DS1086L Datasheet, PDF (10/16 Pages) Maxim Integrated Products – 3.3V Spread-Spectrum EconOscillator

3.3V Spread-Spectrum EconOscillator
Table 1. Register Summary
REGISTER ADDR MSB
BINARY
PRESCALER 02h JS4 JS3 JS2 JS1 JS0
PRESCALER
—
P1
P0
X_X
X_X
X_X
DAC (MSB)
08h
b9
b8
b7
b6
b5
DAC (LSB)
OFFSET
ADDR
RANGE
WRITE EE
—
b1
b0
X₀
X₀
X₀
0Eh
X₁
X₁
X₁
b4
b3
0Dh
X₁
X₁
X₁
X₁ WC
37h
X_X
X_X
X_X
b4
b3
3Fh
NO DATA
X₀ = Don’t care, reads as zero.
X₁ = Don’t care, reads as one.
X_X = Don’t care, reads indeterminate.
X = Don’t care.
Table 2. Offset Settings
OFFSET
FREQUENCY RANGE (MHz)
OS - 6
30.7 to 35.8
OS - 5
33.3 to 38.4
OS - 4
35.8 to 41.0
OS - 3
38.4 to 43.5
OS - 2
41.0 to 46.1
OS - 1
43.5 to 48.6
OS*
46.1 to 51.2
OS + 1
48.6 to 53.8
OS + 2
51.2 to 56.3
OS + 3
53.8 to 58.9
OS + 4
56.3 to 61.4
OS + 5
58.9 to 64.0
OS + 6
61.4 to 66.6
*Factory default setting. OS is the integer value of the five LSBs
of the RANGE register.
The output frequency is determined by the following
equation:
(MIN FREQUENCY OF SELECTED OFFSET RANGE)
f_{OUTPUT =}
+ (DAC VALUE × 5kHz STEP SIZE)
PRESCALER
where: min frequency of selected OFFSET range is the
lowest frequency (shown in Table 2 for the correspond-
ing offset).
DAC value is the value of the DAC register (0 to 1023).
Prescaler is the value of 2^x where x = 0 to 8.
LSB
LO/HiZ P3 P2
X_X
X_X X_X
b4
b3 b2
X₀
X₀ X₀
b2
b1 b0
A2
A1 A0
b2
b1 b0
FACTORY
DEFAULT
01100000
00XXXXX
01111101b
00000000b
111-----b
11110000b
xxx-----b
—
ACCESS
R/W
R/W
R/W
R/W
R/W
R/W
R
—
See the Example Frequency Calculations section for a
more in-depth look at using the registers.
________________Register Definitions
The DS1086L registers are used to program the output
frequency, dither percent, dither rate, and 2-wire
address. Table 1 shows a summary of the registers and
detailed descriptions follow below.
PRESCALER (02h)
The PRESCALER word is a two-byte value containing
control bits for the prescaler (P3 to P0), output control
(Lo/HiZ), the jitter rate (JS4 to JS3), as well as control
bits for the jitter percentage (JS2 to JS0). The
PRESCALER word is read and written using two-byte
reads and writes beginning at address 02h.
JS4 to JS3: Jitter Rate. This is the frequency of the tri-
angle wave generator and the modulation frequency
that the output is dithered. It can be programmed to the
master oscillator frequency, f_OSC, divided by either
8192, 4096, or 2048.
JS4 JS3
JITTER RATE
0
0
f_OSC/8192
0
1
f_OSC/4096 (default)
1
0
f_OSC/2048
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