CXA1999 SONY [Sony Corporation], CXA1999 Datasheet - Page 11

• Manufacturer Part Number: CXA1999
• Description: IF Amplifier for M-ary FSK Pagers
• Manufacturer: SONY [Sony Corporation]

6) Quick Charge
7) Detector
In order to hasten the rising time from when power is turned on, the CXA1999N features a quick charge
circuit. Therefore, the quick charge circuit eliminates the need to insert a capacitor between the detector
output and the LPF as is the case with conventional ICs, but connects a capacitor to Pin 7 to determine the
average signal level during steady-state reception. The capacitance of the capacitor connected to Pin 7
should be chosen such that the voltage does not vary much due to discharge during battery saving.
Connect a signal for controlling the quick charge circuit to Pin 14. Setting this pin high enables the quick
charge mode, and setting this pin low enables the steady-state reception mode. Quick charge is used
when the power supply is turned on. The battery saving must be set high at the time.
Connect Pin 14 to GND when quick charge is not being used.
The detector is of quadrature type. To perform phase shift, connect a ceramic discriminator to Pin 8.
The phase shifting capacitor for the quadrature detector is incorporated. The demodulated FM (FSK) signal
with the detector will be output to DET OUT (Pin 9) through the internal primary LPF.
DET OUT output impedance is 200 Ω or less. The DET OUT output is the anti-phase output to NRZ OUT.
The CDBM455C28 (MURATA MFG. CO., LTD.) ceramic discriminator is recommended for the CXA1999N.
(Pin number 14)
(Pin number 4)
(Pin number 6)
Power supply
Quick charge
Battery save
7
4.7k
V
CC
8
—11—
Fig. 3
H
H
L
L
Ceramic discriminator
CDBM455C28
Timing
active
9
DET OUTPUT
battery
saving
CXA1999N