MAS9180AETC00 查看數據表（PDF） - Micro Analog systems

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MAS9180AETC00

AM Receiver IC

Micro Analog systems 

TYPICAL APPLICATION (Continued)

DA9180.004

15 September, 2005

Note 2: AGC Capacitor

The AGC and DEC capacitors must have low leakage currents due to very small signal currents through the

capacitors. The insulation resistance of these capacitors should be at minimum 100 MΩ. Also probes with at

least 100 MΩ impedance should be used for voltage probing of AGC and DEC pins. DEC capacitor can be low

leakage chip capacitor.

Note 3: Power Down / Fast Startup Control

Both power down and fast startup are controlled using the PDN pin. The device is in power down (turned off) if

PDN = VDD and in power up (turned on) if PDN = VSS. Fast startup is triggered automatically by the falling edge

of PDN signal, i.e., controlling device from power down to power up. The VDD must be high before falling edge of

PDN to guarantee proper operation of fast startup circuitry. The startup time without proper fast startup control

can be several minutes but with fast startup it is shortened typically to few seconds.

Note 4: Optional Control for AGC On/Hold

AON control pin has internal pull up which turns AGC circuit on all the time if AON pin is left unconnected.

Optionally AON control can be used to hold and release AGC circuit. Stepper motor drive etc. can produce

disturbing amount of noise which can shift the input amplifier gain to unoptimal level. This can be avoided by

controlling AGC hold (AON=VSS) during stepper motor drive periods and releasing AGC (AON=VDD) when

motors are not driven.

Note 5: Ferrite Antenna

The ferrite antenna converts the transmitted radio wave into a voltage signal. It has an important role in

determining receiver performance. Recommended antenna impedance at resonance is around 150 kΩ.

Low antenna impedance corresponds to low noise but often also to small signal amplitude. On the other hand

high antenna impedance corresponds to high noise but also large signal. The optimum performance where

signal-to-noise ratio is at maximum is achieved in between.

The antenna should have also some selectivity for rejecting near signal band disturbances. This is determined by

the antenna quality factor which should be approximately 100. Much higher quality factor antennas suffer from

extensive tuning accuracy requirements and possible tuning drifts by the temperature.

Antenna impedance can be calculated using equation 1 where f0, L, Qant and C are resonance frequency, coil

inductance, antenna quality factor and antenna tuning capacitor respectively. Antenna quality factor Qant is

defined by ratio of resonance frequency f0 and antenna bandwidth B (equation 2).

Rantenna

=

2π

⋅

f0

⋅ L ⋅ Qantenna

=

Qantenna

2π ⋅ f0 ⋅ C

=

2π

1

⋅B⋅C

Qantenna

=

f0

B

Equation 1.

Equation 2.

Table 4 below presents some antenna manufacturers for timesignal application.

Table 4. Antenna Manufacturers and Antenna Types in Alphaphetical Order for Timesignal Application

Manufacturer

Antenna Type

Dimensions

Web Link

HR Electronic GmbH 60716 (60kHz)

60708 (77.5kHz)

Sumida

ACL80A (40kHz)

ø 10 x 60 mm

ø 10 x 80 mm

http://www.hrelectronic.com/

http://www.sumida.com/

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