UTC TA31142
LINEAR INTEGRATED CIRCUIT
FUNCTIONAL DESCRIPTION
The UTC TA31142 IF receiver IC incorporates a mixer, crystal-based local oscillator, IF amplifier, quadrature FM
demodulator, bit-rate filter, and 1–bit comparator and is capable of demodulating 2-level FSK input signals. In
addition, 1.0V regulator and 1.1V low battery alarm functions are provided.
POWER-DOWN FUNCTION
The entire receiver IC may be powered up and down through the control of the BS input (pin13). During power
down operation, the quiescent current consumption of the IC drops to approximately 0µA. The high input impedance
of the BS pin allows for direct interfacing with the CMOS output of an off-chip micro controller.
CHARGE / DISCHARGE CIRCUITRY
The function of the charge / discharge circuitry is for both fast and slow charging / discharging of the capacitor
used for storing the voltage reference level of the FSKREF pin. The CHARGE input (pin14) should be enabled
(CHARGE=high=fast charge) immediately after transition of the receiver IC from power-down to normal operation in
order to reduce the charging / discharging time for coarse adjustment of the FSKREF voltage to the appropriate dc
level (i.e. dc level of LPFOUT pin) and consequently to minimize the erroneous output of the 1-bit comparator.
During actual data reception, the CHARGE pin should be set to low (CHARGE=low=slow charge) for fine adjustment
of the FSKREF voltage.
1-bit COMPARATOR
The integrated 1-bit comparator operates as a data slicer and “squares up” the bit-rate filtered output from the
quadrature demodulator. The decision threshold voltage level for the 1-bit comparator is stored on an external
capacitor connected to the FSKREF pin.
REGULATOR
The on-chip 1.0V regulator requires a suitable off-chip PNP transistor to achievc regulation. The external PNP
transistor should have an hFE>200 for V
CE
>=0.1V.
LOW BATTERY ALARM
The low battery alarm output, ALM, is normally low, but rises to 1.1V (=VCC) when the VCC voltage falls below
approximately 1.1V.
UTC
UNISONIC TECHNOLOGIES
CO., LTD.
4
QW-R103-015,A
UTC-IC [ UNISONIC TECHNOLOGIES ]
