Rainbow Electronics DS1094L - Manual (Page 6)

DS1094L
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.
Multiphase Spread-Spectrum EconOscillator
6 _____________________________________________________________________
GND
MASTER
OSCILLATOR
1MHz TO 2MHz
PRESCALER
DIVIDE BY
1, 2, 4, OR 8
TRIANGLE
WAVE
GENERATOR
2-WIRE
SERIAL
INTERFACE
TWO/THREE/
FOUR-PHASE
GENERATOR
DAC
PRESCALER
ADDR
D0 D1 D2 D3 X X X X
P0 P1 J0 J1 PH0 PH1 D0 D1
A0 A1 A2 WC X X X X
V CC
V
CC
SCL
SDA
DITHER RATE
DITHER %
EEPROM
WRITE EE
COMMAND
OUT2
OUT1
OUT3
OUT4
2-WIRE ADDRESS BITS
PHASE SELECT PRESCALER SETTING
EEPROM WRITE CONTROL
CONTROL REGISTERS
DAC SETTING
f MOSC f OSC
f MOSC
f MOD
f OUT
DS1094L
Functional Diagram
DAC VALUE (dec) DAC REGISTER f MOSC
0 00h 1.0MHz
1 01h 1.1MHz
2 02h 1.2MHz
— — —
10 0Ah 2.0MHz
11 to 15 0Bh to 0Fh Reserved
Table 1. Master Oscillator Settings
BITS P1, P0 DIVISOR f OSC =
00 2 0 f
MOSC
/1
01 2 1 f MOSC /2
10 2 2 f MOSC /4
11 2 3 f MOSC /8
Table 2. Prescaler Settings