DS1094L Datasheet, PDF (6/11 Pages) Dallas Semiconductor – Multiphase Spread-Spectrum EconOscillator

Multiphase Spread-Spectrum EconOscillator
Functional Diagram
SDA
2-WIRE
CONTROL REGISTERS
DS1094L
SERIAL
2-WIRE ADDRESS BITS
SCL
INTERFACE
f_OUT
WRITE EE
COMMAND
X X X X WC A2 A1 A0
ADDR
EEPROM WRITE CONTROL
DAC SETTING
MASTER
OSCILLATOR
1MHz TO 2MHz
f_MOSC
PRESCALER
DIVIDE BY
1, 2, 4, OR 8
f_OSC
TWO/THREE/
FOUR-PHASE
GENERATOR
OUT1
OUT2
OUT3
EEPROM
X X X X D3 D2 D1 D0
DAC
f_MOD
OUT4
DITHER RATE
V_CC
DITHER %
TRIANGLE
WAVE
f_MOSC
V_CC
D1 D0 PH1 PH0 J1 J0 P1 P0
GENERATOR
GND
PRESCALER
PRESCALER SETTING
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
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
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 2. Prescaler Settings
BITS P1, P0
00
01
10
11
DIVISOR
2⁰
2¹
2²
2³
f_OSC =
f_MOSC/1
f_MOSC/2
f_MOSC/4
f_MOSC/8
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