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DA6181B.002

5 May, 2011

TYPICAL APPLICATION (Continued)

Note 3: Power Down / Fast Startup Control

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

PDN1 = PDN2 = VDD and in power up with other three PDN1 and PDN2 control bit combinations (see table 1 on

page 4). Fast startup is triggered automatically when moving from power down to power up. The VDD must have

been high before moving from power down to power up to guarantee proper operation of fast startup circuitry.

Additionally the device should have been kept in power down state at least 50ms before power up. This

guarantees that the AGC capacitor voltage has been completely pulled to VDD during power down. The startup

time without proper fast startup control can be several minutes. With fast startup it is shortened typically to a 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 of analog clock or

watch can produce disturbing amount of noise which can shift the input amplifier gain to non optimal 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. The AGC should be in hold only during disturbances and kept on other

time released since due to leakage the AGC can still change slowly when in hold.

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 100 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.

C

B

C

f

Q

Q

L

f

R

res

ant

ant

res

ant

⋅

⋅

=

⋅

⋅

=

⋅

⋅

⋅

=

π

π

π

2

1

2

2

Equation 1.

B

f

Q

res

Equation 2.

Table 4 below presents some antenna suppliers for time signal application.

Table 4. Antenna Suppliers and Antenna Types in for Time Signal Application

Supplier

Antenna Type

Dimensions

Web Link

Micro Analog

Systems Oy

A10X60-77.5K222PY

A10X100-77.5K222PY

A3.5X4X15-7.87MH

A2X3X21-0.92MH

A3.75X3.75X23.6-0.92MH

ø 10 x 60 mm

ø 10 x 100 mm

3.5 x 4 x 15 mm

2 x 3 x 21 mm

3.75x3.75x23 mm

http://www.mas-

oy.com/en/products/radio-controlled-

clock-rcc/antennas/

HR Electronic

GmbH

60716 (60 kHz)

60708 (77.5 kHz)

ø 10 x 60 mm

http://www.hrelectronic.com/

Hitachi Metals

AN-T702Sxx

AN-T702Mxx

AN-T702Lxx

19 x 5.5 x 6.3 mm

28 x 5 x 5 mm

50 x 5 x 5 mm

http://www.hitachi-

metals.co.jp/e/prod/prod06/p06_12.html

Premo

RCA-SMD-77A (77.5 kHz)

RCA-SMD-60A (60 kHz)

75 x 15 x 6.3 mm

http://www.grupopremo.com/

Sumida

ACL80A (40 kHz)

ø 10 x 80 mm

www.sumida.co.jp/jeita/XJA021.pdf