RX3140 Datasheet, PDF (5/8 Pages) List of Unclassifed Manufacturers – RX3140 Low Power IF Receiver IC

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RX3140
Functional Description
The RX3140 IF receiver IC incorporates a mixer, crystal-based local oscillator, IF ampli-
fier, quadrature FM demodulator, bit-rate filter, and 1-bit comparator and is capable of
demodulating 2-level FSK input signals. In addition, 1.0 V regulator and 1.1 V low bat-
tery alarm functions are provided.
Power-down Function
The entire receiver IC may be powered up and down through the control of the BS input
(pin 13). During power down operation, the quiescent current consumption of the IC
drops to approximately 0 µA. The high input impedance of the BS pin allows for direct
interfacing with the CMOS output of an off-chip microcontroller.
Charge/Discharge Circuitry
The function of the charge/discharge circuitry is for both fast and slow charging/discharg-
ing of the capacitor used for storing the voltage reference level of the FSKREF pin. The
CHARGE input (pin 14) 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 appro-
priate dc level (i.e. dc level of the LPFOUT pin) and consequently to minimize the errone-
ous 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 fil-
tered 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 1.0 V regulator requires a suitable off-chip PNP transistor to achieve regula-
tion. The external PNP transistor should have an h_FE > 200 for V_CE ≥ 0.1 V .
Low Battery Alarm
The low battery alarm output, ALM, is normally low, but rises to 1.1 V (≈ VCC) when the
VCC voltage falls below approximately 1.1 V.
Revision B
Page 5
May 2000