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HT8656 talking back features operating voltage: 4.5v~5.5v adm algorithm dram selection: C 64k C 256k sampling rate selection: C 32kb C 16kb auto stop recording C 0.5 seconds silence is detected C recording capacity is full built-in 2-stage microphone amplifier built-in dram refresh circuit voltage type d/a output current type d/a output auto record and playback auto power-off low power consumption applications toys education games general description the HT8656 is a single chip cmos lsi for talking back applications using an adm algo- rithm. functions of the ic consist of record- ing/playing as well as auto power off. it starts recording when a sound input is detected, and stops to play back when silence lasts 0.5 sec- onds during recording. the auto power off func- tion is activated once a rec/play cycle has been implemented 64 times or an interval of silence exceeds 2 minutes. the HT8656 provides a recording capacity of 2 seconds for dram of 64k and 8 seconds for dram of 256k at a 32kb sampling rate and double recording capacity at a 16kb sampling rate. a higher sampling rate will result in sounds of better quality but sacrifice the record- ing time, and vice versa. 1 5th may 98
pin assignment block diagram HT8656 2 5th may 98
pad coordinates chip size: 3276.6 3530.6 ( m m) 2 * the ic substrate should be connected to vdd in the pcb layout artwork. unit: m m pad no. x y pad no. x y 1 C1488.19 1613.92 16 1488.19 C1615.19 2 C1488.19 1277.87 17 1488.19 C377.19 3 C1488.19 906.53 18 1488.19 C124.71 4 C1488.19 653.80 10 1488.19 130.30 5 C1488.19 C355.60 20 1488.19 384.05 6 C1488.19 C635.51 21 1488.19 651.51 7 C1488.19 C937.26 22 1488.19 1089.41 8 C1488.19 C1378.46 23 1488.19 1363.73 9 C1396.75 C1615.19 24 1436.88 1615.19 10 C1170.43 C1615.19 25 1226.57 1615.19 11 C964.69 C1615.19 26 973.84 1615.19 12 C399.03 C1615.19 27 723.65 1615.19 13 C145.29 C1615.19 28 473.20 1615.19 14 1033.27 C1615.19 29 C1052.83 1615.19 15 1239.01 C1615.19 HT8656 3 5th may 98
pin description pin no. pin name i/o internal connection description 1, 2 a6, a7 o cmos dram address output 3~8 a5~a0 o cmos dram address output 9 rasb o cmos dram row address strobe 10 wrb o cmos dram write enable 11 data i/o cmos dram data input/output 12 a8 o cmos dram address output 13 casb o cmos dram column address strobe 14 osc2 o oscillator output 15 osc1 i oscillator input 16 ledb o nmos open drain led indicator: idle: led is turned on record: led flashes play: led is turned off 17 start o nmos open drain system start pin 18 motor o cmos motor drive output (active high) when playing back 19 vss i negative power supply (gnd) 20 bias i for internal amp bias de-coupling 21 ain1 i internal amp first stage input (inverted) 22 ao1 o internal amp first stage output 23 ain2 i internal amp second stage input (inverted) 24 iout (8656a) o voltage type audio output for an external power amp 24 iout (8656b) o current type audio output for an external transistor 25 vdd i positive power supply 26 testb i pull-high for ic test only 27 16kb i pull-high 32kbps/16kbps sampling rate selection: open/high: 32kbps low: 16kbps 28 ms i pull-high 64k/256k dram size selection: open/high: 64k low: 256k HT8656 4 5th may 98
absolute maximum ratings* supply voltage ................................. C0.3v to 6v storage temperature................. C50 c to 125 c input voltage................. v ss C0.3v to v dd +0.3v operating temperature............... C20 c to 70 c *note: these are stress ratings only. stresses exceeding the range specified under absolute maxi- mum ratings may cause substantial damage to the device. functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability. electrical characteristics (ta=25 c) symbol parameter test conditions min. typ. max. unit v dd conditions v dd operating voltage 4.5 5.5 v i dd operating current 5v no load, f osc =640khz 1.53.0ma i stb standby current 5v 600 800 m a i o max. aud source current 5v v oh =0.6v C1.5 C3.0 ma i ol motor source current 5v v oh =4.5v C1 C3.5 ma i ol led sink current 5v v ol =0.5v 3.0 5.0 ma v ih h input voltage 0.7v dd v dd v v il l input voltage 0 0.3v dd v v out max. vout output voltage 5v r l >50k w 1.5v p-p f osc oscillating frequency 5v r osc =43k w 640 khz functional description the HT8656 is a single chip lsi with an exter- nal dram. it is designed for talking back appli- cations. the recording length of the ic is determined by the data rate along with the size of an external memory. sounds coming from an external microphone are coded through an in- ternal adm algorithm and saved in an external memory until the memory is full or an interval of silence lasts over 0.5 seconds. once recording is terminated, the ic will play back the recorded sounds automatically. record function the HT8656 provides two kinds of sampling rate and dram size selection to determine the recording capacity. the recording capacity is determined as shown on the following table. HT8656 5 5th may 98
dram type (ms) sampling rate (16kb) recording capacity 64kb 32kb 2 seconds 64kb 16kb 4 seconds 256kb 32kb 8 seconds 256kb 16kb 16 seconds recording starts whenever a sound input is detected. it then stops once a 0.5 seconds si- lence is detected or the recording capacity is full. after that, talking back comes into play. play function the HT8656 stops to play back the recorded sounds when an interval of silence lasts 0.5 seconds during recording. its sampling rate is the same as the rate of recording sounds. power control the HT8656 provides a start pin for power control. the start pin is of high impedance and switch q is turned off initially. after the start pin is triggered, it will remain at a low level and switch q is turned on. the start pin is of high impedance and the chips power is switched off when a rec/play cycle has been implemented 64 times or an interval of silence lasts over 2 minutes. motor the HT8656 provides a motor driving pin. the motor is turned on during playing but off once talking back is terminated. led the led pin displays the status of the HT8656. led is switched on when the ic is in the standby state. its intensity varies inversely with the sound volume when the ic is in the recording state. in the playing state, the led is switched off. HT8656 6 5th may 98
flowchart HT8656 7 5th may 98
application circuits lm386 output dice form * the ic substrate should be connected to vdd in the pcb layout artwork. HT8656 8 5th may 98
package form HT8656 9 5th may 98
two transistor output dice form * the ic substrate should be connected to vdd in the pcb layout artwork. HT8656 10 5th may 98
package form HT8656 11 5th may 98

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