TEMIC U4224B-CFLG3, U4224B-CFL, T4224B-CC, T4224B-CF Datasheet

U4224B

Time Code Receiver

Description

The U4224B is a bipolar integrated straight through receiver circuit in the frequency range of 40 to 80 kHz.
The device is designed for radio controlled clock applications.

Features

D

D

Very low power consumption

D

Very high sensitivity

D

High selectivity by using two crystal filters

D

Power down mode available

Only a few external components necessary

D

Digitalized serial output signal

D

AGC hold mode

Block Diagram

GND

V

CC

IN

PON

3

1

2

Power Supply

4561314 7 8

SB

Q1A Q1B Q2A Q2B REC INT

15

AGC

Amplifier

TCO

16

Decoder

Rectifier &

Integrator

93 7727 e

11

10

12

FLB

FLA

9

DEC

SL

TELEFUNKEN Semiconductors

Rev . A3, 02-Apr-96

1 (17)

U4224B

Pin Description

Pin Symbol Function

SO 16 L

1 V
2 IN Amplifier – Input
3 GND Ground
4 SB Bandwidth control
5 Q1A Crystal filter 1
6 Q1B Crystal filter 1
7 REC Rectifier output
8 INT Integrator output

9 DEC Decoder input
10 FLA Low pass filter
11 FLB Low pass filter
12 SL AGC hold mode
13 Q2A Crystal filter 2
14 Q2B Crystal filter 2
15 PON Power ON/OFF control
16 TCO Time code output

CC

Supply voltage

V

CC

IN

GND

SB

Q1A

Q1B

REC

INT

1

2

3

4

5

6

7

8

U4224B

93 7729 e

16

15

14

13

12

11

10

TCO

PON

Q2B

Q2A

SL

FLB

FLA

9

DEC

IN

A ferrite antenna is connected between IN and VCC. For
high sensitivity the Q of the antenna circuit should be as
high as possible, but a high Q often requires temperature
compensation of the resonant frequency. Specifications
are valid for Q > 30. An optimal signal to noise ratio will
be achieved by a resonant resistance of 50 to 200 kW.

V

CC

IN

94 8379

SB

A resistor RSB is connected between SB and GND. It con­trols the bandwidth of the crystal filters. It is
recommended: R
10 kW for 60 kHz WWVB and R
40 kHz.

= 0 W for DCF 77.5 kHz, RSB =

SB

= open for JG2AS

SB

94 8381

SB

GND

2 (17)

TELEFUNKEN Semiconductors

Rev . A3, 02-Apr-96

U4224B

Q1A, Q1B

In order to achieve a high selectivity, a crystal is con­nected between the pins Q1A
serial resonance frequency of the time code transmitter
(e.g. 60 kHz WWVB, 77.5 kHz DCF or 40kHz JG2AS).

The equivalent parallel capacitor of the filter crystal is
internally compensated. The compensated value is about

0.7 pF . If the full sensitivity and selectivity is not needed,
the crystal filter can be substituted by a capacitor of 10 pF
for DCF and WWVB and 22 pF for JG2AS.

Q1A

94 8382

and Q1B. It is used with the

Q1B

GND

REC

Rectifier output and integrator input: The capacitor C1
between REC and INT is the lowpass filter of the rectifier
and at the same time a damping element of the gain
control.

94 8374

SL

AGC hold mode: SL high (VSL = VCC) sets normal func­tion, SL low (V
the voltage V
amplifier gain.

94 8378

= 0) disconnects the rectifier and holds

SL

at the integrator output and also the AGC

INT

V

CC

SL

INT

Integrator output: The voltage V
for the AGC. The capacitor C2 between INT and DEC
defines the time constant of the integrator. The current
through the capacitor is the input signal of the decoder.

is the control voltage

INT

94 8375

REC

GND

DEC

Decoder input: Senses the current through the integration
capacitor C2. The dynamic input resistance has a value of
about 420kW and is low compared to the impedance of
C2.

DEC

94 8376

GND

INT

GND

FLA, FLB

Lowpass filter: A capacitor C3 connected between FLA
and FLB supresses higher frequencies at the trigger
circuit of the decoder.

