ISD1820 Datasheet PDF learn more.
Part number : ISD1820
Functions : This is a kind of recording IC.
Package information : DIP 14 Pin
Manufacturer : ISD, AMBITION
The texts in the ISD1820 Datasheet PDF file :
The American ISD company recently launched a single-chip 8-20 second single-segment voice recording and playback circuit ISD1810 in 2001. Its basic structure is exactly the same as ISD1110 and 1420. It adopts CMOS technology, contains an oscillator, microphone preamplifier, and automatic gain. Control, anti-aliasing filter, speaker driver and FLASH array. [ … ]
ISD1820 Use operation
The power supply voltage is 3-5V. In the recording and playback mode, press and hold the REC recording button to record. The REC LED will light up, and the recording will stop when the button is released. There are three situations for playback:
1. Edge-triggered play, press the PE button once to play out the entire voice, unless the power is off or the voice is over, the play cannot be stopped;
2. Level trigger playback, press and hold the PL button to play, and release the button to stop;
3. Loop playback, turn on the loop playback switch, and press the PE button to start loop playback, which can only be stopped when the power is turned off. In the pass-through mode, the pass-through switch is closed, and the microphone will be The loudspeaker is played out through the loudspeaker to form the function of a megaphone.
Pin arrangement :
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. The decoupling capacitor should be 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 are combined on this pin.
3. Recording (REC) is active at high level. As long as the REC becomes high (regardless of whether the chip is in a power-saving state or playing sound), the chip starts recording. During recording, REC must remain high. After the REC goes low or the memory is full, the recording cycle ends, and the chip automatically writes an information end mark (EOM), so that subsequent playback operations can be stopped in time. Then the chip automatically enters the power saving state. Note: The rising edge of REC has 84 ms protection Vibrate to prevent false triggering of keys.
4. Edge-triggered playback (PLAYE) When a rising edge occurs at this end, the chip starts to play. Play the sound until the EOM mark or the end of memory, which Then the chip automatically enters the power saving state. After starting to play, you can release PLAYE.
5. Level triggered playback (PLAYL) When this end changes from low to high, the chip starts to play. Playback continues until this end returns to low level, or encounters EOM Flag, or end of memory. After the sound is played, the chip automatically enters the power saving state.
6. Recording indicator (/RECLED) When in recording state, this end is low and can drive LED. In addition, when the playback encounters the EOM mark, this The terminal outputs 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. The external microphone should be coupled to this end through a series capacitor. The coupling capacitance value and the 10KΩ input impedance at this end determine the low-frequency cut-off point of the chip frequency band.
8. Microphone reference (MIC REF) This terminal is the reverse input of the preamplifier. When the microphone is connected in differential form, 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, making the recording change greatly Distortion at volume (from whispering to loud noise) can be kept to a minimum. Generally, 4.7uF capacitors can achieve satisfactory results in most situations.
10. Speaker output (SP+, SP-) This pair of output terminals can directly drive speakers above 8Ω. When using single-ended, it must be connected between the output end and the speaker Coupling capacitor, and double-ended output can increase the power to 4 times without using capacitor. SP+ and SP- are connected through an internal 50KΩ resistor, When not playing, it is suspended.
11. External clock (XCLK) There is a pull-down component inside this end, which is only for testing and does not need to be connected.
12. Oscillation resistance (ROSC) This terminal connects the oscillation resistance to VSS. The resistance value of the oscillation resistance determines the recording and playback time.
13. Through mode (FT) This terminal allows the external voice signal connected to the MIC input terminal to pass through the AGC circuit, filter and speaker inside the chip The driver directly reaches the speaker output. Usually the FT terminal is low. To achieve the pass-through function, the FT terminal needs to be connected to high level, and at the same time REC and PLAYE And PLAYL remains low.