DS1091L_12 Datasheet, PDF (6/9 Pages) Maxim Integrated Products – Automotive Temperature Range Spread-Spectrum EconOscillator™

DS1091L
Automotive Temperature Range
Spread-Spectrum EconOscillator™
Detailed Description
The DS1091L clock generator is capable of output fre-
quencies from 130kHz to 66.6MHz over the full automo-
tive temperature range (-40°C to +125°C). The device
can also produce a spread-spectrum (dithered) square-
wave output using four pin-selectable dither percent-
ages. Both center (DS1091LUA) and down (DS1091LUB)
dithering options are available. The device also features
two selectable dither rates.
The DS1091L is shipped from the factory programmed to
a customer-specified frequency.
Spread Spectrum
The DS1091L can reduce radiated emission peaks. The
dither percentage is controlled by the state of the SEL0
and SEL1 pins. The output frequency can be dithered
at 0%, ±1%, ±2%, and ±4%, centered around the pro-
grammed frequency (for the DS1091LUB this can be
down dithered by 0%, -2%, -4%, and -8%).
The two select pins SEL0 and SEL1 provide a means of
selecting the dither magnitudes as follows:
A triangle-wave generator injects a control signal into the
master oscillator to dither its output. The dither rate is a
function of the output frequency, f_OUT, as well as the set-
ting of the DR pin (see the equation below). Figure 1A and
Figure 1B show a plot of the output frequency vs. time.
DITHER
RATE
=
f_OUT
2ⁿ
where n is defined in Table 2 as a function of output
frequency. For example, for an output frequency of
27.0MHz, the dither rate would be 13.2kHz for DR = 1
and 6.6kHz for DR = 0.
Power-Up
Upon the application of power, the DS1091L output is
held in the low state until t_PU has elapsed. This removes
any possibility of erroneous output transitions during ini-
tial power-up.
Table 1. Dither Magnitude
SEL1
LOGIC
LEVEL
0
0
1
1
SEL0
LOGIC
LEVEL
0
1
0
1
DITHER MAGNITUDE (%)
DS1091LUA
No dither
Q1
Q2
Q4
DS1091LUB
No dither
-2
-4
-8
Table 2. Value of n w.r.t. Output Frequency
OUTPUT FREQUENCY f_OUT
(MHz)
f_OUT (min)
0.130
0.261
0.522
1.043
2.084
4.168
8.334
16.668
33.334
f_OUT (max)
0.260
0.521
1.042
2.083
4.167
8.333
16.667
33.333
66.667
n
DR = LOGIC
LEVEL 1
4
5
6
7
8
9
10
11
12
DR = LOGIC
LEVEL 0
5
6
7
8
9
10
11
12
13
DS1091L Frequency Spreading Profile as a Function of Dither %
PROGRAMMED fOUT+
(1%, 2%, OR 4% OF fOUT)
PROGRAMMED fOUT
PROGRAMMED fOUT-
(1%, 2%, OR 4% OF fOUT)
IF DITHER AMOUNT = 0%
DITHER
AMOUNT
(±1%, ±2%,
OR ±4%)
1
DITHER FREQ
PROGRAMMED fOUT
PROGRAMMED fOUT-
(2%, 4%, OR 8% OF fOUT)
1
DITHER FREQ
IF DITHER AMOUNT = 0%
DITHER
AMOUNT
(-2%, -4%,
OR -8%)
TIME
Figure 1A. Center Dithered
Maxim Integrated
TIME
Figure 1B. Down Dithered
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