HT8656
Talking Back
Features
Operating voltage: 4.5V~5.5V
ADM algorithm
DRAM selection:
64K
256K
Sampling rate selection:
32Kb
16Kb
Auto stop recording
0.5 seconds silence is detected
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.
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5th May '98
Pin Assignment
Block Diagram
HT8656
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5th May '98
Pad Coordinates
Chip size: 3276.6
3530.6 (
m)
2
* The IC substrate should be connected to VDD in the PCB layout artwork.
Unit:
m
Pad No.
X
Y
Pad No.
X
Y
1
1488.19
1613.92
16
1488.19
1615.19
2
1488.19
1277.87
17
1488.19
377.19
3
1488.19
906.53
18
1488.19
124.71
4
1488.19
653.80
10
1488.19
130.30
5
1488.19
355.60
20
1488.19
384.05
6
1488.19
635.51
21
1488.19
651.51
7
1488.19
937.26
22
1488.19
1089.41
8
1488.19
1378.46
23
1488.19
1363.73
9
1396.75
1615.19
24
1436.88
1615.19
10
1170.43
1615.19
25
1226.57
1615.19
11
964.69
1615.19
26
973.84
1615.19
12
399.03
1615.19
27
723.65
1615.19
13
145.29
1615.19
28
473.20
1615.19
14
1033.27
1615.19
29
1052.83
1615.19
15
1239.01
1615.19
HT8656
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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
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5th May '98
Absolute Maximum Ratings*
Supply Voltage ................................. 0.3V to 6V
Storage Temperature................. 50
C to 125
C
Input Voltage................. V
SS
0.3V to V
DD
+0.3V
Operating Temperature............... 20
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
--
1.5
3.0
mA
I
STB
Standby Current
5V
--
--
600
800
A
I
O
Max. AUD Source Current
5V
V
OH
=0.6V
1.5
3.0
--
mA
I
OL
MOTOR Source Current
5V
V
OH
=4.5V
1
3.5
--
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
--
1.5
--
V
P-P
f
OSC
Oscillating Frequency
5V
R
OSC
=43k
--
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
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5th May '98
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