Multiphase Spread-Spectrum EconOscillator
DS1094L
Functional Diagram
SDA
SCL
CONTROL REGISTERS
2-WIRE
SERIAL
INTERFACE
2-WIRE ADDRESS BITS
DS1094L
f
OUT
WRITE EE
COMMAND
X
X
X
X WC A2 A1 A0
DAC SETTING
MASTER
OSCILLATOR
f
MOSC
PRESCALER
DIVIDE BY
1, 2, 4, OR 8
OUT1
OUT2
OUT3
OUT4
f
OSC
TWO/THREE/
FOUR-PHASE
GENERATOR
ADDR
EEPROM WRITE CONTROL
1MHz TO 2MHz
EEPROM
X
DAC
V
CC
V
CC
DITHER RATE
DITHER %
D1 D0 PH1 PH0 J1 J0 P1 P0
X
X
X
D3 D2 D1 D0
f
MOD
TRIANGLE
WAVE
GENERATOR
f
MOSC
GND
PRESCALER SETTING
PRESCALER
PHASE SELECT
Detailed Description
The DS1094L consists of a master oscillator, prescaler,
phase generator, and triangle-wave generator (used to
dither the master oscillator), which are all programma-
ble using the 2-wire interface and stored in NV memory.
Master Oscillator
The master oscillator is responsible for generating the
timing (frequency) of the outputs. The master oscillator
frequency, f
MOSC
, can be programmed anywhere
between 1MHz to 2MHz in 100kHz steps. The master
oscillator is programmed using the DAC register. The four
MSBs of the DAC register are don’t cares, while the four
LSBs (D3 to D0) are the DAC value. The master oscillator
frequency is determined using the following equation:
f
MOSC
= 1MHz + (DAC value x 100kHz)
Valid values for DAC are 0 to 10 (dec). DAC values
greater than 10 exceed the 2MHz limit and are not per-
mitted.
The master oscillator also determines the spread-spec-
trum dither frequency. This is described in
the Triangle
Wave Generator
section.
Table 1. Master Oscillator Settings
DAC VALUE (dec)
0
1
2
—
10
11 to 15
DAC REGISTER
00h
01h
02h
—
0Ah
0Bh to 0Fh
f
MOSC
1.0MHz
1.1MHz
1.2MHz
—
2.0MHz
Reserved
Table 2. Prescaler Settings
BITS P1, P0
00
01
10
11
DIVISOR
2
0
2
2
1
f
OSC
=
f
MOSC
/1
f
MOSC
/2
f
MOSC
/4
f
MOSC
/8
2
2
3
6
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DALLAS [ DALLAS SEMICONDUCTOR ]
