MC44864 データシートの表示（PDF） - Motorola => Freescale
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MC44864 Datasheet PDF : 12 Pages
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MC44864
Figure 8. Output Voltage (D/A Converters)
VDA = VTUN ± Vstep (D0 +2 D1 +4 D2 +8 D3 + 16 D4)
D5 = 1 positive sign; D5 = 0 negative sign
VTUN: Tuning Voltage set by PLL
Vstep: Voltage Step (LSB) of the D/A Converters
Figure 9. Range Selection of the D/A Converters
Input Data
S0
S1
0
0
1
0
0
1
1
1
Typ. Step Size
Vstep
225 mV
125 mV
70 mV
40 mV
Guaranteed
Range 31
Steps
6.25 V
3.40 V
1.90 V
1.05 V
The D/A Converters
The D/A converters convert 5 bit into analog current of
which the polarity is switched by the sixth bit. The reference
voltage of the converters is programmed by two bits (S0, S1
of the RA–byte) to determine the scaling factor. The analog
currents are then converted into voltages and added to their
respective operational amplifier nominal bias. The resulting
voltages at Pins 6, 7 and 8 are the tuning voltages (VTUN, see
Figure 4) at Pin 5 plus any offset provided by information in
the D/A converters.
If the data bits D0 to D4 are all “0”, the three D/A output
voltages on Pins 6, 7 and 8 are equal to the tuning voltage
(Pin 5) within the DAC offset voltages.
The four amplifiers have the same output characteristics
with the maximum output voltage being 1.5 V lower than
VCC2 in the worst case. The four analog outputs are
short–circuit protected. At power–up, the D/A outputs are
undetermined.
The D/A converters are guaranteed to be monotonic with a
voltage step variation of ±0.5 LSB.
The D/A converters work correctly as long as the PLL loop
is active. VTUN is then between 0.3 V and VCC2 – 1.5 V. If the
loop saturates, the DACs do not work.
The DAC–OFFSET is defined as the difference between
the DAC output voltage (with bits D0 to D4 = 0) and the tuning
voltage (PLL active). The DAC operation is guaranteed from
0.3 V to VCC2 – 1.5 V. On typical samples, the DACs will
operate down to 0.2 V.
DAC Offset
(VDAC – VTUN)
Figure 10. Definition of DAC Offset
±50 mVmax
10
±700 mVmax
20
30 V
VTUN
MOTOROLA ANALOG IC DEVICE DATA
11
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