Part Number : ISD1820
Function : Voice recorder IC
Package : DIP 14 Pin type
Manufacturers : ISD
This module board is based on ISD1820, which is a single-chip single-message record/playback device. Recordings are stored into on-chip non-volatile memory, providing zero-power message storage. With the embedded Flash memory employed, data retention up to 100 years and typical 100,000 erase/record cycles can be reached. Time for recording is 8-20 seconds
1. Power (VCC) : The different power buses used by the analog and digital circuits inside the chip are merged at this pin to minimize noise. Decoupling capacitor should Get as close as possible to the chip.
2. Ground wire (VSSA, VSSD) : The different ground wires of the analog and digital circuits inside the chip converge on this pin.
3. Recording (REC) : High level is effective, as long as REC becomes high (regardless of whether the chip is in the power-saving state or playing sound), the chip will start recording. During recording,
REC must remain high. After REC goes low or the memory is full, the recording cycle ends, and the chip automatically writes an end of information mark (EOM), So that subsequent replay operations can be stopped in time. Then the chip automatically enters the power saving state. Note: The rising edge of REC has 84 millisecond anti-shake to prevent false triggering of keys.
4. Edge-triggered playback (PLAYE) : When a rising edge occurs at this end, the chip starts to play. The sound continues until the EOM mark or the end of the memory, the chip automatically enters Power saving state. After playing, you can release PLAYE.
5. Level trigger playback (PLAYE) : When this end changes from low to high, the chip starts to play. Continue until this end returns to low level or encounters EOM mark, or memory bundle. After the sound is played, it will automatically enter the power-saving state.
6. Recording indication (/RECLED) : When in recording state, this end is low and can drive LED. In addition, when the playback encounters the EOM mark, enter a Low-level pulse. This pulse can be used to trigger PLAYE to realize loop playback.
7. Microphone input (MIC) : This end is connected to the on-chip preamplifier. The on-chip automatic gain control circuit (AGC) controls the gain of the preamplifier. External microphone Should be coupled to the secondary end through a series capacitor. The coupling capacitance value and the 10KΩ input impedance at this end determine the low frequency cut-off of the chip frequency band point.
8. Microphone reference (MIC REF) : This terminal is the reverse input of the preamplifier. When the microphone is connected in a differential form, the noise can be reduced and the common mode rejection ratio can be improved.
9. Automatic gain control (AGC) : AGC dynamically adjusts the front gain to compensate for the wide variation of microphone input level.
Distortion can be kept to a minimum when the volume changes greatly (from whispering to loud noise). Usually 4.7µF capacitor is used in most occasions
Satisfactory results can be obtained under the following conditions.
10. Speaker input (SP+, SP-): The input terminal can directly drive speakers above 8Ω. For single-ended use, a coupling capacitor must be connected between the output Terminal output can increase the power up to 4 times without using capacitors. SP+ and SP- are connected through an internal 50KΩ resistor, When not playing, it is suspended.
11. Oscillation resistance (ROSC) : This terminal connects the oscillation resistance to VSS. The resistance value of the oscillation resistance determines the recording and playback time.
12. Through mode (FT) : This terminal allows the external language signal connected to the MIC input terminal to pass through the AGC circuit, filter and speaker driver inside the chip and directly
Reach the output. Normally the FT terminal is low. To achieve the pass-through function, the FT terminal needs to be connected to the high point level, and at the same time REC, PLAYE and PLAYL
Keep it low.
1. Power input: DC 2.4-5.5V
2. With internal audio amplifier, this board can drive 8 Ohm 0.5W speaker directly.
3. Microphone is on board
4. Board dimension: 54mm x 38mm
5. All the pins of ISD1820 are extended out with an connector, which can powered and
controlled by microprocessor directly
Module image :
1. Voice Recorder
2. Microcontroller based audio playback
3. Sound recorder