DS1091LUA+027 MAXIM [Maxim Integrated Products], DS1091LUA+027 Datasheet - Page 5

• Manufacturer Part Number: DS1091LUA+027
• Description: Automotive Temperature Range Spread-Spectrum Econoscillator
• Manufacturer: MAXIM [Maxim Integrated Products]

The DS1091L is a clock generator that is capable of
output frequencies from 130kHz to 66.6MHz over the
full automotive temperature range (-40°C to +125°C).
The device also is capable of producing a spread-
spectrum (dithered) square-wave output using four pin-
selectable dither percentages. Both center (DS1091LA)
and down (DS1091LB) 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.
The DS1091L has the ability to reduce radiated emis-
sion 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 programmed frequency (for the DS1091LB
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
setting of the DR pin (see the equation below). Figure 1
shows a plot of the output frequency versus time.
GND
V
WHERE
CC
f
DITHER RATE
MOSC
V
IS THE MASTER OSCILLATOR FREQUENCY.
CC
Detailed Description
DS1091L
DITHER RATE DIVIDER
=
f
Spread Spectrum
OUT
2
n
DR
Spread-Spectrum Econoscillator
OUT
f
_____________________________________________________________________
MOSC
Automotive Temperature Range
FACTORY-PROGRAMMED
MASTER OSCILLATOR
as well as the
TRIANGLE WAVE GENERATOR
SEL1
(DITHER %)
f
DITHER
SEL0
where n is defined in Table 2 as a function of output fre-
quency. For example, for an output frequency of
27.0MHz, the dither rate would be 13.2kHz for DR = 0
and 6.6kHz for DR = 1.
Table 2.
Table 1.
LOGIC LEVEL
OUTPUT FREQUENCY f
f
OUT
f
16.668
33.334
MOSC
0.130
0.261
0.522
1.043
2.084
4.168
8.334
SEL1
(min)
0
0
1
1
(MHz)
LOGIC LEVEL
f
OUT
16.667
33.333
66.667
0.260
0.521
1.042
2.083
4.167
8.333
SEL0
(max)
0
1
0
1
OUT
f
OUT
DR = LOGIC
DS1091LA
LEVEL 1
No Dither
Block Diagram
DITHER MAGNITUDE
±1%
±2%
±4%
OUT
10
11
12
4
5
6
7
8
9
n
DR = LOGIC
DS1091LB
LEVEL 0
No Dither
10
11
12
13
-2%
-4%
-8%
5
6
7
8
9
5