ML22Q54 OKI [OKI electronic componets], ML22Q54 Datasheet - Page 27

• Manufacturer Part Number: ML22Q54
• Description: 2-Channel Mixing Oki ADPCM Algorithm-Based Speech Synthesis LSI
• Manufacturer: OKI [OKI electronic componets]

Examples of circuits that convert the PWM output signal to an Analog signal when PWM output is selected
(OPTANA pin = “H”) are given below.
1. Example Using Active LPF
The LPF primary side is configured as below using an OP amplifier.
LPC cutoff frequency, f
Ratio of resistors R
OP amplifier, set R
2. Example Using LC Filter
Secondary LPF is configured using a coil (L) and a capacitor (C). This configuration can directly drive a speaker.
However, a buffer is required between the PWM output and the LC filter.
LPF cutoff frequency, f
In the case of secondary Butterworth type LC filter, the constants are obtained by the following equations:
Here, R
OKI Semiconductor
Converting PWM Signal to Analog Signal
L = 1.4142
L
stands for the output load resistance and f
1
1
:R
to R
2 f
2
1
ML2250f
C
C
= 1:2.
2
C
, is determined by
, is determined by
determines the voltage amplification factor. To set the amplification factor 2 times of the
OUT(+)
OUT(–)
ML2250f
OUT(+)
OUT(–)
C =
R
R
R
1
1
2
f
f
1.412
C
C
=
=
2
2 R
C
R
stands for cutoff frequency of LC filter.
C
1
1
1
L
LC
–
+
1
2
C
C
R
L
L
1
(2 f
1
2
.
C
C
2
)
C
C
R
R
3
3
Speaker amplifier
ML2252/54-XXX, ML22Q54
FEDL2250DIGEST-01
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