February 1997
ML2035
Serial Input Programmable Sine Wave Generator
GENERAL DESCRIPTION
The ML2035 is a monolithic sinewave generator whose
output is programmable from DC to 25kHz. No external
components are required. The frequency of the sinewave
output is derived from either an external crystal or clock
input, providing a stable and accurate frequency
reference. The frequency is programmed by a 16-bit serial
data word. The ML2035 has a V
OUT
amplitude of ±V
CC
/2.
The ML2035 is intended for telecommunications and
modem applications that need low cost and accurate
generation of precise test tones, call progress tones, and
signaling tones.
FEATURES
s
s
s
Programmable output frequency - DC to 25kHz
Low gain error and total harmonic distortion
3-wire SPI compatible serial microprocessor interface
with double buffered data latch
Fully integrated solution - no external components
required
Frequency resolution of 1.5Hz (±0.75Hz) with a
12MHz clock input
Onboard 3 to 12MHz crystal oscillator
Synchronous or asynchronous data loading capability
Compatible with ML2031 and ML2032 tone detectors
and ML2004 logarithmic gain/attenuator
s
s
s
s
s
BLOCK DIAGRAM
5kΩ
5kΩ
CLK IN
8
-
VOUT
CRYSTAL
OSCILLATOR
8-BIT
DAC
8
PHASE
ACCUMULATOR
& 512 POINT
SINE LOOK-UP
TABLE
16
16-BIT DATA LATCH
SMOOTHING
FILTER
6
+
VCC
5
÷4
ZERO
DETECT
GND
7
LATI
4
VSS
SCK
2
16
16-BIT SHIFT REGISTER
1
SID
3
1
ML2035
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings are those values beyond which
the device could be permanently damaged. Absolute
maximum ratings are stress ratings only and functional
device operation is not implied.
V
CC ..............................................................................................
6.5V
V
SS .............................................................................................
-6.5V
V
OUT ....................................................
V
SS
- 0.3V to V
CC
+ 0.3V
Voltage on any other pin ........ GND - 0.3V to V
CC
+ 0.3V
Input Current ........................................................ ±25mA
Junction Temperature .............................................. 150ºC
Storage Temperature Range ...................... –65ºC to 150ºC
Lead Temperature (Soldering, 10 sec) ...................... 260ºC
Thermal Resistance (q
JA
) .................................... 110ºC/W
OPERATING CONDITIONS
Temperature Range
ML2035CP ................................................. 0ºC to 70ºC
ML2035IP ............................................... -40ºC to 85ºC
V
CC
Range ................................................... 4.5V to 5.5V
V
SS
Range ................................................. -4.5V to -5.5V
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, V
CC
= 4.5V to 5.5V, V
SS
= -4.5V to -5.5V, CLK IN = 12.352MHz, C
L
= 100pF, R
L
= 1kW,
T
A
= Operating Temperature Range (Note 1)
SYMBOL
OUTPUT
HD
Harmonic Distortion
(2nd and 3rd Harmonic)
SND
Signal to Noise + Distortion
20Hz to 5kHz
5kHz to 25kHz
200Hz to 3.4kHz,
f
OUT
BW = 20Hz to 4kHz
20Hz to 25kHz,
f
OUT
BW = 20 Hz to 75kHz
V
GN
Gain Error
20Hz < f
OUT
< 5kHz
5kHz < f
OUT
< 25kHz
ICN
Idle Channel Noise
Power Down Mode, Cmsg Weighted
Power Down Mode, 1kHz
PSRR
Power Supply Rejection Ratio
200mV
P-P
, 0 - 10kHz
Sine, Measured on V
OUT
V
OS
V
P-P
V
OUT
Offset Voltage
Peak-to-Peak Output Voltage
±V
CC
/2
V
CC
V
SS
-20
50
-40
-40
±75
-45
-40
-45
-40
±0.15
±0.3
0
dB
dB
dB
dB
dB
dB
dBrnc
nV/ÖHz
dB
dB
mV
V
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
OSCILLATOR
V
IL
CLK
V
IH
CLK
I
IL
CLK
I
IH
CLK
C
IN
CLK
t
CKI
CLK IN Input Low Voltage
CLK IN Input High Voltage
CLK IN Input Low Current
CLK IN Input High Current
CLK IN Input Capacitance
CLK IN On/Off Period
t
R
= t
F
= 10ns, 2.5V Midpoint
30
12
3.5
-250
250
1.5
V
V
µA
µA
pF
ns
LOGIC (LATI, SID, SCK)
V
IL
V
IH
I
IL
I
IH
Input Low Voltage
Input High Voltage
Input Low Current
Input High Current
V
IN
= 0V
V
IN
= V
CC
2.0
-1
1
0.8
V
V
µA
µA
3
ML2035
FUNCTIONAL DESCRIPTION
The ML2035 is composed of a programmable frequency
generator, a sine wave generator, a crystal oscillator, and a
serial digital interface. The ML2035 frequency and sine
wave generator functional block diagram is shown in
Figure 3.
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
accumulator which is clocked at f
CLK 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:
f
OUT
=
f
CLKIN
×
(D15 - D0)
DEC
2
23
(1)
(3)
For example, if V
OUT(P-P)
= 2.5V:
must be limited to 25kHz for V
CC
= 5V. V
OUT
can drive a
1kW, 100pF loads, provided the slew rate limitations
mentioned above are not exceeded.
The output offset voltage, V
OS
, is a function of the peak-to-
peak output voltage and is specified as:
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
GND of the ML2035. 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 GND.
An external clock can drive CLK IN directly if desired. The
frequency of this clock can be anywhere between 0 and
12MHz.
The crystal must have the following characteristics:
1. Parallel resonant type
2. Frequency: 3MHz to 12.4MHz
3. Maximum equivalent series resistance of 15W at a drive
levels of 1µW to 200µW, and 30W at drive levels of
10nW to 1µW
4. Typical load capacitance: 18pF
5. Maximum case capacitance: 7pF
The frequency of oscillation will be a function of the
crystal parameters and PC board capacitance. Crystals that
meet these requirements at 12.352000MHz are M-tron
3709-010 12.352 for 0ºC to 70ºC and 3709-020 12.352
for -40ºC to 85ºC operation.
The frequency resolution and the minimum frequency are
the same and is given by the following equation:
f
∆f
MIN
=
CLKIN
(2)
2
23
When f
CLK IN
= 12.352MHz,
Df
MIN
= 1.5Hz (±0.75Hz).
Lower frequencies are obtained by using a lower input
clock frequency.
Due to the phase quantization nature of the frequency
generator, 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 fundamental. 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 V
OUT
is a sinusoid with the second and third
harmonic distortion components at least 45dB below the
fundamental.
The ML2035 provides a peak sinewave voltage of ±V
CC
/2,
referenced to GND.
The analog section is designed to operate over a range
from DC to 25kHz. Due to slew rate limitations, the peak-
to-peak output voltage must be limited to V
OUT(P-P)
£
(125kV x Hz)/f
OUT
. Since the ML2035 peak-to-peak output
voltage is equal to V
CC
, the maximum output frequency
5
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