HOLTEK HT8955A

HT8955A
Voice Echo
Features
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Operating voltage: 5.0V
Long delay time
– 0.8 seconds (SEL=VSS, 256K DRAM)
– 0.2 seconds (SEL=VDD/open, 64K DRAM)
25kHz sampling rate
Continuous variable delay time
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•
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Built-in pre-amplifier
Low distortion
High S/N ratio
Wide frequency response
PCM 10-bit A/D and D/A converters
24-pin DIP package
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Echo generators
Sound effect generators
Applications
•
•
Mixers
Karaoke systems
General Description
when combined with an external DRAM
(41256/4164). The HT8955A is superior to a
conventional BBD delay unit in its low distortion, high S/N ratio and long delay time. Its
sophisticated low pass filter will not end in the
normal applications due to the high sampling
rate (25~50kHz). Hence, the HT8955A is excellent for audio delay system applications. It is
offered in a 24-pin dual-in-line package.
The HT8955A is a CMOS LSI digital audio
signal delay processor. It is designed for
audio system applications including echo
generators, karaoke systems, sound effect
generators, etc.
The chip consists of a built-in pre-amplifier,
on-chip oscillator, DRAM interface, 10-bit A/D
and D/A converters as well as control logic. It
provides continuously adjustable delay time up
to 0.8/0.2 seconds at a sampling rate of 25kHz
Pin Assignment
Block Diagram
1
5th May ’98
HT8955A
Unit: µm
Pad Coordinates
Pad
No.
X
Y
1
2
3
4
5
6
7
8
9
10
11
12
13
–1138.00
–1141.00
–1136.50
–1136.50
–1137.00
–1149.00
–854.50
–548.00
–198.50
111.50
461.00
773.00
1122.50
796.50
523.50
201.50
–163.00
–507.00
–774.00
–853.50
–831.50
–831.50
–831.50
–831.50
–831.50
–831.50
Pad
No.
X
Y
14
15
16
17
18
19
20
21
21
22
23
25
1141.50
1141.50
1141.50
1141.50
1141.50
896.00
645.00
435.00
335.00
150.00
–35.00
–264.00
–547.00
–197.50
111.50
461.00
770.50
811.00
810.50
794.00
794.00
779.00
779.00
806.00
Chip size: 2170 × 2200 (µm)2
* The IC substrate should be connected to VSS in the PCB layout artwork.
Pin Description
Pin No. Pin Name I/O
Internal
Connection
Description
Internal pre-amplifier bias
Connects to a decoupling capacitor
1
BIAS
O
OP Non-inverted
2
IN
I
OP Inverted
Audio signal input pin (inverted)
3
PREO
O
OP OUTPUT
Pre-amplifier output pin
4
OUT
O
—
5
SEL
I
Pull-High
6
OSC1
I
—
System oscillator input
7
OSC2
O
—
System oscillator output
8
OSC3
I
—
Delay time control oscillator input
9
OSC4
O
—
Delay time control oscillator output
10
VSS
I
—
Negative power supply (GND)
11
A6
O
CMOS OUT
Connects to DRAM A6
12
A7
O
CMOS OUT
Connects to DRAM A7
Delayed audio signal output pin
DRAM type selection:
VDD or Open: 64Kb
VSS: 256Kb
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HT8955A
Pin No. Pin Name I/O
Internal
Connection
Description
13
A5
O
CMOS OUT
Connects to DRAM A5
14
A4
O
CMOS OUT
Connects to DRAM A4
15
A3
O
CMOS OUT
Connects to DRAM A3
16
A2
O
CMOS OUT
Connects to DRAM A2
17
A1
O
CMOS OUT
Connects to DRAM A1
18
A0
O
CMOS OUT
Connects to DRAM A0
19
RASB
O
CMOS OUT
Connects to DRAM RASB
20
WRB
O
CMOS OUT
Connects to DRAM WRB
21
DATA
I/O
CMOS I/O
Data I/O pin
22
A8
O
CMOS I/O
Connects to DRAM A8
23
CASB
O
CMOS I/O
Connects to DRAM CASB
24
VDD
I
—
Positive power supply
Absolute Maximum Ratings*
Supply Voltage ................................. –0.3V to 6V
Storage Temperature................. –50°C to 125°C
Input Voltage................. VSS–0.3V to VDD+0.3V
Operating Temperature............... –20°C to 70°C
*Note: These are stress ratings only. Stresses exceeding the range specified under “Absolute Maximum 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.
(Ta=25°C)
Electrical Characteristics
Symbol
Test Conditions
Parameter
VDD
Conditions
—
Min.
Typ.
Max.
Unit
4.5
5.0
5.5
V
VDD
Operating Voltage
—
IOP
Operating Current
5V
No load,
fOSC=640kHz
—
2.5
8
mA
AV
Pre-amplifier Voltage Gain
5V
RL>100kΩ
Open loop
—
2000
—
V/V
AV
Comparator Voltage Gain
5V
RL>100kΩ
Open loop
—
2000
—
V/V
VIL
“L” Input Voltage
—
—
0
—
0.3VDD
V
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HT8955A
Symbol
Test Conditions
Parameter
VDD
Conditions
Min.
Typ.
Max.
Unit
0.7VDD
—
VDD
V
1
1.5
—
V
VIH
“H” Input Voltage
—
—
VOMAX
Maximum Output Voltage
5V
RL>470kΩ
5V
SEL=open, 25kHz
sampling rate
0.15
0.2
—
s
5V
SEL=VSS, 25kHz
sampling rate
0.6
0.8
—
s
Td
Maximum Delay Time
Td
S/N
Signal to Noise Ratio
5V
VO=1V, 400Hz
BW=10kHz
—
55
—
dB
THD
Total Harmonic Distortion
5V
VO=1V, 400Hz
BW=7kHz
—
0.5
—
%
Functional Description
demands an external resistor between the
OSC3 and OSC4 pins. By altering the oscillation resistor, its delay time can be continuously
adjusted up to 0.8/0.2 seconds at a 25kHz sampling rate for DRAM of 256Kb/64Kb.
The HT8955A is a single chip LSI with an external DRAM. It is designed for processing audio
signal delay. The chip includes a built-in preamplifier, 10-bit A/D and D/A converters. The
A/D and D/A converters ensure low distortion as
well as high S/N ratio of the audio delay system.
The chip also provides two sets of oscillation
circuit for system sampling rate and audio echo
delay time.
Playing function block diagram
DRAM selection
The HT8955A can interface with a DRAM for
storing delay signals. The type along with the
maximum delay time of DRAM is determined
by the status of the SEL pin as shown:
DRAM
Type
Delay Time
VDD or Open
64Kb
0.2 seconds
VSS
256Kb
0.8 seconds
SEL Connection
System oscillator
The HT8955A provides two oscillators, one for
the sampling rate and one for echo delay time.
The sampling rate oscillator requires an external resistor between the OSC1 and OSC2 pins.
A higher sampling rate (25~50kHz) can thus be
derived by adjusting the oscillation resistor
without having a sophisticated low pass filter.
The delay time oscillator, on the other hand,
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HT8955A
Application Circuits
Low cost echo
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HT8955A
Basic KARAOKE system
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HT8955A
Basic KARAOKE system with pre-emphasis
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5th May ’98