t4225b ATMEL Corporation, t4225b Datasheet - Page 4

• Manufacturer Part Number: t4225b
• Description: Low-cost Time-code Receiver
• Manufacturer: ATMEL Corporation

INT
Integrator output: The voltage V
for the AGC. The capacitor C
defines the time constant of the integrator. The current
through the capacitor is the input signal of the decoder.
FLA, FLB
Lowpass filter: A capacitor C
and FLB suppresses higher frequencies at the trigger
circuit of the decoder.
Q2A, Q2B
According to Q1A/Q1B, a crystal is connected between
the Pins Q2A and Q2B. It is used with the serial resonant
frequency of the time-code transmitter (e.g., 60 kHz
WWVB, 77.5 kHz DCF or 40 kHz JG2AS). The equi-
valent parallel capacitor of the filter crystal is internally
compensated. The value of the compensation is about
0.7 pF.
T4225B
4 (16)
94 8383
FLB
Q2A
Figure 10.
Figure 11.
Figure 9.
3
2
INT
connected between FLA
between INT and DEC
GND
INT
is the control voltage
Q2B
GND
FLB
94 8377
94 8375
PON
If PON is connected to GND, the receiver will be
activated. The set-up time is typically 0.5 s after applying
GND at this pin. If PON is connected to V
will switch to power-down mode.
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 power-down mode
(PON = high), TCO will be high.
An additional improvement of the driving capability may
be achieved by using a CMOS driver circuit or an NPN
transistor with pull-up resistor connected to the collector
(see figure 14). When using a CMOS driver, this circuit
must be connected to VCC.
94 8380
Pin16
TCO
VCC
PON
100 k
W
Figure 12.
Figure 13.
Figure 14.
10 k
94 8395 e
GND
W
PON
TCO
VCC
Rev. A3, 03-Dec-98
VCC
TCO
CC
94 8373
, the receiver