MC145173 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

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MC145173

Dual-Band PLL Frequency Synthesizer with ADC and Frequency Counter

Motorola => Freescale 

The switch point is precisely controlled by use of a

comparator. The reference for the comparator is internally

set to approximately 33% of VDD. The input has a small

amount of hysteresis voltage (approximately 50 mV).

If not used, this pin should be tied to VDD or VSS.

Input D

Digital Input (Pin 6)

Input D is a general–purpose digital input which may be

used for MCU port expansion. The state of this input is indi-

cated by the In D bit in both the A and F registers. That is, the

state of the pin may be read from either register. (See Fig-

ures 21 and 22.)

This pin is a standard CMOS input with a switch point at

approximately 50% of VDD. Input D has a hysteresis voltage

of approximately 600 mV.

If not used, this pin should be tied to VDD or VSS.

Output A

Open–Drain Digital Output (Pin 12)

Output A is a general–purpose digital output which may be

used for MCU port expansion. An N–channel MOSFET tied

to VSS is used to drive this open–drain output. Thus, an ex-

ternal pull–up device is required at this pin. The state of this

output is determined by the Out A bit in the C register. (See

Figure 17.)

Upon power–up, this pin is low. If not used, Output A

should be tied to VSS or floated.

Output B

Digital Output (Pin 13)

Output B is a general–purpose digital output which may be

used for MCU port expansion. This is a standard totem–pole

(push–pull) CMOS output. The state of this output is deter-

mined by the Out B bit in the C register. (See Figure 17.)

Upon power–up, this pin is low. If not used, Output B

should be floated.

Output C

Digital Output (Pin 14)

Output C is a general–purpose digital output which may be

used for MCU port expansion. This is a standard totem–pole

(push–pull) CMOS output. The state of this output is deter-

mined by the Out C bit in the C register. (See Figure 17.)

Upon power–up, this pin is low. If not used, Output C

should be floated.

Output D

Digital Output (Pin 22)

Output D is a general–purpose digital output which may be

used for MCU port expansion. This is a standard totem–pole

(push–pull) CMOS output. The state of this output is deter-

mined by the Out D bit in the R register. (See Figure 18.)

Upon power–up, this pin is low. If not used, Output D

should be floated.

ADC INPUT PINS

Input A, Input B

Analog Inputs (Pins 9, 8)

These are inputs to the 2–channel multiplexer which feeds

the 6–bit analog–to–digital converter (ADC). The selected

channel is determined by the Chan bit in the C register.

Each pin is a high–impedance input which appears as

a mostly–capacitive load of approximately 6 pF.

If not used, these pins should be tied to VSS or VDD.

REFERENCE PINS

OSCin /OSCout

Reference Oscillator Input/Output (Pins 1, 24)

These pins form a reference oscillator when connected to

terminals of an external parallel–resonant crystal. Frequen-

cy–setting capacitors of appropriate values as recom-

mended by the crystal supplier are connected from each pin

to ground (up to a maximum of 30 pF each, including stray

capacitance). An external feedback resistor of 1 to 10 MΩ is

connected directly across the pins to ensure linear operation

of the amplifier. The MC145173 is designed to operate with

crystals from 2 to 15 MHz. However, frequencies are re-

stricted to 9.5 to 10.4 MHz when the ADC is utilized. (See

Figure 13.)

If desired, an external clock source can be ac coupled to

OSCin. A 0.01 µF coupling capacitor is used for measure-

ment purposes and is the minimum size recommended for

applications. The input capacitance of the OSCin pin is

approximately 6 pF. An external feedback resistor of approxi-

mately 10 MΩ is required across the OSCin and OSCout pins

in the ac–coupled case. (See Figure 12.) OSCout is an inter-

nal node on the device and should not be used to drive any

loads (i.e., OSCout is unbuffered). However, the buffered

REFout is available to drive external loads in the HF mode.

The external signal level must be at least 1 V p–p; the mini-

mum and maximum frequencies are given in the AC Electri-

cal Characteristics table. These frequencies apply for R

Counter divide ratios as indicated in the table. For very small

ratios, the maximum frequency is limited to the divide ratio

times 1 MHz (Reason: the phase/frequency detectors are

limited to a maximum input frequency of 1 MHz).

If an external source is available which swings from at

least the VIL to VIH levels listed in the DC Electrical Charac-

teristics table, then dc coupling can be used. In the dc–

coupled case, no external feedback resistor is needed.

OSCout must be a No Connect to avoid loading an internal

node on the MC145173, as noted above. For frequencies be-

low 2 MHz, a signal level of at least VIL and VIH is needed,

and dc coupling must be used. The R counter is a static

counter and may be operated down to dc. However, wave

shaping by a CMOS buffer may be required to ensure fast

rise and fall times into the OSCin pin at these low frequen-

cies.

Each rising edge on the OSCin pin causes the R counter to

decrement by one. In the standby mode, OSCin is pulled low

by an on–chip FET.

REFout

Open–Drain Reference Frequency Output (Pin 23)

This output is the buffered output of the crystal–generated

reference frequency or externally provided reference source.

MOTOROLA

MC145173

9

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