LC78833M Datasheet, PDF (9/11 Pages) Sanyo Semicon Device – Digital Audio 16-Bit D/A Converter with Built-In Digital Filters

LC78833M, 78833V
• Resistor string D/A converter
This 8-bit D/A converter uses a total of 256 (= 2⁸) unit-resistance (R) resistors connected in series to voltage divide
the potential applied to the ends of that resistor string into 256 equal intervals. Of these resistor-divided potentials,
two adjacent potentials, V1 and V2, are selected by a switching circuit according to the value of the upper 8 bits
(D15 to D8) of the data. These two potentials are output to the PWM D/A converter. Note that these potentials are
related as follows:
V2 – V1 = (VH – VL)/256
• PWM D/A converter
This 4-bit D/A converter divides (by 16) the interval between the two potentials, V1 and V2, output by the resistor-
string D/A converter. This circuit outputs one or the other of the V1 and V2 potentials from the CH1OUT (or
CH2OUT) pin according to the value of the middle 4 bits (D7 to D4) of the data.
• Level shifting D/A converter
This 4-bit D/A converter is implemented by connecting the variable resistors VRH and VRL in series at the ends of
the resistor-string D/A converter. The values of the VRH and VRL variable resistors are modified according to the
value of the low-order 4 bits of the data as follows:
— The value of VRH + VRL is held fixed regardless of the value of the data.
— The values of VRH and VRL are changed in R/256 unit steps (where R is the value of the resistor-string D/A
converter unit resistors) over the range zero to 15·R/256.
This causes the resistor-string D/A converter V1 and V2 outputs to change in ∆V/256 steps (where ∆V = (VH –
VL)/256) over the range 0 to 15 × ∆V/256 according to the value of the lower 4 bits of the data.
— The Vref H/L and REFH/L pins
The Vref H/L pins provide the reference voltage to the resistor string, and are normally connected to AV_DD and
AGND, respectively. REFH and REFL are each connected to AGND through a capacitor of about 10 µF.
The maximum output amplitude is acquired when Vref H is 5.0 V and Vref L is 0 V. The internal resistors RH
and RL cause the output range to be between 0.7 V (minimum) and 3.5 V (maximum) (2.8 Vp-p) for 0 dB.
Filter Characteristics (as calculated)
4× oversampling
Ripple: Less than ±0.1 dB
Attenuation: –35 dB or lower
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