5 (8)

DA9178.001

10 Dec, 2003

TYPICAL APPLICATION (Continued)

AGC Amplifier

Power Supply/Biasing

Demodulator

&

Comparator

RFP

RFM

VDD

VSS

PDN

AGC

DEC

OUT

QOP

QI

QOM

AON

+

1.4 V

Receiver

Output

C

AGC

10 µF

C

DEC

47 nF

Note 3

Power Down /

Fast Startup

Control

Note 2

Note 1

Note 4

Optional

Control

for AGC on/hold

Ferrite

Antenna

Antenna

Frequency

Selection

Figure 3

Dual band application circuit of external compensation capacitance version MAS9178A5.

Note 1: Crystal

The crystal as well as ferrite antenna frequencies are chosen according to the time-signal system (Table 1). The

should be used when fixed 0.875 pF compensation capacitance of MAS9178A1 does not match well with used

crystal’s shunt capacitance.

It should be noted that grounded crystal package has reduced shunt capacitance. This value is about 85% of

floating crystal shunt capacitance. PCB traces of crystal and external compensation capacitance should be kept

at minimum to minimize additional parasitic capacitance which can cause capacitance mismatching.

In dual band receiver configuration the crystals can be connected in parallel thus external compensation

is also possible to connect other crystal from QOP pin and the other crystal from QOM pin to common QI pin

(figure 3). In this circuit configuration no external compensation capacitor is required since the crystals

compensate each other. The sensitivity of dual band receiver configuration will be lower than that of single band

receiver configuration since the noise band width of crystal filter with two parallel crystals is double.

Time-Signal System

Location

Antenna Frequency

Recommended Crystal Frequency

DCF77

Germany

77.5 kHz

77.503 kHz

MSF

United Kingdom

60 kHz

60.003 kHz

WWVB

USA

60 kHz

60.003 kHz

JJY

Japan

40 kHz and 60 kHz

40.003 kHz and 60.003 kHz

Table 1

Time-Signal System Frequencies