480 Seconds Voice Record/Playback Circuit with PCB Layout Using ISD17240 IC

Project has been designed for record & playback multi voice massages applications using nuvton ISD17240 IC.  Messages are stored in flash memories made in unique Multilevel Storage Technology (MLS).  Circuit  provides high quality audio recording and simple operations.  Circuit operates in dual mode standalone or micro-controller SPI mode.  Onboard tactile switches for standalone mode and 10 (2×5) pin box header connector for SPI mode.  160-480 Seconds voice massage recording capacity.

ISD1700 product is recommend for new designs in the 20 to 480 seconds storage duration (See Table1 below for cross reference parts) because of its simpler interface automatic power-down and new features such automatic message management, PWM speaker driver, volume control, vAlert, Erase operation, and configurable current (AUD) or voltage (AuxOut) output to drive external power amplifier.

NOTE : The PCB board can accommodate following ICs ISD1730, ISD1740, ISD1760, ISD17120 and ISD17240.






  • Supply 2.4 to 5 VDC (5 VDC @ 100 mA)
  • 26 to 80 Seconds selectable voice recording capacity
  • Selectable sampling rates 4KhZ To 12Khz
  • Directly drive 8 Ohms speaker or typical buzzer
  • Analog audio out to driver external audio amplifier
  • Digital volume control via onboard tactile switch
  • Dual mode operation stand alone or micro-controller
  • SPI Interface (4 wire serial interface)
  • 10 (2×5) Pin box header for SPI interface
  • Full control on memory and analog path configuration audio input, output and mix in SPI mode
  • Automatic power-down after each operations cycle (standalone mode)
  • Onboard tactile switch for Record, Play, Erase, FWD, Volume control, Reset and Feed-Through
  • Onboard power indication, record play indication
  • Voice message fed in via microphone or analog signal in
  • ISD1740 provides a PWM class D speaker driver and speaker output simultaneously
  • 100 Years message retention
  • 100,000 Record cycles
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 80 mm x 76 mm




SW1 (Recording)

Push switch for triggering REC function Recording initialized by HL edge of this signal, continues when it stays at L and stops when LH edge occurs or memory is full.  In standalone mode, massages are recorded sequentially until end of memory.  The location where recording of individual message starts is determine by the internal record pointer. Addressable record and playback operations are accessible only in SPI mode.

SW2 (Reset)

Push switch for triggering reset function – device enter into the initial state and initializes all pointers to the default state without erasing recording massages.

SW3 (Play)

Push switch for triggering the Play function – playback of current massage in memory.  Beginning of current massage determined by the internal playback pointer.  Short Low pulse start the playback of this massage and next pulse low stop this operation.

SW4 (Erase)

Push switch for triggering the erase function – Erasing the first or last message in memory or global erasing the all message (whole memory).  Short Low pulse erases the current message.  Holding this input for more then 3Seconds initiates the global erase operations.


Push switch for triggering the FWD function – Forward operations, advance to the next massage.  Short pulse causes. In standby mode advance from current message to the next message (one message forward) and setting the pointer the playback pointer on it.  During the playback-halting this process, advancing to the next massage and restarting the playback from beginning.

SW6 (Volume)

Push switch for triggering Volume – Control of audio volume on speaker output, Analog audio output and Aux/Audio output.  There are 8 steps of volume control.  Default value after power on is maximum.  Repeated low pulses decrease the level by 1 step until the minimum value reached and then increase the volume by one step until maximum value reached and so on.

SW7 (FT)

Push switch for triggering the FT function – In stand alone mode, it configures the analog path as feed-through path from ANA IN audio input to Speakers output and Aux Audio output.






PCB Top Silk Screen


PCB Top layer


PCB Bottom Layer


Bill Of Material


The Nuvoton ISD1700 ChipCorder Series is a high quality, fully integrated, single-chip 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 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 stand-alone or micro-controller (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 output.



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