MC145170P2 데이터 시트보기 (PDF) - Freescale Semiconductor

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MC145170P2

PLL Frequency Synthesizer with Serial Interface

Freescale Semiconductor 

Pin Connections

CLK typically switches near 50% of VDD and has a Schmitt-triggered input buffer. Slow CLK rise and fall

times are allowed. See the last paragraph of Din for more information.

NOTE

To guarantee proper operation of the power-on reset (POR) circuit, the CLK

pin must be held at the potential of either the VSS or VDD pin during power

up. That is, the CLK input should not be floated or toggled while the VDD

pin is ramping from 0 to at least 2.7 V. If control of the CLK pin is not

practical during power up, the initialization sequence shown in Figure 15

must be used.

ENB

Active-Low Enable Input (Pin 6)

This pin is used to activate the serial interface to allow the transfer of data to/from the device. When ENB

is in an inactive high state, shifting is inhibited, Dout is forced to the high-impedance state, and the port is

held in the initialized state. To transfer data to the device, ENB (which must start inactive high) is taken

low, a serial transfer is made via Din and CLK, and ENB is taken back high. The low-to-high transition on

ENB transfers data to the C, N, or R register depending on the data stream length per Table 7.

NOTE

Transitions on ENB must not be attempted while CLK is high. This puts the

device out of synchronization with the microcontroller. Resynchronization

occurs when ENB is high and CLK is low.

This input is also Schmitt-triggered and switches near 50% of VDD, thereby minimizing the chance of

loading erroneous data into the registers. See the last paragraph of Din for more information.

Dout

Three-State Serial Data Output (Pin 8)

Data is transferred out of the 16-1/2-stage shift register through Dout on the high-to-low transition of CLK.

This output is a No Connect, unless used in one of the manners discussed below.

Dout could be fed back to an MCU/MPU to perform a wrap-around test of serial data. This could be part

of a system check conducted at power up to test the integrity of the system's processor, PC board traces,

solder joints, etc.

The pin could be monitored at an in-line QA test during board manufacturing.

Finally, Dout facilitates troubleshooting a system and permits cascading devices.

3.2 Reference Pins

OSCin /OSCout

Reference Oscillator Input/Output (Pins 1, 2)

These pins form a reference oscillator when connected to terminals of an external parallel-resonant crystal.

Frequency-setting capacitors of appropriate values as recommended by the crystal supplier are connected

MC145170-2 Technical Data, Rev. 5

10

Freescale Semiconductor

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