The SM1155 series are CMOS melody LSIs that, together with a battery and piezoelectric buzzer, operate in
one of 3 melody modes determined by bonding options. They also feature an oscillator stop function in non-
play mode and a variable pull-down resistance function that responds to input levels in order to reduce power
consumption, reduce cost, and extend battery life, making them ideal in a wide range of applications including
the hold sound for telephones and toys.
FEATURES
I
I
I
I
I
I
I
I
I
I
Requires few external components
1.2 to 3.6V wide operating voltage range
Low power consumption
3 melody modes (bonding option)
Oscillator stop function in non-play mode
Power saving pull-down resistor built-in
RC oscillator circuit
Power-ON initialization function
Wide pitch dynamic range (G
3
to D
7
)
8-pin SOP package
PINOUT
(Top view)
T2
T1
TG
VSS
1
8
TC
VDD
OUT
OUT
55
2
3
4
7
6
5
ORDERING INFORMATION
D e vice
S M 1 1 5 5
×××1
S
S M 1 1 5 5
×××2
S
S M 1 1 5 5
×××3
S
8-pin SOP
P ackag e
PACKAGE DIMENSIONS
(Unit: mm)
+0
0.15
−
0 .1
.05
4.4
±
0.2
6.2
±
0.3
0.695typ
0.05
±
0.05
5.2
±
0.3
1.5
±
0.1
0 to 10
1.27
0.4
±
0.1
0.10
0.12
M
NIPPON PRECISION CIRCUITS—1
0.4
±
0.2
SM1155 series
PAD DESCRIPTION
Number
1
2
Name
T2
T1
i/o
–
Test pins (must be open)
Melody mode control input
S M 1 1 5 5
×××1
S
3
TG
ip
1
H
S M 1 1 5 5
×××2
S
S M 1 1 5 5
×××3
S
L/open
4
5
6
7
8
VSS
OUT
OUT
VDD
TC
–
o
–
–
Ground
Piezoelectric speaker driver outputs. Both pins are LOW in non-play mode. OUT is LOW and O U T is HIGH
during output for a musical rest note. Both pins are HIGH during the gap between musical notes.
Supply. The rear surface of the chip is V
D D
level.
Test pins (must be open)
S M 1 1 5 5
×××1S/
2S/ 3S
Level hold 1
Level hold 2
One-shot
Non-play
Function
1. Built-in pull-down resistor (the resistance of the pull-down resistor varies with the applied voltage, as described in the Electrical Characteristics).
SPECIFICATIONS
Absolute Maximum Ratings
P arameter
Supply voltage range
Input voltage range
Operating temperature range
Storage temperature range
Symbol
V
DD
−
V
SS
V
IN
T
opr
T
stg
Condition
Rating
−0.3
to 5.0
V
S S
−
0.2 to V
D D
+ 0.2
−20
to 80
−55
to 125
Unit
V
V
°C
°C
Electrical Characteristics
T
a
= 25°C, V
SS
= 0V, V
DD
= 1.5V
P arameter
Operating voltage
Current consumption
1
Current consumption
2
T G L OW -level input voltage
TG HIGH-level input voltage
T G L OW -level input current
TG HIGH-level input current
O U T, O U T LOW -level output current
O U T, O U T HIGH-level output current
Internal oscillator frequency
1. Measurement circuit
Symbol
V
DD
I
D D 1
I
D D 2
V
IL
V
IH
I
IL
I
IH
I
O L
I
O H
f
O S C
V
IL
= 0.4V
V
IH
= 1.5V
V
O L
= 0.75V
V
O H
= 0.75V
f
0
= 50kHz
Non-play mode
Melody modes: O U T, O U T open
Condition
Rating
min
1.2
–
–
–
V
D D
– 0.2
1.4
1.4
2.0
2.0
–20
2. Measurement circuit
typ
1.5
0.01
25
–
–
3.0
3.0
–
–
–
max
3.6
0.3
50
V
S S
+ 0.2
–
6.0
6.0
–
–
+20
Unit
V
µA
µA
V
V
µA
µA
mA
mA
%
A
VDD
A
VDD
1.5V
VSS
1.5V
TG
VSS
NIPPON PRECISION CIRCUITS—2
SM1155 series
FUNCTIONAL DESCRIPTION
Melody Modes
When TG goes HIGH (V
DD
), melody play starts.
Level hold 1 (SM1155×××1S)
When TG goes HIGH, melody play starts and continues while TG is held HIGH. When TG goes open circuit or
LOW, melody play stops, even if during mid melody.
TG
OUT
1 TUNE
REPEAT
REPEAT
Oscillator
Pull-down resistance
135kΩ
(2-pin parallel resistance)
500kΩ
135kΩ
Level hold 2 (SM1155×××2S)
When TG goes HIGH, a single melody play starts. Melody play continues until the single melody ends or TG
goes open circuit or LOW, whichever occurs first.
TG
OUT
1 TUNE
Oscillator
Pull-down resistance
270kΩ
1MΩ
270kΩ
1MΩ
270kΩ
NIPPON PRECISION CIRCUITS—3
SM1155 series
One-shot (SM1155×××3S)
When TG goes HIGH, a single melody play starts. Melody play continues until the melody ends, even if TG
goes open circuit or LOW mid melody. However, if the TG input goes HIGH again during melody play, the
melody play restarts from the beginning.
TG
OUT
1 TUNE
1 TUNE
From the begining
Oscillator
Pull-down resistance
270kΩ
1MΩ
270kΩ
1MΩ
270kΩ 270kΩ
1MΩ 1MΩ
270kΩ
NIPPON PRECISION CIRCUITS—4
SM1155 series
Power-save Function
As shown in the preceding timing diagrams, the oscillator stops during non-play mode and the pull-down resis-
tance value changes in response to both HIGH-level and LOW-level inputs (power-save pull-down resistor) to
reduce power consumption and extend battery life.
Non-play oscillator stop function
When melody play ends, regardless of the state of TG, the internal oscillator stops and is placed in a standby
state. In this state, the current consumption, including input pin pull-down resistor current (I
IH
max), does not
exceed 3.3µA.
Power-save pull-down resistor
The resistance of the TG input pull-down resistor changes in response to the input voltage. The pull-down
resistance is 500kΩ when the input is HIGH, and the pull-down resistance is 135kΩ when the input is LOW.
Furthermore, if a light-dependent resistor (CdS) cell is employed as a switch (the pull-down resistance is max-
imum when the CdS resistance is minimum (light) and the pull-down resistance is minimum when the CdS
resistance is maximum (dark)), the combined resistance can be increased, decreasing current consumption.
Musical Specifications
Maximum program steps
A maximum of 64 steps can be programmed into internal mask-programmable ROM. Each step represents
either a note (sound pitch and length), a rest note, or a jump. The maximum number of jumps is 7.
Note length (including rests)
Eight rhythm values, from sixteenth note to half note, for notes and rests can be programmed, as shown in the
following table.
Code
Ty p e
0
Note
Rest
1
2
3
4
5
6
7
Also, notes and rests longer than half notes and rests can be created using a tie to connect the notes. This
requires 2 program steps in ROM.
Tempo
The tempo for the standard quarter note can be selected from the following 16 options.
Code
=
0
697
1
348
2
232
3
174
4
139
5
116
6
99.4
7
87
8
77.3
9
69.6
A
63.3
B
58
C
53.5
D
49.7
E
46.4
F
43.5
Pitch and scale
The SM1155 series devices support 3.5 octaves ranging from G
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