ML2036 View Datasheet(PDF) - Fairchild Semiconductor
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ML2036
Fairchild Semiconductor
ML2036 Datasheet PDF : 12 Pages
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PRODUCT SPECIFICATION
ML2036
Functional Description
The ML2036 is composed of a programmable frequency
generator, a sine wave generator, a crystal oscillator, and
a serial digital interface. The ML2036 frequency and sine
wave generator functional block diagram is shown in
Figure 4.
Programmable Frequency Generator
The programmable frequency generator produces a digital
output whose frequency is determined by a 16-bit digital
word.
The frequency generator is composed of a phase accumula-
tor which is clocked at fCLK IN/4. The value stored in the
data latch is added to the phase accumulator every 4 cycles
of CLK IN. The frequency of the analog output is equal to
the rate at which the accumulator overflows and is given by
the equation:
fOUT = f--C----L---K----I-N----X----(---D---2-1--2--5-3----–----D-----0----)--D----E---C--
(1)
The frequency resolution and the minimum frequency are
the same and is given by the following equation:
∆fMIN = f--C---2-L--2-K--3--I-N--
(2)
When fCLK IN = 12.352MHz, ∆fMIN = 1.5Hz (±0.75Hz).
Lower frequencies are obtained by using a lower input clock
frequency.
Due to the phase quantization nature of the frequency gener-
ator, spurious tones can be present in the output range of
–55dB relative to fundamental. The energy from these tones
is included in the signal to noise + distortion specification.
The frequency of these tones can be very close to the funda-
mental. Therefore, it is not practical to filter them out.
Sinewave Generator
The sinewave generator is composed of a sine look-up table,
a DAC, and an output smoothing filter. The sine look-up
table is addressed by the phase accumulator. The DAC is
driven by the output of the look-up table and generates a
staircase representation of a sine wave.
The output filter smoothes the analog output by removing the
high frequency sampling components. The resultant voltage
on VOUT is a sinusoid with the second and third harmonic
distortion components at least 45dB below the fundamental.
The ML2036 has a VREF input that can be tied to VCC or
generated from an external voltage. With the GAIN input
equal to a logic “1”, the sine wave peak-to-peak voltage is
equal to ±VREF; with the GAIN equal to a logic “0”, the
peak voltage is ±VREF/2. However, the overall output volt-
age swing is limited to no closer than 1.5V to either rail.
This means that to avoid clipping, VREF can only be tied to
VCC when GAIN is a logic “0”. The sinewave output is
referenced to AGND.
The analog section is designed to operate over a range from
DC to 50kHz. Due to slew rate limitations, the peak-to-peak
output voltage must be limited to VOUT(P-P) ≤ (125kV x
Hz)/fOUT. For example, an output at 50kHz must be limited
to 2.5VP-P. VOUT can drive a 1kΩ, 100pF load and swing
to within 1.5V of VCC and VSS, provided the slew rate
limitations mentioned above are not exceeded.
The output offset voltage, VOS, is a function of the peak-to-
peak output voltage and is specified as:
VOS(MAX) = ±-2---.--5----+-----V---1-O--0--U-0---T---(--P-----–---P---)
(3)
For example, if VOUT(P-P) = 2.5V:
VOS(MAX) = ±2----.--5-1---+0----0-2----.-5-- = ±50mV
Crystal Oscillator
The crystal oscillator generates an accurate reference clock
for the programmable frequency generator. The internal
clock can be generated with a crystal or external clock.
If a crystal is used, it must be placed between CLK IN and
DGND of the ML2036. An on-chip crystal oscillator will
then generate the internal clock. No other external capacitors
or components are required. The crystal should be a parallel-
resonant type with a frequency between 3MHz to 12.4MHz.
It should be placed physically as close as possible to the
CLK IN and DGND.
An external clock can drive CLK IN directly if desired. The
frequency of this clock can be anywhere between 0 and
12MHz.
SCK
SID
LATI
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Figure 5. Serial Interface Timing.
REV. 1.0.2 7/26/01
7
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