FLB

FLB

94 8377

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Rev . A3, 02-Apr-96

3 (17)

U4224B

Q2A, Q2B

According to Q1A, Q1B a crystal is connected between
the pins Q2A and Q2B. It is used with the serial resonance
frequency of the time code transmitter (e.g. 60 kHz
WWVB, 77.5 kHz DCF or 40 kHz JG2AS). The equi­valent parallel capacitor of the filter crystal is internally
compensated. The value of the compensation is about

0.7 pF.

Q2A Q2B

94 8383

GND

PON

If PON is connected to GND, the U 4224 B receiver IC
will be activated. The set-up time is typical 0.5s after
applying GND at this pin. If PON is connected to V

CC

, the

receiver will go into power down mode.

V

CC

PON

94 8373

TCO

The digitized serial signal of the time code transmitter can
be directly decoded by a microcomputer. Details about
the time code format of several transmitters are described
separately .

The output consists of a PNP*NPN push-pull-stage. It
should be taken into account that in the power down mode
(PON = high) TCO will be high.

V

CC

An additional improvement of the driving capability may
be achieved by using a CMOS driver circuit or a NPN
transistor with pull-up resistor connected to the collector
(see figure KEIN MERKER). Using a CMOS driver this
circuit must be connected to V

100 k

W

CC

.

10 k

V

CC

W

TCO

pin16
TCO

94 8395 e

Figure 1.

Please note:

The signals and voltages at the pins REC, INT , FLA, FLB,
Q1A, Q1B, Q2A and Q2B cannot be measured by stan­dard measurement equipment due to very high internal
impedances. For the same reason the PCB should be pro­tected against surface humidity.

Design Hints for the Ferrite Antenna

The bar antenna is a very critical device of the complete
clock receiver. But by observing some basic RF design
knowledge, no problem should arise with this part. The IC
requires a resonance resistance of 50 kW to 200 kW. This
can be achieved by a variation of the L/C-relation in the
antenna circuit. But it is not easy to measure such high
resistances in the RF region. It is much more convenient
to distinguish the bandwidth of the antenna circuit and
afterwards to calculate the resonance resistance.

Thus the first step in designing the antenna circuit is to
measure the bandwidth. Figure 4 shows an example for
the test circuit. The RF signal is coupled into the bar
antenna by inductive means, e.g. a wire loop. It can be
measured by a simple oscilloscope using the 10:1 probe.
The input capacitance of the probe, typically about 10 pF ,
should be taken into consideration. By varying the
frequency of the signal generator, the resonance
frequency can be determined.

RF - Signal

generator

77.5 kHz

Scope

4 (17)

94 8380

PON

TCO

GND

wire loop

Probe
10 : 1

w

10 M

W

C

res

94 7907 e

TELEFUNKEN Semiconductors

Rev . A3, 02-Apr-96

U4224B

Afterwards, the two frequencies where the voltage of the
rf signal at the probe drops 3 dB down can be measured.
The difference between these two frequencies is called
the bandwidth BW
of the capacitor C

of the antenna circuit. As the value

A

in the antenna circuit is well known,

res

it is easy to compute the resonance resistance according
to the following formula:

+

R

res

2@p@BW

1

@

C

res

A

whereas

is the resonance resistance,

R

res

is the measured bandwidth (in Hz)

BW

A

is the value of the capacitor in the antenna circuit

C

res

(in Farad)
If high inductance values and low capacitor values are

used, the additional parasitic capacitances of the coil
must be considered. It may reach up to about 20 pF. The
Q-value of the capacitor should be no problem if a high
Q-type is used. The Q-value of the coil is more or less
distinguished by the simple DC-resistance of the wire.
Skin effects can be observed but do not dominate.

Therefore it shouldn’t be a problem to achieve the recom­mended values of resonance resistance. The use of thicker
wire increases Q and accordingly reduces bandwidth.
This is advantageous in order to improve reception in
noisy areas. On the other hand, temperature compen­sation of the resonance frequency might become a

problem if the bandwidth of the antenna circuit is low
compared to the temperature variation of the resonance
frequency . Of course, Q can also be reduced by a parallel
resistor.

