Introduction
The Nuvoton ISD1700 ChipCorder Series is a high quality, fully integrated, singlechip multi-message voice record and playback device ideally suited to a variety of electronic systems. The message duration is user selectable in ranges from 26 seconds to 120 seconds, depending on the specific device. The sampling frequency of each device can also be adjusted from 4 kHz to 12 kHz with an external resistor, giving the user greater flexibility in duration versus recording quality for each application. Operating voltage spans a range from 2.4 V to 5.5 V to ensure that the ISD1700 devices are optimized for a wide range of battery or line-powered applications.
The ISD1700 is designed for operation in either standalone or microcontroller (SPI) mode. The device incorporates a proprietary message management system that allows the chip to self-manage address locations for multiple messages. This unique feature provides sophisticated messaging flexibility in a simple push-button environment. The devices include an on-chip oscillator (with external resistor control), microphone preamplifier with Automatic Gain Control (AGC), an auxiliary analog input, anti-aliasing filter, Multi-Level Storage (MLS) array, smoothing filter, volume control, Pulse Width Modulation (PWM) Class D speaker driver, and current/voltage output.
The ISD1700 devices also support an optional “vAlert” (voiceAlert) feature that can be used as a new message indicator. With vAlert, the device flashes an external LED to indicate that a new message is present. Besides, four special sound effects are reserved for audio confirmation of operations, such as “Start Record”, “Stop Record”, “Erase”, “Forward”, “Global Erase”, and etc.
Recordings are stored into on-chip Flash memory, providing zero-power message storage. This unique single-chip solution is made possible through Nuvoton’s patented Multi-Level Storage (MLS) technology. Audio data are stored directly in solid-state memory without digital compression, providing superior quality voice and music reproduction.
Voice signals can be fed into the chip through two independent paths: a differential microphone input and a single-ended analog input. For outputs, the ISD1700 provides a Pulse Width Modulation (PWM) Class D speaker driver and a separate analog output simultaneously. The PWM can directly drive a standard 8Ω speaker or typical buzzer, while the separate analog output can be configured as a single-ended current or voltage output to drive an external amplifier.
While in Standalone mode, the ISD1700 devices automatically enter into power down mode for power conservation after an operation is completed.
In the SPI mode, the user has full control via the serial interface in operating the device. This includes random access to any location inside the memory array by specifying the start address and end address of operations. SPI mode also allows access to the Analog Path Configuration (APC) register. This register allows flexible configuration of audio paths, inputs, outputs and mixing. The APC default configuration for standalone mode can also be modified by storing the APC data into a non-volatile register (NVCFG) that is loaded at initialization. Utilizing the capabilities of ISD1700 Series, designers have the control and flexibility to implement voice functionality into the highend products.
