ds1075 ETC-unknow, ds1075 Datasheet - Page 3

• Manufacturer Part Number: ds1075
• Description: Econoscillator/divider
• Manufacturer: ETC-unknow

PIN DESCRIPTIONS
Input/Output Pin (IN/OUT): This pin is the main oscilla-
tor output, with a frequency determined by clock refer-
ence, M and N dividers. Except in programming mode
this pin is always an output and will be referred to as
“OUT”. In programming mode this pin will be referred to
as “IN”.
External Oscillator Input (OSCIN): This pin can be
used to supply an external reference frequency to the
device.
Crystal Oscillator Connection (XTAL): A crystal can
be connected between this pin and OSCIN to provide an
alternative frequency reference. If a crystal is not used
this pin should be left open.
Output Enable Function (OE pin): The DS1075 also
features a “synchronous” output enable. When OE is at
a high logic level the oscillator free runs. When this pin is
taken low OUT is held low, immediately if OUT is already
low, or at it’s next high–to–low transition if OUT is high.
This prevents any possible truncation of the output
pulse width when the enable is used. While the output is
disabled the master oscillator continues to run (produc-
ing an output at OUT0, if the EN0 bit = 0) but the internal
counters (/N) are reset. This results in a constant phase
relationship between OE’s return to a high level and the
resulting OUT signal. When the enable is released OUT
will make its first transition within one to two clock peri-
ods of the master clock.
Power–Down/Select Function (PDN/SELX pin): The
Power–Down/Select (PDN/SELX) pin has a user–se-
lectable function determined by one bit (PDN bit) of the
user–programmable memory. According to which func-
tion is selected, this pin will be referred to as PDN or
SELX.
If the Power–Down function is selected (PDN bit = 1) a
low logic level on this pin can be used to make the device
stop oscillating (active low) and go into a reduced power
consumption state. The “Enabling Sequencer” circuitry
will first disable OUT in the same way as when OE is
used. Next OUT0 will be disabled in a similar fashion.
Finally the oscillator circuitry will be disabled. In this
mode both outputs will go into a high impedance state.
The power consumption in the power–down state is
much less than if OE is used because the internal oscil-
lator (if used) is completely powered down. Even if an
external reference or a crystal is used all of the on–chip
buffers are powered down to minimize current drain.
Consequently the device will take considerably longer
to recover (i.e., achieve stable oscillation) from a pow-
er–down condition than if the OE is used.
If the Select function is chosen (PDN bit = 0) this pin can
be used to switch between the internal oscillator and an
external reference (or crystal) on the fly. When this
mode is chosen the E/I select bit is overridden, a high
logic level on SELX will select the internal oscillator, a
low logic level will select the external reference (or crys-
tal oscillator).
Reference Output (OUT0 pin): A reference output,
OUT0, is also available from the output of the reference
select mux. This output is especially useful as a buffered
output of a crystal defined master frequency. OUT0 is
unaffected by the OE pin, but is disabled in a glitchless
fashion if the device is powered down. If this output is
not required it can be permanently disabled by setting
the EN0 bit to one, and there will be a corresponding
reduction in overall power consumption.
USER–PROGRAMMABLE REGISTERS
The following registers can be programmed by the user
to determine operating frequency and mode of opera-
tion. Details of how these registers are programmed can
be found in a later section, in this section the function of
the registers are described. The register settings are
non–volatile, the values being stored automatically in
EEPROM when the registers are programmed.
Note: The register bits cannot be used to make mode or
frequency changes on the fly. Changes can only be
made by powering the device up in “Programming”
mode. For them to be become effective the device must
then be powered down and powered up again in
“Operation” mode.
For programming purposes the register bits are divided
into two 9–bit words, the “MUX” word determines mode
of operation and prescaler values. The “DIV” word sets
the value of the programmable divider.
101697 3/16
DS1075