Temperature compensation of the resonance frequency is
a must if the clock is used at different temperatures.
Please ask your dealer of bar antenna material and of ca­pacitors for specified values of temperature coefficient.

Furthermore some critical parasitics have to be consid­ered. These are shortened loops (e.g. in the ground line of
the PCB board) close to the antenna and undesired loops
in the antenna circuit. Shortened loops decrease Q of the
circuit. They have the same effect like conducting plates
close to the antenna. To avoid undesired loops in the
antenna circuit it is recommended to mount the capacitor

as close as possible to the antenna coil or to use a

C

res

twisted wire for the antenna coil connection. This twisted
line is also necessary to reduce feedback of noise from the
microprocessor to the IC input. Long connection lines
must be shielded.

A final adjustment of the time code receiver can be done
by pushing the coil along the bar antenna. The maximum
of the integrator output voltage V

at pin INT indicates

INT

the resonant point. But attention: The load current should
not exceed 1 nA, that means an input resistance w 1 G

W

of the measuring device is required. Therefore a special
DVM or an isolation amplifier is necessary .

Absolute Maximum Ratings

Parameters Symbol Value Unit
Supply voltage V
Ambient temperature range T
Storage temperature range R
Junction temperature T
Electrostatic handling

± V

(MIL Standard 883 D), excepted pins 5, 6, 13 and 14

Thermal Resistance

Parameters Symbol Value Unit
Thermal resistance R

TELEFUNKEN Semiconductors

Rev . A3, 02-Apr-96

CC

amb

stg

j

ESD

thJA

5.25 V
–25 to +75
–40 to +85

125

2000 V

70 K/W

_

C

_

C

_

C

5 (17)

U4224B

Electrical Characteristics

VCC = 3 V, reference point pin 3, input signal frequency 80 kHz, T

= 25 _C, unless otherwise specified

amb

Parameters Test Conditions / Pin Symbol Min. Typ. Max. Unit
Supply voltage range pin 1 V
Supply current pin 1

without reception signal
with reception signal = 200mV
OFF-mode

CC

I

CC

1.2 5.25 V

30

15

25

0.1

Set-up time after VCC ON VCC = 1.5 V t 2 s
AGC AMPLIFIER INPUT; IN pin 2
Reception frequency range f
Minimum input voltage R

= 100 kW, Q

res

> 30 V

res

Maximum input voltage V
Input capacitance to ground C

in

in
in
in

40 80 kHz

1 1.5

40 80 mV

1.5 pF

TIMING CODE OUTPUT; TCO pin 16
Output voltage

HIGH
LOW

R

= 870 kW to GND

LOAD

R

= 650 kW to V

LOAD

CC

V

OH

V

OL

VCC-0.4

0.4

Output current
HIGH
LOW

V
V

TCO
TCO

= VCC/2
= VCC/2

I

SOURCE

I

SINK

3
4

10
12

Decoding characteristics DCF77 based on the values of

the application circuit
page KEIN MERKER:
TCO pulse width 100 ms

t
t

100
200

60

160

90

190

130
230

TCO pulse width 200 ms

m

A

m

A

m

A

m

V

V
V

mA
mA

ms
ms

Delay compared with the
transient of the RF signal:

drop down (start transition)
rise for 100 ms pulse
(end transition)
rise for 200 ms pulse
(end transition)

Decoding characteristics WWVB based on the values of

the application circuit
page KEIN MERKER:
TCO pulse width 200 ms
TCO pulse width 500 ms
TCO pulse width 800 ms

Delay compared with the
transient of the RF signal:

drop down (start transition)
rise (end transition)

t

t

t

200

t

500

t

800

t

s

e1

e2

30
25

10

140
440
740

t

s

t

e

45
20

60
55

30

200
500
800

80
45

ms
ms

ms

ms
ms
ms

ms
ms

6 (17)

TELEFUNKEN Semiconductors

Rev . A3, 02-Apr-96