MC13176

3

MOTOROLA RF/IF DEVICE DATA

PIN FUNCTION DESCRIPTIONS

Pin

Symbol

Internal Equivalent

Circuit

Description/External

Circuit Requirements

1 & 4

Osc 1,

Osc 4

1

0sc 1

10k

4

Osc 4

10k

VCC

CCO Inputs

The oscillator is a current controlled type. An external oscillator

coil is connected to Pins 1 and 4 which forms a parallel

resonance LC tank circuit with the internal capacitance of the

IC and with parasitic capacitance of the PC board. Three

base–emitter capacitances in series configuration form the

capacitance for the parallel tank. These are the base–emitters

at Pins 1 and 4 and the base–emitter of the differential amplifier.

The equivalent series capacitance in the differential amplifier is

varied by the modulating current from the frequency control

circuit (see Pin 6, internal circuit). A more thorough discussion

is found in the Applications Information section.

5

VEE

VEE

VEE

VEE

5

Subcon

Supply Ground (VEE)

In the PCB layout, the ground pins (also applies to Pins 10 and

15) should be connected directly to chassis ground. Decoupling

capacitors to VCC should be placed directly at

the ground returns.

6

ICont

ICont

6

Reg

VCC

Frequency Control

For VCC = 3.0 Vdc, the voltage at Pin 6 is approximately 1.55

Vdc. The oscillator is current controlled by the error current from

the phase detector. This current is amplified to drive the current

source in the oscillator section which controls the frequency of

the oscillator. Figures 8 and 9 show the

∆fosc versus ICont,

Figure 5 shows the

∆fosc versus ICont at – 40°C, + 25°C and

+85

°C for 320 MHz. The CCO may be FM modulated as shown

in Figures 17 and 18, MC13176 320 MHz FM Transmitter. A

detailed discussion is found in the Applications Information

section.

7

PDout

4.0k

VCC

4.0k

7

PDout

Phase Detector Output

The phase detector provides

± 30 µA to keep the CCO locked at

the desired carrier frequency. The output impedance of the

phase detector is approximately 53 k

Ω. Under closed loop

conditions there is a DC voltage which is dependent upon the

free running oscillator and the reference oscillator frequencies.

The circuitry between Pins 7 and 6 should be selected for

adequate loop filtering necessary to stabilize and filter the loop

response. Low pass filtering between Pin 7 and 6 is needed so

that the corner frequency is well below the sum of the divider

and the reference oscillator frequencies, but high enough to

allow for fast response to keep the loop locked. Refer to the

Applications Information section regarding loop filtering and FM

modulation.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

ARCHIVED BY FREESCALE SEMICONDUCTOR, INC. 2005