sm1350 Nippon Precision Circuits Inc, (NPC), sm1350 Datasheet - Page 10

• Manufacturer Part Number: sm1350
• Description: High Tone Quality Melody Lsi
• Manufacturer: Nippon Precision Circuits Inc, (NPC)

SM1350 series
Melody Output Circuit
The volume control circuit comprises a P-channel current-summing D/A converter, a built-in constant-current
source and an external variable resistor. The circuit is set for either BTL output or A-class output by master-
slice option.
BTLoutput
The BTL output comprises a pair of 9-bit D/A converters and 4 external transistors (2 × NPN + 2 × PNP) to
drive a speaker.
V
DD
VDD
MSB
MSBN
C
SPEAKER
SP
SPN
VSS VOL
VSS
Figure 4. BTL output circuit
A-class output circuit
The A-class output circuit comprises a single 10-bit D/A converter with current output on SP. The D/A con-
verter MSB is set ON immediately after the oscillator starts, and the current output that results is the center
point above and below which the converter current output varies in response to the waveform amplitude. The
SP output is current-to-voltage converted for connection to audio equipment or amplifiers. In A-class output
mode, the 4 sound generator waveforms are time multiplexed, so an integrating circuit must be connected
between SP and the amplifier to recover the signal.
V
DD
VDD
BUSYN
AMP
SPEAKER
SP
VSS VOL
V
SS
Figure 5. A-class output circuit
Note: Refer to the "TIMING DIAGRAMS" section to confirm melody timing specifics.
NIPPON PRECISION CIRCUITS INC.—10