Holtek Semiconductor Inc HT8955A Datasheet
Features
•
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
Applications
•
Mixers
•
Karaoke systems
General Description
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 oscillato r, 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 s ampling rate of 25kHz
HT8955A
Voice Echo
•
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
•
Echo generators
•
Sound effect generators
when combined with an external DRAM
(41256/4164). The HT8955A is superior to a
conventional BBD delay un it in its low distortion, high S/N ratio and long delay time. Its
sophisticated lo w pa ss filter wil l not e nd in the
normal application s due to the high sampling
rate (25~50kHz). Hence, the HT8955A is excellent for audio delay sys tem applications. It is
offered in a 24-pin dual-in-line package.
Pin Assignment Block Diagram
1 5th May ’98
HT8955A
Pad Coordinates Unit: µm
Pad
No.
1 –1138.00 796.50 14 1141.50 –547.00
2 –1141.00 523.50 15 1141.50 –197.50
3 –1136.50 201.50 16 1141.50 111.50
4 –1136.50 –163.00 17 1141.50 461.00
5 –1137.00 –507.00 18 1141.50 770.50
6 –1149.00 –774.00 19 896.00 811.00
7 –854.50 –853.50 20 645.00 810.50
8 –548.00 –831.50 21 435.00 794.00
9 –198.50 –831.50 21 335.00 794.00
10 111.50 –831.50 22 150.00 779.00
11 461.00 –831.50 23 –35.00 779.00
12 773.00 –831.50 25 –264.00 806.00
13 1122.50 –831.50
Chip size: 2170
* The IC substrate should be connected to VSS in the PCB layout artwork.
× 2200 (µm)
2
XY
Pad
Pin Description
Pin No. Pin Name I/O
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 — Delayed audio signal output pin
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
Internal
Connection
Description
Internal pre-amplifier bias
Connects to a decoupling capacitor
DRAM type selection:
VDD or Open: 64Kb
VSS: 256Kb
No.
XY
2 5th May ’98
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
Absolu te Maximum Ra tin g s*
Supply Voltage.................................–0.3V to 6V Storage T emperature.................–50°C to 125°C
Input Voltage................. V
–0.3V to VDD+0.3V Operating Temperature...............–20°C to 70°C
SS
*Note: These are stress ra tings on ly. Stresses exceeding the range spe cified un der “Abso lute Maxi-
mum Ratings” ma y 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 condition s may affect device reliability.
Electrical Characteristics (Ta=25°C)
Symbol Parameter
V
DD
I
OP
A
V
A
V
V
IL
Operating Voltage — — 4.5 5.0 5.5 V
Operating Current 5V
Pre-amplifier Voltage Gain 5V
Comparator Voltage Gain 5V
“L” Input Voltage — — 0 — 0.3V
Test Conditions
V
DD
Conditions
No load,
f
=640kHz
OSC
>100kΩ
R
L
Open loop
>100kΩ
R
L
Open loop
3 5th May ’98
Min. Typ. Max. Unit
—2.58mA
—2000—V/V
—2000—V/V
V
DD
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