maximum current it can provide. The new AVR devices allow optimised battery charging combined with USB functions. The analog to digital converter can be used to sense motion or pressure in the end application and the high-speed PWM is ideal for low cost motor control.
Features include a 10-bit ADC with 12 channels, a built-in temperature sensor allowing compensating thermal effects on analog performance and a programmable gain x1, x10, x40 and x200 giving more flexibility to measure differential voltages for current monitoring. A high-speed timer with three PWM channels with complementary outputs and programmable dead-times allows 8-bit resolution PWM with a frequency of 500 kHz, and up to 11-bit resolution PWM with a frequency over 60 kHz.
A hardware flow control on the USART eases the connection to other devices when bridging with USB at high baud rates and digital inputs with TTL thresholds ease interfacing with 3 V devices in mixed 5 and 3 V applications. An on-chip 3,3 V regulator can deliver up to 50 mA and supply external devices in USB powered applications. Jitter and accuracy of the on-chip 8 MHz calibrated RC oscillator can support serial communication without a crystal. All devices include a hardware multiplier, one USART, one SPI, one TWI, two 8-bit and two 16-bit timers with PWM and 26 programmable I/Os.
ATmega16U4 features 16 KBytes of in-system programmable (ISP) Flash, 1 KBytes of RAM and 512 Bytes of EEPROM. ATmega32U4 features 32 KBytes of (ISP) Flash, 2,5 KBytes of RAM and 1 KByte of EEPROM. Both are available in 44-pin packages.
An extensive software library is offered to support the most relevant USB classes for the embedded market: mass storage device (MSD), human interface device (HID), device firmware upgrade (DFU), communication device class (CDC), audio class, etc. Examples of composite devices actually combine several classes in one device, for instance audio and HID can be combined to make a headset with remote control, toys, etc.
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